Rao Soujanya G, Walter James S, Jamnia Ali, Wheeler John S, Damaser Margot S
Research Service, Hines VA Hospital, Hines, Illinois, USA.
Neurourol Urodyn. 2003;22(4):277-83. doi: 10.1002/nau.10120.
Mathematical models are useful for developing predictive parameters for characterizing the biomechanics of voiding dysfunction. The goal of this project was to test a one-dimensional steady flow model used to predict the minimum cross-sectional urethral area from urodynamic data.
Nine adult female subjects underwent video-urodynamic testing. By using Bernoulli's formula and the Torricelli theorem, the minimum urethral area was predicted from pressure and flow rate at the moment of maximum flow rate during voiding. This prediction was compared with the minimum cross-sectional area of the urethra, which was calculated from minimum urethral diameter as measured from fluoroscopy, assuming a circular cross-section.
The maximum flow rate during voiding was 14.4 +/- 3.0 mL/sec. Mean bladder, abdominal, and detrusor pressures simultaneous with maximum flow rate were 63 +/- 7, 29 +/- 6, and 33 +/- 6 cm H(2)O, respectively. Mean minimum cross-sectional area of the urethra from fluoroscopy was 8.0 +/- 2.0 mm(2). Mean minimum cross-sectional area of the urethra predicted by the mathematical model was 5.0 +/- 1.0 mm(2) using bladder pressure and 7.0 +/- 2.0 mm(2) using detrusor pressure. There were no significant differences between the three cross-sectional area measures. However, when area predictions were expressed as percentage of fluoroscopic measurements, the estimate from detrusor pressure (97 +/- 13%) was significantly larger than the estimate from bladder pressure (69 +/- 7%).
A steady flow model is accurate enough on average to describe urine flow in the urethra. However, it may not be sufficiently accurate to aid in diagnosis of individuals.
数学模型有助于开发用于表征排尿功能障碍生物力学的预测参数。本项目的目标是测试一种一维稳定流模型，该模型用于根据尿动力学数据预测尿道最小横截面积。
9名成年女性受试者接受了影像尿动力学检测。利用伯努利公式和托里拆利定理，根据排尿过程中最大尿流率时刻的压力和尿流率预测尿道最小面积。将该预测结果与尿道最小横截面积进行比较，后者是根据荧光透视测量的最小尿道直径计算得出的，假设尿道横截面积为圆形。
排尿过程中的最大尿流率为14.4±3.0毫升/秒。与最大尿流率同时测得的平均膀胱压、腹压和逼尿肌压分别为63±7、29±6和33±6厘米水柱。荧光透视测得的尿道平均最小横截面积为8.0±2.0平方毫米。数学模型使用膀胱压预测的尿道平均最小横截面积为5.0±1.0平方毫米，使用逼尿肌压预测的为7.0±2.0平方毫米。这三种横截面积测量结果之间无显著差异。然而，当将面积预测值表示为荧光透视测量值的百分比时，逼尿肌压的估计值（97±13%）显著大于膀胱压的估计值（69±7%）。
稳定流模型平均而言足够准确，可以描述尿道中的尿流情况。然而，它可能不够准确，无法辅助个体诊断。
