Cataldo Anna Roto, Fei Jie, Hutchinson Karen J, Sloutsky Regina, Starr Julie, De Rossi Stefano M M, Awad Louis N
Department of Physical Therapy, Sargent College of Health and Rehabilitation Sciences, Boston University, Boston, MA 02215, USA.
Bioengineering (Basel). 2024 Dec 10;11(12):1250. doi: 10.3390/bioengineering11121250.
Indirect calorimetry is the gold standard field-testing technique for measuring energy expenditure and exercise intensity based on the volume of oxygen consumed (VO, mL O/min). Although heart rate is often used as a proxy for VO, heart rate-based estimates of VO may be inaccurate after stroke due to changes in the heart rate-VO relationship. Our objective was to evaluate in people post stroke the accuracy of using heart rate to estimate relative walking VO (wVO) and classify exercise intensity. Moreover, we sought to determine if estimation accuracy could be improved by including clinical variables related to patients' function and health in the estimation.
Sixteen individuals post stroke completed treadmill walking exercises with concurrent indirect calorimetry and heart rate monitoring. Using 70% of the data, forward selection regression with repeated k-fold cross-validation was used to build wVO estimation equations that use heart rate alone and together with clinical variables available at the point-of-care (i.e., BMI, age, sex, and comfortable walking speed). The remaining 30% of the data were used to evaluate accuracy by comparing (1) the estimated and actual wVO measurements and (2) the exercise intensity classifications based on metabolic equivalents (METs) calculated using the estimated and actual wVO measurements.
Heart rate-based wVO estimates were inaccurate (MAE = 3.11 mL O/kg/min) and unreliable (ICC = 0.68). Incorporating BMI, age, and sex in the estimation resulted in improvements in accuracy (MAE Δ: -36.01%, MAE = 1.99 mL O/kg/min) and reliability (ICC Δ: +20, ICC = 0.88). Improved exercise intensity classifications were also observed, with higher accuracy (Δ: +29.85%, from 0.67 to 0.87), kappa (Δ: +108.33%, from 0.36 to 0.75), sensitivity (Δ: +30.43%, from 0.46 to 0.60), and specificity (Δ: +17.95%, from 0.78 to 0.92).
In people post stroke, heart rate-based wVO estimations are inaccurate but can be substantially improved by incorporating clinical variables readily available at the point of care.
间接测热法是基于耗氧量（VO，毫升氧气/分钟）来测量能量消耗和运动强度的金标准现场测试技术。虽然心率常被用作VO的替代指标，但由于心率与VO关系的改变，中风后基于心率的VO估计可能不准确。我们的目的是评估中风后患者使用心率来估计相对步行VO（wVO）和对运动强度进行分类的准确性。此外，我们试图确定在估计中纳入与患者功能和健康相关的临床变量是否可以提高估计准确性。
16名中风后患者完成了跑步机步行运动，同时进行间接测热法和心率监测。使用70%的数据，采用重复k折交叉验证的前向选择回归来构建仅使用心率以及结合即时可用临床变量（即体重指数、年龄、性别和舒适步行速度）的wVO估计方程。其余30%的数据用于通过比较（1）估计的和实际的wVO测量值以及（2）基于使用估计的和实际的wVO测量值计算的代谢当量（METs）的运动强度分类来评估准确性。
基于心率的wVO估计不准确（平均绝对误差=3.11毫升氧气/千克/分钟）且不可靠（组内相关系数=0.68）。在估计中纳入体重指数、年龄和性别可提高准确性（平均绝对误差变化：-36.01%，平均绝对误差=1.99毫升氧气/千克/分钟）和可靠性（组内相关系数变化：+20，组内相关系数=0.88）。还观察到运动强度分类得到改善，准确性更高（变化：+29.85%，从0.67提高到0.87）、卡帕值（变化：+108.33%，从0.36提高到0.75）、敏感性（变化：+30.43%，从0.46提高到0.60）和特异性（变化：+17.95%，从0.78提高到0.92）。
在中风后患者中，基于心率的wVO估计不准确，但通过纳入即时可用的临床变量可得到显著改善。
