Increasing intrathoracic pressure in acute ventricular failure improved cardiac function by increasing LV stroke work, dependent on adequate LV filling and decreased LV afterload.
Do phasic increases in intrathoracic pressure improve cardiac function in a canine model of acute ventricular failure?
Elevations in intrathoracic pressure can augment cardiac function in acute ventricular failure by decreasing LV afterload, provided there is adequate LV filling.
p-value: p=<0.01
We studied the cardiovascular effects of phasic increases in intrathoracic pressure (ITP) by high-frequency jet ventilation in an acute pentobarbital-anesthetized intact canine model both before and after the induction of acute ventricular failure by large doses of propranolol. Chest and abdominal pneumatic binders were used to further increase ITP. Respiratory frequency, percent inspiratory time, mean ITP, and swings in ITP throughout the respiratory cycle were independently varied at a constant-circulating blood volume. We found that pertubations in mean ITP induced by ventilator adjustments accounted for all observable steady-state hemodynamic changes independent of respiratory frequency, inspiratory time, or phasic respiratory swings in ITP. Changes in ITP were associated with reciprocal changes in both intrathoracic vascular pressures (P less than 0.01) and blood volume (P less than 0.01). When cardiac function was normal, left ventricular (LV) stroke volume decreased, whereas in acute ventricular failure, LV stroke volume increased in response to increasing ITP when apneic LV filling pressure was high (greater than or equal to 17 Torr) and did not change if apneic LV filling pressure was low (less than or equal to 12 Torr). However, in all animals in acute ventricular failure, LV stroke work increased with increasing ITP. Our study demonstrates that the improved cardiac function seen with increasing ITP in acute ventricular failure is dependent upon adequate LV filling and decreased LV afterload in a manner analogous to that seen with arterial vasodilator therapy in heart failure.
Pinsky et al. (Mon,) conducted a other in Acute ventricular failure. Phasic increases in intrathoracic pressure (ITP) by high-frequency jet ventilation vs. Normal cardiac function (baseline) was evaluated on Hemodynamic changes including intrathoracic vascular pressures and blood volume (p=<0.01). Increasing intrathoracic pressure in acute ventricular failure improved cardiac function by increasing LV stroke work, dependent on adequate LV filling and decreased LV afterload.
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