Effects of Different Ventilation Modes on Intracranial Pressure and Carbon Dioxide Partial Pressure during Bariatric Surgery: a Prospective, Randomized, Controlled Study
Authors: Jia Yu-Long , Chen Bo , Zhang Xiao‐Yu , Chou Chen-Xu , Duan Xia‐Guang 
Published: September 2024

Background Obesity is linked to the retention of carbon dioxide, headaches, and idiopathic intracranial hypertension. Although studies indicate that different ventilation modalities may change intracranial pressure and carbon dioxide partial pressure, their impact on bariatric surgery patients remains unclear. This study aimed to monitor, compare, and analyze respiratory mechanics, carbon dioxide partial pressure, and intracranial pressure under three ventilation modes: pressure control (PC), volume control (VC), and pressure-regulated volume control (PRVC) during bariatric surgery to explore the clinical significance and value of the PRVC ventilation mode.
Methods This was a prospective, randomized, controlled clinical study. Ninety patients who underwent bariatric surgery were randomly randomized into three groups: Group I utilized pressure control ventilation (PC), Group II used volume control ventilation (VC), and Group III utilized pressure-regulated volume control ventilation (PRVC). Measurements were obtained at five time points: before pneumoperitoneum (T1), 5 minutes after pneumoperitoneum (T2), 10 minutes after pneumoperitoneum (T3), 15 minutes after pneumoperitoneum (T4), and 20 minutes after pneumoperitoneum (T5). The collected parameters included: intracranial pressure (ICP, measured through the optic nerve sheath diameter [ONSD]), esophageal pressure (PES), average airway pressure (PAWM), peak airway pressure (PAP), arterial carbon dioxide partial pressure (PaCO2), end-tidal carbon dioxide concentration or partial pressure (ETCO2), tidal volume (TV), mean arterial pressure (MAP, calculated as MAP = diastolic pressure + 1/3 pulse pressure difference), and heart rate (HR).
Results In all three breathing modes, pneumoperitoneum induced various degrees of increase in the ONSD, PAWM, PAP, and PES. There were no significant differences in PAWM among the groups at any time point (P > 0.05). However, the PES was much higher in the VC mode following pneumoperitoneum than in the PC and PRVC modes. Compared to the other two groups, the TV was considerably lower in the PC group following pneumoperitoneum (P < 0.05). PaCO2 and ETCO2 increased in the PC and VC groups following pneumoperitoneum, resulting in significant increases in ONSD, MAP, and HR (P < 0.05), but the PRVC group showed no significant changes in ONSD, MAP, and HR (P > 0.05).
Conclusion The results of this study demonstrate that the PRVC mode can successfully prevent increases in ICP, PAWM, PAP, and PES caused by pneumoperitoneum. It also prevents abnormal TV fluctuations during surgery, ensuring the stability of the patient's vital signs during the perioperative period. Therefore, the PRVC mode is the ideal ventilation mode for laparoscopic bariatric surgery. Additionally, ONSD ultrasound assessment, a noninvasive method for evaluating the ICP, can be safely employed during laparoscopic bariatric surgery.