Heart Rate Variability as an Indicator Associated With the Improvement of Dysmenorrhea After the Warm-water Footbath

Overview

The effect of warm-water footbath in improving primary dysmenorrhea (PD) was rarely investigated previously. We aimed to exam the hypothesis that warm-water footbath is effective to reduce the pain of PD, and the effect is associated with changes in the autonomic nervous system (ANS) activity. The quasi-experimental study was carried out enrolling 68 college students) with PD. The enrolled participants were randomized into two groups and received interventions (footbath (n=35) versus sitting only (n=33)) for 20 minutes per day on their menstruation days 1 and 2. After the interventions, we analyzed the association among intervention (with footbath versus without footbath), heart rate variability (HRV) changes and changes of pain scales (Pain Visual Analog Scale and short-form McGill Pain Questionnaire).

Dysmenorrhea is the most common gynecological condition affecting 16% to 95% of adolescents and young women, and reduce their quality of life. Primary dysmenorrhea (PD), a term denoting the dysmenorrhea in the absence of underlying pathology, is commonly referred to as period pain or menstrual cramps by the lay press and public. The effect of warm-water footbath in improving primary dysmenorrhea (PD) was rarely investigated previously. We aimed to exam the hypothesis that warm-water footbath is effective to reduce the pain of PD, and the effect is associated with changes in the autonomic nervous system (ANS) activity. This study was approved by the Institutional Review Board of Saint Mary Hospital Luodong (SMHIRB102015). This study with a quasi-experimental design was conducted in a nursing college in Northern Taiwan during the study period from December 1, 2013, to June 30, 2014. Participants were eligible for enrollment if they: (1) were healthy female students aged 16-20 years of the nursing college; (2) had regular menstrual cycles; (3) experienced dysmenorrhea within 6 months before the enrollment; (4) had dysmenorrhea with severity higher than five scores of the pain visual analog scale (PVAS); and (5) had no experience of pregnancy. The exclusion criteria included individuals whom: (1) had irregular menstrual cycles; (2) had circulation problem of legs such as peripheral arterial occlusive disease or deep vein thrombosis; (3) had wounds or skin lesions over legs; and (4) had taken any medications which affect ANS activity. The suggested participant's number estimated by the G-Power was 34 when setting the calculated power as 0.8 and α as 0.05. Considering participant loss during the study process, we decided to enroll 68 participants. All enrolled participants were randomized into the footbath group (n=35) and control group (n=33). The baseline demographic data, as well as relevant information about menstrual cycles and dysmenorrhea of all participants, were documented at enrollment. All the participants were arranged to stay in an air-conditioned, quiet room from 5:30 to 6:30 p.m. on their menstruation days 1 and 2. After sitting quietly for 20 minutes, the participants in the "footbath group" received legs soaking from the heel to the Sanyinjiao (SP6) acupoint (above the ankle) 24 in 42 ℃ water with air bubbles and vibration given to the soles for 20 minutes, whereas the participants in the "control group" kept on sitting quietly without legs soaking during the additional 20-minute period. PVAS and Short-Form McGill Pain Questionnaire (SF-MPQ) were fulfilled as pain assessment by all participants twice, including a "pre-test" before the intervention of menstruation day 1 and a "post-test" after the intervention of menstruation day 2. HRV was measured at four time points (before and immediately after the interventions on days 1 and 2) to assess ANS function for all participants. The interventions were "warm-water footbath for 20 minutes" for the "footbath group" and "sitting quietly without footbath for 20 minutes" for the "control group." Then we evaluated the influence of warm-water footbath on dysmenorrhea and several variables, including HRV indices and stiffness index.