Effect of prolonged inspiratory time on gas exchange during robot-assisted laparoscopic urologic surgery.

ABSTRACT

BACKGROUND: Gas exchange disturbance may develop during urologic robotic laparoscopic surgery with the patient in a steep Trendelenburg position. This study investigated whether prolonged inspiratory time could mitigate gas exchange disturbances including hypercapnia. METHODS: In this randomized cross-over trial, 32 patients scheduled for robot-assisted urologic surgery were randomized to receive an inspiratory to expiratory time ratio (IE) of 11 for the first hour of pneumoperitoneum followed by 12 for last period of surgery (group A, n = 17) or IE of 12 followed by 11 (group B, n = 15). Arterial blood gas analysis, airway pressure and hemodynamic variables were assessed at four time points (T1 10 min after induction of general anesthesia, T2 1 h after the initiation of pneumoperitoneum, T3 1 h after T2 and T4 at skin closure). The carry over effect of initial IE was also evaluated over the next hour through arterial blood gas analysis. RESULTS: There was a significant decrease in partial pressure of oxygen in arterial blood (PaO2) for both groups at T2 and T3 compared to T1 but in group B the PaO2 at T4 was not decreased from the baseline. Partial pressure of carbon dioxide in arterial blood (PaCO2) increased with IE of 12 but did not significantly increase with IE of 11; however, there were no differences in PaO2 and PaCO2 between the groups. CONCLUSION: Decreased oxygenation by pneumoperitoneum was improved and PaCO2 did not increase after 1 h of IE of 11; however, the effect of equal ratio ventilation longer than 1 h remains to be determined. There was no carryover effect of the two different IE ratios.