Stewart Camille L, Mulligan Jane, Grudic Greg Z, Convertino Victor A, Moulton Steven L
From the Department of Surgery (C.L.S., S.L.M.), School of Medicine, University of Colorado; and Flashback Technologies, Inc. (J.M., G.Z.G., S.L.M.), Boulder; and Division of Pediatric Surgery (S.L.M.), Children's Hospital of Colorado, Aurora, Colorado; and US Army Institute of Surgical Research (V.A.C.), Fort Sam Houston, San Antonio, Texas.
J Trauma Acute Care Surg. 2014 Dec;77(6):892-7; discussion 897-8. doi: 10.1097/TA.0000000000000423.
Humans are able to compensate for low-volume blood loss with minimal change in traditional vital signs. We hypothesized that a novel algorithm, which analyzes photoplethysmogram (PPG) wave forms to continuously estimate compensatory reserve would provide greater sensitivity and specificity to detect low-volume blood loss compared with traditional vital signs. The compensatory reserve index (CRI) is a measure of the reserve remaining to compensate for reduced central blood volume, where a CRI of 1 represents supine normovolemia and 0 represents the circulating blood volume at which hemodynamic decompensation occurs; values between 1 and 0 indicate the proportion of reserve remaining.
Subjects underwent voluntary donation of 1 U (approximately 450 mL) of blood. Demographic and continuous noninvasive vital sign wave form data were collected, including PPG, heart rate, systolic blood pressure, cardiac output, and stroke volume. PPG wave forms were later processed by the algorithm to estimate CRI values.
Data were collected from 244 healthy subjects (79 males and 165 females), with a mean (SD) age of 40.1 (14.2) years and mean (SD) body mass index of 25.6 (4.7). After blood donation, CRI significantly decreased in 92% (α = 0.05; 95% confidence interval [CI], 88-95%) of the subjects. With the use of a threshold decrease in CRI of 0.05 or greater for the detection of 1 U of blood loss, the receiver operating characteristic area under the curve was 0.90, with a sensitivity of 0.84 and specificity of 0.86. In comparison, systolic blood pressure (52%; 95% CI, 45-59%), heart rate (65%; 95% CI, 58-72%), cardiac output (47%; 95% CI, 40-54%), and stroke volume (74%; 95% CI, 67-80%) changed in fewer subjects, had significantly lower receiver operating characteristic area under the curve values, and significantly lower specificities for detecting the same volume of blood loss.
Consistent with our hypothesis, CRI detected low-volume blood loss with significantly greater specificity than other traditional physiologic measures. These findings warrant further evaluation of the CRI algorithm in actual trauma settings.
Diagnostic study, level II.
人类能够在传统生命体征变化极小的情况下补偿少量失血。我们假设一种新算法，通过分析光电容积脉搏波（PPG）波形来持续估计代偿储备，与传统生命体征相比，在检测少量失血时将具有更高的敏感性和特异性。代偿储备指数（CRI）是衡量补偿中心血容量减少所剩余储备的指标，CRI为1表示仰卧位血容量正常，0表示发生血流动力学失代偿时的循环血容量；1和0之间的值表示剩余储备的比例。
受试者自愿捐献1单位（约450 mL）血液。收集人口统计学和连续的无创生命体征波形数据，包括PPG、心率、收缩压、心输出量和每搏输出量。PPG波形随后由该算法处理以估计CRI值。
收集了244名健康受试者（79名男性和165名女性）的数据，平均（标准差）年龄为40.1（14.2）岁，平均（标准差）体重指数为25.6（4.7）。献血后，92%（α = 0.05；95%置信区间[CI]，88 - 95%）的受试者CRI显著下降。使用CRI下降0.05或更大作为检测1单位失血量的阈值时，曲线下面积为0.90，敏感性为0.84，特异性为0.86。相比之下，收缩压（52%；95% CI，45 - 59%）、心率（65%；95% CI，58 - 72%）、心输出量（47%；95% CI，40 - 54%）和每搏输出量（74%；95% CI，67 - 80%）变化的受试者较少，曲线下面积值显著较低，检测相同失血量时特异性显著较低。
与我们的假设一致，CRI检测少量失血的特异性显著高于其他传统生理指标。这些发现值得在实际创伤环境中对CRI算法进行进一步评估。
诊断性研究，二级。
