More complicated than it looks: the vagaries of calculating intra-abdominal pressure.

Activities thought to induce high intra-abdominal pressure (IAP), such as lifting weights, are restricted in women with pelvic floor disorders. Standardized procedures to assess IAP during activity are lacking and typically only focus on maximal IAP variably defined. Our intent in this methods article is to establish the best strategies for calculating maximal IAP and to add area under the curve and first moment of the area as potentially useful measures in understanding biologic effects of IAP. Thirteen women completed a range of activities while wearing an intravaginal pressure transducer. We first analyzed various strategies heuristically using data from 3 women. The measure that seemed to best represent maximal IAP was an average of the 3, 5, or 10 highest values, depending on activity, determined using a top-down approach, with peaks at least 1 second apart using algorithms written for Matlab computer software, we then compared this strategy with others commonly reported in the literature quantitatively using data from 10 additional volunteers. Maximal IAP calculated using the top-down approach differed for some, but not all, activities compared with the single highest peak or to averaging all peaks. We also calculated area under the curve, which allows for a time component, and first moment of the area, which maintains the time component while weighing pressure amplitude. We validated methods of assessing IAP using computer-generated sine waves. We offer standardized methods for assessing maximal area under the curve and first moment of the area for IAP to improve future reporting and application of this clinically relevant measure in exercise science.