Effect of Volume Controlled Ventilation Versus Pressure Controlled Ventilation on Gas Exchange and Cardiovascular Response in Morbid Obese Patients Undergoing Laparoscopic Gastric Sleeve

Abstract

Managing ventilation and oxygenation during laparoscopic procedures in severely obese patients undergoing weight loss surgery presents many challenges. There is no specific guideline on the ventilation modes for this group of patients. Although several studies have been performed to determine the optimal ventilatory settings in these patients, the answer is yet to be found. The aim of this study was to compare the efficacy and safety of pressure controlled ventilation versus volume controlled ventilation in laparoscopic gastric sleeve surgery. The use of volume-controlled ventilation (VCV) is common, as this has been the only available mode on ventilators for a long time. This mode utilizes a constant flow to deliver a target tidal volume (Vt) and thus insures a satisfactory minute ventilation (MV), despite frequently seen high-pressure levels in morbid obese patients. On the contrary, the decelerating inspiratory flow used during pressure-controlled ventilation (PCV) generates high initial flow rate, causing more rapid alveolar inflation. This allows a homogeneous distribution of ventilation leading to better ventilation–perfusion matching. At the same time, pressure limits and uniform distribution of forces within the lung reduce the risk of volu- and barotraumas. The present study was conducted on 60 morbidly obese adult patients of ASA physical status I-II, scheduled for laparoscopic gastric sleeve surgery. Their age ranged from 20-50 years, body mass index (BMI) > 35 kg/ m², and of both sexes. General anesthesia with endotracheal intubation and controlled ventilation was conducted in all patients; all patients' lungs were ventilated using VCV. After pneumoperitoneum, patients were divided into two equal groups. Group V; received VCV and group P; received PCV. In the present study, it was observed that PCV does not adversely affect hemodynamics when compared to VCV as there was no statistically difference in hemodynamics (BP and HR) between both groups. Also the present study showed the superiority of PCV in decreasing the risk of barotrauma and volutrauma in morbid obese patients during pneumoperitoneum. This was proved by significant lower PIP and lower tidal volume required by group P compared to group V in maintaining normocarbia. It was also shown in this study that PCV provides better oxygenation than VCV where significant higher PaO2 was observed in group P compared to group V. This is due to its unique characteristic decelerating flow pattern where it delivers high flow early in inspiration, thus a larger proportion of tidal volume is delivered early in the inspiratory phase, and the lung is maintained at a higher volume allowing more alveoli to participate in gas exchange.