Six-minute walking test versus shuttle walking test: responsiveness to bronchodilation in patients with bronchiectasis

Abstract

Introduction: As a result of the structural changes in the lung tissue, the main impact of the bronchiectasis (BCT) is the alteration in pulmonary function which is characterized by obstruction and, in a subset of patients, by restriction. In the obstructive patients is usual the prescription of bronchodilators (BD). Objective: To analyze which field test, either six- minutes walk test (6MWT) or shuttle endurance test (STE), is more responsive to BD and to contrast exercise responses between the 6MWT and shuttle incremental test (SIT) and to compare the performance in 6MWT and SIT between the patients with obstructive and restrictive pattern. Methods: This is a randomized, double blind, placebo-controlled and crossover study in which 31 patients with BCT will performe two 6MWT and STE, on separate days (48 h), preceded by placebo or BD (400 mg of salbutamol). The cardiopulmonary and metabolic parameters will be monitored in all tests by a telemetry system of gas exchange. There is no additional visit for SIT because it has already been performed in another ongoing study with the same patients. Expected results: Our hypothesis is that the STE will be more responsive to BD, because the rhythm of walking is maintained during the whole test and the patient increases the time performing the test while in the 6MWT patients have to increase the speed of walking to achieve a greater distance. The submaximal responses to 6MWT and SIT will be different due to the intrinsic characteristics of each test (self-paced and external-paced, respectively). Finally, the responses in ventilation (respiratory rate, tidal volume and ventilation) would be similar between the patients with the obstructive and restrictive patterns, because both patterns determine inability to increase the tidal volume during exercise, resulting in high respiratory rate and peak ventilation/maximum voluntary ventilation ratio. (AU)