From the Mayo Clinic Alix School of Medicine (R.T.R.); Department of Anesthesiology and Perioperative Medicine (K.L.W., W.W.P., E.K.G., M.J.J., T.B.C., C.C.W.), and Department of Physiology and Biomedical Engineering (D.R.H., C.R.H.), Mayo Clinic, Rochester, Minnesota; Department of Kinesiology (C.C.W.), Michigan State; East Lansing, Michigan; and Battlefield Health and Trauma Center for Human Integrative Physiology (V.A.C.), US Army Institute of Surgical Research, JBSA Fort Sam Houston, San Antonio, Texas.
J Trauma Acute Care Surg. 2024 Aug 1;97(2S Suppl 1):S98-S104. doi: 10.1097/TA.0000000000004377. Epub 2024 May 15.
The Compensatory Reserve Metric (CRM) provides a time sensitive indicator of hemodynamic decompensation. However, its in-field utility is limited because of the size and cost-intensive nature of standard vital sign monitors or photoplethysmographic volume-clamp (PPG VC ) devices used to measure arterial waveforms. In this regard, photoplethysmographic measurements obtained from pulse oximetry may serve as a useful, portable alternative. This study aimed to validate CRM values obtained using pulse oximeter (PPG PO ).
Forty-nine healthy adults (25 females) underwent a graded lower body negative pressure (LBNP) protocol to simulate hemorrhage. Arterial waveforms were sampled using PPG PO and PPG VC . The CRM was calculated using a one-dimensional convolutional neural network. Cardiac output and stroke volume were measured using PPG VC . A brachial artery catheter was used to measure intra-arterial pressure. A three-lead electrocardiogram was used to measure heart rate. Fixed-effect linear mixed models with repeated measures were used to examine the association between CRM values and physiologic variables. Log-rank analyses were used to examine differences in shock determination during LBNP between monitored hemodynamic parameters.
The median LBNP stage reached was 70 mm Hg (range, 45-100 mm Hg). Relative to baseline, at tolerance, there was a 47% ± 12% reduction in stroke volume, 64% ± 27% increase in heart rate, and 21% ± 7% reduction in systolic blood pressure ( p < 0.001 for all). Compensatory Reserve Metric values obtained with both PPG PO and PPG VC were associated with changes in heart rate ( p < 0.001), stroke volume ( p < 0.001), and pulse pressure ( p < 0.001). Furthermore, they provided an earlier detection of hemodynamic shock relative to the traditional metrics of shock index ( p < 0.001 for both), systolic blood pressure ( p < 0.001 for both), and heart rate ( p = 0.001 for both).
The CRM obtained from PPG PO provides a valid, time-sensitized prediction of hemodynamic decompensation, opening the door to provide military medical personnel noninvasive in-field advanced capability for early detection of hemorrhage and imminent onset of shock.
Diagnostic Tests or Criteria; Level III.
代偿储备指标（CRM）提供了一种对血流动力学失代偿具有时间敏感性的指标。然而，由于标准生命体征监测器或用于测量动脉波形的光电容积脉搏波（PPG VC）设备的尺寸和成本密集性质，其在现场的实用性受到限制。在这方面，脉搏血氧仪获得的光容积描记图测量值可能是一种有用的便携式替代方法。本研究旨在验证使用脉搏血氧仪（PPG PO）获得的 CRM 值。
49 名健康成年人（25 名女性）接受了分级下体负压（LBNP）方案以模拟出血。使用 PPG PO 和 PPG VC 采集动脉波形。使用一维卷积神经网络计算 CRM。使用 PPG VC 测量心输出量和每搏量。使用肱动脉导管测量动脉内压。使用三导联心电图测量心率。使用具有重复测量的固定效应线性混合模型来检查 CRM 值与生理变量之间的关联。对数秩分析用于检查 LBNP 期间监测的血流动力学参数在休克判定方面的差异。
中位 LBNP 达到 70mmHg（范围 45-100mmHg）。与基线相比，在耐受阶段，心排量下降 47%±12%，心率增加 64%±27%，收缩压下降 21%±7%（p<0.001 均为）。使用 PPG PO 和 PPG VC 获得的 CRM 值与心率（p<0.001）、心排量（p<0.001）和脉压（p<0.001）的变化相关。此外，它们相对于休克指数的传统指标（两者均为 p<0.001）、收缩压（两者均为 p<0.001）和心率（两者均为 p=0.001）更早地检测到血流动力学休克。
PPG PO 获得的 CRM 提供了一种有效的、时间敏感的血流动力学失代偿预测，为军事医务人员提供了非侵入性的现场高级能力，用于早期发现出血和即将发生的休克。
诊断测试或标准；三级。
