Ventricular assist by synchronous, cardiac cycle-specific increases in intrathoracic pressure

To study the differential hemodynamic effects of cardiac cycle-specific ITP (intrathoracic pressure) pulses delivered by high-frequency jet ventilation (f approximately=2.5 Hz) at constant mean ITP, the authors varied their timing within single cardiac cycles during acute and chronic ventricular failure, preload-dependent left ventricular (LV) filling, and acute endotoxemia. Such pulses affect ventricular loading and mediate a spectrum of cardiac responses, depending on timing, contractility, intravascular volume, and vasomotor tone. With LV failure, ventricular assist is maximal during systolic pulses which reduce LV afterload and transmural aortic input impedance. When cardiac performance is preload-dependent, diastolic pulses maintain cardiac output at apneic levels when timed near the completion of ventricular filling.<>