Arterial Hypoxaemia in Acute Myocardial Infarction

Summary: Serial measurements of arterial pO2, pCO2 and pH were made in 99 patients admitted to a coronary care unit with acute myocardial ischaemia or infarction. Samples were taken whilst the patients breathed room air and air enriched with oxygen in a concentration of approximately 40% via nasal cannulae. The degree of arterial hypoxaemia on room air correlated well with the degree of left ventricular failure. The increase in arterial oxygen tension produced by oxygen enrichment of the inspired air was greater in those with mild than in those with severe left ventricular dysfunction. The return of the arterial oxygen tension to normal after myocardial infarction may be protracted, suggesting that prolonged oxygen administration is advisable in the more severely ill patients. Levels of arterial pCO2 and pH were not found to be helpful in management.