Novel Natural Fill Telemetric Pressure Flow Study of Discomfort and Bladder Outlet Obstruction

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Edmund Tate
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1 Novel Natural Fill Telemetric Pressure Flow Study of Discomfort and Bladder Outlet Obstruction Hyoun-Joong Kong, Sunmee Park, Tack Lee, Ji Youl Lee, Hee Chan Kim and Seung-June Oh* From the Interdisciplinary Program, Biomedical Engineering Major, Graduate School (HJK, SP), Departments of Biomedical Engineering (HCK) and Urology (SJO), College of Medicine and Institute of Medical and Biological Engineering, Medical Research Center (HCK), Seoul National University, Seoul, and Departments of Urology, Inha University College of Medicine (TL), Incheon and College of Medicine, Catholic University of Korea (JYL), Bucheon, Korea Purpose: We evaluated the accuracy of natural fill telemetric pressure flow study performed in a private room, and assessed patient discomfort and experience after the procedure compared to those of standard pressure flow study. Materials and Methods: In 58 patients with lower urinary tract symptoms/ benign prostatic hyperplasia free uroflowmetry, and natural fill telemetric and standard pressure flow studies were prospectively performed. Immediately after each step patients were asked to rate the experience in terms of pain, embarrassment, bother, boredom and repeat testing. Subjective items and objective urodynamic parameters were compared among the 3 tests. Results: Maximum urine flow on natural fill telemetric pressure flow study was not different from that on free uroflowmetry. In contrast, maximum flow, detrusor pressure at maximum flow and bladder contractility index on the standard pressure flow study were significantly lower than on the natural fill pressure flow study. However, the bladder outlet obstruction index was not significantly different between the 2 studies, and the bladder outlet obstruction and bladder contractility indexes correlated well. There were also no differences in bother and embarrassment scores. However, natural fill telemetric pressure flow study was superior in terms of pain and boredom scores. Patients were more willing to undergo repeat natural fill telemetric pressure flow study than standard pressure flow study. Time to complete the test was significantly shorter for the natural fill study than for the standard study. Conclusions: Flow rate differences between pressure flow studies and free uroflowmetry are not due to mechanical obstruction by the catheter but to other factors, such as the bladder filling method. Objective parameters on the natural fill telemetric pressure flow study correlated with standard pressure flow study findings. The natural fill telemetric pressure flow study shortened the time needed for the test and may decrease the discomfort of the standard pressure flow study. Key Words: prostate, prostatic hyperplasia, urinary bladder neck obstruction, urodynamics, pain Abbreviations and Acronyms BCI bladder contractility index BOO bladder outlet obstruction BOOI BOO index BPH benign prostatic hyperplasia ICS International Continence Society NFT-PFS natural fill telemetric PFS Pabd abdominal pressure PC personal computer Pdet detrusor pressure PdetQmax Pdet at Qmax PFS pressure flow study Pves vesical pressure PVR post-void residual urine Qmax maximum urinary flow rate S-PFS standard PFS Submitted for publication December 23, Study received Seoul National University Hospital institutional review board approval. Supported by Research Foundation Grant KUA-2006-HCMC060TO38 funded by the Korean Urological Association. * Correspondence: Department of Urology, Seoul National University Hospital, Yeongeondong, Jongno-gu, Seoul, Korea (telephone: ; FAX: ; sjo@snu.ac.kr). A significant proportion of patients with low urinary flow rate in the older male population have detrusor underactivity or BOO. PFS is considered the gold standard for diagnosing BOO in patients with BPH. 1 However, general urologists are confronted with several limitations in its application For another article on a related topic see page /09/ /0 Vol. 182, , August 2009 THE JOURNAL OF UROLOGY Printed in U.S.A. Copyright 2009 by AMERICAN UROLOGICAL ASSOCIATION DOI: /j.juro

602 NATURAL FILL TELEMETRIC PRESSURE FLOW STUDY in patients with BPH. The procedure is invasive and time-consuming.

Therefore, it not only causes significant discomfort but also usually does not guarantee patient privacy.

To overcome these problems several noninvasive urodynamic measurement methods have been designed. 2 4 However, none of these newer methods are universally accepted as a replacement for S-PFS.

2 602 NATURAL FILL TELEMETRIC PRESSURE FLOW STUDY in patients with BPH. The procedure is invasive and time-consuming. It is usually performed in an open laboratory space where patients wear pressure lines connected to a urodynamic machine during the procedure. Therefore, it not only causes significant discomfort but also usually does not guarantee patient privacy. Also, it may not reflect the actual voiding pattern since it is usually done after nonphysiological bladder filling during cystometry. To overcome these problems several noninvasive urodynamic measurement methods have been designed. 2 4 However, none of these newer methods are universally accepted as a replacement for S-PFS. We designed a telemetric wireless PFS device to diagnose BOO, decrease patient discomfort and provide privacy during testing. We also modified the S-PFS method so that the procedure could be performed without artificial bladder filling, ie with natural physiological filling of urine. The telemetric device was designed to transmit real-time pressure and flow signals to a laptop computer using Bluetooth technology. To our knowledge this wireless natural fill PFS method has not been previously described. We evaluated the accuracy of NFT-PFS to assess patient discomfort and the general experience after NFT-PFS compared to after S-PFS. MATERIALS AND METHODS A prospective study was performed on an outpatient basis between May 2007 and March This study was approved by the Seoul National University Hospital institutional review board and informed consent was obtained from all patients. Study inclusion criteria were age greater than 50 years, complaints of lower urinary tract symptoms suggestive of BPH and the ability to read informed consent. Study exclusion criteria included active urinary tract infection, bladder stones, previous urinary surgery or any genitourinary malignancy and any urethral abnormality such as urethral stricture or congenital urethral anomaly. To perform telemetric urodynamic monitoring we developed a new NFT-PFS system composed of custom-made pressure and flow measurement devices. For the pressure measurement device Pves and Pabd were acquired through a 6Fr fluid filled double lumen catheter and a 5Fr rectal balloon catheter, and converted into electrical signals with 2 disposable pressure transducers. Analog Pves and Pabd signals were sampled at 25 Hz with a 24 bit analog-to-digital converter and transmitted to the master laptop computer using a Bluetooth Parani-ESD100 transceiver (Sena Technologies, Seoul, Korea). Overall device operation was controlled by a low power consuming microcontroller unit. The whole device was portable enough to hang on the waist (fig. 1). For the flow measurement device the flow volume signal was sensed with a load cell transducer. It was also sampled at 25 Hz and wirelessly transmitted to the laptop computer. Except for the transducer the device had the same analog-to-digital converter, Bluetooth transceiver and microcontroller unit as the pressure measurement device. The resolution of the pressure and flow sensing devices was 25 V/mm Hg and 1 V/gm, respectively. The PC program was developed to acquire, plot and analyze Pabd, Pves and flow volume data transmitted to the Bluetooth module embedded in the laptop computer. Flow rate was determined as the first derivative of flow volume data, which was smoothed with a moving average filter 5 to suppress the effect of locally, rapid high frequency components or noise caused by load cell transducer sensitivity. The size of the averaging window was 3 times the device sampling frequency, ie 25 Hz. Simultaneously Pdet was calculated by subtracting Pabd from Pves without a filtering method. After pressure and flow data acquisition was completed the ICS nomogram, voided volume, and opening, closure and maximum Pdet were extracted from Pdet and flow data (fig. 2). To measure pressure and flow volume accurately the pressure and flow volume calibration functions were included in the PC program. Pves and Pabd were accurately A B C Figure 1. Wireless portable pressure (A) and flow (B) measurement devices, and device placement for NFT-PFS (C)

3 NATURAL FILL TELEMETRIC PRESSURE FLOW STUDY 603 Figure 2. PC program and representative NFT-PFS results adjusted using a water column and a 100 cm ruler, and flow volume was calibrated with a poise that had the same weight as 300 ml water. When the same water pressure and weight were applied to the conventional Solar S-PFS system (Medical Measurement Systems, Enschede, The Netherlands), resulting pressure and volume values were the same as with the NFT-PFS system. The study procedure involved 3 steps. After a patient underwent free uroflowmetry at visit 1 PVR volume was subsequently measured on ultrasound. The patient was instructed to visit the clinic again while holding urine for the next examination (step 1 free uroflowmetry). At the next visit NFT-PFS was done in patients with a bladder volume of more than 150 ml on ultrasound. Urodynamic and rectal catheters connected to the pressure measurement device were inserted into the proper place, as in standard filling cystometry. The patient was asked to void with the flowmeter alone in a private room while wearing the pressure measurement device on the waist. Pves, Pabd and flow data were monitored with the master laptop computer outside the room in wireless fashion (step 2 NFT-PFS). Subsequent procedures, including filling cystometry and S-PFS, were performed in standard ICS fashion (step 3 S-PFS), as previously described. 6 A single dose of antibiotic medication was prescribed after the procedure (fig. 3). Immediately after each step patients were asked to rate the experience at each step of the procedure in terms of pain, embarrassment, bother, boredom and undergoing repeat testing. The examiner also rated pain and patient compliance for each step. Subjective answers were given using a 10-point visual analog scale. Subjective items, such as patient or examiner rated discomfort, and objective urodynamic parameters, including time to complete the test, voided volume, Qmax, PdetQmax, BOOI and BCI, were compared among the 3 tests. All terminology conforms to ICS standards. 1 Data are shown as the mean SD and p 0.05 was considered statistically significant. RESULTS A total of 58 patients with a mean age of years participated in this study. Average prostate volume on transrectal ultrasound was ml. Mean International Prostate Symptom Score symptom and quality of life scores were and , respectively (table 1). Patients reported that free uroflowmetry was better than the other 2 tests. Bother and embarrassment scores were not different between S-PFS and NFT-PFS but the NFT-PFS was superior in terms of pain and boredom scores. Patients were more willing to repeat NFT-PFS if necessary than S-PFS. The examiner also reported that patients were more tolerant of NFT-PFS than of S-PFS. Time to complete the test was significantly shorter for NFT-PFS than for S-PFS. Qmax on NFT-PFS was not different from Qmax on free uroflowmetry. In contrast, Qmax, PdetQmax and BCI on S-PFS were significantly lower than on NFT-PFS (table 2). However, BOOI was not significantly different on S-PFS vs NFT-

604 NATURAL FILL TELEMETRIC PRESSURE FLOW STUDY Figure 3. Study protocol PFS. BOOI and BCI correlated well in the 2 studies (Pearson s correlation coefficient 0.76, p 1 and 0.

4 604 NATURAL FILL TELEMETRIC PRESSURE FLOW STUDY Figure 3. Study protocol PFS. BOOI and BCI correlated well in the 2 studies (Pearson s correlation coefficient 0.76, p 1 and 0.680, p 1, respectively, fig. 4). DISCUSSION Pressure flow studies are important in patients with a low urinary flow rate to differentiate BOO from poor detrusor contractility. 7 However, such testing is not widely done by urologists in clinical practice. There have been many attempts to develop noninvasive urodynamic tests and nonurodynamic methods, such as prostate volume, bladder wall thickness, bladder weight and intravesical prostatic protrusion. However, these tests are not considered sufficient to diagnose bladder outlet obstruction. The only current gold standard test that is universally accepted is PFS. 1 The NFT-PFS method in this study is a novel test that applies 2 concepts. 1) We used wireless technology, which allows the patient to void in a private space. Privacy should be maximally guaranteed in the laboratory environment, where the patient is Table 1. Baseline patient characteristics Mean SD International Prostate Symptom Score: Storage symptom Voiding symptom Mean SD serum PSA (ng/ml) Mean SD prostate transitional zone vol (ml) Standard fill cystometry: Mean SD max cystometric capacity (ml) No. involuntary detrusor contraction (%) 9 (15.8) actually voiding, so that cortical inhibition affects the result minimally. The laboratory environment should be patient friendly, ie the patient must be relaxed and the environment should be private. 2) We adopted the natural fill concept, which enables the patient to void voluntarily with natural sensations on uroflowmetry. Natural sensations are not influenced by artificial bladder filling. Therefore, information on patient flow on NFT-PFS is closely associated with information on free uroflowmetry. We found significant differences in S-PFS and NFT- PFS outcome parameters. Following ICS guidelines 8 S-PFS is performed after artificial fill cystometry. Flow results on subsequent PFSs are different from those of free uroflowmetry. This was confirmed by ambulatory urodynamic study results, which also reflect natural filling. 9 Klevmark suggested that bladder behavior is different during artificial and natural filling, and argued that artificial filling decreases detrusor contractility. 10,11 We also confirmed that after artificial filling there are differences during subsequent bladder emptying. There was also a significant difference in PVR between free uroflowmetry and natural filling PFS. Since post-void residual urine is an aspect of detrusor contractility, this presumably indicates that detrusor contractility is slightly lower during a study with vs without a catheter, although this cannot be assessed directly because BCI cannot be measured on free uroflowmetry. S-PFS was subsequently performed after filling cystometry. S-PFS is performed under the influence of artificial, nonphysiological, rapid bladder filling. Since we used the same 6Fr

5 NATURAL FILL TELEMETRIC PRESSURE FLOW STUDY 605 Table 2. Urodynamic results Mean SD Free Uroflowmetry p Value NFT-PFS Mean SD S-PFS Mean SD p Value Voided vol (ml) PVR (ml) Bladder capacity at volitional void (ml)* Qmax (ml/sec) PdetQmax (cm H 2 O) Not applicable Pressure (cm H 2 O): Open Not applicable Closed Not applicable Slope Not applicable BOOI Not applicable BCI Not applicable Pt rated: Pain Embarrassment Bother Boredom Repeat test Time to complete test (mins) Examiner rated: Pain Compliance * Voided volume plus post-void residual volume. Ten-point visual analog scale. caliber urodynamic catheter, we believe that the filling rate was the main factor in the difference between the 2 PFS results. However, the cause of the major differences may be cortical inhibition. Detrusor contractility may also be decreased by the lack of privacy during conventional PFS, in addition Telemetric PFS 4 2 Difference r=0.76, p<1-2 p= Standard PFS Mean Telemetric PFS Difference r=0.68, p< p< Standard PFS Mean Figure 4. NFT-PFS and S-PFS urodynamic parameters, including BOOI (A) and BCI (B) (Pearson s correlation coefficient 0.76, p 1 and 0.68, p 1, respectively).

6 606 NATURAL FILL TELEMETRIC PRESSURE FLOW STUDY to artificial bladder filling. Currently it is not clear which factor had a major influence on the difference. Further study with a prospective design using artificial bladder filling with vs without privacy may confirm this. In this context it might be difficult to match nomograms from S-PFS and NFT-PFS with a single standard ICS nomogram. The standard nomogram may not represent studies done with this technique, given these differences in flow and pressure values. We compared outcomes based on the assumption that the 2 studies are based on the same principle. To obtain the highest quality results we believe that PFS should reflect the actual patient physiological voiding pattern. To accurately determine BOO the urinary flow reflecting natural physiological filling is desirable. A new BOO nomogram for natural filling conditions should be established before widespread application of NFT-PFS in clinical practice. It would be advantageous to perform NFT-PFS to show that actual clinical treatment outcomes were improved by better patient diagnosis and selection using natural filling. Bother and embarrassment scores were not different for S-PFS and NFT-PFS in this study, which may have been due to the sequence of the procedures. Catheters for Pves and Pabd were inserted just before NFT-PFS and thereafter no further catheter reinsertion was necessary for S-PFS. This might have caused significant bias in favor of S-PFS in terms of the patient rating. Since patients with a volume of less than 150 ml in the bladder had to wait for the bladder to fill further for the telemetric study, the actual time to complete the telemetric test might have been longer in some patients. Since NFT-PFS can provide a better study environment for patients and requires less time to complete, it can be used in patients with lower urinary tract symptoms/bph in an office based practice. CONCLUSIONS Our results show that flow rate differences between PFS types and free uroflowmetry are not due to mechanical obstruction by the catheter but to other factors, such as the bladder filling method before the study. Objective parameters of this novel NFT-PFS method correlate with those of standard PFS and may also decrease patient discomfort due to PFS. Time needed to perform NFT-PFS was less than that for S-PFS. ACKNOWLEDGMENTS Soojin Hwang, Jin-Young Kim, Kwi Shik Kim and Sang-A Byun provided support. Professor Ja Hyeon Ku assisted with statistics. REFERENCES 1. Abrams P, Cardozo L, Fall M et al: The standardisation of terminology of lower urinary tract function: report from the Standardisation Sub-committee of the International Continence Society. Neurourol Urodyn 2002; 21: Gleason DM, Bottaccini MR and McRae LP: Noninvasive urodynamics: a study of male voiding dysfunction. Neurourol Urodyn 1997; 16: Ozawa H, Kumon H, Yokoyama T et al: Development of noninvasive velocity flow video urodynamics using Doppler sonography. Part II: clinical application in bladder outlet obstruction. J Urol 1998; 160: Pel JJ and van Mastrigt R: Non-invasive measurement of bladder pressure using an external catheter. Neurourol Urodyn 1999; 18: Oppenheim AV, Willsky AS and Nawab SH: Signals and Systems, 2nd ed. Upper Saddle River: Prentice Hall 1997; p Ku JH, Kim SW, Kim HH et al: Patient experience with a urodynamic study: a prospective study in 208 patients. J Urol 2004; 171: Webster GD and Guralnick ML: The neurourologic evaluation. In: Campbell s Urology, 8th ed. Edited by PC Walsh, AB Retik, ED Vaughan Jr, AJ Wein, LR Kavoussi, AC Novick et al. Philadelphia: WB Saunders 2001; pp Schafer W, Abrams P, Liao L et al: Good urodynamic practices: uroflowmetry, filling cystometry, and pressure-flow studies. Neurourol Urodyn 2002; 21: Rosario DJ, MacDiarmid SA, Radley SC et al: A comparison of ambulatory and conventional urodynamic studies in men with borderline outlet obstruction. BJU Int 1999; 83: Klevmark B: Natural pressure-volume curves and conventional cystometry. Scand J Urol Nephrol, suppl., 1999; 201: Klevmark B: Volume threshold for micturition. Influence of filling rate on sensory and motor bladder function. Scand J Urol Nephrol, suppl., 2002; 210: 6.

CHAPTER 6. M.D. Eckhardt, G.E.P.M. van Venrooij, T.A. Boon. hoofdstuk :49 Pagina 89

CHAPTER 6. M.D. Eckhardt, G.E.P.M. van Venrooij, T.A. Boon. hoofdstuk :49 Pagina 89 hoofdstuk 06 19-12-2001 09:49 Pagina 89 Urethral Resistance Factor (URA) Versus Schäfer s Obstruction Grade and Abrams-Griffiths (AG) Number in the Diagnosis of Obstructive Benign Prostatic Hyperplasia