A Simplified Approach to the Diagnosis of Elevated Intra-abdominal Pressure

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Abstract
Previous methods described to measure bladder pressure require additional setup, making these techniques complex and time consuming. We describe a simple U-tube technique and investigate its accuracy for measuring intra-abdominal pressure (IAP). Warm saline was infused into the peritoneum of five pigs to increase IAP. Indirect methods of measuring IAP included bladder, inferior vena cava (IVC), and gastric pressures. Bladder pressure was measured by both the standard and U-tube technique. IVC pressure was measured via a femoral line and gastric pressure was transduced through an orogastric tube. In addition, 30 patients undergoing laparoscopy were prospectively investigated. Insufflated abdominal pressure readings were obtained and compared with bladder pressures measured by the U-tube technique (n = 20) and standard technique (n = 10). In the animal study, U-tube manometry had the highest degree of correlation (r2 = 0.98) and the lowest bias (0.51 ± 1.63 mm Hg). The bladder pressure measured by the U-tube technique was between 0.1 and 0.9 mm Hg less than the directly measured IAP (95% confidence interval). There was a high degree of correlation between IAP and the standard technique for bladder pressure (r2 = 0.93), IVC pressure (r2 = 0.93), and gastric pressure (r2 = 0.90). Strong correlation also existed between the U-tube and standard techniques for measuring bladder pressure (r2 = 0.96). In humans, a strong correlation between insufflated abdominal pressure and bladder pressure (U-tube technique, r2 = 0.79; standard technique, r2 = 0.53) was also encountered. The accuracy of the U-tube manometry technique for measuring intra-abdominal pressure is comparable to previously described techniques. The U-tube technique is simple, does not require additional equipment, and can be performed by any member of the medical team.