11.2 Obstructive, Restrictive & Vascular Lung Disease
Key Takeaways
- Obstruction lowers FEV1/FVC; restriction lowers TLC with a normal or high FEV1/FVC ratio—use volumes, not the ratio alone, to confirm restriction.
- Chronic bronchitis is clinical (productive cough ≥3 months in 2 consecutive years); emphysema is structural airspace enlargement with wall destruction (centriacinar–smoking upper lobe; panacinar–α1-antitrypsin lower lobe).
- Intrinsic restriction (ILD: IPF, sarcoid, HP) vs extrinsic (neuromuscular, obesity, kyphoscoliosis, pleural) differ by DLCO and lung parenchymal involvement.
- Pulmonary hypertension groups separate pre-capillary arterial disease, left-heart passive PH, lung/hypoxia PH, CTEPH, and multifactorial forms—right-heart strain is the shared endpoint.
- ARDS is acute diffuse alveolar damage with noncardiogenic edema (exudate, hyaline membranes) and severe shunt physiology; PE creates dead space and V/Q mismatch, not primary left-heart failure edema.
11.2 Obstructive, Restrictive & Vascular Lung Disease
Quick Answer: Obstruction = ↓FEV1/FVC with flow limitation; restriction = ↓TLC. Split COPD into chronic bronchitis (airway inflammation/mucus) vs emphysema (acinar destruction; centriacinar smoking vs panacinar AAT). Restrictive disease is intrinsic ILD or extrinsic pump/chest-wall failure. Vascular items map PE dead space, PH groups, ARDS DAD/shunt, and sleep apnea intermittent hypoxemia.
Pathology and pathophysiology of lung disease on the CBSE integrate spirometry, histology buzzwords, and hemodynamic consequences. Start every vignette by asking: airflow obstruction, restricted expansion, or pulmonary vascular bed problem—then refine.
Obstructive Disease Framework
Obstructive disorders share increased resistance to expiratory flow. Hallmark spirometry is reduced FEV1 with reduced FEV1/FVC (classically <0.7 in adults for COPD staging contexts, but know the conceptual ratio drop). FVC may fall but less than FEV1. RV and TLC often rise with air trapping. Flow-volume loops show concavity of the expiratory limb.
Asthma
Asthma is reversible airway obstruction driven by bronchial hyperresponsiveness, smooth muscle constriction, mucosal edema, and mucus. Early/acute phases involve mast-cell mediators (histamine, leukotrienes, prostaglandins); late phases recruit eosinophils and Th2 cytokines (IL-4, IL-5, IL-13) with IgE in allergic asthma. Histology (fatal asthma): smooth muscle hypertrophy, basement membrane thickening, eosinophilic inflammation, Curschmann spirals, Charcot–Leyden crystals, mucus plugs. Triggers include allergens, exercise, cold air, aspirin/NSAID sensitivity in AERD (with nasal polyps), and β-blockers. ABG in mild attack: hypoxemia with respiratory alkalosis (hyperventilation); rising PaCO2 is an ominous sign of fatigue and impending failure.
COPD: Chronic Bronchitis vs Emphysema
Chronic bronchitis is a clinical diagnosis: productive cough for ≥3 months in each of two consecutive years. Mechanism centers on mucus gland hyperplasia (Reid index), goblet cell metaplasia, small-airway inflammation/fibrosis, and impaired mucociliary clearance—often smoking-related. Hypoxemia and hypercapnia can be prominent (“blue bloater” stereotype), with secondary polycythemia and cor pulmonale risk from chronic hypoxic vasoconstriction.
Emphysema is permanent enlargement of airspaces distal to terminal bronchioles with wall destruction and without obvious fibrosis. Centriacinar (centrilobular) emphysema affects respiratory bronchioles predominantly in upper lobes, strongly smoking-associated. Panacinar emphysema involves the entire acinus, preferentially lower lobes, classic for α1-antitrypsin deficiency (imbalance of proteases such as neutrophil elastase vs antiproteases). Loss of alveolar attachments decreases radial traction on airways → early collapse, air trapping, ↑compliance, ↓DLCO (surface area loss). “Pink puffer” stereotype reflects dyspnea and hyperinflation with relatively preserved oxygenation until late disease—use as a mnemonic only; real patients overlap.
| Feature | Chronic bronchitis | Emphysema |
|---|---|---|
| Definition core | Clinical productive cough criteria | Structural acinar destruction |
| Dominant lesion | Mucus glands, small airways | Alveolar wall loss |
| DLCO | Often nearer normal early | Decreased |
| Classic subtype links | Smoking airways disease | Centriacinar–smoke; panacinar–AAT |
| Cor pulmonale | Common with chronic hypoxemia | Variable; with advanced disease |
Bronchiectasis
Bronchiectasis is permanent abnormal dilation of bronchi from chronic necrotizing infection and inflammation, with impaired clearance and recurrent infections. Causes include post-infectious damage, CF, primary ciliary dyskinesia (Kartagener: situs inversus, sinusitis, bronchiectasis), immunodeficiency, and airway obstruction. Patients have copious purulent sputum, hemoptysis risk, and obstructive or mixed spirometry. Imaging shows dilated thick-walled airways; pathology shows chronic inflammation and destruction of bronchial walls.
Restrictive Lung Disease
Restriction means reduced expansion: ↓TLC is the defining measurement. FEV1 and FVC both fall, so FEV1/FVC is normal or elevated. Separate intrinsic (parenchymal) from extrinsic (extrapulmonary) causes.
Intrinsic Restriction (ILD)
Interstitial diseases thicken the interstitium, reduce compliance, impair diffusion (↓DLCO), and cause tachypnea with small tidal volumes. Classic examples:
- Idiopathic pulmonary fibrosis (IPF): progressive fibrosis, usual interstitial pneumonia pattern—heterogeneous fibrosis, fibroblastic foci, honeycomb change, predominantly subpleural/lower lobe. Restrictive PFTs, low DLCO, exertional desaturation.
- Sarcoidosis: noncaseating granulomas, often bilateral hilar lymphadenopathy; can involve lung parenchyma. CD4-driven immune response; hypercalcemia via macrophage 1α-hydroxylase activity is a high-yield systemic link. Restrictive pattern when interstitial involvement is significant.
- Hypersensitivity pneumonitis (HP): immune-mediated response to inhaled organic antigens (e.g., thermophilic actinomycetes, bird proteins). Acute: flu-like with neutrophilic/lymphocytic alveolitis; chronic: fibrosis if exposure continues. Poorly formed granulomas and lymphocytic interstitial inflammation are classic. Type III/IV hypersensitivity mechanisms are often invoked in teaching schemas.
Other intrinsic patterns: pneumoconioses (silica upper lobes/nodules; asbestosis lower lobes/fibrosis + pleural plaques; coal workers), drug/radiation fibrosis, and connective-tissue-disease ILD.
Extrinsic Restriction
Extrinsic causes limit chest expansion without primary alveolar wall fibrosis: severe obesity, kyphoscoliosis, ankylosing spondylitis chest-wall limitation, pleural effusion/thickening, neuromuscular weakness (ALS, Guillain–Barré, myasthenia—↓inspiratory pressures), and abdominal compartment processes. DLCO is often relatively preserved when corrected for volume (or less reduced than in ILD), and imaging may show small lungs without diffuse interstitial markings of IPF.
| Pattern | TLC | FEV1/FVC | DLCO theme | Examples |
|---|---|---|---|---|
| Obstructive | Normal/↑ | ↓ | ↓ in emphysema; variable otherwise | Asthma, COPD, bronchiectasis |
| Intrinsic restrictive | ↓ | Normal/↑ | ↓ | IPF, sarcoid, HP, asbestosis |
| Extrinsic restrictive | ↓ | Normal/↑ | Often nearer normal | Obesity, NM weakness, kyphoscoliosis |
Pulmonary Hypertension: Group Concept
Pulmonary hypertension (PH) is elevated pressure in the pulmonary arterial system with right ventricular afterload stress. Teaching groups (WHO-style concept):
- Pulmonary arterial hypertension (PAH) — intrinsic pulmonary arteriopathy (idiopathic, connective tissue disease, BMPR2-associated heritable forms, etc.): plexiform lesions in classic PAH pathology teaching.
- PH due to left heart disease — passive backward transmission of elevated left atrial pressure (HF, mitral disease); post-capillary physiology.
- PH due to lung disease and/or hypoxia — COPD, ILD, sleep-disordered breathing, high altitude; HPV and vascular remodeling.
- CTEPH — chronic thromboembolic obstruction and secondary vasculopathy.
- Multifactorial/unclear — hematologic, systemic, metabolic contributors.
Shared consequences: RV hypertrophy/dilation, functional tricuspid regurgitation, right-heart failure. Loud P2, right-sided strain findings, and exertional syncope appear in vignettes.
Pulmonary Embolism Pathophysiology
Acute PE from venous thromboembolism suddenly obstructs pulmonary arterial flow. Effects include increased alveolar dead space (ventilated but underperfused units), V/Q mismatch, hypoxemia, and increased pulmonary vascular resistance with acute RV strain if large. Infarction is less common than in systemic arterial beds because of dual pulmonary/bronchial supply, but peripheral emboli can cause hemorrhagic infarction and pleuritic pain/hemoptysis. Fat emboli (long-bone fracture) add petechiae and neurologic findings; amniotic fluid embolism is catastrophic peripartum; air embolism follows venous air entry. Hypercoagulability, stasis, and endothelial injury (Virchow) set risk.
ARDS Mechanisms
Acute respiratory distress syndrome follows diffuse alveolar capillary endothelial and epithelial injury (sepsis, aspiration, pneumonia, trauma, pancreatitis). Increased permeability produces protein-rich noncardiogenic pulmonary edema, hyaline membranes, and decreased compliance—diffuse alveolar damage (DAD) histology. Severe shunt-like physiology causes refractory hypoxemia; PCWP is not elevated (distinguishes from cardiogenic edema conceptually). Exudative, proliferative, and fibrotic phases describe temporal evolution.
Sleep Apnea: Basic Science
Obstructive sleep apnea (OSA) features recurrent upper-airway collapse during sleep with continued respiratory effort, intermittent hypoxemia/hypercapnia, sleep fragmentation, and sympathetic surges. Associations: obesity, large neck, micrognathia, alcohol/sedatives. Consequences: systemic hypertension, pulmonary hypertension risk, arrhythmias, daytime somnolence, and increased cardiovascular morbidity. Central sleep apnea is reduced ventilatory drive (CNS disease, heart failure/Cheyne–Stokes patterns) without obstructive effort. Polysomnography distinguishes effort vs no effort during apneic events.
Integrated Exam Moves
Young nonsmoker with panacinar lower-lobe emphysema → think AAT deficiency and possible liver disease. Progressive dyspnea, clubbing, honeycombing, restrictive PFTs → IPF pattern. Farmer/bird exposure + interstitial process → HP. Sudden dyspnea after immobilization + RV strain → PE. Sepsis with bilateral infiltrates and refractory hypoxemia → ARDS. Loud snoring, obesity, daytime sleepiness, HTN → OSA.
Mastery check: if you can separate obstruction vs restriction with TLC and FEV1/FVC, contrast chronic bronchitis vs emphysema subtypes, place a PH vignette into a mechanistic group, and explain PE dead space vs ARDS shunt edema, you own this section’s CBSE core.
A 45-year-old never-smoker has progressive dyspnea, lower-lobe panacinar emphysema, and a family history of early COPD and cirrhosis. Which mechanism best explains the lung disease?
Which set best distinguishes intrinsic interstitial lung disease from neuromuscular extrinsic restriction?
In acute ARDS from sepsis, which pathophysiologic statement is most accurate?