Respiratory failure

Respiratory failure is the consequence of lung failure leading to hypoxaemia or respiratory muscle pump failure resulting in alveolar hypoventilation and hypercapnia. Type 1 respiratory failure is defined as a partial pressure of arterial oxygen (PaO2) less than 8.0 kPa or hypoxaemic respiratory failure, and type 2 respiratory failure is defined as PaO2 <8 kPa and a partial pressure of arterial carbon dioxide (PaCO2) >6 kPa or hypercapnic respiratory failure. Diagnosis is made easier by understanding the pathophysiological mechanisms that cause hypoxaemia and hypercapnia. Furthermore, a basic knowledge of acid–base balance allows distinction between acute, acute-on-chronic and chronic type 2 respiratory failure. In addition to the standard assessment, careful consideration must be given to neurological conditions as well as obstructive sleep apnoeas as these are frequently overlooked causes of respiratory failure. Imaging and pulmonary function tests provide useful information to ascertain the diagnosis. Management of these patients will depend on the underlying cause, but the objective of treatment must be to improve oxygenation and/or ventilation to resolve hypoxaemia and hypercapnia.