Key result
High altitude exposure in Lowlanders reset the MSNA operating point upwards (48 vs 22 bursts 100 HB-1, P=0.001), while Sherpa had a lower operating point at 5050 m compared to Lowlanders (P=0.02).
Why the study?
High altitude exposure heightens muscle sympathetic neural activity, but its effect on arterial baroreflex control of MSNA and potential differences between lowland and highland natives remain unknown.
How does high altitude exposure affect arterial baroreflex control of muscle sympathetic nerve activity in Lowlanders compared to Sherpa?
Comparison
Assessment at low altitude vs following gradual ascent to 5050 m and acute hyperoxia
Design
Physiological observational study
Authors
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Normal baroreflex function with upward resetting sustains sympathetic tone at HA; hypothesis-generating for patients with cardiovascular disease.
Observational (n=23)
How does high altitude exposure affect arterial baroreflex control of muscle sympathetic nerve activity in Lowlanders compared to Sherpa?
Absolute Event Rate: 48% vs 22%
p-value: p=0.001
High altitude exposure resets the sympathetic baroreflex operating point upwards in Lowlanders, whereas Sherpa exhibit lower sympathetic vasoconstrictor activity, suggesting a beneficial hypoxic adaptation for blood pressure homeostasis.
Simpson et al. (2019) conducted an observational in High altitude hypoxia (n=23). High altitude exposure (5050 m) vs. Low altitude was evaluated on MSNA operating point (bursts 100 HB-1) (p=0.001). High altitude exposure in Lowlanders reset the MSNA operating point upwards (48 vs 22 bursts 100 HB-1, P=0.001), while Sherpa had a lower operating point at 5050 m compared to Lowlanders (P=0.02).
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