Comparação do teste de caminhada de dois e de seis minutos na avaliação da dessaturação de oxigênio induzida pelo esforço e na capacidade funcional de crianças e adolescentes com fibrose cística

Abstract

The six minute walk test (6MWT) has been used in cystic fibrosis (CF) to assess exercise tolerance, detect exercise-induced desaturation, grade functional status, asses intervention response, stratify patients with indications for lung transplantation, in addition to providing important prognostic information. Although the 6MWT has its recognized value, it can be demotivating for children and adolescents with CF. A more concise test as the two minute walk test (2MWT) may be an interesting alternative for this population. Objective: Determine whether TC2 provides the same information for stress-induced desaturation and functional capacity discrimination as 6MWT in children and adolescents with CF. Method: 51 children and adolescents with CF, normoxemic at rest, performed clinical and anthropometric evaluation, spirometry, two 2MWT and two 6MWT in random order. Measurements of walking distance, oxygen peripheral saturation (SpO2) were evaluated. Stress-induced desaturation was established at SpO2 detection lower than 90% and decline greater than 4% of baseline SaO2 during testing. Statistical analysis: Student's t-test was used to compare the variables between the best 6MWT and 2MWT. Unpaired t-test was used to compare stress-induced desaturation between the 6MWT and 2MWT. The χ 2 test (Fisher's exact) was used to evaluate the association between the desaturation of the 2MWT and the 6MWT. The Odds ratios analysis (OR) and 95% confidence interval (95% CI) was used for the estimation of desaturation. The ROC curve was used to identify a cut-off point for discriminating functional capacity on 2MWT. A value of p≤0.05 was assumed for all tests. Results: The patients evaluated exhibit 10.33 ± 3.60 years old, forced expiratory volume in one second of 2.00 ± 0.88 L and 83.49 ± 29.34% pred. There was a difference in the distance walking between the 2MWT and 6MWT, but no difference between HR, SpO2 and symptoms. The χ 2 showed 75% agreement in the exercise-induced desaturation evaluation between the two tests. The OR analysis showed that those who were unsaturated in 2MWT are 5.5 times more likely to desaturate in the 6MWT (95% CI 1.11–27.15; p = 0.39). The ROC curve identified the distance of 175m (area under the curve: 0.82; p <0.001) to discriminate low or high functional capacity in the 2MWT. Patients who did not desaturate in the 6MWT presented greater walking distance compared to those who desaturated (6MWD: 554 ± 80 vs 502 ± 143m; p <0.05), but in the 2MWT, the patients who desaturated did not show any difference in walking distance than those who did not desaturate (2MWT: 171 ± 30 vs 167 ± 26m; p> 0.05). Conclusion: 2MWT was able to detect exercise-induced desaturation, but was not able to discriminate functional capacity comparable to 6MWT in children and adolescents with CF.