Air Cystometry

Vol. 100, Oct. Printed hi U.S.A.

THE Jo-cRNAL OF UROLOGY

Copyright© 1968 by The \Villiams & Wilkins Co.

AIR CYSTO:METRY W. BRADLEY, S. CLARREN, R. SHAPIRO

AND

J. WOLFSON

From the Divisions of },T eurology and Neurosurgery ancl Department of Radiology, University of Jfinne.sota H ospilals, Minneapolis, JVIinne.sota

Accurate continuous recording of intravesical pressure in retrograde cyston1etry 1 is impeded by fluid viscous drag artifact in the catheter lumen and orifice. 2 Slow filling of the bladder is necessary to obtain a satisfactory cystometrogram. To reduce the duration of the procedure, discontinuous, rapid, interrupted filling of the bladder with large fluid increments may be performed. 3 However, prominent viscous drag artifacts in the catheter when added to the viscoelastic response of the bladder wall to stretch obscures the cystometrogram obtained. 2 Air as a filling medimn in continuous recording cystometry provides rapid, accurate assessment of reflex contraction without viscous drag artifacts. Reflex induction with air cystometry facilitated roentgenographic visualization of vascular flow patterns and muscle perfusion during reflex detrusor contraction. 4 METHOD

Adult mongrel dogs were used in all experiments. The dog was initially anesthetized with intravenous barbiturate, tracheal intubation was performed and an indwelling Foley catheter was introduced into the bladder. Intravenous gallamine triethiodide* was administered and the dog was placed on a positive pressure respirator. t The Foley bag was filled with water, tugged Accepted for publication October 10, 1967. This work was supported by United States Public Health Service, grants NB 06414 and NB 06055. 1 Mossa, A. and Pellacani, P.: Sur Jes fonctions de la vessie. Arch. Ital. de Biol., 1: 291, 1882. 2 Ruch, T. C.: Central control of the bladder. In: Handbook of Physiology, Sect. 1, Neurophysiology. Edited by H. W. Magoun. Baltimore: The Williams & Wilkins Co., vol. 2, p. 1207, 1960. 3 Langworthy, 0. R., Kolb, L. C. and Lewis, L. G.: Physiology of Micturition: Experimental and Clinical Studies With Suggestions as to Diagnosis and Treatment. Baltimore: The Williams & Wilkins Co., 1940. 4 Markland, C., Chou, Bradley, W., Westproblems in the gate, H. and Wolfson, J.: use of intermittent vesical electronic stimulation. Invest. Urol., 4: 168-173, 1966. * American.Cyanamid Co., Danbury, Connecticut. t Model 600-000, Harvard Apparatus Co., Dover, Massachusetts. 451

gently against the vesical neck and corn1ected to a variable flow rate peristaltic pump. t A Foley catheter balloon was filled with 5 cc of water. Pressure recordings were made use of a strain gauge! and strain gauge amplifier.§ Pressure settings were calibrated iu centimeters of water. This introduced an error in measurement when air was used as a filling medium. The output of the strain gauge was recorded on a chart recorder. II Flow rates of the pump were adjustable from a minimum of 1 cc to a maximum of 97 cc per minute resulting in approximately 2 minutes running time to elicit a reflex with threshold of 200 cc. The bladder was completely evacuated before the first cystometrogram and after each run. Each run varied in time from 1 to 90 miuutes depending upon the filling rate and reflex thres-· hold. Foley catheter sizes varied from 12 to 28 French. For visualization of the detrusor musculature, 15 to 20 cc 90 per cent hypaque1r solution was injected through an indwelling polyethylene catheter placed in the femoral artery ,Yith tip at the aortic bifurcation. Tim.ing of Yesical circulation was made possible by use of a SanchezPerez rapid cassette film changer with 12 films taken at intervals of 1 per second. Delineation of the bladder wall was facilitated by toneal injection of air. Films were taken reflex induction and during detrusor contraction developed by an implanted electronic stimulator. RESULTS

·when sequential cystometrograms ..·ith air and with water were performed in the same animal under similar experimental no significant differences were observed in reflex threshold or amplitude. 1Vhen faster 1mmping rates with air were used, a detrusor reflex was

t Model P23Db, Statham Transducers, Inc., Puerto Rico. § Model 311A, Hewlett Pa,clrnrd, Walthani, Massachusetts. II Model 7100B, Hewlett Pachrd, Pasadena, California. 'I[ Winthrop Laboratories, New York, l\ew York.

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BRADLEY AND ASSOCIATES

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time of approximately 25 seconds with flow rate of 97 cc air per minute. B, similar attempt to obtain cystometrogram with water and flow rate of 97 cc per minute. Viscous drag artifact completely obscures record. Foley catheters were 22 French. rapidly obtained without distortion of the cystometrogram (fig. 1, A). A similar attempt with water was precluded by artifact (fig. 1, B). Slower pumping rates displayed large artifacts when water filling was compared to air (fig. 2). Measurement of viscous drag artifact in the external tubing and catheter was conducted by pumping the filling medium into a balloon at a fixed flow rate. Pressure monitoring with the fluid pumped through the external tubing directly into the balloon indicated the amount of viscous drag in the tubing (fig. 3, A). With the catheter added to the circuit, viscous drag was increased. The lumen of the Foley catheter was narrowed at the balloon site resulting in increase of viscous drag artifacts and turbulence effects. These artifacts were then minimized by the use of air (fig. 3, B). When the detrusor reflex was abolished by deep barbiturate anesthesia, the second tonus limb of the cystometrogram 5 was detectable either by air or by water filling (fig. 4). There was considerable difference in tonus limb appearance however due to viscous drag in the water cystometrogram. The use of air resulted in a more accurate portrayal of the elastic characteristics of the bladder. Air cystometry supplemented by intraperiRuch T. C.: The urinary bladder. In: Physiology and 'Biophysics. Edited by T. C. Ruch and H. D. Patton. Philadelphia: W. B. Saunders, chap. 51, p. 1010, 1965. 5

toneal injection of air resulted in clear delineation of the contour and thickness of the bladder wall (fig. 5). Injection of contrast material into the intravesical circulation further increased this visualization, particularly during the capillary and venous stages of filling (fig. 6). With air outlining the inner and outer walls of the bladder, roentgenograms were secured at I-second intervals during reflex induction as well as during electrical stimulation. The injections of contrast material were timed so that they would be in capillary and venous phase during stimulation. Films taken before and after these procedures were superimposed to study patterns of detrusor contractions. A minimal change in contour with a slight decrease in vertical length and a slight increase in fundus width was observed. A second series of studies was performed with a Sanchez-Perez rapid cassette changer. Contrast material was introduced into the abdominal aorta by an automatic injector and 12 films were secured at the rate of 1 per second. Electrical stimulation of the bladder was begun immediately after the start of injection and continued for the duration of exposures. A comparison of these studies revealed 1) slightly greater opacification of the bladder wall during electrical stimulation and 2) slower transit time of the contrast with electrical stimulation up to a delay of several seconds. DISCUSSION

Discontinuous interrupted injection of air in cystometry has been reported 6 and indicated that reflex induction with air was possible. With the use of modern continuous recording cystometry, air facilitates the acquisition of artifactfree information concerning reflex contraction and detrusor structural change. Some of the factors contributing to fluid viscous drag artifacts in cystometry include the cross-sectional area of the fluid path, length of fluid path, velocity of flow, whether flow is laminar or turbulent, turbulence effects at points of changing diameters and most importantly the viscosity of the fluid. The lower viscosity of air (0.181 vs. 1.005 centipoises for water at 20C) 7 6 Golji, H.: Air cystomanometer. J. Urol., 76: 296-299, 1956. 7 Weast R. C.: Handbook of Chemistry and Physics, '1955--1955_ Cleveland: The Chemical Rubber Publishing Co., 46th edit., 1965.

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454

BRADLEY AND ASSOCIATES

FIG. 5. Anteroposterior view of bladder following introduction of 100 cc air extraperitoneally. Note Foley catheter within bladder and delineation of internal and external surfaces of wall of bladder base.

results in approximately a 6-fold decrease in fluid shearing strains in the catheter lumen and orifice. Dramatic reduction of viscous drag artifact in cystometry is one result of the use of air. Faster pumping rates may be used so that reflex induction may be timed to appear during radiographic procedures. The basic clinical observations to be made from a cystometrograrn. include :2 1) The presence or absence of a micturition reflex and its threshold. 2) The amplitude and duration of the detrusor contractile response. These are a function of the compressibility of the filling medium and the sensitivity of the measuring device. 3) The slope of the tonu: limb or pressure-volume filling curve. This response is a function of the tissue properties of the bladder wall. Its accurate measurement is obscured by viscosity orifice artifacts due to fluid drag when water filling is used. 4) The presence of rhythmic low amplitude intravesical activity clue to intrinsic myogenic contractions. The first observation exceeds the others in order of importance and is obtained rapidly with good prEcision by use of air. :\fore precise methods of measuring the third ob:c;ervation arc available

FIG. 6. A, aortogram following injection of 90 per cent hypaque in femoral catheter. Note filling of arteries supplying bladder and inadequate visualization of detrusor muscle contour. B, film taken approximately 10 seconds following aortogram with 90 per cent hypaque. With increased opacification of bladder wall during capillary and venous phase detrusor muscle perfusion is visualized.

4.5:3

AIR CYSTOMETRY

Fra. 7. A, prior to and B, during induction of bladder reflex with air and capillary phase of filling. Amount of gas within bladder is same in both films. Superimposition of films shows that bladder contour and measurements are altered during reflex. Bladder is shorter in vertical diameter and fund us broader. No vascular perfusion patterns were observed during normal reflex induction.

but require biopsy of the bladder wall.8 As shown in the results, air cystometry gives rapid assessn1ent of a detrusor reflex without serious distortion. In the event that a reflex is absent it is also easier to obtain accurate assessment of bladder tonus limbs and the structural properties of the bladder wall. With fast pumping rates with air there is no significant bladder filling error due to renal filtration Comparison of bladder volume of air to pumped volume indicated no significant leakage of air. This fact may be attributed to the pressures involved and the use of the balloon for vesical neck tamponade. These studies demonstrate that blood flow to the bladder is in1peded \Yith muscle contraction induced by electrical stimulation. It is anticipated that similar delay would be increased in the larger human detrusor. Further work is envisioned quantitating blood flow with varying intensity of stimulation, topography of stimulating electrodes and rate of rise of intensity of electrical stimulation. Further comparison of these results with data secured following induc-

Continuous recording air cystometry 1) offers a more rapid and simple method of determination of a detrusor reflex in bladder filling and 2) inclicatcs that most of the artifacts in water cystometry are due to viscous drag in the external tubing and catheter. In addition it may permit the introduction of radiographic technique~ aimed at assessing; neuromuscular function.

8 Swaiman, K. F. and Bradley, W. E.: Quantitation of collagen in the wall of the human urinary bladder. J. Appl. PhysioL, 22: 122-124, 1967.

Dr. Margaret Francis and Mrs. A. Kuehl helped to prepare the illustrations.

tion of spontaneous reflex would then be performed. There are some specific technical problems which make quantitation difficult: 1) the thinness of the bladder wall and 2) the relatively small blood flow to the bladder. Hence, temporary occlusion of the femoral vessels prior to injection of contrast material undoubtedly would eliminate confusing vascular shadows and provide a clearer view of the bladder wall and its blood supply. This procedure may prove of value in investigation of the effects of bladder denervation and chronic infla1nmation. SU:\IMARY