Transesophageal Echo-doppler evaluation of the hemodynamic effects of positive-pressure ventilation after coronary artery surgery.

Transesophageal echocardiography was used to extend knowledge about the impact of positive end-expiratory pressure (PEEP) during mechanical ventilation on right and left ventricular function and right ventricular impedance. At 20 cmH2O PEEP, a progressive increase of right ventricular end-diastolic area was seen (27%) that coincided with a reduction of early left ventricular filling velocity (25%) across the mitral valve, and a decrease of both pulmonary artery flow velocity (end-expiration 27% and end-inspiration 42%) and time-velocity index (end-inspiration 25%). As these changes were not accompanied by a change of the fractional area of contraction, the increase of the right ventricular diameter might be explained by right ventricular compensation due to an imbalance between augmented right ventricular impedance and reduced venous return.