Various systems to measure intravesical and intrarectal pressure during urodynamic testing; especially cystometry, exist. Water filled tube -systems are the most commonly used and should be regarded as the contemporary standard. A water filled system is however sensitive to tube and or patient movement artefacts and prone to erroneous calibration. Air charged catheters are less sensitive to patient and especially tubing- movements, and calibrate easier. However, in vitro tests have demonstrated that air charged catheters respond somewhat slower and relatively damped, especially to rapid pressure changes as in (simulated) coughing, in comparison with water filled systems. The clinical relevance of these observations is unknown.