Lung Function Tests (Obstructive vs Restrictive)

Article status: Temporary high-yield summary

Article Last Updated:25/03/2026

Definition

Lung function test results can be boardly classified into the following 2:

Obstructive pattern → airway narrowing leading to difficulty exhaling air
Resrictive pattern → reduced lung expansion leading to reduced lung volumnes

Main important ones:

Restrictive lung disease causes are split into 1) intrinsic and 2) extrinsic.

Type	Mechanism	Important causes
Intrinsic	Due to disease of the lung parenchyma	Idiopathic interstitial pneumonias (most common: IPF) Connective tissue disease-associated interstitial lung disease Hypersensitivity pneumonitis Pneumoconiosis (e.g. coal work pneumoconiosis, silicosis) Drug-induced interstitial lung disease Primary lung diseases (e.g. sarcoidosis, eosinophilic pneumonia, Langerhans-cell granulomatosis)
Extrinsic	Due to disease outside of the lung parenchyma (i.e. pleura / chest wall / neuromuscular apparatus)	Obesity Chest wall disorders Kyphoscoliosis Thoracic cage deformities (e.g. from multiple thoracotomies / sternotomies, ankylosing spondylitis) Neuromuscular disease (e.g. motor neuron disease, myasthenia gravis, GBS)

Pattern	Subtype	Key findings
Obstructive	—	↓ FEV₁/FVC (<0.7) ↓↓ FEV₁ Normal / ↑ TLC and FVC DLCO ↓ in COPD (specifically if there is emphysema) Normal / ↑ in asthma Normal in bronchiectasis and cystic fibrosis (may be reduced in advanced disease)
Restrictive	Intrinsic	↓ DLCO Normal / ↑ FEV₁/FVC (>0.7) ↓ FEV₁ ↓↓ TLC and FVC
Restrictive	Extrinsic	↑ DLCO Normal / ↑ FEV₁/FVC (>0.7) ↓ FEV₁ ↓↓ TLC and FVC

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