Lecamwasam H S, Yalla S V, Cravalho E G, Sullivan M P
Division of Urology, Brockton/West Roxbury Veterans Affairs Medical Center, Harvard Medical School, Boston, Massachusetts 02132, USA.
Neurourol Urodyn. 1998;17(6):621-35. doi: 10.1002/(sici)1520-6777(1998)17:6<621::aid-nau6>3.0.co;2-4.
The maximum watts factor (WFmax) is often used to characterize detrusor contractility. It was recently shown that the WFmax may increase in some patients with chronic outlet obstruction. It is, however, unclear whether this increase reflects a dependence of the WFmax on the degree of outlet obstruction or whether it represents a true increase in detrusor contractility secondary to chronic outlet obstruction. Therefore, this study was performed to investigate this issue using a canine model of acute outlet obstruction. Urodynamic studies were performed on adult canines with surgically exposed lower urinary tracts. Pressure transducers were used to measure the intravesical and the distal urethral pressures, whereas an ultrasonic flow meter was used to obtain a simultaneous measure of the urinary flow rate. Detrusor contractions were induced by electrically stimulating the pelvic nerves bilaterally. Varying degrees of outlet obstruction were created using an inflatable sphincter cuff secured around the bladder outlet. The WFmax, the detrusor pressure at voiding terminus (Pdet.clos), and the passive urethral resistance (R) were computed from measured pressure-flow rate data at each degree of outlet obstruction. The WFmax was not significantly correlated to either the sphincter cuff volume (r = 0.025, p = 0.871), the Pdet.clos (r = 0.286, p = 0.073) or the R (r = 0.110, p = 0.509). The WFmax was not significantly different among mild, moderate, and severe degrees of outlet obstruction (p = 0.176). Our results suggest that the WFmax is independent of the degree of acute outlet obstruction (defined in terms of the sphincter cuff volume, Pdet.clos and R). This validates the current practice of using the WFmax to evaluate detrusor function in patients with voiding dysfunction regardless of outlet resistance. Further, since the WFmax is independent of outlet obstruction acutely, it is reasonable that it would also be independent of outlet obstruction under chronic conditions. Our results, therefore, also imply that the increase in the WFmax with chronic outlet obstruction may represent a true increase in detrusor contractility and not a WFmax dependence on outlet resistance.
最大瓦特因子（WFmax）常被用于表征逼尿肌收缩力。最近有研究表明，部分慢性出口梗阻患者的WFmax可能会升高。然而，目前尚不清楚这种升高是反映了WFmax对出口梗阻程度的依赖性，还是代表了慢性出口梗阻继发的逼尿肌收缩力的真正增加。因此，本研究采用急性出口梗阻犬模型对此问题进行了调查。对成年犬进行手术暴露下尿路后进行尿动力学研究。使用压力传感器测量膀胱内压和尿道远端压力，同时使用超声流量计测量尿流率。通过双侧电刺激盆神经诱导逼尿肌收缩。使用围绕膀胱出口固定的可充气括约肌袖带造成不同程度的出口梗阻。根据每个出口梗阻程度下测量的压力-流率数据计算WFmax、排尿末期逼尿肌压力（Pdet.clos）和被动尿道阻力（R）。WFmax与括约肌袖带体积（r = 0.025，p = 0.871）、Pdet.clos（r = 0.286，p = 0.073）或R（r = 0.110，p = 0.509）均无显著相关性。轻度、中度和重度出口梗阻程度之间的WFmax无显著差异（p = 0.176）。我们的结果表明，WFmax与急性出口梗阻程度（根据括约肌袖带体积、Pdet.clos和R定义）无关。这验证了目前使用WFmax评估排尿功能障碍患者逼尿肌功能的做法，而不考虑出口阻力。此外，由于WFmax在急性情况下与出口梗阻无关，因此在慢性情况下它也与出口梗阻无关是合理的。因此，我们的结果还意味着，慢性出口梗阻时WFmax的增加可能代表逼尿肌收缩力的真正增加，而不是WFmax对出口阻力的依赖性。
