Inhomogeneity of ventilation distribution as a predictor in the AVD-Glittre test in women with rheumatoid arthritis

Abstract

Introduction: A rheumatoid arthritis is a chronic disease that affects the connective tissue, presents extra-articular signs and progressive joint injuries. Considered as autoimmune, characterized as destructive polyarthritis, which can cause different levels of functional impairment. In general, an RA symmetrically involves small joints, with pain, morning stiffness and limited movement for more than an hour. However, these signs may vary according to the patient. Metacarpophalangeal joints, proximal interphalangeal joints, wrists, metatarsophalangeal joints and knees are often more affected, although other joints may be affected. In addition to joint involvement, other structures may be affected, such as the respiratory system, airways, pleura and parenchyma.Although pulmonary involvement is the most common extra-articular manifestation of rheumatoid arthritis (RA), traditional pulmonary function testsdo not show a good correlation with the field tests usually performed in these patients. In recent decades, there has been increasing use of the measurement of ventilation distribution inhomogeneity through the nitrogen single-breath washout (N2SBW) test and, also, of the evaluation of functional capacity during exercise using the Glittre-activities of daily living test (GA-T). Methods: To investigate the contribution of ventilation inhomogeneity to exercise performance, 43 women with RA underwent the N2SBW test and the GA-T; in addition, they underwent spirometry, measurement of diffusing capacity for carbon monoxide (DLco), measurement of respiratory muscle strength, and evaluation of physical function through the Health Assessment Questionnaire Disability Index (HAQ-DI). Results: The GA-T time showed significant correlations with DLco (rs = -0.397, P = 0.008), forced vital capacity/DLco (rs = 0.307, P = 0.044), phase III slope of the N2SBW test (SIIIN2, rs = 0.644, P < 0.0001) and HAQ-DI (rs = 0.482, P = 0.001). In the multiple regression analysis, SIIIN2 and HAQ-DI were the only variables predictive of GA-T time, explaining 40% of its variability. In conclusion, although the extent of the disease as assessed by computed tomography was associated with the GA-T time, there were no significant correlations between the time since diagnosis or disease activity with GA-T time. Conclusion: Thus, the GA-T may be a more valid measure of functional status in patients with RA and may more reliably reflect damage to lung function.