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Abstract:

In the field of dermatology, non invasive aspiration devices that can measure the biomechanical properties of skin are clinically used. They are presumed to measure properties of the dermal component of the skin, consisting of collagen and elastin fibers. It seems logical that these devices could be applied for similar measurements at the level of the vaginal wall. One such device (DermaLab skin probe; Cortex Technology, Hadsund, Denmark) has already been used for that purpose. The aspiration device, has a diameter of 2cm and a height of 1.5cm. The probe suctions at a preset vacuum pressure the vaginal wall into an opening of a 10 mm diameter (=aperture). During this process it measures the actual pressure (stress) and vaginal wall displacement (strain). In Epstein’s study (1),a single location was measured, i.e. on the left lateral vaginal wall, 2cm above the hymenal ring. That device was not designed for intravaginal use, so that we searched for an alternative. Also, a 10 mm aperture may cause aspiration of compliant vaginal tissue into the probe, causing uninterpretable recordings. Last, prolapse is a site specific condition so that one may need site specific measurements. Herein we tested a prototype device, derived from the Cutometer MPA 580 (Courage and Khazaka Electronic GmbH, Cologne, Germany). This device which is designed for intravaginal use, has a length of 20 cm and the largest diameter of the device is 3 cm. It’s prototypes have either a 6 or 8 mm aperture. Study design, materials and methods In total 45 consecutive patients, referred for pelvic floor ultrasound with a variety of pelvic floor problems, first underwent clinical assessment using the POP-Q classification. This was followed by a first elasticity measurement (aperture:6mm), whereafter the pelvic floor ultrasound was done, followed again by a second measurement (aperture:8mm). First outcome variable was the ability to introduce the probe for measurement. If it failed, the reason for it was noted. If successful, a typical vaginal elasticity measurement consisted of a single cycle with an aspiration pressure of 300 mbar, an aspiration pressure comparable to dermal measurements. Both suction and relaxation time consist of 5 sec after an initial 10 sec pretime without aspiration. The measurements were taken at four places: two on the anterior vaginal wall, at point Aa and 5 cm above the hymenal ring (=Aa-2 cm), and two on the posterior wall, at point Ap and 5 cm above the hymenal ring (=Ap-2 cm). The Cutometer MPA580 software displays a series of plots and parameters (=recording), among which R0: firmness of the vaginal wall; R2: overall elasticity and R7: ratio of elastic recovery to the total deformation, which are representative for the entire measurement. After measurement, the recording was judged to be interpretable or not, based on its quality. If not, up to three attempts were made to obtain a better recording. In its absence, the entire measurement for this location was classified as failed. Descriptive statistics and factor analysis were done using, JMP®7 software (SAS Institute Inc., Cary, NC, 2007). Factor analysis allows to determine which experimental conditions affect the measurements in a significant way and which experimental conditions could be considered as irrelevant. Results Introduction failure: of the 45 patients (range 28-83yrs ) enrolled, in 11 patients (24.4%) the probe could not be inserted either because of pain or discomfort (n=8) or because of vaginal bleeding that particular day (n=3). Though at first glance invasiveness of elasticity measurement is no different from that of transvaginal ultrasound, the need for measurements without lubrification gel in an atrophic vagina of a patient without prolapse is difficult (failure rate in ≤grade I resp. grade II+ prolapse: 15.5% vs. 0%: p0.003). Once the elasticity measurement probe could be introduced, the second insertion, after the pelvic floor ultrasound was always successful. Measurement failure and interpretable results: This left us with 34 patients, and up to 4*34=136 measurements with the 6 mm resp. the same for the 8 mm device. Elasticity measurements typically took less than 5 min. The usability of the recordings with each of the apertures are displayed in table 1. The overall usability rate of recordings was (165/272; 60.66%), but that with the 6 mm aperture device were more frequently usable than those with the 8 mm.