Differences of diaphragmatic muscle contraction between female patients with chronic neck pain and asymptomatic controls: A case-control study based on ultrasonography.

ABSTRACT

BACKGROUND: Recent systematic reviews and meta-analyses show that individuals with chronic neck pain (CNP) have altered respiratory muscle strength and abnormal respiratory mechanics. However, no study has investigated the diaphragmatic function in individuals with CNP compared to asymptomatic peers. OBJECTIVES: This study aimed to compare the respiratory muscle strength and diaphragmatic function between patients with CNP and asymptomatic controls. DESIGN: Observational, case-control study. METHODS: A total of 25 women with CNP and 23 asymptomatic controls participated in this case-control study. The visual analog scale and neck disability index were used to assess the pain and disability characteristics of the CNP group. Maximum inspiratory and expiratory pressures (MIP and MEP) were measured to determine respiratory muscle strengths. The diaphragmatic function (muscle thickness in deep inspiration, Tins; and at the end of calm expiration, Texp; muscle thickness change, ΔT; contraction ratio, CR) were evaluated by two-dimensional ultrasonography. RESULTS: The MIP (p = 0.001, d = 1.11), ΔT (p = 0.033, d = 0.63), and CR (p = 0.012, d = 0.75) of the diaphragm were found significantly reduced in the CNP group compared to asymptomatic controls whilst MEP, Tins, and Texp of the diaphragm were similar between study groups (p > 0.05). The intensity of neck pain was moderately correlated with MIP (r = -0.48), Tins (r = -0.46), and ΔT (r = -0.42) while NDI (r = -0.42) had a moderate correlation with Tins (p < 0.05). CONCLUSION: The present findings revealed that women with CNP have altered diaphragmatic function. Thus, screening and targeting diaphragm may improve the rehabilitation process in CNP. However, further experimental studies regarding the efficacy of breathing exercise approaches are needed.