Comparison of measurements obtained with microtip and external water pressure transducers

The aim of this study was to compare pressure readings obtained with catheter-mounted microtip and external water pressure transducers using a mechanical model for vesical pressure during Valsalva straining and coughing. The two catheter-mounted pressure transducers were simultaneously placed in a vinyl i.v. bag designed to mimic the parameters of the human bladder to allow comparison of simultaneous readings from both transducers. Simulated cough and Valsalva maneuvers of various strengths at different volumes (100 ml, 200 ml, 300 ml) were performed and the pressure readings generated by the two systems compared. The Pearson correlation coefficient between the systems was 0.998 for coughs and 0.998 for Valsalva efforts. Data were also analyzed by volume and strength of simulated cough and Valsalva effort, and correlations were found to be high (> or = 0.940) for all subgroup analyses. Mean absolute differences between events recorded by the two systems were small, as indicated by the y-intercept of 3.76 cmH2O pressure. Neither transducer recorded consistently higher pressures than the other. We concluded that there is a high correlation between pressure measurements obtained from microtip and external water pressure transducers during simulated cough and Valsalva efforts in this model. As similar correlation should exist in vivo, urodynamic data generated by the two transducer types should be comparable.