Continuous positive-pressure ventilation does not alter ventricular pressure-volume relationship

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Abstract
To determine whether alterations in the mechanical properties (i.e., stiffening) of the right and left ventricles contribute to the decrease in right and left ventricular end-diastolic volumes during continuous positive-pressure ventilation (CPPV), 6 dogs anesthetized with chloralose urethane and ventilated with a volume ventilator were studied. Ventricular volumes were studied by withdrawing or infusing blood. Pressure-volume curves, constructed by plotting transmural ventricular end-diastolic pressures against ventricular end-diastolic volumes, did not change during CPPV (12 cm H2O positive end-expiratory pressure) compared to intermittent positive-pressure ventilation (0 cm H2O end-expiratory pressure). Decreased ventricular end-diastolic volumes during CPPV result primarily from a decrease in venous return. Alterations in the mechanical properties of the ventricles do not play a significant role in this response.