Does an innovative vaginal biofeedback device accurately compare with real-time transperineal ultrasound for measuring the direction of urethral movement?
Optimal voluntary pelvic floor muscle contraction (VPFMC) has lift and squeeze components; however, there are no validated tools in physiotherapy practice that provide biofeedback for both simultaneously. This study compares a vaginal biofeedback (VBFB) device containing a tri-axial accelerometer and a force-sensitive resistor with real-time transperineal ultrasound (TPUS) with respect to measuring the direction of urethral movement. Fifteen asymptomatic adult females were recruited for the study, and data collection in private physiotherapy practice was approved by a university research ethics committee. Pelvic floor muscle strength was assessed vaginally using the modified Oxford scale (MOS). Using simultaneous
TPUS and VBFB, five maximal VPFMCs and five Valsalva manoeuvre images were captured on TPUS, and the angles of proximal urethral inclination (PUI) and internal urethral meatus position (IUMP) were measured. The VBFB device stored pitch angle and force (N) measurements on its online database. Primary outcomes (pitch and PUI) were compared for percentage agreement and agreement using Cohen’s kappa coefficient (κ). correlations between pitch, PUI, N, IUMP and the MOS were assessed using Spearman’s rho (ρ) (P < 0.01). Subgroups of VPFMC and Valsalva were similarly analysed. Strong agreement (95.33%, κ = 0.92) and correlation (ρ = –0.653, P < 0.01) were found between VBFB (pitch) and TPUS
(PUI). The agreements between pitch and PUI were 96% and 94.67% for VPFMC and Valsalva, respectively. Secondary outcomes demonstrated significant (P < 0.01) correlations between IUMP, and both PUI (ρ = 0.669) and pitch (ρ = –0.673). Pitch and PUI both correlated for VPFMC (ρ = 0.384). Pitch correlated with MOS (ρ = 0.422) and N (ρ = 0.318) for VPFMC, and with N for Valsalva (ρ = –0.534). Proximal urethral inclination was associated with IUMP (ρ = 0.504) for Valsalva. The VBFB device exhibited high levels of agreement and significant correlation with TPUS in the assessment of the direction of urethral movement.
Keywords: biofeedback, pelvic floor muscle exercises, transperineal ultrasound.