Intra-abdominal pressure measurement method via the urinary-tube: bedside validation of a biomechanical model integrating urine column height and bladder urinary volume.

Abstract

The objective of this work was to demonstrate the possibility of accurately measuring intra-abdominal pressure (IAP) by using a common urine drainage bag (U-Tube) as a hydrostatic column of measurement. This has been done by integrating urine column height (h) and bladder urinary volume (BUV) in the IAP measurement method. Seventy-eight newly admitted patients in a 22 bed university hospital intensive care unit (ICU) were studied. Two U-Tube IAP measurement methods were compared with the "Gold-standard" closed-system repeated measurement technique with bladder pressure transducer: U-Tube method I, where h (in cm) alone assesses IAP (in cm H2O) and U-Tube method II, integrating BUV according to a basic biomechanical model of bladder wall compliance to give a more accurate IAP estimation. Correlation rate using linear regression analysis was better between the Gold standard method and method II than method I with R = 0.901, P < 0.0001 and R = 0.682, P < 0.0001, respectively. For method II, Bland-Altman analysis showed a mean bias of -1.0 +/- 0.1 mm Hg (limits of agreement -3.4-1.4, percentage error +/-7.7%). Area under the receiver operator characteristics curves to screen intra-abdominal hypertension (IAP >or=12 mm Hg) was significantly greater with method II than with method I: 0.99 versus 0.93, P < 0.05; sensitivity and specificity of method II were 95% and 98%, respectively. By integrating urine column height and BUV in the measurement method, it may be conceivable to screen IAH at the bedside via a U-Tube in ICU; bladder wall compliance should be estimated to avoid the emergence of false-positive subjects due to the possible occurrence of bladder wall compliance alteration before or during the ICU stay.