ABSTRACT
Respiratory failure is a common and important event that is frequently associated with severe exacerbations of chronic obstructive pulmonary disease (COPD) (1). Despite the definition of COPD exacerbation being based mainly on clinical outcomes, episodes of exacerbations are commonly characterized by worsening of pulmonary gas exchange, which results in moderate-to-severe hypoxemia with or without hypercapnia. This may represent a worsening in the patient’s premorbid condition or, alternatively, these changes may occur for the first time in someone with less severe COPD who develops a different cause for deterioration, e.g., lobar pneumonia or acute pulmonary edema. In either case, the physiological abnormality is invariably the development of a significant degree of hypoxemia (<60 mm Hg) with a variable risk of carbon dioxide retention (>45 mm Hg) (2).
