Comparison between the 6-minute walk tests performed in patients with chronic obstructive pulmonary disease at different altitudes

Objective: To evaluate the influence of the altitude on the 6-minute walking test in patients with moderate to severe pulmonary disease. Methods: Twenty-nine patients performed the 6-minute walk test at a pulmonary rehabilitation clinic in Santo Andre (above sea level), in Sao Paulo State, and at the Enseada Beach, in Guaruja (at sea level), also in Sao Paulo State. Of these 29 patients, 8 did the test both on hard sand and on asphalt to analyze if there were differences in performance during the tests. Data such as heart rate, oxygen saturation, test distance, and Borg scale were compared. Results: We found no statistical difference in relation to oxygen saturation at rest before the beginning of the walking test in Santo Andre 94.67 +/- 2.26% and at sea level 95.56 +/- 2% (p=0.71). The minimum saturation measured during the test was 87.27 +/- 6.54% in Santo Andre and 89.10 +/- 5.41% in Guaruja (p=0.098). There were no differences in the performed distance between the different kinds of terrains; the distance on sand was 387.75 +/- 5.02m and on asphalt it was 375.00 +/- 6.54m (p=0.654). Regarding oxygen saturation during walking, the pulse oximetry on sand was 95.12 +/- 1.80% and on asphalt it was 96.87 +/- 1.64% (p=1.05). Conclusion: Altitude did not affect the performance of the walking test in patients with moderate to severe pulmonary disease and the results were similar in both cases, on sand and on asphalt.