2.2 Pressure-flow study and pressure-volume analyses
Our protocols of cystometry complied with the guidelines of the International Continence Society (ICS).20 Briefly, a multi-channel urodynamic study, in which warm saline (37 °C) was infused (80 ml/min) into patients’ bladder, was recorded (MMS UD-200, Medical Measurement System, Enschede, Netherlands) and analyzed (Biopac MP36, Biopac Systems, Santa Barbra, US) using computer systems. The vesical pressure (Figure 1A Pves), abdominal pressure (Pabd), detrusor pressure (Pdet), urethral flow (Flow), voided volume (Vvod), infused volume (Vinf), and intra-vesical volume (Vive) were online recorded; and the mean voiding pressure (Figure 1B Pv; the mean Pdet during fluid emission), the voided volume (Vv; the volume of emitted fluid), the voiding time (Tv; the time latency of fluid emission), and the mean voiding resistance (Rv; calculated by Pv/(Vv/Tv)) were off-line analyzed.
Derived from the cystemetry (Figure 2A), the pressure-volume analysis (PVA) of the voiding cycle was established by plotting Pdet against Vive (Figure 2B);18,21 and the trajectory-enclosed area (Apv) was analyzed using an image processing program (Image J, LOCI, Madison, WI, USA).
Although cough and Valsalva tests markedly interfere Pves and Pabd, a previous publication22 and our data (Figure 1A) demonstrated these tests displayed little effect on the Pdet in the cystometry. Moreover, our data discovered cough and Valsalva maneuver impacted trivially on the trajectory of PVA. In addition, cough and Valsalva tests were carried out during the storage phase in our protocol that would hardly affect the voiding dynamics. Therefore, cystometry data of SUI patients who underwent stress tests (coughs and/or Valsalva) were pooled together with those cystometry data without these tests.