Introduction Definition restricted lung expansion results in reduced lung volumes (TLC and FVC) Pathophysiology poor breathing mechanics with normal lung function muscle weakness polio and myasthenia gravis chest wall limitation kyphosis, scoliosis, and morbid obesity ↓ pleural compliance mesothelioma interstitial lung diseases (diffuse parenchymal lung disease - DLCO) results in reduced lung compliance and increased elastic recoil the primary mechanism of resting hypoxemia in patients with interstitial lung disease is a diffusion limitation, with DLCO defect contributing to hypoxemia with activity increased expiratory flow rates due to increased radial traction (result of increased elastic recoil) on airway walls prevents small degree of dynamic collapse of conducting airways found in normal lungs types acute acute interstitial pneumonia (AIP) presents similar to acute respiratory distress syndrome (ARDS) neonatal respiratory distress syndrome drug toxicity (bleomycin, busulfan, and amiodarone) chronic idiopathic interstitial pneumonias most common is idopathic pulmonary fibrosis (IPF) non-specific interstitial pneumonia, respiratory bronchiolitis, desquamative interstitial pneumonia, cryptogenic organizing pneumonia, and lymphocytic interstitial pneumonia pneumoconioses coal miner's silicosis asbestosis sarcoidosis may also show obstructive or mixed pattern on PFT's pulmonary Langerhans cell histiocytosis hypersensitivity pneumonitis (may be acute, subacute, or chronic) lymphangiomyomatosis (primarily young women) Studies Pulmonary function tests FEV1 sec/FVC ratio should be normal approximately normal because both FEV1 sec and FVC are reduced ↓ FVC and TLC key finding for restrictive lung diseases (TLC must be reduced)