Table 1.

Factors affecting respiratory mechanics

Increased airway resistance	Reduced compliance
Tube (small diameter, sputum retention)	Chest wall
Central airways	Edema
Tracheostomy malposition	Elevated abdominal pressure
Sputum plug	Pleural fluid and ascites
Corpus alienum (after trauma)	Obesity
Tracheomalacia or tracheal stenosis	Lung
Small airways	Intrinsic positive end-expiratory pressure
Asthma and chronic obstructive pulmonary disease	Alveolar filling (edema, pus, and collapse)
Acute respiratory distress syndrome	Pneumonia
	Interstitial lung disease and fibrosis