Continuous monitoring of right atrial oxygen tension in patients with myocardial infarction.

Right atrial oxygen tension (RAPvO2) was measured continuously in 26 patients admitted to a coronary care unit with acute myocardial infarction. A catheter incorporating a Clark type oxygen sensor at its tip was inserted percutaneously into the right atrium. Insertion was simple, safe and comparable to the introduction of a standard central venous pressure line. RAPvO2 correlated well with the patients' clinical condition and reflected both cardiac and pulmonary function. When breathing air 11 of the patients had sustained RAPvO2 levels of less than 34 mmHg (4.53 kPa). In this group there were eight deaths. Fifteen patients had an RAPvO2 greater than 34 mmHg (4.53 kPa) except for transient falls related to movement and in this group there were no deaths (p less than 0.002). The correction of arterial hypoxaemia by oxygen therapy raised RAPvO2 and lowered the heart rate. In some patients Dopamine and transvenous pacing raised RAPvO2 and could be adjusted with reference to the continuous recording. Movement often caused marked falls in RAPvO2 especially in the seriously ill. Evidence relating RAPvO2 to mixed venous oxygen and tissue oxygen is reviewed.