Respiratory Failure

Abstract

Respiratory failure may be defined as impairment of respiratory function of such degree that the pressure of CO2 (Pco3) in arterial blood rises above normal limits or the pressure of oxygen (Po„) in arterial blood falls below normal limits. Respiratory failure should be distinguished from breathlessness. Two types of respiratory failure can be distinguished by the presence or absence of hypercapnia. The causes of these two types are discussed and the importance of disturbed relationships between ventilation and perfusion of the lung is emphasized. Respiratory failure may result from lesions or disorders of function at any of the following sites: brain ; spinal cord ; motor neurone ; neuromuscular junction ; respiratory muscles ; thoracic cage ; pulmonary circulation ; lung ; airway. The physiological features of clinical importance are reviewed. The diagnosis of hypoxaemia and hypercapnia and the value of blood gas measurements are discussed. The particular usefulness of measurements of Pco2is emphasized. So long as the patient breathes air, death from hypoxia sets a limit to the severity of the hypercapnia and acidaemia. More severe respiratory failure can develop rapidly if O2is breathed, and the lungs may then deteriorate. Some principles of management of respiratory failure are stated. © 1965, British Medical Journal Publishing Group. All rights reserved.