Responsiveness and validity of the six-minute walk test in individuals with traumatic brain injury

Abstract

Background: A simple test of aerobic fitness for patients with traumatic brain injury (TBI) that is valid, reliable, and responsive to change is needed to provide clinicians a functional measure of cardiorespiratory capacity.

Objective: The purpose of this study was to examine the validity and responsiveness to change of the Six-Minute Walk Test (6MWT) in individuals with TBI.

Design: A cohort, pretest-posttest, comparison study was conducted.

Methods: Twenty-one patients performed the 6MWT upon admission to and prior to discharge from a postacute rehabilitation facility. Heart rate and distance traveled were recorded. A physiologic cost index (PCI) (beats per meter) was calculated based on steady-state heart rate. At discharge, all participants were able to perform a graded treadmill exercise test to exhaustion during which peak oxygen consumption (Vo(2)) was measured.

Results: Between admission and discharge, mean total distance increased from 342.6 m (SD=127.0) to 408.9 m (SD=124.2), and work increased from 27,185 kg·m (SD=10,528) to 34,114 kg·m (SD=12,057). The effect size indexes were 1.10 and 1.12 for distance and work, respectively. Correlations (r) between the discharge peak Vo(2) and the discharge 6MWT distance, PCI, and work were .58, -.61, and .47, respectively.

Limitations: Stratification by gait speed may have improved responsiveness, especially for the slow ambulators.

Conclusions: All measures correlated well with peak Vo(2), establishing an acceptable level of criterion-related (concurrent) validity. The addition of heart rate and calculating the PCI was only slightly better at predicting peak Vo(2), albeit nonsignificant, than a simple measure of total distance. The 6MWT provides a good estimate of peak aerobic capacity, and some measures are more responsive to change than others in patients recovering from TBI.

Figures

Figure 1.

The peak oxygen consumption (V̇o2) of the 21 participants during graded exercise testing matched with their total distance covered during the Six-Minute Walk Test at discharge. PI=prediction interval.

Figure 2.

The peak oxygen consumption (V̇o2) of the 21 participants during graded exercise testing matched with Six-Minute Walk Test physiologic cost index (PCI) at discharge. PI=prediction interval.

Figure 3.

The peak oxygen consumption (V̇o2) of the 21 participants during graded exercise testing matched with Six-Minute Walk Test work at discharge. PI=prediction interval.