Intra-abdominal Pressure in the Morbidly Obese

Background: Recent data suggests that increased intra-abdominal pressure (IAP) is one factor associated with the morbidity of morbidly obese patients, who have a BMI >35 kg/m². IAP has been proposed to be an abdominal compartment syndrome (ACS). This study investigated the characteristics of IAP in morbidly obese patients. Methods: 45 morbidly obese patients (mean BMI 55±2 kg/m²) had IAP measured using urinary bladder pressure. Results: The mean IAP for the morbidly obese group was 12±0.8 cmH₂O, increased when compared to controls (IAP=0±2 cmH₂O). The IAP correlated to the sagittal abdominal diameter, an index of the degree of central obesity (r=+0.83, P<0.02); however, it did not correlate to basal insulin, body weight, or BMI. The end-expiratory IAP did not change when measured after the laparotomy incision was made, but IAP measured in the last 15 patients increased during the first 2 postoperative days. The IAP for patients with pressure-related morbidity (gastroesophageal reflux disease, hernia, stress incontinence, diabetes, hypertension, and venous insufficiency) was 12±1 cmH₂O, while those without these morbidities had an IAP of 9±0.8 cmH₂O. Conclusion: We conclude that IAP is increased in morbid obesity. This increased IAP is a function of central obesity and is associated with increased morbidity. The degree of IAP elevation correlates with increased co-morbidities. We also conclude that elevation in IAP in morbid obesity is not a true ACS but represents a direct mass effect of the visceral obesity.