e·Sense® is the only single-use, electronic urodynamics catheter available on the market with an in-vivo pressure sensor at the distal tip. T-DOC® Air-Charged catheters (ACC) use pressure-sensing air balloons to assess internal pressures. Water-filled catheters (WFC) with external transducer domes have long been accepted as the gold standard in urodynamic studies (UDS). The aim of this novel study was to compare pressure accuracy and frequency response of e·Sense catheters, ACC and WFC in a bench model.

A pressure-controlled chamber was used in a body temperature water bath to assess pressure accuracy of Laborie (6Fr, dual lumen) WFC, e·Sense (7Fr, single sensor), and ACC (7Fr, single sensor). The catheters were connected to a Nexam urodynamic system, while a pressure controller ramped to various levels between 0 and 250 cmH20. Zeroing was done at atmospheric pressure and body temperature. After each pressure adjustment, 30 seconds of stabilization was allowed before readings were taken. Pressure readings were compared to a calibrated gauge to assess accuracy.

Frequency response was also assessed. Using a reference sensor, all three catheter types were subjected to a logarithmic frequency sweep from 0.5 to 30Hz over 120 seconds. The frequency analysis identified where the signal was attenuated to 71% and 50% of the original amplitude. 

A sample size of 29 was selected for each catheter to achieve 95% confidence and 90% reliability for variable data with a normal distribution.

Frequency response results showed that e·Sense did not attenuate in the 0.5 to 30 Hz range. ACC was attenuated to 71% of the signal at 3.19 ± 0.59 Hz and 50% of the signal at 5.34 ± 0.83 Hz. WFC was attenuated to 71% of the signal at 10.6 ± 1.8 Hz and 50% of the signal at 14.3 ± 2.5 Hz. The catheters were exposed to pressure for a period of 22 minutes after a 3 minute warm-up as shown in Figure 1 below.

Across the range of pressures, average error ± SD (percent error ± SD) was -0.21 ± 0.64 cmH20 (-0.49 ± 0.92%) for e·Sense, -1.96 ± 1.90 cmH20 (-2.61 ± 2.31%) for ACC, and 1.76 ± 1.55 cmH20 (1.30 ± 2.19%) for WFC. Results at each pressure level tested are shown in Figure 2 below.

Lab results suggest that e·Sense provides more accurate measurements with significantly lower variation between catheters across the clinically relevant range. e·Sense has more consistent inter-catheter measurements across all pressure ranges measured compared to both ACC and WFC. Data also suggests that e·Sense supports fast transient pressure signals, that cannot be detected with ACC or WFC.

In this novel study, all catheter types demonstrated clinically relevant measurements. For ACC and WFC at low pressures, larger inter-catheter variations exist. This variability seems intrinsic to ACCs as a technology, although more investigation is needed. e·Sense demonstrated high repeatability at a wide range of frequencies and pressures. The accuracy and fast response times of e·Sense may be advantageous to measure spasms or sphincter abnormalities that are otherwise undetectable with ACC and WFC. e·Sense catheters also simplify the user experience by removing the need for water- or air-system setup. These attributes make e·Sense ideal for UDS and Urology research, among other potential uses. Future areas of investigation include studying the impacts of water catheter accessory variability on WFCs, air charge volume variability on ACC, and the effect of temperature on the “zero point” of e·Sense catheters.