The Effects of Negative Pressure External High Frequency Oscillation on Cerebral Blood Flow and Cardiac Output of the Monkey

The cerebral and systemic hemodynamic effects of negative pressure ventilation by external high frequency oscillation, utilizing a thoracoabdominal chamber, were investigated in six healthy adult monkeys. Cardiac output and cerebral blood flow were compared on external high frequency oscillation and conventional, positive pressure, mechanical ventilation in each animal. Cardiac output was measured by thermodilution and cerebral blood flow was measured by the intraarterial Xenon133 clearance technique. Oxygen delivery and consumption and systemic and pulmonary vascular resistances were calculated. There was no significant difference between the two ventilatory modes for any of these variables. Cardiac index on conventional mechanical ventilation was 2.87 +/- 0.39 1 X min-1 X m-2 (mean +/- SD) and on external high frequency oscillation was 2.96 +/- 0.87 1 X min-1 X min-2. Cerebral blood flow was 43.9 +/- 9.1 ml X 100 g-1 X min-1 on conventional and 39.0 +/- 9.0 ml X 100 g-1 X min-1 on external high frequency ventilation. External high frequency oscillation is not associated with any adverse cardiovascular or cerebrovascular effects and could be introduced for short-term human trials.