Intra- and interobserver variability during in vitro validation of two novel methods for intra-abdominal pressure monitoring

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Abstract
Intra-abdominal pressure (IAP) measurement techniques vary in automaticity and reproducibility. This study evaluated the intra- and interobserver variability of two new IAP measurement techniques. A one-half open, 30-l container was used with two IAP catheters (Foley Manometer, balloon-tipped catheter) contained in a 100-ml infusion bag. To simulate intra-abdominal hypertension the container was filled with water using 5-cm increments (0–25 cmH2O). Pressure was determined by observers using the Foley Manometer and simultaneously recorded using an IAP monitor. Observers were blinded to the reference levels. Fifteen observers conducted three pressure readings at each of the six pressure levels with the Foley technique, giving 270 readings. These were paired with the automated monitor readings and the height of the water column. The intra- and interobserver coefficients of variation were low for both methods. The Spearman correlation coefficient was higher than 0.9 for all paired measurements and Bland-Altman analysis comparing the reference H2O column to both measurement techniques showed a very good agreement at all pressure intervals (bias 0.1±0.6 cmH2O) and a consistent, low underestimation of the reference water column pressure by both techniques. Both the Foley Manometer and the IAP monitor are reliable and reproducible methods to measure IAP in this in vitro model. The coefficient of variation for each technique is low and decreases with increasing IAP, the monitor giving more reproducible results than the Foley Manometer.