Comparison of arterial to end-tidal carbon dioxide gradient P (a-ET)CO(2) in volume versus pressure controlled ventilation in patients undergoing robotic abdominal surgery in the Trendelenburg position. A randomised controlled study

BACKGROUND AND AIMS: Robotic surgery is increasingly prevalent as an advancement in care. Steep head-down positions in pelvic surgery can increase the ventilation-perfusion mismatch and increase ventilatory requirements to offset carbon dioxide (CO(2)) increases consequent to pneumoperitoneum. The primary objective was to assess the impact of two ventilatory strategies, volume versus pressure-controlled ventilation on the arterial to end-tidal carbon dioxide gradient P (a-ET)CO(2) in patients undergoing robotic surgery in the Trendelenburg position. The effects on alveolar to arterial oxygen gradient P (A-a)O(2), peak airway pressure (P(aw))(,) dynamic compliance (C(dyn)) and haemodynamics were also assessed. METHODS: Fifty-one patients, 18-75 y, American Society of Anesthesiologists I-III undergoing robotic surgery in Trendelenburg position were randomised to volume-controlled ventilation (Group VCV) or pressure-controlled ventilation (Group PCV). The P (a-ET)CO(2) was measured at baseline T0, 10 min after Trendelenburg position T1, 2 h of surgery T2, 4 h T3 and at T(e,) 10 min after deflation. The P (A-a) O(2), P(aw), C(dyn), heart rate and blood pressure were also measured at the same time. RESULTS: The P (a-ET)CO(2) at T1, T2, T3 and at T(e) was lower in Group PCV versus Group VCV. The P(aw) was lower at T1, T2, and T3 and C(dyn) higher at T3 and Te in Group PCV at comparable minute ventilation. Haemodynamics and P (A-a)O(2) were comparable between the groups. CONCLUSION: Pressure-controlled ventilation reduces P (a-ET)CO(2) gradient, P(aw) and improves C(dyn) but does not affect P (A-a) O(2) or haemodynamics in comparison to volume-controlled ventilation in robotic surgeries in the Trendelenburg position.