VENTILATION BY EXTERNAL HIGH-FREQUENCY OSCILLATIONS IMPROVES CARDIAC-FUNCTION AFTER CORONARY-ARTERY BYPASS-GRAFTING

Objective: To compare the effects of ventilation with intermittent pos itive pressure and external high frequency oscillation by the Hayek Os cillator during the first 5 h after coronary artery bypass grafting. M ethods: Eleven patients were randomized to intermittent positive press ure ventilation throughout the observation period (5 h), while 13 pati ents were initially ventilated with intermittent positive pressure ven tilation, then by external high-frequency oscillations for 4 h, changi ng to positive pressure ventilation for the last hour. Results: Cardia c index, stroke volume index, right ventricular stroke work index, rig ht ventricular end-diastolic volume index and mixed venous oxygen satu ration were significantly increased during ventilation with external h igh-frequency oscillations, and arteriovenous oxygen content differenc e was significantly reduced. There were no significant interor intragr oup differences in fluid accumulation, mean arterial blood pressure, a rterial blood gases, pulmonary artery pressure, central venous pressur e, pulmonary capillary wedge pressure, heart rate, systemic vascular r esistance index, pulmonary vascular resistance index, intrapulmonary s hunt fraction, right ventricular ejection fraction, right ventricular end-systolic volume index and left ventricular stroke work index. Conc lusions: Ventilation by external high-frequency oscillations increases cardiac index and improves tissue perfusion. The increased pumping of the heart is probably caused by changes of the intracardiac pressure- volume relationship. The Hayek Oscillator may have distinct cardiovasc ular benefits as ventilatory assistance in postoperative cardiac surgi cal patients. (C) 1997 Elsevier Science B.V.