| Abstract: Aims: Concerns exist that air in the transducer tubing, urinary catheter or bladder may lead to inaccurate intra-abdominal pressure (IAP) measurements.1, 2 We hypothesize that the dampening effect of air should have no effect on a non-dynamic mean pressure measurement such as IAP.3
Methods: A laboratory model was designed to simulate IAP. The model consisted of a 210-liter container (the “Abdomen”) with a urinary catheter exiting its base. The catheter tip was sealed within a 100 ml bag (the “bladder”). A commercially available IAP measuring device (AbViser, Wolfe Tory Medical) was connected to the proximal end of the catheter and interfaced with a transducer and monitor. A column of fluid was placed within the container to simulate IAP pressures of 10, 20, 30, and 40 mm Hg. Six different air/fluid volumes were infused into the system 30 times each (10 each -air first, air last, or air mixed with fluid throughout) and pressures were measured. The gold standard was the calculated pressure exerted by the water column (1.36 cm water exerts 1 mm Hg). Pressure differences of > ± 2mm Hg were considered clinically important in measured versus calculated pressure.
Results: No clinically important differences occurred at any volume of air infused (see table).
Discussion: Peak systolic and to a lesser extent diastolic pressures are affected by the dynamic response of a monitoring system, while mean pressures are not.3 Since IAP measurements are reported as a mean measurement, the dynamic response of the monitoring system should not be important. As demonstrated in this study, air within the transducer line, urinary catheter and “bladder” has no impact on accuracy of IAP measurement in an IAP model. |
