Contribution of lung function in predicting distance covered in the 6-min walk test in obese Brazilian women

Obesity affects the respiratory system through various mechanisms, including systemic inflammation and direct mechanical hindrance due to fat deposition in the chest and abdomen. In addition, changes in the neural control of respiration and increases in thoracic blood volume can promote abnormalities in lung function. Thus, determining relationships between the distance covered in the 6-min walk test (6MWT) and demographic and lung function variables may help us better understand the mechanisms involved in reduced functional exercise capacity in obesity. To explore the determinants of the 6-min walking distance (6MWD) and evaluate the influence of lung function on the distance covered, 263 obese Brazilian women performed the 6MWT and underwent spirometry and respiratory muscle strength measurement. The mean age was 41.8±11.1 years. The mean body mass index (BMI) was 45±8 kg/m2. The 6MWD showed correlations with height (r=0.319), age (r=-0.281), weight (r=-0.370), BMI (r=-0.561), forced vital capacity (FVC, r=0.443), expiratory peak flow (r=0.278), maximal inspiratory pressure (MIP, r=0.326), and maximal expiratory pressure (r=0.259), all with P<0.0001. In the stepwise forward regression analysis, BMI, FVC, age, and MIP were the independent predictive variables for 6MWD, explaining 41% of its variability. The reference equation including lung function was as follows: 6MWD (m) = 513.6 - (4.439 × BMIkg/m2) + (1.136 × FVC%predicted) - (1.048 × ageyrs) + (0.544 × MIP%predicted). Thus, the inclusion of lung function in a reference equation for 6MWD contributes to a better prediction of the distance covered in this population.

肥胖可通过多种机制影响呼吸系统，包括全身性炎症，以及因胸腹部脂肪沉积引发的直接机械性阻碍。此外，呼吸神经调控的改变与胸腔血容量增加，均可诱发肺功能异常。因此，探究6分钟步行试验（6-min walk test，以下简称6MWT）的步行距离与人口学及肺功能变量之间的关联，或有助于我们更好地理解肥胖人群功能性运动能力下降的相关机制。为探究6分钟步行距离（6-min walking distance，以下简称6MWD）的影响因素，并评估肺功能对步行距离的影响，263名巴西肥胖女性完成了6MWT，并接受了肺量测定及呼吸肌力量检测。受试者的平均年龄为41.8±11.1岁，平均体重指数（body mass index，以下简称BMI）为45±8 kg/m²。6MWD与身高（r=0.319）、年龄（r=-0.281）、体重（r=-0.370）、BMI（r=-0.561）、用力肺活量（forced vital capacity，以下简称FVC，r=0.443）、峰值呼气流速（expiratory peak flow，r=0.278）、最大吸气压力（maximal inspiratory pressure，以下简称MIP，r=0.326）及最大呼气压力（maximal expiratory pressure，r=0.259）均存在显著相关性，所有相关系数的P值均<0.0001。在逐步向前回归分析中，BMI、FVC、年龄及MIP是6MWD的独立预测变量，可解释其41%的变异度。包含肺功能指标的参考方程如下：6MWD（m）= 513.6 - (4.439 × BMIkg/m²) + (1.136 × FVC%predicted) - (1.048 × ageyrs) + (0.544 × MIP%predicted)。综上，在针对该人群的6MWD参考方程中纳入肺功能指标，可有效提升步行距离的预测准确性。