Several intravaginal manometers aim to measure pelvic floor muscle (PFM) pressure during maximal voluntary contraction, but none, up until now, have the ability to reliably measure intravaginal pressure during a Valsalva manoeuver. The possibility to acquire reliable intravaginal pressures during a Valsalva task is likely to be useful both for understanding the role of intra-abdominal pressure variations on pelvic floor dysfunction such as prolapse or urinary incontinence, and for decision making when choosing PFM safe exercises. The aim of this study is to test the reliability of intravaginal pressure measurements during PFM maximal voluntary contraction and Valsalva manoeuver while lying and standing using the FemFit®, a new intra-vaginal pressure profile device.

Twenty healthy adult women participated in this prospective test-retest cohort study. Exclusion criteria were: pregnancy, pathology or medication likely to interfere with PFM function. One physiotherapist (FR) coordinated three sets of repeated measurements using the FemFit®. For each set, three PFM maximal voluntary contractions and Valsalva manoeuvers were acquired in lying and standing positions. Two sets were done on the same day, with 15 min rest between them (session 1: T1, T2), and a third set was done approximately a month apart (session 2: T3) at the same time of the day (±2 hours) and at the same phase of the women’s menstrual cycle. Participants were asked to not perform PFM training between sessions. 
The FemFit® contains an array of eight pressure sensors (MS5803-02BA, Measurement Specialties, United States), which are mounted onto a flexible printed circuit (FPC) board to allow the device to conform to the anatomy of the vagina. It has a total length of 80 mm, a maximum width of 20 mm and a 4.1 mm thickness, which allow the absolute pressures within the vagina to be measured, without the device imposing a pressure on the vaginal walls (Figure 1). The contoured edges cover a distance of 55 mm and are designed to sit within the rugae of the vaginal wall to reduce device movement. The cover is made out of a soft, biocompatible silicone (MED-4901, NuSil, United States), and cast using a silicone transfer press. Data is transmitted to an Android tablet for data logging and real-time display and user feedback. Each pressure sensor sampled at a rate of 100 Hz. 
Before each measurement session the FemFit® was disinfected, covered with a condom and lubricated with hypo-allergenic gel. The physiotherapist, then, inserted the FemFit® into the participant’s vaginal cavity in an anterio-posterior axis. The device position in the vagina was verified after every task. Further, at the end of the session, women were asked for any discomfort related to the FemFit®. Test-retest reliability on lying and standing positions was assessed using intraclass correlation coefficient (ICC) and Bland-Altman plots. The mean maximum pressure (across sensors 1 to 8) from 3 PFMC/Valsalva trials (for each set and position) was used for the analysis.

Demographics of the participants are summarized in Table 1. One participant was excluded for not being able to follow the physiotherapist instructions and three did not return for the second evaluation for reasons outside of the scope of the study. The FemFit® unit had to be repositioned on two occasions between Valsalva trials, in the lying position and on four occasions between Valsalva trials, in the standing position. No women reported any discomfort during the assessment sessions. 
Among the data set, 45 of the 48 pressure profiles obtained were adequate for analysis. All comparisons showed excellent reliability (intra or inter sessions, Table 2).

Results from this test-retest study indicate excellent repeatability for PFM maximal voluntary contraction and Valsalva both on standing and lying positions within and between sessions. For all PFM maximal voluntary contraction comparisons the repeatability results were reinforced by the Bland-Altman plot analysis, which showed narrow limits of agreement. Similar results were observed for the Valsalva in lying position within and between sessions. However, for the Valsalva task, especially during standing, even though excellent ICC results were observed, a higher difficulty level in measuring this condition was suggested by wider 95% confidence interval and limits of agreement on Bland-Altman plots (spanning 31.3 to 43.3 mmHg). This was confirmed by our observation and need to reposition the unit in the vagina. 
In another reliability study, using a manometer (air-filled silicone balloon) excellent repeatability was also reported for PFM maximum contraction measurements in lying and standing [2]. However, the validity of such measurements can be questioned as the large size balloon will alter the size of the vaginal cavity and therefore could influence the pressure measure as oppose to the proposed device. 
Further, no reliability studies using a manometer were found for Valsalva manoeuvers. In contrary to other types of manometers which would have to be held in place during PFM contraction or Valsalva tasks not to be removed from the vagina, the small size FemFit® was shown never to be displaced during the contraction task and most of the time for the Valsalva tasks, in the lying or standing position.

Our research findings are original as they suggest that intravaginal pressures can be reliably measured during PFM maximal voluntary contraction and Valsalva manoeuver while lying and standing, using the FemFit®. No discomfort was experienced during measurement, and the FemFit remained in position most of the time. Only the Valsalva task, in standing position showed high variability within and between sessions. More research is needed to assess the FemFit validity to characterize intravaginal pressure profiles, distinguishing patterns of pressure distribution corresponding to each task and body position.

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