Left Atrial End-diastolic Pressures Research Articles

Left Ventricular Preload Determines Systolic Pressure Variation during Mechanical Ventilation in Acute Lung Injury

Background: Systolic pressure variation (SPV) predicts responsiveness to volume loading during mechanical ventilation and may be related to changes in LV preload and the resultant changes in stroke volume (SV). We, therefore, tested the relations between LV preload, output and SPV in an acute lung injury (ALI) model during mechanical ventilation. Methods: ALI was created by oleic acid infusion (0.07 ml/kg) in 8 anesthetized dogs. We measured LV, RV, aortic, left atrial (LA) and pericardial pressures, LV area (A LVED ) and SV during mechanical ventilation with positive endexpiratory pressures (PEEP) of 0, 6, 12 and 18 cmH2O at LV end-diastolic pressures of 5, 12 and 18 mmHg. Results: Throughout these ranges of PEEPs and filling pressures, SPV was inversely related to LV preload [A LVED and transmural LV end-diastolic pressure; (PLVEDtm)] (r = −0.87 and r = −0.89, P <0.0001 respectively). Both preload measures were closely related to SV (both r = 0.90, P <0.0001). Changes in estimated P LVEDtm (LA end-diastolic pressure – RV end-diastolic pressure) matched changes in P LVEDtm (r = 0.95, P < 0.0001). Alternative measures of arterial pressure variation (pulse pressure variation, SV variation and delta down) behaved similarly when compared to SPV (r = 0.91, 0.97, and 0.78, P < 0.001, respectively). Conclusions: The inverse relations between SPV and LV preload and output indicate that LV preload is a major determinant of SPV. An estimate of LV preload based on measurements from the flow-directed catheter (i.e., wedge pressure – right atrial pressure) may predict volume responsiveness in mechanically ventilated patients.

Circulatory support by a left ventricular balloon pump.

The ability of a left ventricular balloon pump to provide support of the circulation when myocardial function had been severely impaired was examined in six dogs. When the unassisted damaged left ventricle could not maintain systemic blood flows adequate for survival, left ventricular balloon pumping resulted in peripheral blood flows which ranged from 37 to 77 ml/min/kg. These balloon-generated blood flows have been maintained for periods up to three hours. Assist of the circulation by balloon pumping was accompanied by an increase in systemic arterial blood pressure and a decrease in left atrial end-diastolic pressure. The effectiveness of left ventricular balloon pumping was reduced in hypovolemia and in the presence of ventricular extrasystolic beats. Left ventricular balloon pumping was not effective in generating a sustained peripheral flow of blood when the heart was fibrillating.