Explorando o uso de equações de referência para o teste da caminhada de 6 minutos no contexto da reabilitação pulmonar em indivíduos com doenças respiratórias crônicas

Abstract

Introduction: The 6-minute walk test (6MWT) has been identified as the main test for the assessment of functional exercise capacity (FEC) in individuals with chronic respiratory diseases (CRD), in the context of Pulmonary Rehabilitation (PR). To interpret the results of the 6MWT, it is common to use reference equations, which allow the identification of individuals with reduced or preserved FEC. However, little is known about the applicability of reference equations for the 6MWT in the context of PR. Objective: To explore the use of reference equations for the 6MWT in the context of PR in individuals with CRD. Methods: This is an exploratory study that retrospectively analyzed data from patients with CRD who participated in the PR program of a public hospital within 2017 and 2019. Sociodemographic and clinical data, lung function, health-related quality of life, evaluated by the Short Form 36 Health Survey (SF 36), and the FEC, through the 6MWT, all assessed before and after the PR program. The 6MWT was performed twice before and after PR, and the test with the greatest distance was used for analysis. The following 6MWT reference equation was used, which was developed in a previous study using a multicentric sample of Brazilians: 890.46 – (6.11 x age) + (0.0345 x age2 ) + (48.87 x sex) – (4.87 x Body Mass Index – BMI), with male=1 and female=0. Individuals were classified as: preserved or reduced FEC, if they presented a distance covered in the 6MWT ≥ or < the lower limit of normality, respectively. Results: 117 individuals with complete data for the 6MWT at baseline were included (50% men; median age: 61 years; 39% with chronic obstructive pulmonary disease). The mean distance walked on the 6MWT at baseline was 464 ± 98 meters (85% of predicted), and 76 patients were classified as preserved FEC (65%) and 41 as reduced FEC (35%). Individuals with reduced FEC had statistically lower values for weight, BMI, forced expiratory volume in the first second and forced vital capacity. Of the 117 individuals with CRD, 36 did not present a result for the 6MWT after PR, with 18 individuals from the preserved FEC group (24% of the baseline sample of this group) and the other 18 individuals from the reduced FEC group (44% of the baseline sample of this group) (p=0.02).There was no statistical difference in the comparison of the changes after PR (ie, deltas) in the physical and mental component summaries of the SF 36, or in the distance covered in the 6MWT, between preserved and reduced FEC groups (p>0.05), although the delta of the distance covered in the 6MWT was 2x higher in the group with reduced FEC in comparison with the other group. Conclusion: The use of reference equations for the 6MWT proved to be useful in the context of PR, since it allowed to identify individuals with CRD with worse lung function at baseline, but who seem to benefit more from the physical training of the program.