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Tibetans resident at intermediate altitude (1300 m, 4327 ft) show similar hypoxic ventilatory responses but blunted heart rate responses to poikilocapnic hypoxia
Author(s) -
Moya Esteban A.,
Yu James J.,
Brown Spencer,
Gu Wanjun A.,
Lawrence Elijah A.,
Carlson Ryan,
Brandes Anna,
Wegeng William A.,
Amann Kassaundra,
McIntosh Scott,
Powell Frank L.,
Simonson Tatum S.
Publication year - 2020
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2020.34.s1.06685
Subject(s) - hypoxia (environmental) , hyperoxia , hypoxic ventilatory response , heart rate , effects of high altitude on humans , anesthesia , population , oxygenation , respiratory system , medicine , cardiology , biology , chemistry , oxygen , blood pressure , lung , anatomy , environmental health , organic chemistry
Population living at high altitudes for hundreds of generations exhibit distinct respiratory and cardiovascular responses to hypoxia relative to other populations. The extent of these differences at intermediate altitude is less understood and could provide important insight into ancestry specific physiological responses in the absence of hypoxia. We hypothesized that Tibetans living at intermediate altitude (1300 m, 4327 ft) exhibit an increased hypoxic ventilatory response (HVR) and an elevated hypoxic heart rate response (HHR) compared to Han Chinese examined at the same altitude. To estimate O 2 sensitivity, we measured ventilation (V I ), heart rate (HR) and O 2 saturation (Sat) under hyperoxic conditions (30% O 2 ) and then during a hypoxic stimulus (10% minimum desaturation) keeping end‐tidal CO 2 (EtCO 2 ) levels constant (isocapnia) or allowing changes in the EtCO 2 (poikilocapnia). We quantified HVR and HHR as change in V I and HR between hyperoxia and hypoxia standardized per the change in O 2 Sat (ΔV I /ΔSat and ΔHR/ΔSat respectively). To estimate CO 2 sensitivity, we measured changes in V I and HR responses between poikilocapnic and isocapnic hypoxia and standardized these changes per change in EtCO2 (ΔV I /ΔEtCO 2 and ΔHR/ΔEtCO 2 respectively). We did not find significant differences in ΔV I /ΔSat and ΔV I /ΔEtCO 2 between Tibetan and Han Chinese during isocapnic and poikilocapnic hypoxia. The ΔHR/ΔSat between populations during isocapnic hypoxia was also not significantly different. However, Tibetans exhibited a blunted ΔHR/ΔSat during poikilocapnic hypoxia compared to Han Chinese (35.8% decrease, p < 0.02) with a significant ancestry effect in women (37.6% decrease, p < 0.009). The mean value of ΔHR/ΔEtCO 2 was positive in the Han Chinese group but negative in Tibetan (169% difference, p < 0.02), indicating that Tibetans had a blunted HR response when CO 2 is not controlled. Our results show that HVR responses in Tibetan individuals with high‐altitude ancestry is not different than Han Chinese residents at comparable intermediate altitude, but the HHR to hypoxia during poikilocapnia is blunted in individuals with Tibetan ancestry. These results suggest that, at intermediate altitude, individuals with Tibetan ancestry exhibit an attenuated heart rate response to hypoxia due to an increased contribution of the CO 2 chemosensory response. Support or Funding Information Supported by NIH 1RO1HL145470 and R01 HL‐081823.