Cardiovascular autonomic modulation and activity of carotid baroreceptors at altitude

Luciano Bernardi, Claudio Passino, Giammario Spadacini, Alessandro Calciati, Robert Robergs, Richard Greene, Emilia Martignoni, Inder Anand, Otto Appenzeller

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1. To assess the effects of acute exposure to high altitude on baroreceptor function in man we evaluated the effects of baroreceptor activation on R-R interval and blood pressure control at high altitude. We measured the low-frequency (LF) and high-frequency (HF) components in R-R, non-invasive blood pressure and skin blood flow, and the effect of baroreceptor modulation by 0.1-Hz sinusoidal neck suction. Ten healthy sea-level natives and three high-altitude native, long-term sea-level residents were evaluated at sea level, upon arrival at 4970 m and 1 week later. 2. Compared with sea level, acute high altitude decreased R-R and increased blood pressure in all subjects [sea-level natives: R-R from 1002 ± 45 to 775 ± 57 ms, systolic blood pressure from 130 ± 3 to 150 ± 8 mmHg; high-altitude natives: R-R from 809 ± 116 to 749 ± 47 ms, systolic blood pressure from 110 ± 12 to 125 ± 11 mmHg (P < 0.05 for all)]. One week later systolic blood pressure was similar to values at sea level in all subjects, whereas R-R remained elevated in sea-level natives. The low-frequency power in R-R and systolic blood pressure increased in sea-level natives [R-R-LF from 47 ± 8 to 65 ± 10% (P < 0.05), systolic blood pressure-LF from 1.7 ± 0.3 to 2.6 ± 0.4 In-mmHg2 (P < 0.05)], but not in high-altitude natives (R-R-LF from 32 ± 13 to 38 ± 19%, systolic blood pressure-LF from 1.9 ± 0.5 to 1.7 ± 0.8 In-mmHg2). The R-R-HF decreased in sea-level natives but not in high-altitude natives, and no changes occurred in systolic blood pressure-HF. These changes remained evident 1 week later. Skin blood flow variability and its spectral components decreased markedly at high altitude in sea-level natives but showed no changes in high-altitude natives. Neck suction significantly increased the R-R- and systolic blood pressure-LF in all subjects at both sea level and high altitude. 3. High altitude induces sympathetic activation in sea-level natives which is partially counteracted by active baroreflex. Despite long-term acclimatization at sea level, high-altitude natives also maintain active baroreflex at high altitude but with lower sympathetic activation, indicating a persisting high-altitude adaptation which may be genetic or due to baroreflex activity not completely lost by at least 1 year's sea-level residence.

Original languageEnglish (US)
Pages (from-to)565-573
Number of pages9
JournalClinical science
Issue number5
StatePublished - 1998


  • Autonomic nervous system
  • Baroreflex
  • Heart rate variability
  • High altitude


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