PDF(Pubmed)
Abstract：
The compensatory reserve index (CRI), derived from machine learning algorithms from peripherally obtained photoplethysmography signals, provides a non-invasive assessment of cardiovascular stability, that may be useful clinically. Briefly, the CRI device provides a value between 0 and 1, with 1 reflecting full compensable capabilities and 0 reflecting little to no compensable capabilities. However, the CRI algorithm was developed in younger to middle aged adults, such that it is unknown if older age modulates CRI responses to cardiovascular challenges. In young and older subjects, we compared CRI responses to normothermic and hyperthermic progressive lower body negative pressure (LBNP), and volume loading with saline infusion. Eleven younger (20-36 years) and 10 older (61-75 years) healthy participants underwent (1) graded normothermic LBNP up to 30 mmHg, (2) graded hyperthermic (1.5°C increase in blood temperature) LBNP up to 30 mmHg, and (3) infusion of 15 mL/kg saline (volume loading) with hyperthermia maintained. CRI was obtained throughout each procedure. CRI at 30 mmHg LBNP was 0.18 and 0.24 units greater in the older group during normothermic and hyperthermic LBNP, respectively. However, CRI was not different between age groups at any other LBNP stage, nor did CRI change with volume loading regardless of age. In response to passive hyperthermia alone, regression analyses showed that heart rate was the strongest predictor of CRI. Blood temperature, rate pressure product, and stroke volume were also predictive of CRI but to a lesser extent. In conclusion, age attenuates the reduction in CRI during progressive normothermic and hyperthermic LBNP, but only at 30 mmHg. Second, the CRI was unchanged during volume loading in all subjects. Future studies should determine whether the age differences in CRI reflect age differences in LBNP tolerance.
摘要：
补偿性储备指数(CRI)，从外围获得的光电容积描记术信号的机器学习算法中得出，提供心血管稳定性的非侵入性评估，这可能在临床上有用。简而言之，CRI设备提供0和1之间的值,其中1反映完全可补偿能力,0反映很少或没有可补偿能力。然而,CRI算法是在年轻人到中年人中开发的，因此，尚不清楚年龄是否会调节CRI对心血管挑战的反应。在年轻人和老年人中，我们比较了CRI对常温和高温进行性下体负压（LBNP）的反应，和生理盐水输注的体积负荷。11名年龄较小（20-36岁）和10名年龄较大（61-75岁）的健康参与者接受（1）常温LBNP高达30mmHg，（2）分级高温（血液温度升高1.5°C）LBNP高达30mmHg，和(3)输注15mL/kg盐水(体积负荷)并维持热疗。在整个过程中获得CRI。在常温和高温LBNP期间，老年组的30mmHgLBNPCRI分别高0.18和0.24个单位，分别。然而,CRI在任何其他LBNP阶段的年龄组之间没有差异，无论年龄如何，CRI也不会随容量加载而变化。仅针对被动高热，回归分析显示心率是CRI的最强预测因子.血液温度,速率压力产品，和每搏输出量也可预测CRI,但程度较小.总之,年龄减弱了进行性常温和高温LBNP期间CRI的降低，但只有30mmHg。第二,所有受试者的CRI在容量负荷期间均未改变。未来的研究应确定CRI的年龄差异是否反映了LBNP耐受性的年龄差异。
