Journal
JOURNAL OF APPLIED PHYSIOLOGY
Volume 130, Issue 6, Pages 1786-1797Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/japplphysiol.00499.2020
Keywords
cerebral blood velocity; lower body negative pressure; sex differences
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Funding
- U.S. Army Medical Research and Materiel Command Combat Casualty Care Research Program [W81XWH-11-2-0137]
- William and Ella Owens Medical Research Foundation [T32 AG020494]
- American Heart Association Predoctoral Fellowship [20PRE35210249]
- Ruth L. Kirchstein National Research Service Award (NRSA) F32 Postdoctoral Fellowship [T32 AG020494, 1F32 HL144082-01A1]
- Ruth L. Kirchstein NRSA F31 Predoctoral Fellowship [1 F31 HL134242-01A1]
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The study found that tolerance and cerebral blood velocity responses to simulated hemorrhage were similar between male and female subjects, but the change in etCO2 from baseline was greater in males compared to females at presyncope, suggesting potential sex differences in cerebral vascular sensitivity to CO2 during simulated hemorrhage.
Trauma-induced hemorrhage is a leading cause of disability and death due, in part, to impaired perfusion and oxygenation of the brain. It is unknown if cerebrovascular responses to blood loss are differentiated based on sex. We hypothesized that compared to males, females would have reduced tolerance to simulated hemorrhage induced by maximal lower body negative pressure (LBNP), and this would be associated with an earlier reduction in cerebral blood flow and cerebral oxygenation. Healthy young males (n = 29, 26 +/- 4 yr) and females (n = 23, 27 +/- 5yr) completed a step-wise LBNP protocol to presyncope. Mean arterial pressure (MAP), stroke volume (SV), middle cerebral artery velocity (MCAv), end-tidal CO2 (etCO(2)), and cerebral oxygen saturation (ScO2) were measured continuously. Unexpectedly, tolerance to LBNP was similar between the sexes (males, 1,604 +/- 68 s vs. females, 1,453 +/- 78 s; P = 0.15). Accordingly, decreases (%Delta) in MAP, SV, MCAv, and ScO2 were similar between males and females throughout LBNP and at presyncope (P >= 0.20). Interestingly, although decreases in etCO(2) were similar between the sexes throughout LBNP (P = 0.16), at presyncope, the %Delta etCO(2) from baseline was greater in males compared to females (-30.8 +/- 2.6% vs. -21.3 +/- 3.0%; P = 0.02). Contrary to our hypothesis, sex does not influence tolerance, or the central or cerebral hemodynamic responses to simulated hemorrhage. However, the etCO(2) responses at presyncope do suggest potential sex differences in cerebral vascular sensitivity to CO2 during central hypovolemia. NEW & NOTEWORTHY Tolerance and cerebral blood velocity responses to simulated hemorrhage (elicited by lower body negative pressure) were similar between male and female subjects. Interestingly, the change in etCO(2) from baseline was greater in males compared to females at presyncope, suggesting potential sex differences in cerebral vascular sensitivity to CO2 during simulated hemorrhage. These findings may facilitate development of individualized therapeutic interventions to improve survival from hemorrhagic injuries in both men and women.
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