Introduction A 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 Evaluation 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 VariablesRestrictiveObstructiveTLCDecreasedIncreasedRVDecreasedIncreased (air is trapped)FEV1secDecreasedDecreasedFVCDecreasedDecreasedFEV1sec/FVCNomal to increasedDecreased (hallmark)PaO2DecreasedDecreasedA-a gradientIncreased (i.e. abnormal)Increased (i.e. abnormal) Treatment Treatment varies by the type of obstructive lung disease