One Size Does Not Fit All: Establishing Anticipated Baseline Intravesical Pressures Adjusted for Position and Body...

Accurate measurement of intravesical pressure (Pves) during multichannel urodynamic testing requires zeroing with reference to surrounding atmosphere, establishing a reference level for measuring Pves, and assessing response to coughs. We prospectively evaluated baseline resting Pves in the supine and sitting positions and used statistical modeling to establish reference ranges for patients undergoing urodynamic testing and examine the influence of age, sex, and BMI on these measurements.

We prospectively evaluated adults undergoing multichannel urodynamic testing at a single institution. Initial resting Pves was recorded in both the supine and sitting positions following a standardized protocol using external dome (water-charged) transducers. Linear mixed-effects prediction models assessed associations between Pves and BMI, age, sex, and position.

The sample comprised 468 patients; 77% (n = 360) were overweight or obese. The mean supine and sitting Pves were 12.7 and 26.0 cmH₂O, respectively. The optimal linear mixed-effects model for initial resting Pves included age, BMI, position, and the interaction between these variables. Predicted normal Pves ranged from 0.0 to 26.6 cmH₂O (supine) and 7.3 to 43.6 cmH₂O (sitting). Increasing BMI was strongly correlated with increasing Pves.

We identified model-derived ranges for initial resting Pves in the supine and sitting positions that vary primarily with BMI. While current guideline-recommended ranges remain broadly applicable, patients with higher BMIs are more likely to have values that lie above these thresholds. We also developed an online app that generates expected Pves ranges based on patient-specific characteristics.