Head-to-head comparison of pressures during full cystometry, with clinical as well as in-depth signal-analysis, of air-filled catheters versus the ICS-standard water-filled catheters

Aims: To compare in vivo differences of two catheter systems for urodynamics to further discover their measurement properties. Methods: Side-by-side catheterization with two catheters for intravesical and abdominal pressure during full cystometry in 36 prospectively recruited patients with analysis of mean and absolute differences at urodynamic events and post hoc in-depth signal analysis comparing the full pressure traces of both systems. Results: The mean pressure differences at urodynamic events between air-filled and water-filled systems are small, however, with a large variation, without a systematic difference. The majority of the intersystem differences are significantly larger than 5 cmH ₂O. Further analysis showed that urodynamic event pressure differences of both systems at the start of the test were carried forward throughout the remainder of the test without subsequent or additional tendency to differ. Post hoc whole test signal analysis with pressures equalized from the first sample shows high cross-correlation (>0.981) between the pressure signals per location (rectum and bladder) per test and almost zero-time shift (<0.05 s) of all cystometry pressure samples. Conclusions: We confirm earlier studies that showed random differences at events between air-filled and water-filled pressures during clinical urodynamic testing and confirm that these are intrinsic but not systematic—and still incompletely explained—offset-baseline differences. We determined on closer full measurement analysis after equalizing, that both systems are similar in displaying urodynamic pressure variations and amplitudes. We also confirm that both systems require awareness of intrinsic measurement properties during urodynamic testing and especially may necessitate adjustment of pressure offsets into a quantitative diagnosis of a urodynamic test.