Increased intra-abdominal pressure during laparoscopic surgery causes cephalad displacement of the diaphragm, resulting in the formation of atelectasis, which can be overcome by positive end-expiratory pressure (PEEP). The aim of this prospective study was to investigate the level of optimal PEEP to maintain adequate arterial oxygenation and hemodynamics during robot-assisted laparoscopic radical prostatectomy (RLRP).

One hundred patients undergoing RLRP were randomly allocated to one of five groups (n = 20) (0, 3, 5, 7 and 10 cmH₂O of PEEP). Hemodynamic variables and respiratory parameters were measured at baseline with the patient in the supine position; at 30 min, 1, 2, 3 and 4 h during CO₂ insufflation with the patient in the post-Trendelenburg position; and after deflation in the supine position with increasing PEEP.

The PaO₂ levels and alveolar-arterial difference in oxygen tension (AaDO₂) were improved in patients with PEEPs compared with patients in whom PEEP was not used. The application of PEEP (10 cmH₂O) resulted in higher PaO₂ levels compared to those with lower PEEP levels, but excessive peak airway pressure (PAP) was sometimes observed. The application of a PEEP of 7 cmH₂O resulted in similar PaO₂ levels without causing excessive PAP. There was a significant difference in central venous pressure between the groups, but there were no significant differences in heart rate, mean arterial pressure or minute ventilation between the groups.

A PEEP of 7 cmH₂O is associated with the greater improvement of PaO₂ and AaDO₂ without causing excessive PAP during RLRP.