ACCURATE ASSESSMENT OF RIGHT-VENTRICULAR FUNCTION IN ACUTE RESPIRATORY-FAILURE

Objective: Since right ventricular ejection fraction is highly dependent on afterload, right ventricular ejection fraction may not reflect right ventricular contractile function in acute respiratory failure. Despite a severe reduction in right ventricular ejection fraction, the right ventricle may be able to generate pressure output that is sufficient enough to maintain an adequate distribution of pulmonary perfusion. We tested this hypothesis by assessing the correlation between the right ventricular ejection fraction and the right ventricular end-systolic pressure-volume relationship, and by assessing the correlations between right ventricular ejection fraction and the physiologic deadspace/tidal volume ratio and between the physiologic deadspace/tidal volume ratio and the right ventricular end-systolic pressure-volume relationship. Design: Prospective study. Setting. University hospital intensive care unit (ICU). Patients. Twenty-one patients with acute respiratory failure. Measurements and Main Results. The physiologic deadspace/tidal volume ratio was used as an index of the distribution of pulmonary perfusion. Right ventricular ejection fraction was measured by the thermodilution method. Right ventricular end-diastolic volume index was obtained from the stroke volume index divided by the right ventricular ejection fraction. Right ventricular end-systolic volume index was calculated as the difference between the right ventricular end-diastolic volume index and the stroke volume index. Pulmonary arterial dicrotic notch pressure was used as an estimate of right ventricular end-systolic pressure. Data were collected at baseline and after one or two alterations in preload to define the right ventricular end-systolic pressure-volume relationship. There was no correlation between the right ventricular ejection fraction and the slope of the right ventricular end-systolic pressure-volume relationship line. No correlation was found between the right ventricular ejection fraction and the physiologic deadspace/tidal volume ratio. There was a hyperbolic curvilinear relationship between the physiologic deadspace/tidal volume ratio and the slope of the right ventricular end-systolic pressure-volume relationship line (r2 =.82, p < .0001). When the patients were divided into two groups based on the slope of the right ventricular end-systolic pressure-volume relationship line, the physiologic deadspace/tidal volume ratio was lower in the group with a high slope of the right ventricular end-systolic pressure-volume relationship line (p < .0001). There was no difference in other hemodynamic data between the two groups. Conclusions: These data suggest that in acute respiratory failure, the right ventricular ejection fraction does not reflect right ventricular performance.