COPD, asthma and pulmonary fibrosis
Obstructive and restrictive lung disease: spirometry, COPD, asthma, fibrosis, dust
Obstructive and restrictive lung disease for FCPS Part 1: spirometry, emphysema, bronchitis, asthma, bronchiectasis, fibrosis and pneumoconioses. Each pattern is linked to its mechanism, blood gases and HRCT appearance.
Telling them apart
| Measure | Obstructive | Restrictive (lung) | Restrictive (chest wall, pleura, muscle) |
|---|---|---|---|
| FEV₁ | Low | Low | Low |
| FVC | Normal or low | Low | Low |
| FEV₁/FVC | Below 0.7 | Normal or high | Normal or high |
| TLC | Normal or high | Low | Low |
| RV, FRC and RV/TLC | High (air trapping) | Low | Variable |
| Gas transfer (DLCO) | Low in emphysema, normal in asthma | Low | Normal (KCO often high) |
| Compliance | High in emphysema | Low | Chest wall low |
- The difference that defines them: in obstruction, air cannot get out (ratio falls, RV and FRC rise, so these capacities increase); in restriction, air cannot get in (all volumes fall together, ratio preserved).
- COPD diagnosis: post-bronchodilator FEV₁/FVC below 0.7 in a smoker with symptoms; FEV₁ percentage predicted grades severity. Poor reversibility separates it from asthma.
- Extrapulmonary restriction: fibrothorax after tuberculous empyema or haemothorax (small hemithorax, crowded ribs, thick calcified pleural rind encasing the lung): a restrictive defect with normal KCO, because the lung under the peel is healthy. Also obesity, kyphoscoliosis, neuromuscular weakness (vital capacity falls by over 25% when supine).
Emphysema
- Permanent enlargement of air spaces distal to terminal bronchioles with wall destruction and no obvious fibrosis.
| Type | Cause | Distribution |
|---|---|---|
| Centriacinar | Smoking | Upper lobes |
| Panacinar | α1-antitrypsin deficiency | Lower lobes |
| Paraseptal | Subpleural | Bullae, spontaneous pneumothorax |
- Mechanism: protease–antiprotease imbalance: neutrophil and macrophage elastase outweigh α1-antitrypsin, which smoke oxidises.
- Loss of alveolar walls removes capillary surface (low DLCO) and the radial traction that holds small airways open, so they collapse on expiration: air trapping, pursed-lip breathing (pink puffer).
- Radiology: hyperinflation, low flat diaphragms, narrow heart, low-attenuation areas on CT. ECG shows low-voltage QRS because air insulates the heart.
Chronic bronchitis and its consequences
- Clinical definition: productive cough for at least 3 months in each of 2 consecutive years.
- Pathology: submucosal mucous gland hypertrophy (raised Reid index, above 0.4), goblet cell hyperplasia, squamous metaplasia. In non-smoking village women, indoor biomass smoke is a common cause.
- Pulmonary hypertension in COPD: mainly hypoxic pulmonary vasoconstriction of small arteries, later with vessel remodelling and loss of capillary bed, leading to cor pulmonale (blue bloater).
- Oxygen dissociation: a COPD patient reaching 50% saturation at a PaO₂ of 37 mmHg (normal P50 about 27 mmHg) has a right-shifted curve: chronic hypoxia raises 2,3-DPG, and hypercapnic acidosis adds the Bohr effect, so oxygen unloads more readily in tissues.
Asthma
- Th2-driven type I hypersensitivity: IL-4 (IgE switch), IL-5 (eosinophils, the characteristic cell of atopic asthma), IL-13 (mucus). Mast cells release histamine and leukotrienes in the early phase; eosinophils sustain the late phase.
- Pathology affects medium and small bronchi: smooth muscle hypertrophy, thick basement membrane, mucus plugging. Sputum: Curschmann spirals and Charcot–Leyden crystals.
- During an attack: FEV₁, FVC and peak flow fall; RV, FRC and TLC rise (hyperinflation). Obstruction is reversible (12% and 200 mL improvement in FEV₁).
- Blood gases: an early attack with a respiratory rate of 30/min gives low PaO₂ with low PaCO₂ (respiratory alkalosis) from hyperventilation. A normal or rising PaCO₂ means the patient is tiring: life-threatening.
- Triggers such as cold air and weather change stimulate irritant (rapidly adapting) receptors in the airway epithelium; vagal reflexes cause bronchoconstriction and cough.
- Acute severe asthma: high-flow oxygen and nebulised short-acting beta-2 agonist (salbutamol) first, with ipratropium and systemic steroids.
- Occupational asthma worsens through the working week and settles on holiday: isocyanates, flour.
- ABPA: asthma, very high IgE, eosinophilia, brown mucus plugs, central bronchiectasis.
Bronchiectasis and cystic fibrosis
- Permanent bronchial dilatation from infection plus obstruction or impaired clearance.
- Causes: post-infective (measles, pertussis, TB), cystic fibrosis, primary ciliary dyskinesia (Kartagener: situs inversus, sinusitis, infertility), ABPA, obstructing tumour or foreign body, hypogammaglobulinaemia.
- HRCT: bronchus wider than its accompanying artery (signet ring), lack of tapering, wall thickening.
- Advanced disease is chronically colonised by Pseudomonas aeruginosa (green sputum); ciprofloxacin is the only common oral antibiotic covering it.
- Cystic fibrosis: CFTR chloride channel fails, secretions are dehydrated. Recurrent chest infection, sinusitis, chronic diarrhoea (steatorrhoea) and bronchiectasis in a child: diagnose with the sweat chloride test (above 60 mmol/L). Pancreatic insufficiency causes malabsorption of fat-soluble vitamins; vitamin K deficiency gives a bleeding tendency. Males are infertile (absent vas).
- Traction bronchiectasis in fibrosis: the surrounding scar pulls airways open.
Interstitial lung disease
| Disease | Pathology | HRCT and clues |
|---|---|---|
| Idiopathic pulmonary fibrosis (UIP) | Patchy fibrosis of different ages with fibroblastic foci | Basal, subpleural reticulation, honeycombing, traction bronchiectasis; clubbing, fine crackles |
| NSIP | Uniform fibrosis or inflammation | Ground glass with subpleural sparing; scleroderma |
| Cryptogenic organising pneumonia | Fibroblast plugs in alveoli | Patchy migrating consolidation |
| Hypersensitivity pneumonitis | Poorly formed granulomas (type III and IV) | Upper and mid zones, centrilobular nodules, air trapping; better away from exposure |
| Sarcoidosis | Non-caseating granulomas | Bilateral hilar nodes, perilymphatic nodules; hypercalcaemia |
| Pulmonary alveolar proteinosis | Antibodies block GM-CSF | Crazy paving |
- In fibrosis the lung is stiff (low compliance) and its elastic recoil is high, so airways are held wide open and the FEV₁/FVC ratio can exceed 0.8; thickened membranes lower DLCO and cause exercise desaturation.
Pneumoconioses
| Dust | Lesion | Imaging and consequences |
|---|---|---|
| Silica (stone cutters) | Silicotic nodules; macrophages injured, release fibrogenic cytokines | Upper-zone nodules, eggshell calcification of hilar nodes; TB risk rises |
| Coal | Coal macules; progressive massive fibrosis | Upper-zone conglomerate masses; Caplan syndrome with rheumatoid arthritis |
| Asbestos | Lower-lobe fibrosis; asbestos bodies | Pleural plaques (marker of exposure); mesothelioma; lung carcinoma risk multiplied by smoking |
| Iron (arc welders): siderosis | Iron oxide in macrophages, no fibrosis | Many small dense nodules on X-ray (iron is radio-dense) with normal spirometry and gas transfer; tin and barium behave the same (benign pneumoconioses) |
| Beryllium | Type IV granulomas | Mimics sarcoidosis |
- Anthracosis (carbon in macrophages without fibrosis) is harmless.
Remember Obstruction lowers the FEV₁/FVC ratio and raises RV; restriction lowers TLC with a normal or high ratio.
Exam trap A normal PaCO₂ in a breathless asthmatic is a danger sign, not reassurance.
Exam trap Siderosis looks dramatic on the film but causes no symptoms or functional loss.
How FCPS asks about this
- Capacity that increases in obstructive disease: RV and FRC (TLC normal or high).
- Spirometry in restrictive disease: FEV₁ and FVC both reduced, ratio normal or high.
- Early asthma attack blood gas: low PaO₂, low PaCO₂, respiratory alkalosis.
- Pulmonary hypertension in COPD: hypoxic pulmonary vasoconstriction.
- Bleeding in cystic fibrosis: vitamin K deficiency from fat malabsorption; diagnose with sweat chloride.
- Asymptomatic welder with dense nodules: siderosis.
- Calcified pleural rind after TB empyema: restrictive defect from pleural encasement.
Test yourself on this topic
5 of the 47 questions in our bank on this topic. Choose an answer to see why every option is right or wrong.
A 42-year-old man has slowly worsening breathlessness. Bronchoalveolar lavage returns milky fluid rich in PAS-positive material, and alveoli on biopsy are filled with granular pink material while their walls are normal. What is the underlying cause?
Answer: Antibodies blocking GM-CSF
Autoimmune pulmonary alveolar proteinosis is caused by antibodies against granulocyte-macrophage colony-stimulating factor (GM-CSF). Alveolar macrophages need GM-CSF to mature and break down surfactant, so surfactant lipids and proteins build up in the alveoli. The alveoli fill with PAS-positive material while the interstitium is mostly spared, giving milky lavage fluid. Whole-lung lavage removes the material, and inhaled GM-CSF can help.
Alveolar proteinosis
- Anti-GM-CSF antibodies
- Macrophages cannot clear surfactant
- Alveoli full, walls normal
- Lavage: milky, PAS-positive
Remember Milky PAS-positive lavage = alveolar proteinosis.
Exam trap Secondary alveolar proteinosis occurs with haematological malignancy and heavy dust exposure.
Why the other options are wrong
- Surfactant overproduction by type II cells The problem is clearance by macrophages, not overproduction.
- Left ventricular failure Pulmonary oedema is gravity-dependent with cardiomegaly and does not give milky lavage.
- Atypical pneumonia Infection does not give PAS-positive milky lavage.
- Inhaled silica blocking airways Acute heavy silica exposure is a rare secondary cause, not the usual one.
A 55-year-old woman has 6 weeks of cough, fever and breathlessness despite two courses of antibiotics. Lung biopsy shows plugs of loose fibroblastic tissue filling alveolar ducts and alveoli, with no cause found. What is the diagnosis?
Answer: Cryptogenic organising pneumonia
Cryptogenic organising pneumonia is a pattern of lung injury in which the alveolar exudate organises into intraluminal plugs of granulation tissue (Masson bodies) instead of resolving. It presents as a subacute illness that looks like pneumonia but does not respond to antibiotics. Shadows are typically patchy, peripheral and may migrate. It responds well to glucocorticoids, unlike UIP.
Organising pneumonia
- Intra-alveolar fibroblast plugs (Masson bodies)
- Not helped by antibiotics
- Patchy, migratory shadows
- Responds to steroids
Remember Pneumonia that ignores antibiotics with Masson bodies: organising pneumonia.
Exam trap Organising pneumonia also follows infections, drugs and connective tissue disease; it is cryptogenic only when no cause is found.
Why the other options are wrong
- Usual interstitial pneumonia UIP causes chronic interstitial fibrosis with honeycombing, not intra-alveolar plugs.
- Invasive aspergillosis Shows fungal hyphae invading vessels in neutropenic patients.
- Bronchioloalveolar adenocarcinoma Shows malignant cells lining alveoli.
- Pulmonary infarction Shows necrosis of lung tissue after emboli.
A 56-year-old man has breathlessness that is much worse when he lies flat, so he sleeps sitting up. His heart and lung tissue are normal, and his abdomen moves inwards when he breathes in lying down. Which spirometry finding best supports the likely diagnosis?
Answer: Vital capacity falls over 25% when supine
Bilateral diaphragm weakness, from causes such as motor neurone disease, neuralgic amyotrophy or phrenic nerve injury, gives a restrictive pattern and marked orthopnoea. When the patient lies flat, the abdominal contents push the weak diaphragm up into the chest and the accessory muscles work less well, so vital capacity falls by more than about 25% from the upright value. A normal person loses less than 10%. Paradoxical inward movement of the abdomen on inspiration is a clinical sign.
Diaphragm weakness
- Orthopnoea without heart disease
- High hemidiaphragms
- VC falls over 25% supine
- Paradoxical abdominal movement
Remember Severe orthopnoea with a normal heart: measure supine VC.
Exam trap Bilateral paralysis can be missed on a sniff test because both sides move abnormally together.
Why the other options are wrong
- FEV1/FVC ratio below 0.7 This indicates obstruction.
- Low gas transfer with normal volumes Typical of pulmonary vascular disease.
- Flattened inspiratory flow-volume loop only Suggests variable extrathoracic upper airway obstruction.
- Large rise in FEV1 after salbutamol Suggests asthma.
During surgery for an unrelated problem in a 68-year-old retired shipyard worker, smooth, pearly-white, partly calcified plaques are seen on the parietal pleura over both domes of the diaphragm. The lungs themselves are normal. What do these plaques indicate?
Answer: Past asbestos exposure only
Pleural plaques are discrete areas of hyalinised collagen, often calcified, on the parietal pleura, typically over the diaphragm and the posterolateral chest wall. They appear 20–30 years after asbestos exposure and are markers of that exposure. They are benign, do not turn into mesothelioma and usually cause no symptoms or loss of lung function. Asbestosis is a separate condition: fibrosis of the lung parenchyma, mainly in the lower zones.
Pleural plaques
- Parietal pleura, diaphragm
- Appear 20–30 years after exposure
- Benign, not premalignant
- Marker of asbestos exposure
Remember Calcified diaphragmatic plaques = asbestos was inhaled.
Exam trap Plaques do not become mesothelioma, but they show exposure that raises the risk.
Why the other options are wrong
- Early malignant mesothelioma Mesothelioma causes nodular, encasing pleural thickening, often with effusion.
- Asbestosis of the lung Asbestosis is fibrosis inside the lung, which is normal here.
- Healed tuberculous empyema TB empyema usually leaves unilateral, thick pleural calcification over the lung.
- Rheumatoid pleural disease Rheumatoid disease causes effusions rather than diaphragmatic plaques.
A 38-year-old man from Peshawar had a tuberculous empyema treated with a chest drain 10 years ago. His left chest is flattened and moves poorly, and at thoracotomy a thick, partly calcified pleural peel encases the left lung. What type of lung function defect does he have?
Answer: Restrictive defect from pleural encasement
Fibrothorax is dense fibrosis of the visceral and parietal pleura that follows empyema, haemothorax or tuberculous pleurisy. The thick, often calcified peel encases the lung like a rind and stops it expanding, so the hemithorax shrinks, the ribs crowd together and the mediastinum may shift towards that side. Lung volumes fall with a normal FEV1/FVC ratio, a restrictive pattern. Decortication can restore expansion if the underlying lung is healthy.
Fibrothorax
- After empyema, TB or haemothorax
- Thick, calcified pleural peel
- Small hemithorax, crowded ribs
- Restrictive defect
Remember Old TB empyema with a pleural peel = trapped, restricted lung.
Exam trap KCO is often normal because the lung under the peel is healthy.
Why the other options are wrong
- Obstructive defect from airway narrowing The airways are not narrowed.
- Mixed defect from emphysema No emphysema is described.
- Normal function despite the pleura The thick peel restricts expansion.
- Gas transfer defect with normal volumes Lung volumes are reduced.
Where this sits in the CPSP syllabus
- Diagnostic Radiology, Paper 2: Lungs, heart and vessels, Restrictive and obstructive lung disease
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