Updated: 12/31/2018

Obstructive Lung Disease Overview

Review Topic
  • pftA class of lung diseases characterized by an obstruction to air flow leaving the lungs
  • Types of obstructive lung disease include
    • bronchiectasis 
    • chronic bronchitis 
    • emphysema 
    • asthma
Pathophysiology of Obstructive Lung Disease
  • Obstruction of air leaving the lungs leads to ↑ trapped air in the lungs which results in 
    • ↑ residual volume (RV)
    •  total lung capacity (TLC)
    •  functional reserve capacity (FRC)
    • ↓ in FVC
  • V/Q mismatch
    • ↑ in physiologic dead space results in ↓ ventilation and V/Q mismatch
      • the quantifiable result of a V/Q mismatch is an in the alveolar-arterial gradient (A-a gradient) and PaO2
  • Pulmonary function tests (PFTs)
    • PFTs (spirometry) can be used to distinguish obstructive lung diseases from other types of lung disease (including restrictive lung diseases)
    • the halmark finding of obstructive lung disease is 
      •  ↓ FEV1 sec/FVC ratio 
        • ratio is reduced because FEV1 decreases by a greater amount than FVC
Obstructive vs. Restrictive Lung Disease
TLC Decreased Increased
RV Decreased Increased (air is trapped)
FEV1sec Decreased Decreased
FVC Decreased Decreased
FEV1sec/FVC Nomal to increased Decreased (hallmark)
PaO2 Decreased Decreased
A-a gradient Increased (i.e. abnormal) Increased (i.e. abnormal)
  • Treatment varies by the type of obstructive lung disease

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