Kinematic assessment of patients with chronic obstructive pulmonary disease during the six-minute walk test

Abstract

Introduction:  COPD is considered a public health problem, not only because of its high morbidity and mortality rate, but also because it is preventable as long as the smoker stops smoking. The evaluation of functional capacity is usually performed through field tests, such as the six-minute walk test (6MWT), which is
performed in a 30m-corridor. However, current studies have been used a 10 meters course, due to the physical space limitations. Kinematics in the 6MWT analyzes gait clinically and contributes to the understanding of gait characteristics of the individual. The gait speed decreases with increasing COPD severity and can be used as an indicator of functional capacity. The literature on gait speed and other walking deficits in COPD is scarce. Objective: To evaluate the kinematic profile of patients with COPD during the 6MWT and to evaluate the feasibility of the kinematic evaluation during the 6MWT in a 10m course. Methods: This cross sectional
study included 36 patients with COPD and 19 healthy subjects. Participants were submitted to the 6MWT with kinematic analysis in the course of 10 m. Data were collected using four infrared cameras and a spherical marker covered with retroreflective tape firmly attached to a helmet, which was worn by the participant during the 6MWT. Results: The total distance measured by the
assessor was significantly smaller than both its kinematics (p=0.012) and predicted values (p=0.017) counterparts. The total distance measured by
kinematics was also smaller than the predicted one (p=0.025). The validity was accurate with a very large bias towards underestimating the 6MWD as measured
by the assessor. The majority of participants presented a negative trend for the average speed across half-turns, with a large variability in slope values. Healthy
subjects had higher 6MWD by kinematics, velocity, and mean acceleration than COPD patients. Conclusion: Analysis of whole-body gait kinematics is feasible
using motion capture systems and can be used for assessing the validity of the 6MWT over a 10-meter walkway in the elderly individuals and COPD. The 6MWD
as measured by the assessor seems to underestimate the actual covered distance in the 6MWT. Healthy individuals and COPD have the same profile on
the 6MWT, that is, they reach peak speed and acceleration at the same time during the test.