Lovegrove Jones, Ruth C., Peng, Qiyu, Stokes, Maria, Humphrey, Victor F., Payne, Christopher and Constantinou, Christos E.
Mechanisms of pelvic floor muscle function and the effect on the urethra during a cough
European Urology, 57, (6), . (doi:10.1016/j.eururo.2009.06.011).
Background: Current measurement tools have difficulty identifying the automatic
physiologic processes maintaining continence, and many questions still remain
about pelvic floor muscle (PFM) function during automatic events.
Objective: To perform a feasibility study to characterise the displacement, velocity,
and acceleration of the PFM and the urethra during a cough.
Design, setting, and participants: A volunteer convenience sample of 23 continent
women and 9 women with stress urinary incontinence (SUI) from the general
community of San Francisco Bay Area was studied.
Measurements: Methods included perineal ultrasound imaging, motion tracking
of the urogenital structures, and digital vaginal examination. Statistical analysis
used one-tailed unpaired student t tests, and Welch’s correction was applied when
variances were unequal.
Results and limitations: The cough reflex activated the PFM of continent women to
compress the urogenital structures towards the pubic symphysis, which was
absent in women with SUI. The maximum accelerations that acted on the PFM
during a cough were generally more similar than the velocities and displacements.
The urethras of women with SUI were exposed to uncontrolled transverse acceleration
and were displaced more than twice as far ( p = 0.0002), with almost twice
the velocity ( p = 0.0015) of the urethras of continent women. Caution regarding
the generalisability of this study is warranted due to the small number of women in
the SUI group and the significant difference in parity between groups.
Conclusions: During a cough, normal PFM function produces timely compression
of the pelvic floor and additional external support to the urethra, reducing displacement,
velocity, and acceleration. In women with SUI, who have weaker
urethral attachments, this shortening contraction does not occur; consequently,
the urethras of women with SUI move further and faster for a longer duration
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