Is it feasible to measure intra-abdominal pressure using a balloon-tipped rectal catheter? Results of a validation study

The gold standard to measure intra-abdominal pressure (IAP) is intra-vesical measurement via the urinary bladder. However, this technique is restricted in ambulatory settings because of the risk of iatrogenic urinary tract infections. Rectal IAP measurements (IAPrect) may overcome these limitations, but requires validation. This validation study compares the IAPrect technique against gold standard intra-vesical IAP measurements (IAPves). IAPrect using an air-filled balloon catheter and IAPves using Foley Manometer Low Volume were measured simultaneously in sedated and ventilated patients. Measurements were performed twice in different positions (supine and HOB 45° elevated head of bed) and with an external abdominal pressure belt. Sixteen patients were included. Seven were not eligible for analysis due to unreliable IAPrect values. IAPrect was significantly higher than IAPves for all body positions (p < 0.01) and the correlation between IAPves and IAPrect was poor and not significant in each position (p ≥ 0.25, R2 < 0.6, Lin's CCC < 0.8, bias - 8.1 mmHg and precision of 5.6 mmHg with large limits of agreement between - 19 to 2.9 mmHg, high percentage error 67.3%, and low concordance 86.2%). Repeatability of IAPrect was not reliable (R = 0.539, p = 0.315). For both techniques, measurements with the external abdominal pressure belt were significantly higher compared to those without (p < 0.03). IAPrect has important shortcomings making IAP estimation using a rectal catheter unfeasible because the numbers cannot be trusted nor validated.