Diagnosis and Management of Acute Respiratory Failure

Acute hypoxemic respiratory failure is defined by Pao₂ less than 60 mm Hg or SaO₂ less than 88% and may result from V/Q mismatch, shunt, hypoventilation, diffusion limitation, or low inspired oxygen tension. Acute hypercapnic respiratory failure is defined by Paco₂ ≥ 45 mm Hg and pH less than 7.35 and may result from alveolar hypoventilation, increased fraction of dead space, or increased production of carbon dioxide. Early diagnostic maneuvers, such as measurement of SpO₂ and arterial blood gas, can differentiate the type of respiratory failure and guide next steps in evaluation and management.