Intraoperative Ventilation Patterns in Morbidly Obese Patients Undergoing Laparoscopic Bariatric Surgery

The purpose of this study was to examine ventilation patterns, including tidal volume (TV) and positive end-expiratory pressure (PEEP) selection in morbidly obese patients undergoing laparoscopic Roux-en-Y gastric bypass or laparoscopic sleeve gastrectomy. Intraoperative ventilation data, including TV and PEEP, were abstracted from the electronic anesthesia record (Metavision) at Brigham and Women's Hospital. Ideal body weight (IBW) was calculated using the Devine formula, and TV per kg IBW was calculated for each patient. The mean TV delivered per kg IBW was 7.35 ± 1.07 mL/kg, and 24% (281/1186) of patients received TVs of >8 mL/kg IBW. The median PEEP applied was 5.5 ± 0.6 cmH₂O, and 87% (1035/1186) of patients received PEEP >0 cmH₂O. There was significant variation in both TV and PEEP selection. The significant variation in TV per kg IBW as well as in PEEP values at our institution may reflect the lack of well-established guidelines for intraoperative ventilation. Many patients in this study received inappropriately large TVs (>8 mL/kg IBW), which may be due to calculation of TVs based on total body weight rather than IBW. Patients of shorter stature and higher body mass index appear to be at higher risk for ventilation with inappropriately large TVs.