Effects of Recruitment Maneuver and Positive End-expiratory Pressure on Respiratory Mechanics and Transpulmonary Pressure during Laparoscopic Surgery

Background: The authors tested the hypothesis that during laparoscopic surgery, Trendelenburg position and pneumoperitoneum may worsen chest wall elastance, concomitantly decreasing transpulmonary pressure, and that a protective ventilator strategy applied after pneumoperitoneum induction, by increasing transpulmonary pressure, would result in alveolar recruitment and improvement in respiratory mechanics and gas exchange. Methods: In 29 consecutive patients, a recruiting maneuver followed by positive end-expiratory pressure 5 cm H2O maintained until the end of surgery was applied after pneumoperitoneum induction. Respiratory mechanics, gas exchange, blood pressure, and cardiac index were measured before (T-BSL) and after pneumoperitoneum with zero positive end-expiratory pressure (T-preOLS), after recruitment with positive end-expiratory pressure (T-postOLS), and after peritoneum desufflation with positive end-expiratory pressure (T-end). Results: Esophageal pressure was used for partitioning respiratory mechanics between lung and chest wall (data are mean +/- SD): on T-preOLS, chest wall elastance (E-cw) and elastance of the lung (E-L) increased (8.2 +/- 0.9 vs. 6.2 +/- 1.2 cm H2O/L, respectively, on T-BSL; P = 0.00016; and 11.69 +/- 1.68 vs. 9.61 +/- 1.52 cm H2O/L on T-BSL; P = 0.0007). On T-postOLS, both chest wall elastance and E-L decreased (5.2 +/- 1.2 and 8.62 +/- 1.03 cm H2O/L, respectively; P = 0.00015 vs. T-preOLS), and PaO2/inspiratory oxygen fraction improved (491 +/- 107 vs. 425 +/- 97 on T-preOLS; P = 0.008) remaining stable thereafter. Recruited volume (the difference in lung volume for the same static airway pressure) was 194 +/- 80 ml. Pplat(RS) remained stable while inspiratory transpulmonary pressure increased (11.65 + 1.37 cm H2O vs. 9.21 + 2.03 on T-preOLS; P = 0.007). All respiratory mechanics parameters remained stable after abdominal desufflation. Hemodynamic parameters remained stable throughout the study. Conclusions: In patients submitted to laparoscopic surgery in Trendelenburg position, an open lung strategy applied after pneumoperitoneum induction increased transpulmonary pressure and led to alveolar recruitment and improvement of E-cw and gas exchange.