Antonutto G, Girardis M, Tuniz D, di Prampero P E
Dipartimento di Scienze e Tecnologie Biomediche, Università di Udine, Italy.
Eur J Appl Physiol Occup Physiol. 1995;72(1-2):18-24. doi: 10.1007/BF00964109.
The stroke volume of the left ventricle (SV) was assessed in nine young men (mean age 22.2, ranging from 20 to 25 years) during cycle ergometer upright exercise at exercise intensities from 60 to 150 W (about 20% to 80% of individual maximal aerobic power). The SV was calculated from noninvasive tracings of the arterial blood pressure, determined from photoplethysmograph records and compared to the SV determined simultaneously by pulsed Doppler echocardiography (PDE). Given the relationship SV = As.Z-1 in which A(s) is the area underneath the systolic pressure profile (in millimetres of mercury and second), and Z (in millimetres of mercury and second per millilitre) is the apparent hydraulic impedance of the circulatory system, a prerequisite for the assessment of SV from the photoplethysmograph tracings is a knowledge of Z. The experimental value of Z (hereafter defined Z*) was calculated by dividing A(s) (from the finger photoplethysmograph) by SV as obtained by PDE. When the whole group of subjects was considered, Z* was not greatly affected by the exercise intensity: it amounted to 0.089 (SD 0.028; n = 36). The Z was also estimated independently of any parameter other than heart rate (HR), mean (MAP) and pulse (PP) arterial blood pressure obtained from the photoplethysmograph. A computerized statistical method allowed us to interpolate the experimental values of Z*, HR, PP and MAP by the equation Zm = a.(b + c.HR + d.PP + e.MAP)-1, thus obtaining the coefficients a to e. The mean percentage error between Zm (calculated from the coefficients obtained and Z* was 21.8 (SD 14.3)%. However, it was observed that, in a given subject, Z* was significantly affected by the exercise intensity. Therefore, to improve the estimate of Z a second algorithm was developed to update the experimental value of Z determined initially at rest (Zin). This updated value (Zcor) of Z was calculated as Zcor = Zin. [(f/(i + g.(HR/HRin) + h.(PP/PPin) + 1.(MAP/MAPin)], where HRin, PPin, MAPin, HR, PP, MAP are the above parameters at rest and during exercise, respectively. Also in this case, the coefficients f to 1 were determined by a computerized statistical method using Z* as the experimental reference. The values of Zcor so obtained allowed us to calculate SV from arterial pulse contour analysis as SVF = As.Z-1cor. The mean percentage error between the SVF obtained and the values simultaneously determined by PDE, was 10.0 (SD 8.7)%. It is concluded that the SV of the left ventricle, and hence cardiac output, can be determined during exercise from photoplethysmograph tracings with reasonable accuracy, provided that an initial estimate of SV at rest is made by means an independent high quality reference method.
在9名年轻男性（平均年龄22.2岁，年龄范围为20至25岁）进行自行车测力计直立运动时，评估了左心室每搏输出量（SV），运动强度为60至150瓦（约为个体最大有氧功率的20%至80%）。SV通过无创动脉血压描记图计算得出，动脉血压由光电容积描记图记录确定，并与同时通过脉冲多普勒超声心动图（PDE）测定的SV进行比较。鉴于SV = As.Z-1的关系，其中A(s)是收缩压曲线下的面积（以毫米汞柱和秒为单位），Z（以毫米汞柱和秒每毫升为单位）是循环系统的表观水力阻抗，从光电容积描记图描记评估SV的一个前提条件是了解Z。Z的实验值（以下定义为Z*）通过将A(s)（来自手指光电容积描记图）除以PDE获得的SV来计算。当考虑整个受试者组时，Z受运动强度的影响不大：其值为0.089（标准差0.028；n = 36）。Z也独立于除心率（HR）、平均动脉压（MAP）和脉搏压（PP）之外的任何参数进行估计，这些参数从光电容积描记图获得。一种计算机化统计方法使我们能够通过方程Zm = a.(b + c.HR + d.PP + e.MAP)-1对Z、HR、PP和MAP的实验值进行插值，从而获得系数a至e。根据获得的系数计算出的Zm与Z之间的平均百分比误差为21.8（标准差14.3）%。然而，观察到在给定受试者中，Z受运动强度的显著影响。因此，为了改进Z的估计，开发了第二种算法来更新最初在静息状态下确定的Z的实验值（Zin）。Z的这个更新值（Zcor）计算为Zcor = Zin. [(f/(i + g.(HR/HRin) + h.(PP/PPin) + 1.(MAP/MAPin)]，其中HRin、PPin、MAPin、HR、PP、MAP分别是上述参数在静息和运动时的值。同样在这种情况下，系数f至1通过使用Z*作为实验参考的计算机化统计方法确定。如此获得的Zcor值使我们能够通过动脉脉搏轮廓分析计算SV，即SVF = As.Z-1cor。获得的SVF与PDE同时测定的值之间的平均百分比误差为10.0（标准差8.7）%。得出的结论是，如果通过一种独立的高质量参考方法对静息时的SV进行初始估计，那么在运动期间可以根据光电容积描记图描记以合理的准确度确定左心室的SV，从而确定心输出量。
