SAT0720-HPR PULMONARY FUNCTIONS AND RESPIRATORY MUSCLE PERFORMANCE CORRELATE WITH NIGHT PAIN IN PATIENTS WITH ANKYLOSING SPONDYLITIS COMPARED TO CONTROLS

Abstract

Background: In ankylosing spondylitis (AS), chronic systemic inflammation mainly affects the axial skeleton and involvement the costovertebral and costotransvers joints results in limitation of thoracic and spinal mobility (1,2). There is no study published to evaluate the endurance and strength of respiratory muscle and to investigate the relationship with pain. Objectives: The aim of the study was to investigate the functional status, quality of life, pain, pulmonary function, respiratory muscle strength and endurance patients with AS and compare to healthy controls. Methods: Standard pulmonary function tests, maximum inspiratory pressure (PImax), and maximum expiratory pressure (PEmax) for pulmonary volumes and respiratory muscle strength were applied. Respiratory muscle endurance was recorded using sustained threshold loading of 40% maximal inspiratory pressure. AS group were evaluated by using the functional status and quality of life, the Bath Ankylosing Spondylitis Functional Index (BASFI), Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Ankylosing Spondylitis Quality of Life Questionnaire (ASQoL). The severity of night pain, morning pain and morning stiffness were evaluated by Visual Analog Scale (VAS) in patients with AS. Mann Whitney-U test and Student-t Test were used to compare to groups variables. To evaluate the correlation in AS group Spearman’s Test was used. Results: A total eleven patients (6 female, 5 male; mean age: 41±9.4yrs, body mass index (BMI): 26.1±6.3kg/m2 and duration of disease 22±24.9months) and eleven controls (6 female, 5 male; mean age: 42.9±12.7yrs and BMI: 25±3.6kg/m2) were included in this study. There were no differences in age (p=0.554) and BMI (p=0.922) between the groups. No difference between FEV1% (p=0.069), FEV1/FVC% (p=0.243), PEF% (p=0.490), FEF25-75% (p=0.297), MVV% (p=0.450), PImax (p=0.694), PEmax (p=0.358) and respiratory muscle endurance (p=0.341) in both groups. But FVC% (p=0.041) significantly lower in AS group compare to controls. In addition to PImax (r= -0.800, p=0.003), PEmax (r=-0.683, p=0.021) and respiratory muscle endurance (r=-0.683, p=0.021) were correlated the night pain level in AS group. The respiratory muscle endurance (r=-0.675, p=0.023) was correlated the duration of disease. No correlations to the functional status, quality of life indexes and pulmonary functions in AS group. Conclusion: This study shows that patients with AS have clearly reduced maximal PImax and PEmax, indicating decreased respiratory muscle strength and endurance as night pain levels increased. If indeed the respiratory strength were to be unchanged or even increased the decreased respiratory muscle strength should be due to reduced strength or atrophy of intercostal or accessory muscles, or both. Although the present data do not provide the direct evidence of intercostal muscle atrophy, it is tempting to speculate that immobilization of these muscles due to thoracic rigidity and decreased inspiratory intercostal and accessory activation leading to disuse may be an important factor contributing to it.