Measurement of postoperative pericardial pressure in man.

Pericardial pressure was measured in 18 patients undergoing cardiopulmonary bypass for up to 10 days using a solid state transducer. Mean and phasic pericardial pressure wave forms were similar to those reported in animals. A wide range of mean pressure from 0 to 30 mmHg was recorded, and values of up to 20 mmHg were observed in patients whose postoperative clinical course was uncomplicated. Fluctuations in pericardial pressure during spontaneous and artificial respiration were small, suggesting that concomitant left ventricular diastolic pressure changes were mainly the result of alterations in diastolic filling. Relative ventricular and pericardial distensibilities were estimated from the ratio of the slopes of diastolic pressure with time, which showed that up to 25 per cent of left ventricular diastolic pressure was supported by the pericardium and 75 per cent by the myocardium. Measurement of pericardial pressure had clinical value in 2 patients in confirming and excluding the presence of pericardial tamponade.