Feasibility of the 6-Minute Walk Test in Healthy Adults at High Altitude on Aconcagua

Abstract

Background

The 6-minute walk test (6MWT) has been used as an inexpensive, noninvasive single measurement of functional status in patients with cardiovascular diseases such as chronic obstructive pulmonary disease and congestive heart failure. The 6MWT has not been applied to the high-altitude setting.

Objective

Perform a feasibility study of the 6MWT in a high-altitude setting.

Methods

Study design: prospective observational cohort study. Setting: Plaza de Mulas base camp (4365 m), Aconcagua Provincial Park, Argentina. Inclusion criteria: volunteer trekkers to Aconcagua (6962 m) during January 2009 who signed written informed consent. Exclusion criteria: pregnant women, age <18 years. Study protocol: Subjects completed a questionnaire that included demographic information. Heart rate (HR), respiratory rate (RR), blood pressure, and oxygen saturation (Sao₂) were measured for all subjects before and after completion of a 6MWT using a standardized protocol on a 40-m course. Six-minute walk distance (6MWD) and maximal heart rate (max HR) during 6MWT were recorded. Statistical analysis: means, standard deviations, 95% confidence intervals (CIs), and t tests were calculated for normally distributed data using Stata (Stata Corp, College Station, TX).

Results

A total of 124 subjects completed the 6MWT. One hundred nine (88%) were male and 15 (12%) were female. Subject demographics (mean ± SD) were as follows: age 40.1 ± 11.7 years; weight 75.5 ± 10.4 kg; height 1.77 ± 0.10 m; body mass index 24.2 ± 2.8. Mean 6MWD was 457.5 m (95% CI: 442.8–472.2; range 190–750) with max HR 115.3 ± 13.0 bpm. There was a significant change in HR (82.4 vs 102.4 bpm, P <.001), RR (17.9 vs 20.3 bpm, P <.001), and Sao₂ (84.8 vs 78.5%, P <.001) before and after completion of the 6MWT.

Conclusions

This study provides the first published data on reference values for 6MWT recorded in the field at high altitude. Future studies are needed to determine if 6MWT or change in vital signs are prognostic factors for the development of acute mountain sickness or successful summiting at extreme altitude.