Effects of positive end-expiratory pressure (PEEP) in cardiac surgery patients

The role of positive end-expiratory pressure (PEEP) in the postoperative course of cardiac surgery patients remains questionable. In this prospective study, we examined the effect of different levels of PEEP on arterial oxygenation, SvO2 and PvO2 values, and on haemodynamic indices, during the early postoperative period in cardiac surgery patients. Upon transfer to the ICU, 67 adult patients with normal preoperative respiratory status were randomly assigned to receive zero PEEP (Group A), 5 cmH2O (Group B), or 10 cmH2O PEEP (Group C) during mechanical ventilatory support. PaO2/FIO2 ratio, mixed venous PvO2 and SvO2, and cardiac index, were measured 30 min, 4 h and 8 h after application of mechanical ventilation in the ICU, just prior to extubation, half an hour after extubation, and 4 h post-extubation. We found no statistically significant differences (P = n.s.) in arterial oxygenation expressed by PaO2/FIO2 ratio, SvO2 and PvO2 values, and in cardiac index among the three groups at any study interval. We conclude that low levels of PEEP have no advantage over zero PEEP in improving gas exchange in the early postoperative course of patients following open heart surgery.