1. Hemorrhage at high altitude: impact of sustained hypobaric hypoxia on cerebral blood flow, tissue oxygenation, and tolerance to simulated hemorrhage in humans.
- Author
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Rosenberg, Alexander, Anderson, Garen, McKeefer, Haley, Bird, Jordan, Pentz, Brandon, Byman, Britta, Jendzjowsky, Nicholas, Wilson, Richard, Day, Trevor, and Rickards, Caroline
- Subjects
Central hypovolemia ,Cerebral blood velocity ,Hypoxia ,Internal carotid artery blood flow ,Lower body negative pressure ,Humans ,Cerebrovascular Circulation ,Male ,Altitude ,Adult ,Female ,Hypoxia ,Hemorrhage ,Oxygen ,Oxygen Consumption ,Carotid Artery ,Internal ,Oxygen Saturation ,Lower Body Negative Pressure - Abstract
With ascent to high altitude (HA), compensatory increases in cerebral blood flow and oxygen delivery must occur to preserve cerebral metabolism and consciousness. We hypothesized that this compensation in cerebral blood flow and oxygen delivery preserves tolerance to simulated hemorrhage (via lower body negative pressure, LBNP), such that tolerance is similar during sustained exposure to HA vs. low altitude (LA). Healthy humans (4F/4 M) participated in LBNP protocols to presyncope at LA (1130 m) and 5-7 days following ascent to HA (3800 m). Internal carotid artery (ICA) blood flow, cerebral delivery of oxygen (CDO2) through the ICA, and cerebral tissue oxygen saturation (ScO2) were determined. LBNP tolerance was similar between conditions (LA: 1276 ± 304 s vs. HA: 1208 ± 306 s; P = 0.58). Overall, ICA blood flow and CDO2 were elevated at HA vs. LA (P ≤ 0.01) and decreased with LBNP under both conditions (P
- Published
- 2024