CORRELATION OF PRESSURE MEASUREMENTS BETWEEN MICROTIP AND WATER BASED CATHETERS

Andrew F. Hundley, MD, Anthony G. Visco, MD

   Objective: To compare pressure measurements between a microtip transducer and water perfusion catheter using an in vitro bladder model during simulated coughs and Valsalva maneuvers.

   Material and Methods: A prospective study designed to compare the simultaneous readings from both a microtip transducer and water perfusion catheter in an effort to correlate their measurements using a simulated bladder model. An 8Fr microtip and a 6Fr double lumen water perfusion catheter were inserted through separate access ports of a standard intravenous (IV) bag immediately after both catheters were calibrated. Pressure readings were recorded from both systems simultaneously while the external surface of the IV bag was exposed to maneuvers designed to simulate coughs and Valsalva efforts of various strengths and at different volumes (100cc, 200cc, 300cc). A minimum of one hundred events was performed for both coughs and Valsalva maneuvers at each strength and volume level. The data generated between the two systems were then correlated using Pearson correlation coefficients for each event.

   Results: All pressure readings were compared between the microtip and water-based systems and found to have an overall correlation coefficient of 0.9979. The correlation for all coughs was 0.9977 and for all Valsalva efforts was 0.9977. When data were analyzed by volume, correlation was noted to be 0.9986 for 100cc, 0.9971 for 200cc and 0.9983 for 300cc. Data were also analyzed by strength of simulated cough and Valsalva efforts at each volume, and the correlation coefficients were found to be similarly high, all greater than 0.9487.

   Conclusion: There is an extremely high correlation between pressure measurements obtained from microtip transducer and water perfusion catheters during simulated cough and Valsalva efforts in this in vitro model. We would expect similar correlation to exist in vivo. Thus, urodynamic data generated by these two different systems should be comparable.

   Key Words: microtip catheter, water perfusion catheter, urodynamics