Pressure/cross-sectional area relations in the proximal urethra of healthy males Part III: The time dependent pressure response following forced dilation: standardization of a technique

Abstract

The urethral response to a sudden forced dilation was studied in ten healthy male volunteers aged from 27 to 71 years. Measurements were performed from the bladder neck and beyond the region of high pressure using a specially designed probe. The pressure response after dilation showed a characteristic course, which could be described by a double exponential function of the form: P(t) = P(equ) + P(alpha)e(-t/tau(alpha) + P(beta)e(-t/tau(beta) where P(t) is pressure at time t, P(equ) is equilibrium pressure after dilation, P(alpha) and P(beta) are pressure decay, and tau(alpha) and tau(beta) are time constants. The size and velocity of dilation, as well as the degree of distension before dilation, proved of significance for the magnitude of the pressure response. The characteristics of the pressure response are given by the properties of the periluminal structures strained during dilation, and are thus predominantly determined of elastic, collagen, muscular, and glandular components. However, a high degree of relaxation after straining, and a modest stiffness, indicates that the muscular component dominates the response. The significance of the prostatic tissues remains unclear.

Urethral pressure reflectometry; a novel technique for simultaneous recording of pressure and cross‐sectional area: a study of feasibility in the prostatic urethra

“…Pressure and elastance recordings show the same tendencies as reported in most of the earlier trials on healthy volunteers from our centre [5–9], with both values increasing steadily from the bladder neck to the sphincter area. The overlapping values of pressure from the prostate to the sphincter area were primarily caused by two of the patients with indwelling catheters.…”

“…Another reason for choosing this method is that our velocity rates are low. The highest rate tested during this trial was approximately 10 mm 2 /s (20 cmH 2 O/s) compared with earlier trials where the lowest rate was 50 mm 2 /s [ 6,23,24 ] . When we take into account that our highest rate was abandoned, the lowest rate in the earlier trials was a minimum of 10 times higher than the highest rate in our trial.…”

“…Most earlier trials with simultaneous measurement of P and CA in the urethra were performed as stress–relaxation, a technique where the urethra is opened with fast dilations to a certain level of CA. Stabile pressure is awaited, and a new fast dilation is made with the same level of CA after which stabile pressure is awaited again [6,7,21,22]. We chose to use a steady inflation/deflation cycle.…”

“…In theory, a probe like that may show exactly where the urethra is obstructed, contrary to indirect measurements with pressure‐flow, and subsequently make treatment more direct and localized, giving a smaller surgical trauma and hopefully fewer side effects from surgery. One such method, which allowed simultaneous measurement of P and CA directly in the resting male urethra, seemed promising in giving a better understanding of BPO [4–9]. However, it was never implemented in the clinical setting or commercialized, primarily because the catheters were large and stiff, could only measure the CA 2 mm at a time and in the range from 11 to 102 mm 2 .…”