Characterization of pressure changes in the lower urinary tract during coughing with special reference to the demands on the pressure recording equipment

Abstract

The exact demands on urodynamic equipment for measurement of coughs and cough associated pressure changes in the lower urinary tract have been analyzed from high‐speed pressure recordings using a double microtip transducer and a storage oscilloscope. The equipment was tested in vitro by the step‐test method. The natural frequency response was 175.6 Hz and the rise‐time 2.5 ms, resulting in accurate measurements of frequencies up to about 60 Hz which is way above the clinically measured frequencies. Four men and 2 women, all of whom were healthy volunteers, were examined in the supine position with an empty bladder. Pressures were measured in the bladder and in the external sphincter zone of the urethra. The spectral power density of the bladder and urethral pressures were calculated by Fourier analysis. The pressure changes in the urethra were in all volunteers equal to or slower than in the bladder. The analysis of the spectral power density showed that 99% of the pressure changes could be recorded with an instrument capable of recording 9 Hz frequencies, i.e., with a sampling rate of 18 Hz or more. © 1994 Wiley‐Liss, Inc.

Conversion of urodynamic pressures measured simultaneously by air-charged and water-filled catheter systems

“…Kim et al conducted a frequency assessment of select urodynamic signals, and concluded that CLPP and VLPP tests occur with frequency contributions as high as 14 and 7 Hz, respectively. The clinical urodynamic signals collected from the literature for our study show the relevant time to peak pressure as approximately 0.2–0.25 sec (or 4–5 Hz) for CLPPs and 1–2 sec (or 0.5–1 Hz) for VLPPs . This is consistent with the suggestion by Hogan et al that valsalva be defined as lasting more than 2 sec.…”

“…The CLPP signals obtained from literature have time to peak pressure 0.2–0.25 sec, while the VLPP signals have time to peak pressure 1–2 sec . Thus, VLPPs are in the range of slowly changing signals in which ACCs measured peak pressures similar to those measured simultaneously by WFCs.…”

“…The published urodynamic signals, two coughs and two valsalvas, were recreated in the test chamber. In addition, to simulate CLPP and VLPP data encompassing the range of clinical values, amplitude of each example pressure signal was held constant while duration was varied; then duration of each example was held constant while amplitude was varied (Fig.…”

“…An example cough leak point pressure, reprinted from Thind et al with permission, that ( A ) was digitized, ( B ) copied, and ( C ) modified by changing amplitude while original signal duration was held constant, and ( D ) modified by changing duration while original signal amplitude was held constant. Example of a typical response to a signal in the pressure chamber ( E ) from a water filled catheter (WFC), an air charged catheter (ACC), and the reference pressure (RP), during one simulated 0.8 sec cough event digitized from Thind et al…”

Air filled, including “air‐charged,” catheters in urodynamic studies: does the evidence justify their use?

“…Cough tests are generally considered to generate the fastest changing (i.e., highest frequency) intravesical pressure signal in UDS testing. Therefore, Thind et al assessed the frequency spectrum of cough tests in six healthy volunteers: four men and two women . They found that 99% of the power of the bladder pressure signal in a cough occurs at frequencies of 9 Hz or less.…”