Cyclic Changes in Arterial Pulse during Respiratory Support Revisited by Doppler Echocardiography

It has long been known that there are cyclic changes in arterial pressure during mechanical ventilation. They are caused by cyclic changes in both the right and left ventricular stroke output, occurring in opposite phases. As a result, arterial pulse pressure is increased during inspiration and decreased during expiration. A cyclic improvement in left ventricular systolic function could thus be expected during mechanical lung inflation. We tested this hypothesis in 31 septic patients who were mechanically ventilated in controlled mode by combining left ventricular measurements by transesophageal echocardiography with invasive arterial pressure recordings and Doppler analysis of pulmonary venous flow and right and left ventricular stroke volume. Lung inflation by tidal ventilation significantly improved left ventricular stroke volume (26 ± 0.4 cm3/m2 [mean ± SEM] vs. 22.3 ± 0.4 cm3/m2 at end deflation). Beat-to-beat analysis of pulmonary venous flow velocity illustrated the boosting effect of lung inflatio...