Gait-speed and oxygen flow during six-minute walk test predicts mortality in patients with advanced lung disease
The six-minute walk test (6MWT) is a useful tool to predict outcomes in patients with advanced lung diseases. Greater distance walked has been shown to have more favorable prognostic value compared to other recorded variables. We reviewed the medical records of 164 patients with advanced lung disease who underwent lung transplant evaluation. Results of the 6MWT (distance walked, oxygen required, and mean gait speed) were recorded and analyzed with respect to mortality. 6MWT mean oxygen (O2) flow via nasal cannula was 3.5 ± 3.7 L/min. The distance walked in meters (m) and % predicted were inversely associated with mortality, OR: 0.995 (0.992-0.998) and 0.970 (0.950-0.990), respectively. Patients who walked < 200 meters (OR: 2.1 (1.1-4.0)) or < 45% of predicted, OR: 2.7 (1.2-5.7) had higher mortality. O2 flow during the test had a direct association with mortality (OR: 1.1 (1.0-1.2). In multivariate analysis, O2 flow > 3.5 L/min remained predictive of mortality, OR: 1.1 (1.0-1.2). Mean gait speed was higher in patient who lived compared with patients who died (mean 0.83 ± 0.35 m/mim vs mean 0.69 ± 0.33 m/min, respectively, p= 0.03). Gait speed was a predictor of survival, OR 3.4 (1.1, 10.6). O2 flow during the 6MWT was an independent predictor of mortality in patients with advanced lung disease. The patients that required more than 3.5 L/m of O2 had a higher mortality. Faster gait speed during the 6MWT was also associated with better survival.
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