Functional capacity incorporating dynamic ventilation in women with systemic sclerosis: A comparison between performance in the 6-minute walk test and the AVD-Glittre test

Abstract

Introduction: Functional capacity at the level of submaximal exertion has been increasingly used as a measure of outcome in systemic sclerosis (SS). However, it is necessary to know the ventilatory requirements of the different field tests for their proper indication in people with SSc. Objectives: To compare the ventilatory dynamics measured at submaximal effort between the ADL-Glittre test (TGlittre) and the 6-minute walk test (6MWT) and, secondarily, to evaluate the correlations of these measures with clinical and functional variables in women with SSc. Methods: This is a cross-sectional study in which 30 women with SSc underwent TGlittre and 6MWT, both coupled to a portable device (Spiropalm®) capable of providing the ventilatory requirements. In addition, evaluations of physical function were made using the Health Assessment Questionnaire Disability Index (HAQ-DI) and pulmonary function using spirometry. Results: In relation to the 6MWT, the median of the distance traveled in 6 min (DTC6') was 344 (282–410) meters, and 25 (83.3%) participants did not reach 80% of the expected distance. In relation to TGlittre, the median time in TGlittre was 147 (107–188) seconds, and 18 (60%) participants exceeded 120% of the predicted time. There was agreement between the 2 tests for the following variables measured at the end of the test: heart rate (interclass correlation coefficient-ICC = 0.883, P < 0.0001), respiratory reserve (ICC = 0.816, P < 0.0001), peripheral oxygen saturation (ICC = 0.752, P = 0.0009), inspiratory capacity (ICC = 0.690, P < 0.0001) and minute peak ventilation (ICC = 0.433, P = 0.007). There was a weak correlation between the 6MWD' and the TGlittre time (rs = -0.353, P = 0.05). The 6MWD' correlated significantly with HAQ-DI (rs = -0.606, P = 0.0004), forced vital capacity (CVF, rs = 0.427, P = 0.018). TGlittre time correlated significantly with HAQ-DI (rs = 0.440, P = 0.015) and FVC (rs = -0.404, P = 0.026). Conclusion: In women with SSc, the 6MWT and TGlittre require almost the same ventilatory requirements, although the performance of these patients is worse in the 6MWT when compared to TGlittre. The interrelationship between the 6MWT' and the TGlittre time is weak. Both the 6MWT and TGlittre time are associated with physical function and pulmonary function.