Effect of positive end-expiratory pressure on intraoperative pulmonary function in patients undergoing urological retroperitoneal laparoscopic surgery in mode of protective ventilation

Abstract

Objective To evaluate the effect of positive end-expiratory pressure (PEEP) on intraoperative pulmonary function in the patients undergoing urological retroperitoneal laparoscopic surgery in the mode of protective ventilation. Methods Forty patients of both sexes, aged 30-64 yr, with body mass index of 16-29 kg/m2, of American Society of Anesthesiologists physical status Ⅰ or Ⅱ, scheduled for elective retroperitoneal laparoscopic ureterolithotomy, were randomly divided into 2 groups (n=20 each) using a random number table: control group (group C) and PEEP group (group P). After induction of general anesthesia, the patients were endotracheally intubated.Intermittent positive pressure ventilation (tidal volume [VT] 6 ml/kg, respiratory rate [RR] 12 breaths/min, inspiratory/expiratory ratio [I∶E] 1∶2, fraction of inspired oxygen 50%) was performed from the end of intubation until the onset of pneumoperitoneum.After the onset of pneumoperitoneum, the patients were ventilated (VT 6 ml/kg, RR 22 breaths/min, I∶E 1.0∶1.5), and the end-tidal pressure of carbon dioxide was maintained at 35-45 mmHg in group C. After the onset of pneumoperitoneum, the patients were ventilated (VT 6 ml/kg, RR 22 breaths/min, I∶E 1.0∶1.5, PEEP 5 cmH2O), and the end-tidal pressure of carbon dioxide was maintained at 35-45 mmHg in group P. At 5 min before pneumoperitoneum (T1), at 10, 30 and 60 min of pneumoperitoneum (T2-4), immediately after the end of pneumoperitoneum (T5), and at 5 min before extubation (T6), arterial blood samples were collected for blood gas analysis.Peak airway pressure and mean airway pressure were also recorded.Dynamic lung compliance, oxygenation index, respiratory index, dead space fraction and alveolar-arterial oxygen gradient were calculated. Results Compared with group C, mean airway pressure was significantly higher at T2-4, oxygenation index was significantly higher at T3, alveolar-arterial oxygen gradient difference was significantly lower at T3 and T6, and respiratory index was significantly lower at T6 (P 0.05). Conclusion PEEP (5 cmH2O) can improve the intraoperative pulmonary function in the patients undergoing urological retroperitoneal laparoscopic surgery in the mode of protective ventilation. Key words: Positive-pressure respiration; Respiratory function tests; Laparoscopy; Urologic surgical procedures