Bladder pressure monitoring during intermittent catheterization: a comparison of gauges and methods

We previously have investigated a technique for serial bladder pressure measurements in patients with spinal cord injury (SCI) using intermittent catheterization. In the current study, we compared an FDA-approved digital gauge with the previously studied analog gauge and studied the effects of hydrostatic pressure differences.

Either a digital or an analog pressure gauge was attached to each subject's catheter just before bladder catheterization. Both immediate and stable pressures were recorded. The bladder was then drained until nearly empty and pressure was again recorded (almost empty bladder pressure). Detrusor pressure was estimated as full minus almost empty bladder pressure. Bladder pressures greater than 40 cm H2O were presumed to represent bladder contractions. To investigate the effects of hydrostatic pressure, additional measurements, adjusting the level of the air-urine meniscus, were obtained in three subjects.

Recordings were made from nine SCI subjects using both gauges. Estimates of detrusor pressure, with and without bladder contractions, and associated bladder volumes, were not significantly different between digital and analog gauges. In the absence of bladder contractions, detrusor pressure with the meniscus at the end of the catheter (5 +/- 1 cm H2O) was significantly lower than that recorded with no adjustment of the urine meniscus (12 +/- 1 cm H2O).

Standardizing measurement techniques to equalize hydrostatic pressures should facilitate reliable estimates of detrusor pressure. Frequent monitoring of bladder pressure using this technique may assist with the urological care of SCI patients.