Journal of Applied Physiology, Vol 69, Issue 6 2120-2125, Copyright © 1990 by American Physiological Society
Hemodynamic effects of synchronous high-frequency jet ventilation in mitral regurgitation
K. L. Stein, D. J. Kramer, A. Killian and M. R. Pinsky
Department of Anesthesiology and Critical Care Medicine, University of Pittsburgh, Pennsylvania 15213.
We tested the hypothesis that increases in intrathoracic pressure (ITP), by
decreasing the pressure gradient for anterograde left ventricular (LV)
ejection, should augment cardiac output in acute mitral regurgitation (MR).
In a pentobarbital-anesthetized closed-chest canine model, LV stroke volume
(SLLV) was measured by integration from an aortic flow probe signal. MR was
induced by a regurgitant ring. ITP was elevated over apnea by means of
intermittent positive-pressure ventilation (IPPV), asynchronous (asynch)
high-frequency jet ventilation (HFJV), and cardiac cycle-specific (synch)
HFJV. IPPV resulted in the greatest increase in ITP. MR caused a fall in
SVLV and a rise in LV filling pressure that were not altered by IPPV.
Compared with IPPV or apnea, both asynch and synch HFJV increased SVLV and
reduced LV filling pressures (P less than 0.05). Systolic synch HFJV
induced a greater increase in SVLV (32%) than diastolic synch HFJV (26%)
despite similar ventilatory settings. Our data suggest that when LV
contractility is normal but MR impairs forward flow, cardiac cycle-specific
increases in ITP will augment forward flow.
