Medicine – Acute Asthma

Acute asthma is a sudden or progressive worsening of asthma symptoms caused by increased bronchial smooth-muscle constriction, airway inflammation, mucosal oedema, and mucus production. Patients develop worsening breathlessness, wheeze, cough, and chest tightness, together with a measurable reduction in expiratory airflow.

A severe asthma attack can progress rapidly to life-threatening respiratory failure, so recognising markers of severity and starting treatment promptly are essential.

1. Mortality

Asthma continues to cause preventable deaths in the UK, although the older figure of approximately 1,500 deaths per year varies between years and should not be regarded as a fixed contemporary number.

Many fatal attacks are associated with delayed recognition of severity, inadequate use of anti-inflammatory treatment, or delayed escalation of emergency care.

Assessment of Acute Asthma

The severity of an acute attack should be assessed using the patient’s clinical appearance, ability to speak, respiratory rate, heart rate, oxygen saturation, peak expiratory flow (PEF), and—when indicated—arterial blood gases.

An important correction to the older notes is that some listed findings, particularly PEF <33%, silent chest, hypoxaemia, and normal or raised PaCO₂, are markers of life-threatening asthma, rather than merely severe asthma.

2. Severe Acute Asthma

In adults, acute severe asthma is suggested by the presence of any of the following major features.

Difficulty Speaking

The patient may be unable to complete sentences in one breath because of severe breathlessness.

Speech becoming increasingly fragmented is an important bedside indication of worsening respiratory distress.

Tachycardia

A heart rate ≥110 beats/minute is a marker of acute severe asthma.

Tachycardia can result from respiratory distress, hypoxaemia, sympathetic activation, and β₂-agonist treatment.

Tachypnoea

A respiratory rate ≥25 breaths/minute is commonly used in modern UK adult criteria for acute severe asthma.

The older threshold of >30/min still indicates substantial respiratory distress but is not the usual current threshold for defining acute severe asthma.

Peak Expiratory Flow

A PEF of 33–50% of the patient’s best or predicted value indicates acute severe asthma.

Peak flow provides an objective measurement of the degree of airflow obstruction and should be recorded whenever the patient is capable of performing the manoeuvre safely.

3. Life-Threatening Asthma

Life-threatening asthma is suggested by particularly severe clinical or physiological abnormalities.

These patients require immediate treatment, senior medical involvement, and consideration of intensive care.

Peak Flow Below 33%

A PEF <33% of the patient’s best or predicted value is a major marker of life-threatening asthma.

This represents very severe expiratory airflow limitation.

Silent Chest

A silent chest is an ominous finding.

Although wheezing is characteristic of asthma, extremely severe airflow obstruction can reduce airflow so dramatically that little or no wheeze is audible.

Therefore, disappearance of wheeze in a deteriorating patient does not necessarily indicate improvement.

Hypoxaemia

Significant hypoxaemia indicates severe impairment of ventilation and gas exchange.

Oxygen saturation should therefore be monitored continuously in a severe attack.

Normal or Raised PaCO₂

A normal or elevated arterial PaCO₂ is a particularly concerning finding in acute asthma.

Early in an asthma attack, patients usually hyperventilate and therefore have a low PaCO₂.

As obstruction becomes extreme and respiratory muscles fatigue, the patient can no longer maintain adequate ventilation. PaCO₂ then returns toward normal and subsequently rises.

Therefore:

Low PaCO₂ → expected during significant acute asthma.

Normal PaCO₂ → concerning for deterioration.

Raised PaCO₂ → severe ventilatory failure and potentially impending respiratory arrest.

Other Life-Threatening Features

Additional warning signs include cyanosis, poor respiratory effort, exhaustion, hypotension, arrhythmia, altered consciousness, and confusion.

These features indicate that the patient may be approaching respiratory failure.

4. Pulsus Paradoxus

Pulsus paradoxus refers to an exaggerated fall in systolic blood pressure during inspiration.

It may occur in severe asthma because large changes in intrathoracic pressure influence ventricular filling.

Although historically included in severity assessment, it is not routinely relied upon in modern acute asthma assessment, because simpler clinical and physiological measurements are more useful.

Management of Acute Severe Asthma

Treatment should begin immediately while severity is being assessed.

The major aims are to correct hypoxaemia, reverse bronchoconstriction, suppress airway inflammation, and recognise patients requiring intensive respiratory support.

5. Oxygen

Patients who are hypoxaemic should receive supplemental oxygen, titrated to an appropriate oxygen saturation.

The older instruction to automatically administer unrestricted high-flow oxygen to every patient has been replaced by controlled oxygen therapy guided by oxygen saturation.

In adults with acute asthma, a target oxygen saturation of approximately 94–98% is commonly used.

6. Nebulised β₂-Agonists

A rapidly acting inhaled β₂-agonist, most commonly salbutamol, is a cornerstone of treatment.

In severe attacks, repeated or continuous nebulised therapy may be required.

Nebulisers can be driven by oxygen when appropriate in significantly hypoxaemic patients.

7. Ipratropium Bromide

Nebulised ipratropium bromide should be added to β₂-agonist treatment in severe or life-threatening asthma.

The combination produces greater bronchodilation than either treatment alone in severe attacks.

8. Systemic Corticosteroids

Systemic corticosteroids should be administered early because acute asthma involves significant airway inflammation as well as bronchoconstriction.

Oral prednisolone is often appropriate when the patient can swallow and absorb medication.

Intravenous hydrocortisone can be used when oral treatment is unsuitable.

Steroids do not produce immediate bronchodilation, but they reduce airway inflammation and decrease the likelihood of ongoing deterioration and relapse.

Additional Treatment

9. Intravenous Magnesium Sulfate

Intravenous magnesium sulfate may be considered in severe or life-threatening asthma that responds inadequately to initial inhaled bronchodilator treatment.

Magnesium has a bronchodilator effect and can be useful in selected severe attacks.

It is not routinely required for every asthma exacerbation.

10. Intravenous Aminophylline

Intravenous aminophylline was historically used more frequently in severe asthma.

It is no longer routinely recommended because the additional bronchodilator benefit is limited and adverse effects, including nausea, vomiting, arrhythmias, and seizures, can occur.

It may occasionally be considered in specialist-managed refractory cases.

11. Intravenous Salbutamol

Intravenous β₂-agonists such as salbutamol are also not routinely used when effective inhaled or nebulised therapy can be delivered.

They may occasionally be considered in highly selected refractory cases under specialist supervision.

12. Antibiotics

Antibiotics are not routinely indicated in acute asthma.

Most asthma exacerbations are not caused by bacterial infection, and purulent-looking sputum alone does not necessarily indicate bacterial disease.

Antibiotics should be given when there is convincing evidence of a bacterial infection, such as bacterial pneumonia.

Respiratory Failure

13. When to Consider Intensive Care

Urgent intensive care assessment should be considered when the patient is deteriorating despite appropriate treatment or develops features such as exhaustion, altered consciousness, worsening hypoxaemia, rising PaCO₂, poor respiratory effort, or haemodynamic instability.

A patient with severe asthma can deteriorate very rapidly.

14. Mechanical Ventilation

Mechanical ventilation may become necessary when respiratory failure develops despite maximal medical treatment.

Important indications include worsening hypercapnia, severe hypoxaemia, exhaustion, reduced consciousness, respiratory arrest, or inability to maintain adequate ventilation.

Intubation and ventilation of a patient with severe asthma are challenging because severe airflow obstruction and air trapping can produce dynamic hyperinflation and dangerously high intrathoracic pressures, so experienced critical-care management is essential.

15. Severe vs Life-Threatening Asthma – Note Form

Acute Severe Asthma

Speech: unable to complete sentences in one breath.

Respiratory rate: ≥25/min.

Heart rate: ≥110/min.

PEF: 33–50% of best or predicted.

Life-Threatening Asthma

PEF: <33% of best or predicted.

Chest examination: silent chest.

Oxygenation: significant hypoxaemia.

PaCO₂: normal or raised.

Cyanosis: may be present.

Respiratory effort: poor or decreasing.

Neurological state: exhaustion, confusion, or reduced consciousness.

Cardiovascular features: hypotension or arrhythmia may develop.

16. Immediate Management – Note Form

Oxygen: controlled supplemental oxygen, generally targeting SpO₂ around 94–98%.

Bronchodilator: repeated or nebulised salbutamol.

Antimuscarinic: add nebulised ipratropium in severe or life-threatening attacks.

Steroids: give systemic corticosteroids early.

Magnesium: consider IV magnesium sulfate if the response to initial treatment is inadequate.

Antibiotics: only when bacterial infection is suspected or confirmed.

Aminophylline/IV salbutamol: not routine; reserve for selected refractory cases with specialist input.

Ventilation: consider urgently if respiratory failure, exhaustion, deteriorating consciousness, worsening hypoxaemia, or rising PaCO₂ develops.

Key Clinical Pattern

In acute asthma, a patient initially tends to hyperventilate and lower their PaCO₂. Therefore, a normal PaCO₂ is not reassuring in a severely breathless asthmatic—it may indicate that respiratory muscles are beginning to fail.

Remember the distinction:

Acute severe asthma → PEF 33–50%, RR ≥25/min, HR ≥110/min, inability to complete sentences.

Life-threatening asthma → PEF <33%, silent chest, hypoxaemia, normal/raised PaCO₂, cyanosis, exhaustion, hypotension, arrhythmia, or altered consciousness.

Initial treatment centres on oxygen when hypoxaemic + repeated inhaled/nebulised β₂-agonist + ipratropium + early systemic corticosteroids, with IV magnesium and critical-care support when the response is inadequate.

Medicine – Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a common, progressive respiratory disorder characterised by persistent airflow limitation that is not fully reversible. The airflow obstruction usually develops gradually over years and reflects a combination of small-airway disease, chronic bronchitis, and emphysema.

COPD is associated with substantial morbidity, recurrent exacerbations, reduced exercise tolerance, impaired quality of life, and increased mortality.

1. Definition

COPD is characterised by chronic respiratory symptoms together with persistent airflow obstruction.

The obstruction does not fluctuate markedly over short periods in the way that asthma often does, although some reversibility can still be present.

Modern diagnosis relies on post-bronchodilator spirometry, rather than simply describing airflow obstruction as “fixed.”

2. Main Cause

The most important risk factor is cigarette smoking.

Long-term exposure to tobacco smoke causes chronic airway inflammation, mucus hypersecretion, small-airway narrowing, and destruction of alveolar tissue.

However, COPD can also occur in never-smokers because of factors such as biomass fuel exposure, occupational dusts and fumes, air pollution, impaired lung development, and α1-antitrypsin deficiency.

3. Chronic Bronchitis and Emphysema

Patients with COPD may have varying proportions of chronic bronchitis, small-airway disease, and emphysema.

These abnormalities frequently overlap, so patients do not usually fall neatly into one category.

4. Chronic Bronchitis

Chronic bronchitis is a clinical definition.

Traditionally, it is defined as a productive cough for at least 3 months in each of 2 consecutive years, after excluding other causes of chronic cough.

The condition reflects chronic mucus hypersecretion and airway inflammation.

5. Emphysema

Emphysema is a pathological condition characterised by permanent enlargement of airspaces distal to the terminal bronchioles with destruction of alveolar walls.

This destruction reduces elastic recoil and causes premature airway collapse during expiration.

Although originally defined pathologically, emphysema can now often be identified and quantified on CT imaging.

Clinical Features

6. Chronic Cough

A chronic cough is common and is often productive of sputum.

Some patients may have cough and sputum production for years before significant breathlessness develops.

7. Breathlessness

Progressive exertional breathlessness is one of the most important symptoms of COPD.

It usually worsens gradually over time and eventually may limit ordinary daily activities.

8. Wheeze

Wheeze may occur because of airflow narrowing and dynamic airway collapse.

Its presence does not automatically indicate asthma, since wheeze is common in COPD as well.

9. Recurrent Exacerbations

Patients may experience recurrent acute exacerbations, characterised by a sustained worsening of respiratory symptoms beyond normal day-to-day variation.

Typical features include increased breathlessness, increased cough, greater sputum volume, and sometimes increased sputum purulence.

Exacerbations may be triggered by viral infections, bacterial infections, air pollution, or other environmental factors.

Spirometry

10. FEV₁/FVC Ratio

The diagnosis of persistent airflow obstruction is based on spirometry.

The modern standard is a post-bronchodilator FEV₁/FVC ratio <0.70.

Older teaching sometimes used thresholds such as <75%, but the fixed 0.70 ratio is more commonly used in modern guidelines, with interpretation adjusted for age when appropriate.

11. FEV₁

FEV₁ is useful for assessing the degree of airflow limitation.

An FEV₁ below 80% predicted may support obstructive lung disease, but COPD diagnosis is not based on FEV₁ alone.

Severity assessment now also considers symptoms, exacerbation frequency, hospitalisations, oxygenation, comorbidities, and functional limitation, not just spirometric percentage bands.

Acute Management

12. Bronchodilators

Acute exacerbations are treated with short-acting bronchodilators, typically a short-acting β₂-agonist such as salbutamol, often with an antimuscarinic such as ipratropium.

Nebulised therapy may be used in more severe attacks.

13. Controlled Oxygen Therapy

Oxygen must be given carefully in patients at risk of hypercapnic respiratory failure.

In many acute COPD exacerbations, the usual target oxygen saturation is 88–92% until arterial blood gas results are available.

The aim is to correct dangerous hypoxaemia without causing excessive worsening of CO₂ retention.

14. Corticosteroids

Short courses of systemic corticosteroids are commonly used in moderate or severe exacerbations because they can shorten recovery time and improve lung function.

They are not used simply as an old-style “steroid reversibility trial” to decide long-term treatment.

15. Antibiotics

Antibiotics may be indicated when there is evidence of bacterial infection, especially with increased sputum purulence, increased sputum volume, or more severe exacerbation requiring ventilation.

Chronic Management

16. Smoking Cessation

Smoking cessation is the single most important intervention for patients who smoke.

It slows the accelerated decline in lung function and reduces exacerbations, cardiovascular risk, and overall mortality.

It is more accurate to say that smoking cessation is the most important modifiable measure rather than the only treatment that can influence disease progression.

17. Vaccination

Patients with COPD should receive appropriate influenza vaccination and pneumococcal vaccination.

Other vaccines may also be indicated depending on age and local recommendations.

18. Short-Acting Bronchodilators

Patients with intermittent symptoms may use a short-acting β₂-agonist (SABA) or a short-acting muscarinic antagonist (SAMA) as required.

These drugs provide rapid symptom relief.

19. Long-Acting Bronchodilators

For persistent symptoms, modern treatment generally relies on long-acting bronchodilators.

These include:

LABA – long-acting β₂-agonists

and

LAMA – long-acting muscarinic antagonists.

Many symptomatic patients benefit from LABA + LAMA combination therapy.

This has largely replaced older stepwise regimens based mainly on repeated short-acting bronchodilator use.

20. Inhaled Corticosteroids

Inhaled corticosteroids (ICS) are not routinely given to every patient with COPD.

They are most useful in selected patients with frequent exacerbations, higher blood eosinophil counts, or coexisting asthma features.

ICS is often used in combination with long-acting bronchodilators rather than as monotherapy.

The older practice of giving a steroid trial and continuing ICS only if FEV₁ improves by >15% is no longer the standard approach.

21. Triple Therapy

Patients with persistent exacerbations despite dual bronchodilation may benefit from triple inhaler therapy:

LABA + LAMA + ICS.

The decision depends on symptoms, exacerbation history, blood eosinophils, pneumonia risk, and other clinical factors.

22. Pulmonary Rehabilitation

Pulmonary rehabilitation is an important non-drug treatment for symptomatic patients.

It combines exercise training, education, breathing strategies, and multidisciplinary support and can improve exercise capacity, breathlessness, and quality of life.

23. Long-Term Oxygen Therapy

Long-term oxygen therapy (LTOT) is indicated in selected patients with persistent severe chronic hypoxaemia.

It is not prescribed simply because the COPD is spirometrically “severe.”

Typical eligibility depends on arterial oxygen tension and complications such as pulmonary hypertension, cor pulmonale, or secondary polycythaemia.

Complications

24. Respiratory Failure

Advanced COPD can cause respiratory failure.

Patients may initially develop hypoxaemia and later progress to type 2 respiratory failure with hypercapnia, especially during exacerbations.

25. Recurrent Exacerbations

Frequent exacerbations accelerate functional decline and are associated with worse quality of life and increased mortality.

Patients with repeated exacerbations may require escalation of inhaled therapy and further investigation for contributing factors.

26. Cor Pulmonale

Chronic hypoxaemia can cause hypoxic pulmonary vasoconstriction, leading to pulmonary hypertension.

Over time, this may produce right-sided heart strain and cor pulmonale.

27. Secondary Polycythaemia

Persistent hypoxaemia stimulates erythropoietin production and may cause secondary polycythaemia.

The resulting increase in red cell mass can increase blood viscosity.

28. Pneumothorax

Patients with emphysema may develop bullae, which can rupture and produce a spontaneous pneumothorax.

This may cause sudden pleuritic chest pain and acute worsening of breathlessness.

29. Lung Cancer

COPD is strongly associated with lung cancer, largely because tobacco exposure is a major shared risk factor.

COPD itself may also be associated with additional cancer risk beyond smoking alone.

30. Osteoporosis

Patients with COPD have an increased risk of osteoporosis.

Contributing factors include smoking, low body weight, reduced physical activity, chronic inflammation, vitamin D deficiency, and repeated or prolonged exposure to systemic corticosteroids.

31. Pink Puffer and Blue Bloater

Older teaching divided COPD patients into “pink puffers” and “blue bloaters.”

The pink-puffer pattern was associated mainly with emphysema, marked breathlessness, relatively preserved ventilation, and normal or low PaCO₂ until later disease.

The blue-bloater pattern was associated more with chronic bronchitis, hypoxaemia, hypercapnia, cyanosis, pulmonary hypertension, and cor pulmonale.

These terms are now regarded as historical rather than formal clinical classifications, because most patients have overlapping features.

Key Clinical Pattern

Think of COPD in a patient, usually with a significant smoking or inhalational exposure history, who has progressive exertional breathlessness, chronic cough with or without sputum, wheeze, and recurrent exacerbations.

The key spirometric finding is persistent post-bronchodilator airflow obstruction with FEV₁/FVC <0.70.

Modern long-term treatment centres on smoking cessation, vaccination, long-acting bronchodilators, pulmonary rehabilitation, selective use of inhaled corticosteroids, prevention of exacerbations, and LTOT when severe chronic hypoxaemia is present.

Important complications include respiratory failure, recurrent exacerbations, pulmonary hypertension and cor pulmonale, secondary polycythaemia, pneumothorax, osteoporosis, and lung cancer.

Medicine – Pink Puffer vs Blue Bloater in COPD

The terms “pink puffer” and “blue bloater” are traditional descriptions of two clinical phenotypes of chronic obstructive pulmonary disease (COPD). The pink-puffer pattern was associated mainly with emphysema, whereas the blue-bloater pattern was associated mainly with chronic bronchitis.

These terms are now considered outdated because many patients have overlapping emphysema and airway disease rather than fitting neatly into one category. However, the comparison remains useful for understanding the underlying physiology.

1. Pink Puffer – Emphysema-Predominant Pattern

The traditional pink puffer describes a patient whose COPD is predominantly emphysematous.

Destruction of alveolar walls causes loss of elastic recoil, air trapping, hyperinflation, and reduced surface area for gas exchange. These patients often compensate by increasing their respiratory effort and ventilation.

Hyperventilation

Patients with emphysema may maintain relatively effective alveolar ventilation by increasing their respiratory rate and work of breathing.

This increased ventilation helps remove carbon dioxide and can maintain arterial oxygenation relatively well during the earlier stages of disease.

Carbon Dioxide

Because ventilation is relatively well maintained, PaCO₂ may remain normal or low until advanced disease.

The image associates this with type 1 respiratory failure, but this requires clarification. Type 1 respiratory failure is defined primarily by hypoxaemia with a normal or low PaCO₂, rather than simply by a low carbon dioxide concentration.

Therefore:

Type 1 respiratory failure = low PaO₂ with normal or low PaCO₂.

Breathlessness

Breathlessness is often prominent in emphysema-predominant COPD because patients must work hard to maintain ventilation despite severe airflow obstruction and hyperinflation.

Patients may use accessory respiratory muscles and sometimes adopt pursed-lip breathing, which helps prevent premature small-airway collapse during expiration.

Why “Pink”?

The historical term “pink” refers to the observation that these patients may remain relatively well oxygenated and therefore show less obvious cyanosis, particularly earlier in the disease.

This does not mean that patients with emphysema cannot become hypoxaemic or cyanosed. Both can occur as disease progresses.

Typical Body Habitus

Classically, emphysema-predominant patients were described as thin or underweight.

The increased energy expenditure associated with persistent respiratory effort, together with systemic effects of advanced COPD, can contribute to weight loss and muscle wasting.

2. Blue Bloater – Chronic Bronchitis-Predominant Pattern

The traditional blue bloater describes a patient whose COPD is predominantly associated with chronic bronchitis and severe airway obstruction.

Excess mucus production, airway inflammation, airway narrowing, and mucus plugging impair ventilation and produce substantial ventilation–perfusion mismatch.

Hypoventilation

Compared with the traditional emphysema phenotype, these patients may have relatively inadequate alveolar ventilation.

As ventilation becomes insufficient, carbon dioxide is retained and arterial oxygen falls.

Carbon Dioxide Retention

The resulting hypercapnia may contribute to type 2 respiratory failure.

The complete definition is:

Type 2 respiratory failure = low PaO₂ with raised PaCO₂.

Therefore, the raised carbon dioxide shown in the image is an important distinguishing physiological feature.

Cyanosis

Significant hypoxaemia can cause central cyanosis, producing the historical description “blue.”

Cyanosis is therefore more prominent in the traditional chronic bronchitis phenotype than in the compensated emphysema phenotype.

Breathlessness

The image describes these patients as “cyanosed but not breathless.” This should not be interpreted literally.

Patients with chronic bronchitis-predominant COPD can certainly experience significant breathlessness. The traditional comparison simply suggests that dyspnoea may be less disproportionately prominent than in severe emphysema, despite greater abnormalities in blood gases.

3. Cor Pulmonale

Cor pulmonale is classically associated with the chronic bronchitis-predominant phenotype.

Persistent alveolar hypoxia causes hypoxic pulmonary vasoconstriction. Over time, this increases pulmonary vascular resistance and can produce pulmonary hypertension.

The right ventricle must pump against the increased pulmonary arterial pressure and may eventually develop right-sided heart dysfunction.

Peripheral Oedema

Patients with advanced cor pulmonale may develop peripheral oedema, contributing to the historical term “bloater.”

Other findings can include a raised jugular venous pressure and additional evidence of right-sided cardiac dysfunction.

4. Comparison in Note Form

Pink Puffer

Traditional association: emphysema.

Ventilation: increased or relatively well maintained.

PaO₂: may be relatively preserved in earlier disease, although hypoxaemia can develop later.

PaCO₂: usually normal or reduced initially because of increased ventilation.

Respiratory failure: may develop a type 1 respiratory failure pattern, with low PaO₂ and normal or low PaCO₂.

Breathlessness: usually prominent and often severe.

Cyanosis: less prominent in earlier disease.

Body habitus: classically thin or underweight.

Cor pulmonale: generally develops later and is less characteristic than in chronic bronchitis-predominant disease.

Peripheral oedema: less characteristic unless significant right-sided heart failure develops.

Blue Bloater

Traditional association: chronic bronchitis.

Ventilation: relatively reduced, with a greater tendency toward alveolar hypoventilation.

PaO₂: more markedly reduced because of significant ventilation–perfusion mismatch.

PaCO₂: typically raised because of carbon dioxide retention.

Respiratory failure: more likely to develop type 2 respiratory failure, with low PaO₂ and raised PaCO₂.

Breathlessness: can occur and may be significant, although traditionally described as less prominent relative to the degree of hypoxaemia.

Cyanosis: more prominent because of chronic hypoxaemia.

Body habitus: traditionally described as more oedematous or “bloated,” particularly when cor pulmonale develops.

Cor pulmonale: more characteristic because chronic hypoxia causes pulmonary hypertension and right-heart strain.

Peripheral oedema: may occur as part of right-sided heart dysfunction.

5. Main Physiological Difference

The central difference between the traditional two patterns is how well the patient maintains alveolar ventilation.

In the emphysema-predominant pink-puffer pattern, the patient compensates by breathing harder and maintaining ventilation, so CO₂ tends to remain normal or low for longer.

In the chronic bronchitis-predominant blue-bloater pattern, ventilation is less effective, so oxygen falls and CO₂ rises, creating a greater tendency toward chronic type 2 respiratory failure.

Key Clinical Pattern

The traditional pink puffer represents emphysema-predominant COPD: severe breathlessness, increased respiratory effort, relatively maintained ventilation, and normal or low PaCO₂ until later disease.

The traditional blue bloater represents chronic bronchitis-predominant COPD: greater hypoxaemia, CO₂ retention, type 2 respiratory failure, cyanosis, pulmonary hypertension, cor pulmonale, and peripheral oedema.

For modern clinical practice, it is better to describe the patient’s actual COPD phenotype, symptoms, exacerbation history, spirometry, emphysema burden, oxygenation, and hypercapnia rather than label patients strictly as pink puffers or blue bloaters.

Medicine – Long-Term Oxygen Therapy

Long-term oxygen therapy (LTOT) is the regular administration of supplemental oxygen at home for patients with chronic severe resting hypoxaemia. It is used mainly in chronic respiratory diseases such as advanced COPD when persistent hypoxaemia remains despite optimal treatment of the underlying condition.

The major purpose of LTOT is not simply to relieve breathlessness. In appropriately selected patients with severe chronic hypoxaemia, prolonged oxygen therapy can improve survival and reduce some of the consequences of chronic tissue hypoxia.

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1. Survival Benefit

Classic clinical trials demonstrated a significant survival benefit from long-term oxygen in patients with severe chronic hypoxaemia, particularly when oxygen was used for prolonged periods each day.

Older teaching sometimes describes approximately a 50% improvement in three-year survival in appropriately selected patients. The important clinical principle is that LTOT has a proven mortality benefit in patients with severe chronic resting hypoxaemia.

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2. Duration of Oxygen Therapy

For LTOT to provide its established benefit, oxygen should generally be administered for at least 15 hours per day.

Greater daily use may provide additional benefit, and many patients are therefore encouraged to use oxygen for as much of the day and night as clinically appropriate.

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3. Target Oxygenation

The oxygen flow rate is individually adjusted to correct significant hypoxaemia.

Traditional teaching aims to increase the arterial oxygen tension (PaO₂) above approximately 8 kPa (60 mmHg) while maintaining safe carbon dioxide levels.

The patient’s oxygen requirement should therefore be determined by formal assessment rather than simply prescribing an arbitrary oxygen flow rate.

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Assessment for LTOT

4. Patient Must Be Clinically Stable

LTOT should not normally be permanently prescribed solely on measurements obtained during an acute respiratory exacerbation, because hypoxaemia may improve after recovery.

Assessment is therefore performed when the patient’s underlying disease has been optimally treated and clinically stable.

Older protocols commonly required arterial blood gases on two occasions several weeks apart. Current protocols vary by healthcare system, but the principle remains that chronic hypoxaemia should be confirmed in a stable patient.

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5. Severe Resting Hypoxaemia

A classic indication for LTOT is a resting:

PaO₂ ≤7.3 kPa (55 mmHg)

when measured in a clinically stable patient.

This degree of persistent hypoxaemia is associated with adverse physiological consequences and is the group in which the survival benefit of LTOT is best established.

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6. PaO₂ Between 7.3 and 8.0 kPa

LTOT may also be indicated when the resting PaO₂ is approximately 7.3–8.0 kPa (55–60 mmHg) if there is evidence of complications resulting from chronic hypoxaemia.

Important examples include pulmonary hypertension, peripheral oedema suggesting cor pulmonale, or secondary polycythaemia.

Therefore, a patient does not necessarily need a PaO₂ below 7.3 kPa if there is evidence that chronic hypoxaemia is already producing significant physiological consequences.

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Cor Pulmonale

7. Chronic Hypoxaemia and the Right Heart

Persistent alveolar hypoxia causes pulmonary vasoconstriction.

When this occurs chronically, pulmonary vascular resistance increases and may eventually produce pulmonary hypertension.

The right ventricle must then pump against increased resistance, potentially resulting in right-sided cardiac dysfunction or cor pulmonale.

Correcting chronic hypoxaemia with LTOT can reduce hypoxic pulmonary vasoconstriction and help limit these consequences.

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Carbon Dioxide

8. PaCO₂ May Be Normal or Raised

A raised arterial carbon dioxide tension (PaCO₂) does not automatically exclude a patient from receiving LTOT.

Some patients with advanced COPD have chronic hypercapnic respiratory failure and may still obtain substantial benefit from oxygen when they meet the appropriate hypoxaemia criteria.

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9. Checking the Response to Oxygen

The patient’s response to supplemental oxygen should be assessed to ensure that oxygenation improves appropriately and that treatment does not cause clinically important worsening of hypercapnia or respiratory acidosis.

The older criterion that PaO₂ must rise above 8 kPa without a significant increase in PaCO₂ reflects this concern.

However, chronic hypercapnia itself is not an absolute contraindication to LTOT.

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FEV₁ and LTOT

10. FEV₁ Below 1.5 L

Older criteria sometimes included an FEV₁ below 1.5 L as a requirement for LTOT.

This is now considered outdated as a strict eligibility criterion.

The decision to prescribe LTOT is primarily based on persistent chronic hypoxaemia and its complications, rather than a specific absolute FEV₁ value.

A patient can therefore meet criteria for LTOT without having an FEV₁ below 1.5 L.

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Smoking and Oxygen Therapy

11. Smoking

Older protocols often stated that patients had to be non-smokers before LTOT could be prescribed.

Smoking cessation remains extremely important because continued smoking accelerates COPD progression and substantially reduces the overall benefit of respiratory treatment.

There is also a major fire and burn risk when smoking or using an open flame near supplemental oxygen.

However, whether active smoking represents an absolute contraindication to providing home oxygen varies according to local policies and individual risk assessment. It should therefore not be regarded as a universal physiological eligibility criterion in the same way as PaO₂.

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Practical Use

12. Home Oxygen

LTOT is usually delivered at home using an oxygen concentrator, with the prescribed flow rate determined during specialist assessment.

Patients and household members require education about safe oxygen use, particularly avoidance of smoking, flames, and other ignition sources.

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13. LTOT Is Different from Oxygen for Breathlessness

LTOT should not be prescribed simply because a patient feels breathless.

A patient can have severe breathlessness while maintaining adequate oxygenation, and supplemental oxygen has not demonstrated the same survival benefit in patients who do not have qualifying chronic hypoxaemia.

The key indication is therefore documented persistent hypoxaemia, not breathlessness alone.

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Key Clinical Pattern

Think of LTOT in a clinically stable patient with persistent severe chronic hypoxaemia despite optimal treatment.

The classic threshold is PaO₂ ≤7.3 kPa (55 mmHg), or approximately 7.3–8.0 kPa (55–60 mmHg) when complications of chronic hypoxaemia such as cor pulmonale/pulmonary hypertension or secondary polycythaemia are present.

Oxygen is generally required for at least 15 hours per day, and the prescription should be titrated to improve oxygenation safely.

Remember that the older requirements of FEV₁ <1.5 L and universal exclusion of smokers are not modern physiological criteria for LTOT, while chronic hypercapnia does not automatically exclude treatment.

Medicine – α1-Antitrypsin Deficiency

α1-Antitrypsin deficiency (AATD) is an inherited disorder caused by pathogenic variants in the SERPINA1 gene on chromosome 14. It primarily affects the lungs and liver and is an important genetic cause of early-onset emphysema, particularly in patients who smoke.

1. Inheritance

α1-Antitrypsin deficiency is inherited in an autosomal codominant manner.

This means that both inherited alleles contribute to the amount and type of α1-antitrypsin produced. Different combinations of alleles therefore produce different serum concentrations and different risks of developing disease.

2. Function of α1-Antitrypsin

α1-Antitrypsin (AAT) is a circulating protease inhibitor produced mainly by hepatocytes.

Its major pulmonary role is to protect lung tissue from proteolytic enzymes released by inflammatory cells, particularly neutrophil elastase.

Normally, AAT neutralises elastase and prevents excessive degradation of elastin and other structural proteins within the alveolar walls.

3. Mechanism of Emphysema

When AAT concentrations are severely reduced, the lungs become inadequately protected against neutrophil elastase and other proteases.

Unopposed proteolytic activity gradually destroys alveolar walls, reducing the surface area available for gas exchange and producing emphysema.

Smoking accelerates this process by increasing pulmonary inflammation and neutrophil recruitment while also impairing the protective activity of AAT.

4. Pattern of Emphysema

The characteristic pulmonary abnormality is panacinar or panlobular emphysema.

Unlike the centriacinar emphysema typically associated with cigarette smoking, which often has an upper-lobe predominance, AAT deficiency classically produces emphysema that is most pronounced in the lower lobes and lung bases.

5. Protective Threshold

Severe deficiency increases the likelihood of progressive lung injury.

Older teaching sometimes describes tissue destruction occurring when AAT levels fall below approximately 40% of normal, but contemporary assessment more commonly considers the absolute serum concentration and the patient’s genotype rather than relying on a single percentage threshold.

The greatest pulmonary risk occurs in individuals with severe AAT deficiency, particularly those with the ZZ genotype.

Genotypes

The traditional genotype nomenclature uses letters such as M, S, and Z to describe different forms of the AAT protein.

6. MM Genotype

The MM genotype is considered the normal genotype.

People with PiMM generally have normal circulating α1-antitrypsin concentrations and are not considered to have clinically significant AAT deficiency.

7. MZ Genotype

People with the MZ genotype have one normal M allele and one deficient Z allele.

Serum AAT levels are moderately reduced, traditionally quoted at around 60% of normal, although the exact concentration varies.

Most nonsmokers with MZ do not develop severe early emphysema, but smoking and other respiratory exposures can increase their risk.

8. SZ Genotype

The SZ genotype produces a greater reduction in circulating AAT than MZ.

Older teaching commonly quotes levels of approximately 40% of normal.

The risk of emphysema is intermediate and becomes substantially greater with cigarette smoking.

9. ZZ Genotype

The ZZ genotype is the classic form associated with severe α1-antitrypsin deficiency.

Circulating levels may be only around 10–20% of normal, often quoted historically as approximately 15%.

These patients have a particularly high risk of early-onset panacinar emphysema and liver disease.

Clinical Presentation

10. Early-Onset Emphysema

Severely affected individuals may develop respiratory symptoms in the third or fourth decade of life.

Typical features include progressive exertional breathlessness, wheezing, chronic cough, and reduced exercise tolerance.

Smoking can cause symptoms to appear much earlier and can dramatically accelerate the decline in lung function.

11. Pulmonary Function

Pulmonary function testing typically demonstrates an obstructive ventilatory defect, with reduced FEV₁ and FEV₁/FVC ratio.

Gas transfer may also be reduced because destruction of alveolar walls decreases the surface area available for diffusion.

Liver Disease

12. Mechanism of Liver Injury

AAT deficiency can also cause liver disease, particularly with the Z allele.

The mechanism is different from that causing lung disease. In the liver, abnormal Z-type AAT proteins are misfolded and become retained within hepatocytes rather than being efficiently secreted into the circulation.

This intracellular accumulation causes progressive hepatocellular injury.

13. Clinical Liver Manifestations

Severe AAT deficiency can cause neonatal hepatitis, chronic hepatitis, fibrosis, cirrhosis, and an increased risk of hepatocellular carcinoma.

Thus, the disorder simultaneously produces low circulating AAT—predisposing to lung destruction—and abnormal AAT accumulation in the liver—predisposing to hepatic damage.

Diagnosis

Diagnosis involves measurement of the serum α1-antitrypsin concentration, often followed by phenotyping or SERPINA1 genotyping when deficiency is suspected.

Testing should be considered particularly in patients with emphysema at a young age, basilar-predominant emphysema, unexplained airflow obstruction, unexplained liver disease, or a family history of AAT deficiency.

Management

The most important intervention is complete avoidance of cigarette smoking, including avoiding significant occupational exposure to respiratory irritants.

Treatment of associated COPD includes appropriate inhaled therapies, vaccination, pulmonary rehabilitation, and management of exacerbations.

Selected patients with severe deficiency and established emphysema may be considered for intravenous AAT augmentation therapy, depending on clinical criteria and local availability.

Advanced pulmonary disease may eventually require lung transplantation, while severe liver disease may require liver transplantation.

Key Clinical Pattern

Think of α1-antitrypsin deficiency in a relatively young patient with early-onset emphysema, particularly when CT shows lower-lobe predominant panacinar emphysema.

The key mechanism is failure to inhibit neutrophil elastase → destruction of alveolar walls → emphysema.

Remember the genotype pattern: MM = normal, MZ = mild reduction, SZ = intermediate deficiency, ZZ = severe deficiency.

Also remember the important contrast: lung disease results from too little circulating AAT, whereas liver disease results from accumulation of abnormal AAT within hepatocytes.

Medicine – Pneumonia

Pneumonia is an acute infection of the lung parenchyma involving the alveoli and surrounding tissues. Infection produces inflammation and accumulation of inflammatory exudate within the alveoli, leading to consolidation and impaired gas exchange. Pneumonia may be classified according to where it was acquired, the causative organism, or the patient’s immune status.

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1. Clinical Features

The classic presentation is an acute cough, which may be productive of purulent sputum. However, sputum production is not universal, particularly with viral or so-called atypical infections.

Patients commonly develop fever, breathlessness, malaise, and tachypnoea. Older adults and immunocompromised patients may have less typical presentations, including confusion or functional deterioration without prominent fever.

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Haemoptysis

Haemoptysis may occur because inflammation damages the respiratory mucosa and small pulmonary vessels.

Blood may appear as streaking within sputum, although significant haemoptysis should prompt consideration of complications or alternative diagnoses such as pulmonary embolism, tuberculosis, or malignancy.

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Chest Pain

Chest discomfort may be a nonspecific dull ache or sharp pleuritic chest pain.

Pleuritic pain is caused by inflammation extending to the pleural surface and typically becomes worse during deep inspiration or coughing.

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Sepsis

Severe pneumonia can produce sepsis, with systemic manifestations such as hypotension, altered mental status, tachycardia, tachypnoea, and organ dysfunction.

Sepsis associated with pneumonia requires urgent assessment and treatment.

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Community-Acquired Pneumonia

2. Definition

Community-acquired pneumonia (CAP) refers to pneumonia acquired outside a hospital or similar healthcare environment.

The exact frequency of individual organisms varies considerably with age, geography, vaccination, comorbidities, season, and diagnostic methods, so older fixed percentages should not be regarded as universally applicable.

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3. Streptococcus pneumoniae

Streptococcus pneumoniae (pneumococcus) remains a major bacterial cause of community-acquired pneumonia.

Classically, pneumococcal pneumonia produces acute fever, productive cough, pleuritic chest pain, and lobar consolidation.

Although older texts quote S. pneumoniae as causing 60–75% of CAP, contemporary studies generally find a lower and highly variable proportion.

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Atypical Pneumonias

The traditional term “atypical pneumonia” describes pneumonia caused by organisms such as Mycoplasma pneumoniae, Legionella species, Chlamydia pneumoniae, and Chlamydia psittaci.

These organisms may produce prominent systemic features and relatively little sputum production, although the clinical distinction between typical and atypical pneumonia is not always reliable.

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4. Mycoplasma pneumoniae

Mycoplasma pneumoniae commonly causes respiratory infection in children and younger adults, particularly in households, schools, universities, and other close-contact environments.

It may occur in cyclical epidemics every few years.

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Clinical Pattern of Mycoplasma

The illness may begin with a relatively long prodrome, including headache, malaise, low-grade fever, sore throat, and a persistent dry cough.

Respiratory symptoms can subsequently progress to pneumonia.

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Cold Agglutinins

Mycoplasma pneumoniae infection can stimulate production of cold agglutinins, usually IgM antibodies that react with red blood cells at lower temperatures.

In some patients this can produce haemolytic anaemia, although cold agglutinins are neither sufficiently sensitive nor specific to serve as the main diagnostic test for Mycoplasma infection.

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5. Legionella Pneumonia

Legionella pneumophila causes Legionnaires’ disease, an important cause of potentially severe community-acquired pneumonia.

The organism proliferates in water systems and infection occurs through inhalation of contaminated aerosols rather than usual person-to-person respiratory transmission.

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Environmental Sources

Potential sources include showers, cooling towers, complex plumbing systems, hot-water systems, and other aerosol-producing water sources.

The older association with “air-conditioning” is more accurately understood as an association with contaminated water-containing cooling systems, rather than ordinary air-conditioning units themselves.

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Risk Factors

Legionella infection is more likely to become severe in older adults, smokers, people with chronic lung disease, and immunocompromised patients.

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Extrapulmonary Features

Legionella may produce prominent systemic manifestations in addition to pneumonia.

Patients can develop gastrointestinal symptoms, confusion, headache, neurological abnormalities, and abnormal liver function tests. Jaundice may occasionally occur but is not a defining feature.

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Laboratory Findings

Important laboratory clues include hyponatraemia, sometimes associated with inappropriate antidiuretic hormone activity, and abnormal liver enzymes.

The total white cell count is variable, and lymphopenia may occur.

These findings can support suspicion of Legionella but are not sufficiently specific to establish the diagnosis.

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6. Chlamydial Pneumonia

Chlamydia pneumoniae can cause respiratory infections ranging from mild upper respiratory disease to pneumonia.

Chlamydia psittaci causes psittacosis, which is particularly associated with exposure to infected birds such as parrots, pigeons, and poultry.

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7. Haemophilus influenzae

Haemophilus influenzae is another cause of community-acquired pneumonia.

It is particularly important in patients with chronic respiratory disease, including COPD and bronchiectasis.

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8. Moraxella catarrhalis

Moraxella catarrhalis can cause lower respiratory tract infection and pneumonia, particularly in older adults and patients with chronic lung disease such as COPD.

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9. Viral Pneumonia

Respiratory viruses are important causes of pneumonia and may also predispose to secondary bacterial infection.

Important viruses include influenza, respiratory syncytial virus (RSV), parainfluenza viruses, SARS-CoV-2, and varicella-zoster virus in appropriate clinical circumstances.

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Staphylococcal Pneumonia

10. Staphylococcus aureus

Staphylococcus aureus can cause severe pneumonia and is particularly important following influenza infection.

Damage to the respiratory epithelium caused by influenza facilitates secondary bacterial invasion, which can result in rapidly progressive pneumonia.

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Intravenous Drug Use

People who inject drugs are at increased risk of S. aureus bacteraemia and right-sided infective endocarditis.

Septic emboli from right-sided endocarditis can travel to the lungs and produce multiple peripheral pulmonary infections, nodules, or abscesses.

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Complications

Staphylococcal pneumonia can produce extensive tissue destruction and is associated with lung abscess formation, cavitation, parapneumonic effusion, and empyema.

MRSA should be considered when appropriate epidemiological or healthcare-associated risk factors are present.

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Assessing Severity

11. CURB-65 Score

A commonly used severity assessment for community-acquired pneumonia is the CURB-65 score.

One point is assigned for each of the following:

C – Confusion

U – Urea >7 mmol/L

R – Respiratory rate ≥30/min

B – Blood pressure: systolic <90 mmHg or diastolic ≤60 mmHg

65 – Age ≥65 years

The score ranges from 0 to 5.

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Interpreting CURB-65

In general, 0–1 suggests lower mortality risk, while a score of 2 indicates increased risk and usually warrants consideration of hospital-based assessment or treatment.

A score of 3 or more indicates severe pneumonia and a substantially increased risk of mortality, requiring urgent hospital management and consideration of higher-level care depending on the overall clinical picture.

The score supports rather than replaces clinical judgement.

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Hospital-Acquired Pneumonia

12. Definition

Hospital-acquired pneumonia (HAP) generally refers to pneumonia developing 48 hours or more after hospital admission that was not already incubating when the patient entered hospital.

The spectrum of causative organisms differs from CAP because hospitalised patients may become colonised with more resistant bacteria.

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13. Causative Organisms

Important organisms include Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA) in patients with appropriate risk factors.

Gram-negative organisms are also particularly important and include Klebsiella species, Escherichia coli, Enterobacterales, and Pseudomonas aeruginosa.

The likely pathogen depends strongly on the hospital environment, previous antibiotic exposure, duration of hospitalisation, local resistance patterns, and whether mechanical ventilation is present.

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Anaerobic Infection

Anaerobic bacteria are particularly relevant when there is significant aspiration, especially in patients with impaired consciousness, swallowing dysfunction, or poor dentition.

They are therefore not necessarily routine causes of every case of hospital-acquired pneumonia.

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Pneumocystis Pneumonia

14. Pneumocystis jirovecii

The organism historically called Pneumocystis carinii in humans is now called Pneumocystis jirovecii.

The disease continues to be abbreviated PCP, meaning Pneumocystis pneumonia.

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15. Risk Factors for PCP

PCP occurs predominantly in patients with impaired cell-mediated immunity.

It is classically associated with advanced HIV infection, particularly when the CD4 count is below approximately 200 cells/µL, but it can also occur with transplantation, malignancy, prolonged corticosteroid therapy, and other immunosuppressive treatments.

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16. Clinical Features of PCP

The characteristic presentation consists of progressive breathlessness, fever, and a dry or minimally productive cough.

Symptoms often develop gradually over days to weeks, particularly in patients with HIV.

Hypoxaemia can become severe and may be disproportionately marked compared with the initial chest examination.

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17. Imaging in PCP

A chest radiograph may initially be normal, particularly early in the disease.

The classic abnormality is bilateral diffuse or perihilar interstitial/ground-glass opacity.

High-resolution CT is more sensitive and commonly demonstrates widespread ground-glass opacities.

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18. Diagnosis of PCP

Because P. jirovecii cannot be diagnosed by routine bacterial culture, respiratory material is examined using specific methods.

Samples may be obtained from induced sputum or bronchoalveolar lavage, with the organism demonstrated by staining, immunofluorescence, or PCR.

PCR is highly sensitive but must be interpreted in the clinical context because detection does not always prove active disease.

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Treatment of Pneumonia

19. Community-Acquired Pneumonia

Amoxicillin remains a common first-line antibiotic for uncomplicated, lower-severity community-acquired bacterial pneumonia when pneumococcal infection is likely.

A macrolide, such as clarithromycin, may be used when atypical infection is suspected or as part of broader treatment for more severe disease.

The exact antibiotic regimen should follow local antimicrobial guidelines, disease severity, allergies, comorbidities, and local resistance patterns.

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20. Staphylococcal Pneumonia

When methicillin-sensitive S. aureus is established or strongly suspected, an appropriate antistaphylococcal beta-lactam such as flucloxacillin may be used.

Suspected or confirmed MRSA requires appropriate MRSA-active treatment, such as vancomycin or another agent selected according to local guidelines and susceptibility results.

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21. Hospital-Acquired Pneumonia

Treatment of hospital-acquired pneumonia requires broader consideration of Gram-negative organisms, Pseudomonas, resistant Enterobacterales, and MRSA.

The older universal recommendation of a third-generation cephalosporin plus metronidazole is no longer an appropriate standard regimen for all HAP.

Empirical therapy should instead be determined by local hospital antimicrobial guidelines, previous microbiology, recent antibiotic exposure, illness severity, and individual resistance risk, followed by narrowing of treatment when culture results become available.

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22. Treatment of PCP

The first-line treatment for Pneumocystis jirovecii pneumonia is generally co-trimoxazole (trimethoprim-sulfamethoxazole).

Patients with moderate-to-severe PCP and significant hypoxaemia may additionally require adjunctive corticosteroids, particularly in HIV-associated disease.

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Key Clinical Pattern

Think of pneumonia in a patient with an acute illness characterised by cough, fever, breathlessness, purulent sputum and pleuritic chest pain, with pulmonary infiltrates or consolidation supporting the diagnosis.

For CAP, S. pneumoniae remains a major bacterial pathogen. Remember the characteristic associations: Mycoplasma → younger patients and cold agglutinins; Legionella → water aerosols, hyponatraemia, abnormal LFTs and neurological/GI features; S. aureus → post-influenza pneumonia, cavitation, abscess and empyema.

For severity assessment, remember CURB-65: Confusion, Urea >7, Respiratory rate ≥30, low Blood pressure, and age ≥65. For immunocompromised patients with dry cough + fever + progressive dyspnoea + bilateral ground-glass changes, consider Pneumocystis jirovecii pneumonia.

Medicine – Tuberculosis

Tuberculosis (TB) is a chronic infectious disease caused predominantly by Mycobacterium tuberculosis. It is transmitted mainly through inhalation of airborne particles from a person with infectious pulmonary or laryngeal TB. Although the lungs are the most commonly affected organs, TB can disseminate and involve almost any part of the body.

1. Groups at Increased Risk

The risk of TB is determined by both the likelihood of exposure to M. tuberculosis and the likelihood that latent infection will progress to active disease.

People who have migrated from countries where TB is highly prevalent have an increased risk, particularly during the first several years after migration.

HIV Infection and Immunosuppression

HIV infection is an especially important risk factor because impaired cell-mediated immunity greatly increases the probability that latent TB will reactivate and that newly acquired infection will progress rapidly.

Other forms of immunosuppression, including corticosteroids, transplantation, chemotherapy, and anti-TNF therapy, also increase the risk of active and disseminated TB.

Social Risk Factors

People experiencing homelessness, overcrowded living conditions, poverty, incarceration, or poor access to healthcare may have increased exposure and delayed diagnosis.

Alcohol dependence and substance-use disorders can also increase risk through associated socioeconomic factors, malnutrition, impaired immunity, and difficulty completing treatment.

Primary Tuberculosis

2. Initial Infection

Primary TB refers to infection occurring in an individual who has not previously developed specific immunity to M. tuberculosis.

Inhaled organisms reach the distal airways and alveoli, where they are taken up by macrophages. The infection may initially produce few or no symptoms.

3. Ghon Focus

The initial pulmonary lesion is traditionally called the Ghon focus.

It is usually a small area of granulomatous inflammation located in the peripheral lung, often in the lower part of an upper lobe or upper part of a lower lobe.

4. Lymphatic Spread

Mycobacteria can travel from the initial pulmonary focus through the lymphatic vessels to the regional hilar lymph nodes.

The combination of the pulmonary Ghon focus and involved regional lymph nodes is known as the Ghon complex.

5. Arrest of Primary Infection

In most immunocompetent individuals, an effective cell-mediated immune response develops and controls the infection.

The organisms may be contained within granulomas rather than completely eliminated. Viable bacilli can therefore remain dormant for many years, producing latent TB infection.

6. Development of an Immune Response

After infection, immune sensitisation to M. tuberculosis develops.

A tuberculin skin test (Mantoux test) may therefore become positive several weeks after infection. Interferon-gamma release assays (IGRAs) can also demonstrate immunological sensitisation to TB.

Importantly, these tests indicate TB infection or immune sensitisation but cannot by themselves distinguish latent infection from active TB disease.

7. Clinical Features of Primary TB

Primary infection is frequently asymptomatic.

When symptoms occur, they may include mild fever, cough, fatigue, and occasionally wheezing when enlarged hilar lymph nodes compress an airway.

Erythema nodosum can occur as an immunological reaction to primary TB, although it has many other possible causes.

Post-Primary Tuberculosis

8. Reactivation Disease

Post-primary, or secondary, TB commonly results from reactivation of previously dormant organisms, although reinfection can also occur.

Reactivation is particularly likely when cell-mediated immunity becomes impaired because of ageing, malnutrition, HIV infection, immunosuppressive therapy, or other illnesses.

9. Upper-Lobe Predominance

Post-primary pulmonary TB classically affects the apical and posterior regions of the upper lobes.

These regions have relatively high oxygen tension, which favours growth of M. tuberculosis, an obligate aerobe.

Tissue destruction can lead to caseation and cavitation, allowing large numbers of bacilli to enter the airways and increasing infectiousness.

Miliary Tuberculosis

10. Haematogenous Dissemination

Miliary TB occurs when M. tuberculosis spreads widely through the bloodstream.

This produces numerous tiny granulomatous lesions in multiple organs. The term miliary describes the characteristic appearance of innumerable small lesions resembling millet seeds.

11. Organ Involvement

Miliary TB may involve the lungs, liver, spleen, bone marrow, kidneys, meninges, and other organs.

It is particularly important in young children and immunocompromised individuals but can occur at any age.

Clinical Features

12. Constitutional Symptoms

Active TB commonly produces constitutional symptoms including fever, drenching night sweats, loss of appetite, fatigue, and unintentional weight loss.

The onset may be gradual, with symptoms developing over weeks or months.

13. Cough

Persistent cough is a common manifestation of pulmonary TB.

It may initially be dry but can become productive as pulmonary disease progresses.

14. Haemoptysis

Haemoptysis can occur when cavitating disease or chronic inflammation damages pulmonary or bronchial blood vessels.

Bleeding ranges from minor blood-streaking to potentially life-threatening haemoptysis.

15. Pleural Effusion

TB can involve the pleura and produce a tuberculous pleural effusion.

The fluid is usually an exudate with lymphocyte predominance. Pleural fluid glucose may be reduced, particularly in more intense or chronic disease.

16. Tuberculous Meningitis

Dissemination to the central nervous system can produce tuberculous meningitis, a severe form of extrapulmonary TB.

Patients may develop persistent headache, fever, vomiting, altered consciousness, cranial nerve abnormalities, and neurological deficits.

Early recognition and treatment are essential because neurological complications can be permanent.

Diagnosis

17. Chest Radiograph

In post-primary pulmonary TB, the chest radiograph may demonstrate upper-zone or apical opacification, volume loss, fibrosis, and cavitation.

Primary TB may instead show hilar lymphadenopathy, consolidation, or pleural effusion.

Miliary TB classically produces innumerable tiny bilateral pulmonary nodules.

18. Sputum Examination

Patients suspected of having pulmonary TB should have respiratory samples examined for acid-fast bacilli (AFB).

Traditionally this involved sputum smear microscopy followed by mycobacterial culture.

Modern diagnosis increasingly incorporates rapid molecular tests, which can detect M. tuberculosis DNA and, depending on the assay, identify important drug-resistance markers much faster than conventional culture.

19. Mycobacterial Culture

Mycobacterial culture remains important because it confirms viable organisms and allows detailed drug-susceptibility testing.

Traditional solid cultures may require several weeks, explaining the older teaching that cultures take at least six weeks. Modern liquid culture systems frequently produce results considerably sooner, although final negative cultures may still require prolonged incubation.

20. Urine Examination

Early-morning urine samples can be examined for mycobacteria when genitourinary TB is suspected.

Multiple specimens may be required because organisms are not continuously shed into the urine.

21. Tissue Biopsy

When extrapulmonary TB is suspected, tissue may be obtained from sites such as an enlarged lymph node, pleura, or other affected organ.

Histology may demonstrate caseating granulomatous inflammation, while the tissue can also undergo molecular testing and mycobacterial culture.

22. Bone Marrow Examination

Bone marrow aspiration or biopsy may occasionally be useful in suspected disseminated or miliary TB, particularly when patients have unexplained cytopenias or systemic illness.

It is not a routine investigation for uncomplicated pulmonary TB.

23. Bronchoscopy

Bronchoscopy with bronchial washing or bronchoalveolar lavage can provide diagnostic material when sputum cannot be obtained or remains negative despite strong suspicion of pulmonary TB.

Treatment

24. Standard Initial Therapy

For drug-susceptible active TB, standard treatment generally begins with four drugs, not three:

Rifampicin + isoniazid + pyrazinamide + ethambutol.

These are commonly abbreviated RIPE therapy.

25. Duration of Treatment

For uncomplicated drug-susceptible pulmonary TB, the traditional standard regimen consists of:

2 months: rifampicin + isoniazid + pyrazinamide + ethambutol.

Followed by 4 months: rifampicin + isoniazid.

This gives a total treatment duration of approximately 6 months, although treatment varies according to drug susceptibility, site of disease, response, comorbidities, and national guidelines.

TB meningitis and some other forms of extrapulmonary disease generally require modified and/or longer treatment.

26. Drug Resistance

The older approach of reserving ethambutol only for patients with HIV or people from areas with high resistance is no longer standard.

Four-drug initial therapy is generally used while drug susceptibility is being established, because isoniazid resistance may be present even without obvious risk factors.

Drug-resistant TB requires specialist treatment using regimens determined by molecular and culture-based susceptibility testing.

27. Importance of Adherence

Adherence to the complete treatment regimen is essential.

Poor adherence can result in treatment failure, relapse, continued transmission, and selection of drug-resistant M. tuberculosis.

Adverse Effects of Antituberculous Drugs

28. Rifampicin

Rifampicin can cause hepatotoxicity, gastrointestinal disturbance, rash, and orange-red discoloration of urine, sweat, saliva, and tears.

The discoloration of body fluids is harmless but patients should be warned about it.

Rifampicin is also a powerful hepatic enzyme inducer, producing clinically important interactions with numerous medications, including some anticoagulants, anticonvulsants, hormonal contraceptives, and antiretroviral drugs.

29. Isoniazid

Isoniazid can cause hepatotoxicity and peripheral neuropathy.

Neuropathy results partly from interference with vitamin B6 metabolism and can be prevented or reduced by giving pyridoxine (vitamin B6), particularly in patients at increased risk.

30. Pyrazinamide

Pyrazinamide can cause hepatotoxicity, gastrointestinal symptoms, rash, arthralgia, and hyperuricaemia.

The rise in uric acid may occasionally precipitate acute gout.

31. Ethambutol

The most important adverse effect of ethambutol is optic neuropathy, which can cause reduced visual acuity and impaired colour vision, classically affecting red-green discrimination.

Patients should have appropriate assessment of vision and be advised to report visual changes promptly.

Because ethambutol is largely eliminated through the kidneys, dose adjustment may be necessary in significant renal impairment. Renal dysfunction itself is not the classic toxicity of ethambutol.

Key Clinical Pattern

Think of pulmonary TB in a patient with persistent cough, weight loss, fever, night sweats and haemoptysis, particularly when imaging demonstrates upper-lobe disease with cavitation.

Remember the progression:

Primary infection → Ghon focus and regional lymph nodes → immune containment/latent TB → possible later reactivation as post-primary TB.

Miliary TB results from widespread haematogenous dissemination and can involve multiple organs.

For uncomplicated drug-susceptible pulmonary TB, remember RIPE for the initial 2 months, followed traditionally by rifampicin + isoniazid for another 4 months, with treatment adjusted according to susceptibility results and the clinical form of disease.

Medicine – Pleural Effusion

A pleural effusion is an abnormal accumulation of fluid within the pleural space. The key initial step is to determine whether the fluid is a transudate or an exudate, because this greatly narrows the differential diagnosis.

1. Classification of Pleural Fluid

The standard approach is to use Light’s criteria.

A pleural effusion is classified as an exudate if any one of the following is present:

• Pleural fluid protein : serum protein ratio > 0.5
• Pleural fluid LDH : serum LDH ratio > 0.6
• Pleural fluid LDH > two-thirds of the upper limit of normal serum LDH

If none of these criteria is met, the effusion is usually considered a transudate.

2. Transudative Pleural Effusion

A transudate is generally caused by a systemic disturbance in hydrostatic or oncotic pressure, rather than local pleural inflammation.

Cardiac Failure

Congestive cardiac failure is one of the commonest causes of transudative pleural effusion.

Raised pulmonary venous pressure increases hydrostatic pressure and drives fluid into the pleural space. Effusions are often bilateral, although one side may predominate.

Cirrhosis

Cirrhosis can cause pleural effusion, often through movement of ascitic fluid across small diaphragmatic defects.

This is sometimes referred to as hepatic hydrothorax and is commonly right-sided.

Hypoalbuminaemia

Marked hypoalbuminaemia reduces plasma oncotic pressure, favouring movement of fluid from the vascular compartment into tissues and body cavities, including the pleural space.

Nephrotic Syndrome

In nephrotic syndrome, heavy urinary protein loss causes hypoalbuminaemia and reduced oncotic pressure.

This can result in peripheral oedema, ascites, and pleural effusions.

Hypothyroidism

Hypothyroidism can occasionally cause pleural effusions.

These may be transudative or sometimes borderline/exudative depending on the mechanism, so it is not as classically transudative as heart failure or cirrhosis.

3. Exudative Pleural Effusion

An exudate results from local pleural disease, usually because of increased vascular permeability, inflammation, impaired lymphatic drainage, or direct pleural involvement.

Malignancy

Malignant pleural effusion is a common cause of an exudate.

It may occur with lung cancer, breast cancer, lymphoma, mesothelioma, and other metastatic malignancies. The fluid is often recurrent and may be haemorrhagic.

Parapneumonic Effusion

A parapneumonic effusion develops in association with bacterial pneumonia.

It may be uncomplicated or progress to a complicated parapneumonic effusion or empyema, especially when pleural fluid becomes infected.

Tuberculosis

Tuberculous pleuritis typically causes an exudative effusion.

The fluid is usually lymphocyte-predominant and may have a low glucose concentration.

Subphrenic Abscess

A subphrenic abscess can irritate the adjacent diaphragm and pleura, causing a reactive exudative pleural effusion.

Pulmonary Embolism

Pulmonary embolism can cause a small exudative effusion, especially when pulmonary infarction occurs.

The fluid may be blood-stained.

Pancreatitis

Pancreatitis can cause an exudative pleural effusion, usually through inflammatory spread or a pancreaticopleural fistula.

A clue is a markedly elevated pleural fluid amylase.

Rheumatoid Arthritis

Rheumatoid pleuritis can produce an exudative effusion, often with very low pleural fluid glucose.

The pleural fluid may also have a low pH and high LDH.

Systemic Lupus Erythematosus

SLE can cause pleuritis with an exudative pleural effusion.

This is often associated with other manifestations of active systemic lupus.

4. Low Pleural Fluid Glucose

A reduced pleural fluid glucose concentration suggests that glucose is being consumed by inflammatory cells, bacteria, or metabolically active tissue, or that transport across the pleura is impaired.

Important causes include rheumatoid pleuritis, tuberculosis, malignancy, and empyema.

Rheumatoid Arthritis

Rheumatoid effusions can produce very low glucose levels, sometimes approaching zero.

This is one of the classic laboratory clues to rheumatoid pleuritis.

Tuberculosis

Tuberculous pleural effusions may also have low pleural glucose, particularly in more intense or chronic pleural inflammation.

Malignancy

Malignant effusions can have reduced glucose because of high metabolic activity within the pleural space and impaired glucose transport.

Empyema

In empyema, bacteria and neutrophils consume glucose rapidly, so pleural fluid glucose may become very low.

Empyema is also typically associated with low pH and high LDH.

Key Clinical Pattern

Think of transudates as being caused mainly by systemic pressure or protein problems, especially heart failure, cirrhosis, hypoalbuminaemia, and nephrotic syndrome.

Think of exudates as being caused by local pleural inflammation or infiltration, especially malignancy, pneumonia, TB, pulmonary embolism, pancreatitis, RA, and SLE.

For classification, remember Light’s criteria, and for a particularly low pleural fluid glucose, remember RA, TB, malignancy, and empyema.

Medicine – Bronchiectasis

Bronchiectasis is a chronic respiratory disorder characterised by permanent and abnormal dilatation of the bronchi caused by destruction of the muscular and elastic components of the bronchial walls. Impaired mucus clearance leads to retention of secretions, recurrent infection, and persistent airway inflammation, creating a cycle of further airway damage.

Pulmonary function often demonstrates an obstructive pattern because dilated and damaged airways become narrowed or blocked by retained secretions. However, restrictive or mixed abnormalities can occur when there is extensive associated lung disease.

1. Pathophysiology

Bronchiectasis develops when repeated or severe airway injury damages the bronchial wall and interferes with normal mucociliary clearance.

Secretions accumulate within the affected airways, providing an environment in which bacteria can persist. Recurrent infection causes further inflammation and tissue destruction, resulting in progressively abnormal bronchial dilatation.

This produces a characteristic cycle of:

Impaired mucus clearance → infection → inflammation → bronchial damage → further mucus retention.

Causes of Bronchiectasis

The underlying causes can broadly be divided into congenital or inherited disorders and acquired conditions. In a significant proportion of patients, however, no definite cause is identified.

2. Congenital and Inherited Causes

Selective IgA Deficiency

Selective IgA deficiency can predispose to recurrent respiratory tract infections because IgA plays an important role in protecting mucosal surfaces.

Repeated bacterial infections can eventually damage the bronchial walls and lead to bronchiectasis.

Primary Ciliary Dyskinesia

Primary ciliary dyskinesia is an inherited disorder in which respiratory cilia have abnormal structure or function.

Defective ciliary movement prevents effective removal of mucus and inhaled microorganisms from the respiratory tract. Patients therefore develop recurrent sinus infections, otitis media, chronic productive cough, and bronchiectasis.

Kartagener Syndrome

Kartagener syndrome is a particular phenotype of primary ciliary dyskinesia classically characterised by:

Bronchiectasis + chronic sinusitis + situs inversus.

Situs inversus may include dextrocardia, in which the heart lies predominantly on the right side of the chest.

Male infertility is common because sperm flagella depend on structures similar to respiratory cilia. Female fertility may also be reduced because abnormal ciliary function can interfere with transport through the fallopian tubes.

X-Linked Agammaglobulinaemia

X-linked agammaglobulinaemia, historically called X-linked hypogammaglobulinaemia, causes severe impairment of antibody production.

Affected patients develop recurrent bacterial respiratory infections from childhood. Without adequate treatment, repeated infection can cause permanent airway damage and bronchiectasis.

3. Acquired Causes

Previous Severe Childhood Infection

Severe respiratory infections during childhood can produce permanent bronchial damage.

Classically associated infections include severe bacterial pneumonia, pertussis, and measles, particularly when complicated by significant lower respiratory tract disease.

This form of post-infectious bronchiectasis has become less common in populations with widespread vaccination and improved treatment of childhood infections.

Previous Tuberculosis

Pulmonary tuberculosis can cause substantial destruction and fibrosis of lung tissue.

Following healing, affected areas may develop traction bronchiectasis, particularly in regions of significant pulmonary scarring.

Allergic Bronchopulmonary Aspergillosis

Allergic bronchopulmonary aspergillosis (ABPA) is a hypersensitivity reaction to Aspergillus, occurring mainly in patients with asthma or cystic fibrosis.

Repeated allergic inflammation and mucus plugging can damage the airways and characteristically produce central bronchiectasis.

Bronchial Obstruction

Bronchiectasis may develop distal to an obstructed bronchus because mucus cannot drain normally from the affected segment of lung.

Causes of obstruction include an inhaled foreign body, endobronchial tumour, or other obstructing lesion.

Localised bronchiectasis confined to one particular lobe or segment should therefore raise suspicion of a focal bronchial obstruction.

Pulmonary Fibrosis

Pulmonary fibrosis can distort and pull open the bronchi as the surrounding lung tissue contracts.

This produces traction bronchiectasis, which is commonly seen on high-resolution CT in fibrotic interstitial lung diseases such as idiopathic pulmonary fibrosis and systemic sclerosis-associated ILD.

Cystic Fibrosis

An important additional inherited cause is cystic fibrosis.

Abnormally thick airway secretions impair mucociliary clearance, resulting in recurrent bacterial infection and progressive bronchial destruction. Bronchiectasis is therefore a major pulmonary manifestation of CF.

Idiopathic Bronchiectasis

Despite appropriate investigation, no underlying cause can be identified in some patients.

This is referred to as idiopathic bronchiectasis.

Clinical Features

4. Chronic Productive Cough

The classic symptom is a chronic productive cough, often producing large quantities of mucopurulent or purulent sputum.

Sputum production may increase substantially during infective exacerbations and may be accompanied by fever, worsening cough, and increasing breathlessness.

5. Exertional Breathlessness

Exertional dyspnoea can occur because of airflow obstruction, mucus plugging, recurrent infection, and progressive loss of functioning lung tissue.

Breathlessness tends to become more prominent when disease is extensive or advanced.

6. Haemoptysis

An important additional feature is haemoptysis.

Chronically inflamed airways develop enlarged and fragile bronchial blood vessels that can bleed. Haemoptysis may range from small streaks of blood in the sputum to potentially life-threatening massive bleeding.

7. Cyanosis

Cyanosis is generally a feature of severe or advanced disease and reflects significant impairment of pulmonary gas exchange.

Patients with advanced bronchiectasis may eventually develop chronic respiratory failure.

8. Finger Clubbing

Digital clubbing can occur in bronchiectasis, particularly when the disease is extensive and associated with chronic suppurative infection.

However, clubbing is not present in every patient.

9. Inspiratory Crepitations

Auscultation commonly reveals coarse inspiratory crackles, particularly over the affected areas.

These may be heard during early or mid-inspiration and can sometimes change following coughing as retained airway secretions move.

Wheezing and rhonchi may also occur when significant airflow obstruction is present.

Diagnosis

10. Chest Radiograph

A chest radiograph may demonstrate thickened bronchial walls, parallel linear or “tram-track” shadows, and ring shadows representing dilated bronchi viewed end-on.

However, a normal chest radiograph does not exclude bronchiectasis, particularly when disease is relatively mild.

11. Pulmonary Function Tests

Spirometry commonly demonstrates an obstructive ventilatory defect, with a reduced FEV₁ and FEV₁/FVC ratio.

A restrictive or mixed pattern can occur when there is extensive bronchiectasis or associated pulmonary fibrosis.

12. High-Resolution CT

High-resolution CT (HRCT) of the chest is the key investigation for confirming bronchiectasis.

Characteristic findings include bronchial dilatation, failure of the bronchi to taper normally, and visible airways close to the pleural surface.

A classic CT sign is the “signet-ring sign,” in which a dilated bronchus has a larger diameter than its accompanying pulmonary artery.

HRCT can also demonstrate mucus plugging, bronchial wall thickening, and the anatomical distribution of disease, which may provide clues to the underlying cause.

Key Clinical Pattern

Think of bronchiectasis in a patient with chronic productive cough, recurrent chest infections, purulent sputum, haemoptysis, coarse inspiratory crackles, and sometimes finger clubbing.

Important causes include previous severe infection, primary ciliary dyskinesia/Kartagener syndrome, immunodeficiency, cystic fibrosis, ABPA, previous TB, bronchial obstruction, and pulmonary fibrosis.

The investigation of choice for confirming the diagnosis is high-resolution CT, which demonstrates permanently dilated, non-tapering bronchi, often with the characteristic signet-ring appearance.

Medicine – Cystic Fibrosis

Cystic fibrosis (CF) is a chronic, inherited multisystem disorder caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The abnormal CFTR protein disrupts chloride and bicarbonate transport across epithelial surfaces, producing dehydrated, abnormally thick secretions. The respiratory and gastrointestinal systems are particularly affected, although CF can also cause diabetes, infertility, osteoporosis, and other complications.

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1. Autosomal Recessive Inheritance

Cystic fibrosis is inherited as an autosomal recessive disorder. An affected individual therefore inherits a disease-causing CFTR variant from each parent.

People with only one pathogenic variant are generally healthy carriers.

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2. Carrier Frequency

In populations of Northern European ancestry, approximately 1 in 25 people has traditionally been quoted as carrying a CFTR disease-causing variant.

Carrier frequency varies substantially between different ethnic and geographic populations.

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3. Incidence

Older teaching commonly gives an incidence of approximately 1 in 2,000–2,500 live births in White populations.

The incidence varies by population and has also changed with widespread carrier screening, prenatal testing, and demographic changes.

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4. CFTR Gene

The CFTR gene is located on the long arm of chromosome 7 and encodes the cystic fibrosis transmembrane conductance regulator protein.

CFTR functions primarily as an epithelial chloride and bicarbonate ion channel and also influences the activity of other ion channels.

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5. CFTR Mutations

More than 2,000 CFTR variants have now been identified, although not all cause cystic fibrosis.

The most common disease-causing variant is F508del (ΔF508), which results from deletion of three DNA bases and consequently loss of a phenylalanine residue at position 508 of the CFTR protein.

F508del causes abnormal protein folding and processing, so relatively little functional CFTR reaches the epithelial cell surface.

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6. Abnormal Chloride and Water Transport

Defective CFTR function disrupts the movement of chloride, bicarbonate, sodium, and water across epithelial surfaces.

In the respiratory tract, abnormal ion transport causes dehydration of airway secretions. The resulting mucus becomes thick and difficult to clear, impairing normal mucociliary clearance.

This promotes mucus plugging, chronic bacterial infection, inflammation, and progressive structural damage to the airways.

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Diagnosis

7. Sweat Chloride Test

The sweat chloride test remains an important diagnostic investigation because CFTR dysfunction causes abnormally high concentrations of chloride in sweat.

A sweat chloride concentration of ≥60 mmol/L is consistent with cystic fibrosis in an appropriate clinical setting, usually requiring confirmation according to diagnostic protocols.

Values below this threshold require interpretation according to age, symptoms, newborn screening results, and CFTR genetic testing.

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Why Is Sweat Salty?

In normal sweat ducts, CFTR helps reabsorb chloride, with sodium following.

In cystic fibrosis, defective CFTR reduces chloride reabsorption, leaving increased amounts of chloride and sodium in sweat. This explains the characteristically salty sweat of affected patients.

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8. Life Expectancy

The prognosis of cystic fibrosis has improved dramatically.

Older sources described life expectancy as just over 40 years, but this is now outdated in many countries. Improvements in multidisciplinary care, nutritional support, antimicrobial treatment, and particularly CFTR modulator therapy have substantially increased expected survival.

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Respiratory Manifestations

9. Small-Airway Obstruction and Bronchiectasis

Abnormally thick mucus obstructs the small airways and interferes with mucociliary clearance.

Persistent mucus retention promotes recurrent infection and chronic neutrophilic inflammation. Repeated cycles of obstruction → infection → inflammation → airway damage eventually produce bronchiectasis.

Patients commonly develop chronic cough, sputum production, recurrent respiratory infections, breathlessness, and progressive deterioration in pulmonary function.

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10. Respiratory Infection and Colonisation

Patients with CF are susceptible to chronic and recurrent infection with characteristic respiratory organisms.

Important organisms include Staphylococcus aureus, Haemophilus influenzae, Pseudomonas aeruginosa, and Burkholderia cepacia complex.

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Pseudomonas aeruginosa

Pseudomonas aeruginosa becomes particularly important as patients grow older.

Chronic colonisation can produce progressive airway inflammation and declining lung function. The organism may develop a mucoid phenotype, allowing it to persist within the abnormal airway environment and making eradication increasingly difficult.

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Burkholderia cepacia Complex

Burkholderia cepacia complex is especially important because some strains can cause severe respiratory deterioration and are difficult to treat because of antimicrobial resistance.

Cross-infection between patients with CF is also an important infection-control concern.

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11. Treatment of Respiratory Disease

Pulmonary exacerbations are treated with appropriate antibiotics, guided where possible by respiratory cultures and previous microbiological results.

Some patients receive long-term or inhaled antimicrobial therapy to suppress chronic infection.

Management also includes airway-clearance physiotherapy, exercise, mucolytic therapies, and other treatments designed to improve mucus clearance.

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CFTR Modulator Therapy

A major development in modern treatment is the use of CFTR modulators, which target the underlying abnormal CFTR protein rather than simply treating its consequences.

Different combinations are used according to the patient’s specific CFTR genotype, and highly effective modulator therapy has substantially improved lung function and other outcomes in many eligible patients.

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Gastrointestinal Manifestations

12. Pancreatic Insufficiency

Exocrine pancreatic insufficiency occurs in the majority of patients with classic CF.

Thick secretions obstruct the pancreatic ducts, resulting in progressive pancreatic damage and inadequate delivery of digestive enzymes into the intestine.

This causes fat and protein malabsorption, steatorrhoea, poor weight gain, and deficiencies of fat-soluble vitamins A, D, E, and K.

Treatment includes pancreatic enzyme replacement therapy and nutritional supplementation.

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13. Meconium Ileus

Meconium ileus is an important neonatal presentation of cystic fibrosis.

Abnormally thick intestinal contents obstruct the terminal ileum, producing abdominal distension, failure to pass meconium, and intestinal obstruction shortly after birth.

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Distal Intestinal Obstruction Syndrome

Older children and adults with CF can develop distal intestinal obstruction syndrome (DIOS).

Thick intestinal material accumulates, particularly around the terminal ileum and caecum, producing abdominal pain, distension, and partial or complete intestinal obstruction.

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14. Liver Disease

Abnormal CFTR function can produce thickened bile and obstruction of small intrahepatic bile ducts.

Some patients consequently develop CF-associated hepatobiliary disease, which can include focal biliary fibrosis, multilobular cirrhosis, and portal hypertension.

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15. Gallstones

Gallstones occur more frequently in people with CF.

Altered bile composition and gallbladder dysfunction contribute to their development.

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16. Pancreatitis

Recurrent acute or chronic pancreatitis can occur in some individuals with CF, particularly those who retain a degree of pancreatic exocrine function.

Interestingly, patients with severe pancreatic insufficiency may be less likely to develop pancreatitis because extensive pancreatic destruction has already occurred.

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Other Manifestations

17. Cystic Fibrosis-Related Diabetes

Cystic fibrosis-related diabetes (CFRD) becomes increasingly common with age.

Progressive pancreatic damage reduces insulin secretion, while illness-related insulin resistance may contribute. CFRD has features of both type 1 and type 2 diabetes but represents a distinct form of diabetes associated with CF.

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18. Pneumothorax

Advanced bronchiectasis and structural lung disease can predispose patients to spontaneous pneumothorax.

This may present with sudden worsening of breathlessness and pleuritic chest pain and can be particularly serious in patients who already have significantly reduced pulmonary reserve.

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19. Male Infertility

Almost all men with classic cystic fibrosis are infertile, usually because of congenital bilateral absence or severe abnormality of the vas deferens.

Importantly, spermatogenesis may remain intact, so biological fatherhood may sometimes be possible using assisted reproductive techniques.

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20. Female Reproductive Effects

Women with CF are generally capable of becoming pregnant, although fertility may be reduced.

Abnormally thick cervical mucus, nutritional status, and severity of chronic illness can contribute to reduced fertility.

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21. Osteoporosis

Patients with CF have an increased risk of reduced bone mineral density and osteoporosis.

Contributing factors include chronic inflammation, malabsorption of vitamin D, poor nutritional status, reduced physical activity, delayed puberty, and exposure to systemic corticosteroids in some patients.

This increases the risk of vertebral and other fractures.

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Key Clinical Pattern

Think of cystic fibrosis as an autosomal recessive CFTR disorder causing abnormal epithelial ion and water transport and therefore thick, dehydrated secretions.

The classic pattern is chronic/recurrent respiratory infection + bronchiectasis + pancreatic insufficiency and malabsorption + high sweat chloride.

Important organisms include S. aureus, H. influenzae, P. aeruginosa, and B. cepacia complex, while important extrapulmonary complications include meconium ileus/DIOS, CF-related diabetes, hepatobiliary disease, male infertility, and osteoporosis.

Modern CFTR modulator therapy has transformed the outlook for many patients, making the older life-expectancy figures in traditional notes increasingly outdated.