The compensatory reserve measurement (CRM) has been established to accurately measure the body's total integrated capacity to compensate for physiologic states of reduced central blood volume and predict hemodynamic decompensation associated with inadequate tissue oxygenation. We previously demonstrated that African American (AA) women have a higher tolerance to reductions in central blood volume. Therefore, we tested the hypothesis that the CRM would identify racial differences during simulated hemorrhage, before the onset of traditional signs/symptoms.
We performed a retrospective analysis during simulated hemorrhage using lower-body negative pressure (LBNP) in 23 AA (22 ± 1 years; 24 ± 1 kg/m2) and 31 white women (WW) (20 ± 1 years; 23 ± 1 kg/m2). Beat-by-beat blood pressure (BP) and heart rate (HR) were recorded during progressive lower body negative pressure to presyncope. The BP waveforms were analyzed using a machine-learning algorithm to derive the CRM at each lower body negative pressure stage.
Resting mean arterial BP (AA, 78 ± 3 mm Hg vs. WW, 74 ± 2 mm Hg) and HR (AA, 68 ± 2 bpm vs. WW, 65 ± 2 bpm) were similar between groups. The CRM progressively decreased during LBNP in both groups; however, the rate of decline in the CRM was less (p < 0.05) in AA. The CRM was 4% higher in AA at −15 mm Hg LBNP and progressively increased to 21% higher at −50 mm Hg LBNP (p < 0.05). However, changes in BP and HR were not different between groups.
These data support the notion that the greater tolerance to simulated hemorrhage induced by LBNP in AA women can be explained by their greater capacity to protect the reserve to compensate for progressive central hypovolemia compared with WW, independent of standard vital signs.
Diagnostic test, level II.
From the The John B. Pierce Laboratory (N.S.S.); Department of Obstetrics, Gynecology and Reproductive Sciences (N.S.S.), Yale School of Medicine; Yale School of Public Health (N.S.S.), New Haven, Connecticut, Department of Kinesiology and Applied Physiology (M.M.W.), University of Delaware, Newark, Delaware; Department of Family Medicine (K.A.H.), University of North Carolina School of Medicine, Chapel Hill, North Carolina; US Army Institute of Surgical Research (J.T.H., C.D.N., V.A.C.), and US Army Battlefield Health and Trauma Center for Human Integrative Physiology (J.T.H., V.A.C.), JBSA Fort Sam, Houston, Texas
Submitted: October 15, 2017, Revised: January 23, 2018, Accepted: January 25, 2018, Published online: February 14, 2018.
The article was presented at the Annual Meeting of Experimental Biology, April 22–26, 2017, in Chicago, IL.
Address for reprints: Megan M. Wenner, PhD, Department of Kinesiology and Applied Physiology, STAR Health Sciences Complex 201N, University of Delaware, Newark, DE 19713; email: email@example.com.