Peak expiratory flow rate and thoracic mobility in people with fibromyalgia. A cross sectional study

Background and aims: Fibromyalgia (FM) is characterized by chronic widespread pain and affects approximately 1-3% of the general population. Respiratory function has not been given much consideration in people with FM. Few studies have been published concerning FM and respiratory function and conflicting data still exist. The aim of this study was to compare differences in forced expiration, but also to investigate chest expansion, spinal mobility and segmental pain intensity between a group with fibromyalgia and healthy controls.

Methods: Forty-one women with diagnosed FM based on American College of Rheumatology 1990 criteria and forty-one controls without pain matched for age and gender participated in this cross-sectional study. For evaluation of forced expiration, a Wright peak expiratory flow rate meter was used. A tape measure was used to measure the mobility of the thorax at maximum inhalation and exhalation known as chest expansion. Spinal mobility was measured with the Cervico-thoracic ratio method. The spinal mobility was measured as range of motion from C7 to 15 cm below in flexion and manual palpation was conducted between C7-T5. For differences in pain intensity a palpation-index was defined for each level, respectively; C7-T1, T1-2, T2-3, T3-4 and T4-5 by calculating the mean value for the four different palpation points for each motion segment. A combined measure of expiration and thoracic mobility (expiratory/inspiratory ratio) was calculated by dividing peak expiratory flow rate (L/min) with chest expansion (cm). Statistical analyses included descriptive statistics to describe subjects and controls, means and standard deviation to compare differences between groups and student-t and Chi-square (χ²) tests, using SPSS 22 software. Confidence interval was set to 95%.

Results: In the FM group 17 had the diagnosis for more than 5 years and 24 less than 5 years. The FM group demonstrated significantly lower forced expiration (p < 0.018), less thoracic expansion (p < 0.001), reduced spinal mobility (p < 0.029), higher expiratory-inspiratory ratio value (p < 0.001) and increased palpation pain over C7-T5 (p < 0.001) compared to healthy controls. There were more smokers in the FM group (n = 9) compared to the controls (n = 5) though this difference was not statistically significant (p < 0.24) and excluding the few smokers yielded similar result. No significant correlations for manual palpation, chest expansion, peak expiratory flow rate and spinal mobility were found in the FM group.

Conclusions: Women with FM demonstrated significantly lower forced expiration and thoracic mobility compared to healthy controls.

Implications: The results of this study point to a plausible restriction of respiratory function which in turn may have effect on physical endurance and work capacity in people with FM.