Servicio de Neumología, Hospital Universitario Lucus Augusti, Lugo, Spain.
Respir Care. 2013 Aug;58(8):1329-34. doi: 10.4187/respcare.02290. Epub 2013 Jan 15.
Distance walked during the 6-min walk test (6MWT) predicts mortality in COPD. The body weight of the patient affects the work required to walk. Calculated work during the 6MWT (6MWT work) may account for differences in walk distance resulting from change in body weight. Thus, 6MWT work might be a better predictor of mortality than distance walked. This study was designed to test this hypothesis and to assess if other variables measured during the 6MWT, like continuous oximetry recording, offered additional prognostic information.
This was a retrospective analysis of prospectively collected data; 104 COPD patients were studied. 6MWT was performed in all cases. 6MWT work was calculated as body weight (in kg) × distance walked (in m). Receiver operating characteristic curves were used to assess the value of variables to predict mortality. Additional analysis was performed using Kaplan-Meier survival plots and Cox proportional hazards regression models.
Mean follow-up was 590 ± 472 d. Eleven subjects (10.6%) died. 6MWT work was not better than distance walked to predict mortality (area under the curve 0.77 for 6MWT work vs 0.80 for distance; difference 0.03, 95% CI -0.05 to 0.12, P = .45). Subjects who died had more dyspnea (measured using the Borg scale) after the 6MWT (8.5 vs 4.0, P < .001), lower baseline SpO2 (85% vs 93%, P = .001), worse oxygen saturation during the 6MWT (mean SpO2 while walking 74.0% vs 86.6%, P = .02) and walked less distance (255 m vs 480 m, P = .001). On multivariate analysis, only 6MWT distance and dyspnea after the test correlated independently with mortality (P = .005 for both variables).
6MWT work was not more useful than 6MWT distance to predict mortality. The study confirms that 6MWT distance and dyspnea on exertion are key elements in prognostic evaluation in COPD, while the value of exercise oxygen desaturation is less clear.
在 6 分钟步行测试（6MWT）中行走的距离可预测 COPD 患者的死亡率。患者的体重会影响行走所需的工作量。6MWT 期间的计算工作量（6MWT 工作）可能会解释因体重变化而导致的行走距离差异。因此，6MWT 工作可能比行走距离更能预测死亡率。本研究旨在检验这一假设，并评估 6MWT 期间测量的其他变量（如连续血氧饱和度记录）是否提供了额外的预后信息。
这是一项前瞻性收集数据的回顾性分析；共研究了 104 例 COPD 患者。所有患者均进行了 6MWT。6MWT 工作计算为体重（kg）×行走距离（m）。受试者工作特征曲线用于评估变量预测死亡率的价值。使用 Kaplan-Meier 生存图和 Cox 比例风险回归模型进行了额外的分析。
平均随访时间为 590±472d。11 例（10.6%）患者死亡。6MWT 工作并不能比行走距离更好地预测死亡率（6MWT 工作的曲线下面积为 0.77，而行走距离为 0.80；差值为 0.03，95%CI-0.05 至 0.12，P=0.45）。死亡的患者在 6MWT 后呼吸困难程度更高（使用 Borg 量表测量）（8.5 比 4.0，P<0.001），基线 SpO2 更低（85%比 93%，P=0.001），6MWT 期间血氧饱和度更差（行走时平均 SpO2 为 74.0%比 86.6%，P=0.02），行走距离更短（255m 比 480m，P=0.001）。多变量分析显示，只有 6MWT 距离和试验后呼吸困难与死亡率独立相关（两个变量的 P 值均为 0.005）。
6MWT 工作并不能比 6MWT 距离更能预测死亡率。该研究证实，6MWT 距离和运动后呼吸困难是 COPD 预后评估的关键因素，而运动时的氧饱和度下降的价值则不太明确。
