1 Introduction
Dysfunction of pelvic floor muscle (PFM) is associated with stress urinary incontinence (SUI), anal and fecal incontinence, pelvic organ prolapse (POP), and sexual dysfunction, which will negatively affect quality of life (QOL) in women.[1] [2] [3,4] [5] [6] [7] [8,9]
The PFD can be managed by surgical and conservative therapy. Women with symptomatic PFD who fail or decline conservative therapy are candidates for surgery. Surgical repairs of PFD result in improved prolapse-related symptoms and QOL in most cases.[10,11] [12] [13,14] [15–17] postpartum women with extremely weak muscle strength who were unable to do conventional contraction. Electrical stimulation (ES) is an alternative method for enhancing PFM strength, especially in muscles severely compromised. As a passive treatment, transvaginal ESs (TVESs) use electrodes directly stimulate the PFMs. Subtle different from TVES, electromyogram (EMG)-triggered neuromuscular stimulation is a mode of passive stimulation combined with voluntary PFMT. It requires subjects to voluntarily generate sufficient pelvic muscle activity to a target threshold, then assisting ES begins as soon as EMG activity reaches the target threshold.[18] [19,20] [21,22] [23] [24]
However, the effect of ES on muscle strength of pelvic floor was not settled.[25,26] postpartum women with extremely decreased muscle strength who have difficulty in voluntary PFMT, whether the early onset of involuntary PFMT is required is still need to be discussed. Moreover, optimal protocol for integrating passive ES with active pelvic muscle training has not yet been well established. Hence, we conducted a single-blinded randomized controlled trial (RCT) to evaluate the effect of different protocols in the ES treatment of postpartum women with extremely weak muscle strength. The aim of this single-blinded RCT was to compare the short-term effects of different protocols of ES in postpartum women .
2 Materials and methods
2.1 Population
Sixty-seven postpartum women were successively enrolled at our departments from April 2018 to June 2018. Standardized assessment of extremely weak muscle strength was performed at enrollment. Postpartum women aged 20 to 42 at 7 to 14 weeks after delivery or cesarean section were eligible to participate if they meet the inclusion criteria: postpartum women with weakness of PFM, with or without SUI during pregnancy or after delivery, and POP which is diagnosed according to the International Continence Society and International Urogynecological Association.[1] postpartum women refer to muscle strength at level 0 to 1 measured by via vaginal palpation according to modified Oxford scale.[27]
Major exclusion factors were patients who have overactive pelvic floor dysfunction: urinary retention, constipation, pelvic pain, vulvar pain, and dyspareunia; POP of stage III and stage IV; chronic diseases of nerve and muscle function (such as multiple sclerosis, Parkinson disease myasthenia gravis, etc); malignant tumor, diabetes, and other serious medical diseases; pelvic radiation rectal surgery, spinal surgery, hysterectomy; pelvic inflammation, urinary tract infection and vaginitis; cardiac pacemaker implantation; pregnancy; cognitive impairment; refuse to accept clinical observation. This research was approved by the Ethics Committee of the Women's Hospital School of Medicine Zhejiang University, Hangzhou, China (ID 20170126), and informed written consent was obtained from all participants. This study had been registered in Chinese Clinical Trial Registry (ID ChiCTR-IOR-17013442).
2.2 Treatment and study design
This prospective, single-blinded RCT was conducted in Women's Hospital School of Medicine Zhejiang University. After an initial screening visit, women were randomly assigned to one of the 2 therapy groups on the basis of computer-generated random number. Randomization was performed by concealing the allocations in sequentially numbered, opaque, sealed envelopes. Once enrolled by a physician investigator, eligible volunteers were randomized in 2 groups using a computer-generated randomization list: group A, TVES for 5 times; group B, TVES for 3 times and EMG-triggered neuromuscular stimulation for twice. Vishee neuromuscle stimulator (MyoTrac Infiniti, model SA9800; Thought Technology Ltd, Montreal, Canada) and surface EMG electrode (type VET-A, produced by Nanjing Vishee Medical Technology Co., Ltd, Nanjing, China) were used for ES. Subjects were positioned supine with 45° of hip and knee relaxed and abducted. Electrode was placed in the vagina of the patients. Intravaginal electrode with 2 independent channels was previously cleaned and inserted. The electric parameters for TVES and EMG-triggered neuromuscular stimulation (constant current generator): biphasic pulse, frequency 50 Hz, pulse width was 250 microseconds, time 25 minutes, time on:off 4:8, current intensity: maximal level tolerable.[28] [26] α (2-sided) was 0.05 and the type II error ratio β was 0.1. The sample size calculation was performed using PASS software. Result showed that the sample size was 60; therefore, 67 enrolled patients were enough for this study.
2.3 Measurements
A blinded experienced physiotherapist performed evaluations of pelvic muscle strength via both digital palpation and EMG. Patients were evaluated in the lithotomy position after micturition, with straight knees and leg abducted and instructed to relax the PFM. Muscle strength and questionnaire investigation were given to the subjects before and after the 5 times intervention.
2.4 Digital palpation
Physiotherapists assess PFM strength during vaginal as posed by Laycock and Jerwood.[27]
2.5 Surface electromyography
Neuromuscle stimulator and intravaginal electrode for surface EMG evaluation was described as before. Two channels were connected to a disposable intravaginal electrode for recording electrical activity of PFM construction. Other 2 electrodes were placed in region of abdominal rectus muscles (one on the right side and the other on the left side) to monitor crosstalk of contraction of the abdominal muscles. The EMG chart indicated activity of the abdominal muscle compatible with rest (EMG scale between 0 and 5 μV) is considered as correct PFM contraction. The EMG for pelvic floor evaluation used Glazer protocols following 5-segment assessment sequence: prebaseline for 1 minute rest, muscle electrical signal recorded as mean value of initial rest (pre-mean); 5 rapid contractions with 10 seconds rest between each flicks, recorded as max value of fast contractions (flick-max); five 10 seconds contractions with 10 seconds intervals between each contractions, recorded as mean value of 10 seconds sustained contractions (tonic-mean); endurance, single 1 minute contraction recorded as mean value of 60 seconds sustained contractions (edu-mean); post baseline for 1 minute rest, recorded as mean value of final rest (post-mean).[29]
2.6 Questionnaires
Pelvic Floor Impact Questionnaire Short Form (PFIQ-7), Pelvic Floor Distress Inventory-short form 20 (PFDI-20), and Prolapse and Incontinence Sexual Function Questionnaire Short Form (PISQ-12) were investigated by self-administered method. Patients who undergo stress urinary continence during pregnancy or after delivery were required to complete Incontinence Impact Questionnaire (IIQ-7). If there is any omission during the inspection, the patient will be required to replenish. All subjects completed questionnaire investigation and uploaded the pictures of their EMG reported by “Penyikang” app designed by our research group (no 2017016 and no 2017850 of the computer software works of People's Republic of China Copyright Administration).
2.7 Statistical methods
Data were collected by app of “Penyikang.” We analyzed data according to the intention-to-treat (ITT) as well as per protocol (PP) principle. Women who were randomized, but never started or completed treatment were included for the ITT analyses. However, those women were excluded for the PP analysis. All analyses were conducted on an ITT basis for all efficacy variables. Data from the subjects who had a baseline and postbaseline measurement were included. Quantitative data were expressed as the mean ± standard deviation, including age, body mass index, history of gestation, value of EMG and result of questionnaire, and compared by t test for 2 groups. Numeration data were described as percentage, including change of muscle strength by digital palpation and incidence of correct PFM contraction compared by Chi-squared test. Analysis was executed by SPSS V11.0 (SPSS, Chicago, IL). Statistically differences between groups were tested at a 2-sided with significance level of .05.
3 Results
Flowchart of Figure 1 is given showing the disposition of subjects: group A, n = 34; group B, n = 33. Volunteers were included while 25 of whom withdrew from this single-blinded RCT. Most common cause for withdrew is busy baby-care and unwilling for continuing hospital-based treatment. The anthropometric characteristics are described in Table 1 , no statistically significant had been detected between group A and group B. T test showed no significant differences of EMG and questionnaire result between the 2 groups at the initial of the study (Table 2 ). One of the patients in group A had a history of twin pregnancy, the others were all singleton. Review of baseline data from these groups of all subjects for whom any of these data were available did not disclose evidence of randomization imbalance. After 5 times treatment, questionnaire and muscle strength by both digital palpitation and EMG have been tested. All subjects were interviewed about discomfort that had occurred during follow-up, the most common problem was the increase of vaginal discharge which is considered endurable by subjects.
Figure 1: Flowchart of subject disposition in the trial. ES = electric stimulation, TVES = transvaginal electric stimulation, EMG = electromyogram , PFM = pelvic floor muscle, PFIQ-7 = Pelvic Floor Impact Questionnaire Short Form, PFDI-20 = Pelvic Floor Distress Inventory-short form 20, PISQ-12 = Prolapse and Incontinence Sexual Function Questionnaire Short Form, IIQ-7 = Incontinence Impact Questionnaire.
Table 1: Clinical characteristics of subjects.
Table 2: Comparison of EMG for evaluable subjects.
After 5 times treatment, ITT analysis of digital palpation showed 32% of patients in group A and 18% of patients in group B have elevated muscle strength, respectively (P = .36). PP analysis also found no significant difference in the change of muscle strength (group A vs group B, 45% vs 33%, P = .53).
Table 2 manifests EMG value between the 2 groups during the study. Both groups have elevated EMG valued in flick, tonic, and endurance phase after treatment, but no significant difference had been detected between group A and group B after treatment according to ITT and PP principle. Significant difference of EMG between baseline and endpoint were seen in group A: mean value of contractile amplitude in endurance phase is significantly elevated (Table 2 ); the muscle at tonic phase is more stable than baseline (Table 2 ). Mean value of final rest was significantly elevated after treatment in group A in PP analysis but no in ITT analysis (Table 2 ). Changes of EMG in group B compared with baseline have no significant difference.
At the end of follow-up, no significant difference of questionnaire had been detected between baseline and after treatment in 2 groups according to both ITT and PP principles (Table 3 ). After 5 times treatments, the incidence of correct PFM contraction in group A was both significantly elevated (baseline vs after treatment, ITT analysis, 26% vs 50%, P = .04; PP analysis, 38% vs 71%, P = .02). While in group B, significant difference had only been detected in PP analysis (baseline vs after treatment, ITT analysis, 21% vs 45%, P = .07; PP analysis, 39% vs 83%, P = .01). Although percentage of incidence of correct PFM contraction was elevated in both groups A and B, no significant difference had been found between these 2 group (group A vs group B, P = .57).
Table 3: Comparison of questionnaire for evaluable postpartum women .
4 Discussion
For patients suffered from PFD, loss of muscle strength and its related symptoms bring them declined QOL and cost significant socioeconomic impact. ES is one of the conservative options which available for managing dysfunction of PFM with mild symptoms.[13,14] [19,20] postpartum women with extremely weak muscle strength.
The TVES is a safe and effective choice for elevated muscle strength, and our study also found the most common adverse effect is the increased vaginal fluid which did not serious disturb subjects. Discussions regarding TVES in PFD treatment have dominated research in recent years. Lack of a clear biologic rationale obstruct reasoned choice of ES parameters might contribute to the difficulty of evaluating potential value and benefits of TVES.[30] [28,31] [32]
This study demonstrated that short-time treatment of ES could ameliorate weak muscle strength measured by digital palpation in both groups but no significant difference between 2 groups. The effect of ES treatment on pelvic muscle strength from previous studies is uncertain. For patients with SUI, high qualified research analyzed whether the ES was effective than no treatment: Pereira et al conducted a pilot RCT to treat SUI women over 60 years with surface ES for 6 weeks with 2 weekly sessions of 20 minutes each, did not discovered any significance in PFM pressure between ES group and no treatment[25] [26] [33] postpartum women with extremely weak muscle, both protocol of ES could elevate muscle strength but no significant difference between these 2 protocols. Our study included postpartum women who are in childbearing age and just 7 to 14 weeks after delivery or cesarean section, difference of subject selection might explain the different result from previous study. As digital palpation considered to be subjective and not sufficiently sensitive by some researchers,[34,35]
The Glazer protocol is an electrical physiologic approach integrated with EMG amplitude and standard deviation of pelvic muscle for each contraction and relaxation period for measuring. It had been proven to be reliable and consistently predictive tool in detection and prophylactic intervention for PFD.[36] postpartum women with PFD, another multicenter, single-blinded, randomized trial had been carried out to evaluate ES treatment in pelvic floor rehabilitation in postpartum, they also found TVES could obviously improve pelvic floor electrical physiologic index compared with PFMT group in postpartum 6 and 12 months.[9]
In patients with vulvar vestibulitis syndrome, biofeedback could release vulvar vestibular pain and decreased resting tension levels of EMG.[29]
In clinical trials, QOL has become an important outcome measure. We investigated subjects by 4 kinds of questionnaire before and after ES treatment, and did not discover any significance after treatment. Although applied different investigation tool from our study, previous RCTs both derived that compared with no active treatment, ES could significant improvement QOL in SUI patients.[25,26,33] [24] postpartum women with dysfunction of PFM.[9,33] postpartum women who had been investigated by the same questionnaires. PFD is a chronic disease with long treatment time. Take SUI for example, the guide recommends PFMT for at least 12 weeks.[17]
In postpartum women with SUI, pelvic-floor rehabilitation is recommended.[37] [38] [39]
In conclusion, this study demonstrates that for postpartum women with extremely weak muscle strength receive ES treatment, TVES for 5 times might be more benefit for control ability of pelvic muscle contractions and elevating muscle strength even in short-time treatment. More RCTs with sufficient sample sizes and long-term follow-up are still needed for further study.
Author contributions
Conceptualization: Fengxian Shen.
Data curation: Zhujuan Zhang.
Formal analysis: Fengxian Shen.
Funding acquisition: Zhenwei Xie.
Investigation: Qing Hu, Zhujuan Zhang.
Methodology: Wenjuan Li.
Software: Fengxian Shen.
Supervision: Zhenwei Xie.
Writing – original draft: Wenjuan Li.
Writing – review & editing: Qing Hu, Zhenwei Xie.
Zhenwei Xie orcid: 0000-0001-5996-390X.
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