Traces: making sense of urodynamics testing.

Urodynamics testing is used to describe lower urinary tract function, and diagnose functional disorders affecting the bladder, urethra, and pelvic floor. Urologic clinicians play a central role in urodynamics testing; they are primarily responsible for performing more than 75% of evaluations completed in North America. While the value of a well-done urodynamics assessment is well established, comparatively few clinicians have received formal training in the area. This article describes hydrodynamic principles underlying the measurement of intravesical, abdominal, and detrusor pressures. This is the first in a series of articles that will review principles of best urodynamics practices.

New lumbar method for monitoring cerebrospinal fluid pressure in rats.

OBJECTIVE: Monitoring cerebrospinal fluid pressure or intracranial pressure (ICP) is crucial in the study of neurosurgical disorders. In the present study, we report a new lumbar method for monitoring ICP in rats. METHODS: A PE10 catheter connected to a pressure transducer was placed into the subarachnoid space of L5 through the duramater after laminectomy to record lumbar cerebrospinal fluid pressure (lumbar-ICP). ICP at the cisterna magna (cisterna-ICP) was recorded simultaneously via a catheter in the subarachnoid space at the cisterna magna. Eighteen anesthetized adult male S-D rats were subjected to baseline recording followed by either experimental subarachnoid hemorrhage (SAH) induced by intravascular puncture method or experimental intracerebral hemorrhage (ICH) induced by blood injection with a stereotaxic system. RESULTS: Baseline lumbar-ICP and cisterna-ICP varied between 6 and 8 mmHg, and respiratory variation could be detected. A similar acute response to SAH was recorded in both the lumbar-ICP and cisterna-ICP in all rats. In rats subjected to SAH, the lumbar catheter continuously and accurately monitored lumbar-ICP, and reliable pressure tracings were obtained for up to 24 h after SAH. However, continued cisterna-ICP monitoring was abandoned in two rats in the cisterna magna method due to obstruction of the catheter by blood clots (hematoma). CONCLUSION: This new lumbar-ICP method is simple, safe, easy, and reliable in rats. Continued lumbar-ICP measurements provided monitoring for up to 24 h after experimental manipulation.

Accuracy and reliability of disposable pressure transducers coupled with modern pressure monitors.

OBJECTIVE: To determine the bedside accuracy of direct patient pressure monitoring when used with new and clinically used disposable blood pressure (BP) transducers. DESIGN: Prospective study. SETTING: Laboratory bench and critical care units in an adult and children's hospital. SUBJECTS: Seventy-five bedside patient monitors (25 Marquette Electronics, 25 Spacelab Medical, and 25 Hewlett-Packard), and 100 disposable transducers (50 from Utah Medical Products and 50 from Abbott Critical Care Systems [25 new, 25 clinically used of each manufacturer]) were tested. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: A +/- 2% accuracy requirement for bedside monitors and the +/- 3% American National Standards Institute accuracy standard for disposable BP transducers were used. To test the accuracy of the bedside monitors, a certified transducer simulator was used to apply 100 mm Hg to each bedside monitor. To test the accuracy of the disposable BP transducers, a very accurate (+/- 0.05%) pneumatic dead weight tester was used to apply pressures to the transducer. A digital power supply and a 6 1/2 digit voltmeter were used. The average output of the bedside monitors when 100 mm Hg was applied was 99.90 +/- 0.83 mm Hg, with the worst cases being 98 and 103 mm Hg. For all 100 disposable pressure transducers, the average output was 100.03 +/- 0.55 mm Hg, with the worst cases being 98.53 and 101.36 when 100 mm Hg was applied. There was no important difference in the accuracy of the transducers obtained from the two vendors nor whether the transducers had been used clinically. CONCLUSIONS: All disposable BP transducers tested were much more accurate than the American National Standards Institute standard for accuracy. Even the worst case transducers were twice as accurate as required by the American National Standards Institute standard. Only one bedside monitor was outside the +/- 2% accuracy range (103 mm Hg). Based on these findings, this author recommends that fixed calibration disposable transducers and fixed calibration bedside pressure monitoring systems be used. The clinical risks of air embolism and infection from the calibrating mercury manometer and the complexity of the calibration task are the overriding factors for making these recommendations.