Moon J K, Coggan A R, Hopper M K, Baker L E, Coyle E F
Biomedical Engineering Program, College of Engineering, University of Texas at Austin.
Ann Biomed Eng. 1994 Sep-Oct;22(5):514-23. doi: 10.1007/BF02367087.
This study evaluated impedance cardiography (ZCG) estimates of stroke volume (SV) during exercise. Seven subjects were studied at rest and during progressive cycle exercise in supine and upright positions. SV was determined by ZCG (SVZCG) during exercise and for the first 5 cardiac cycles following exercise. SVZCG was compared with separate measurements of SV by CO2 rebreathing (SVCO2). Static blood resistivity (p) was measured at each level of exercise. No significant differences were found between supine exercise and immediate post-exercise values for the peak of the first derivative of the impedance change (dZ/dtmax), left ventricular ejection time (LVET), or SVZCG. Small differences in dZ/dtmax and SVZCG, but not LVET, were found in exercise to post-exercise cycling in the upright position. Intra-individual SVZCG and SVCO2 were moderately correlated (upright mean r = 0.64, supine r = 0.42) from rest to 70% of peak VO2. Similar correlations were found between Pulse-O2 (VO2/heart rate, used as an index to SV) and both SVZCG (upright r = 0.73, supine r = 0.57) and SVCO2 (upright r = 0.8, supine r = 0.65). The ZCG parameters dZ/dtmax and LVET correlated better with Pulse-O2 (dZ/dtmax: upright r = 0.92, supine r = 0.73; LVET: upright r = -0.9, supine r = -0.9). SVZCG calculated with the Kubicek equation performed as well as SVCO2. ZCG might be a superior method if the inversely correlated parameters, dZ/dtmax and LVET, were not expressed as a product to calculate SV.
本研究评估了运动期间通过阻抗心动图（ZCG）对每搏输出量（SV）的估计。对7名受试者在静息状态下以及在仰卧位和直立位进行递增式自行车运动期间进行了研究。在运动期间以及运动后的前5个心动周期通过ZCG测定每搏输出量（SVZCG）。将SVZCG与通过二氧化碳重呼吸单独测量的每搏输出量（SVCO2）进行比较。在每个运动水平测量静态血液电阻率（p）。仰卧位运动与运动后即刻的阻抗变化一阶导数峰值（dZ/dtmax）、左心室射血时间（LVET）或SVZCG值之间未发现显著差异。在直立位从运动到运动后骑行过程中，dZ/dtmax和SVZCG存在微小差异，但LVET无差异。从静息到峰值摄氧量的70%，个体内的SVZCG和SVCO2呈中度相关（直立位平均r = 0.64，仰卧位r = 0.42）。在脉搏氧（VO2/心率，用作每搏输出量的指标）与SVZCG（直立位r = 0.73，仰卧位r = 0.57）和SVCO2（直立位r = 0.8，仰卧位r = 0.65）之间也发现了类似的相关性。ZCG参数dZ/dtmax和LVET与脉搏氧的相关性更好（dZ/dtmax：直立位r = 0.92，仰卧位r = 0.73；LVET：直立位r = -0.9，仰卧位r = -0.9）。用库比克方程计算的SVZCG与SVCO2表现相当。如果不将呈负相关的参数dZ/dtmax和LVET作为乘积来计算每搏输出量，ZCG可能是一种更好的方法。
