Comparison of Six-Minute Walk Test and Modified Bruce Treadmill Test in Paediatric Patients With Severe Burns: A Cross-Over Study

Abstract

Objective: To compare the six-minute walk test and the Modified Bruce treadmill test in paediatric patients with severe burns.

Subjects: A total of 67 children, aged 7-17 years, with severe burns.

Methods: Participants were assigned to perform the six-minute walk test and the Modified Bruce treadmill test in randomized order on discharge from acute burn care. Primary outcome measure was heart rate. Secondary outcome measures were distance walked, Borg's CR-10 rate of perceived exertion, and maximal oxygen uptake (VO2).

Results: A total of 67 participants were enrolled. Thirty-eight patients completed both tests. The mean six-minute walk test maximum heart rate was 135 ± 19 bpm (range 97-180 bpm) and the mean Modified Bruce treadmill test maximum heart rate was 148 ± 24 bpm (range 100-197 bpm; p ≤ 0.05), with a weak positive correlation of R² = 0.14. The mean six-minute walk test maximum distance was 294 ± 124 m (range 55 to 522 m) while the mean Modified Bruce treadmill test maximum distance was 439 ± 181 m (range 53 to 976 m; p ≤ 0.05), with no correlation of R² = 0.006. The mean RPE CR-10 score for the six-minute walk test was 3 ± 2.5 (range 0-10) vs a mean RPE CR-10 score of 10 ± 0 for the Modified Bruce treadmill test.

Conclusion: The Modified Bruce treadmill test challenges the cardiorespiratory system significantly more than the six-minute walk test, as reflected by maximum heart rate measurements, and the perception of effort (i.e. rate of perceived exertion) by the patient. When possible, the Modified Bruce treadmill test should be used to assess cardiovascular functional capacity. However, the six-minute walk test may be more clinically feasible for use with paediatric patients with burns, and provides information about submaximal functional exercise capacity.

Fig. 1

Distance measured with six-minute walk test (SMWT) and peak VO₂ measured with treadmill test (TM) test shows no correlation.

Fig. 2

Flowchart showing enrolment and inclusion/exclusion of the participants from Shriners Children’s Texas, Galveston, TX and Shriners Hospital for Children, Sacramento, CA, USA in this multicentre prospective trial. SMWT: six-minute walk test; TM: treadmill test.

Fig. 3

Six-minute walk test (SMWT) heart rate vs treadmill test (TM) test heart rate (n = 38) shows a weak positive correlation. HR: heart rate; Max: maximum.

Fig. 4

Bland-Altman plot of the 2 testing methods in terms of heart rate (HR) shows a mean bias of –13 bpm, a lower level of agreement of –62 bpm and an upper level of agreement of 35 bpm. HR: heart rate; TM: treadmill; SMWT: six-minute walk test.

Fig. 5

Distance measured with six-minute walk test (SMWT) and treadmill (TM) test (n = 38) shows no correlation. m: meter.

Fig. 6

Bland-Altman plot of the 2 testing methods in terms of distance shows a mean bias of 144 m, with a lower level of agreement of –301 m and an upper level of agreement of 590 m.