Table 1.

Determinants of O₂ transport and their average values in long-term highland groups and acclimatized newcomers studied at ~3,600–4,300 m

Variable	Acclimatized Newcomer (AN)	Andeans (A)	Tibetans (T)	Ethiopians (E)	Summary
${\text{Pa}}_{\text{CO}}{}_{{}_2}$ or $\mathrm{P}\mathrm{E}{\mathrm{T}}_{\mathrm{C}{\mathrm{O}}_{\mathrm{2}}}$a, mmHg	30b (Refs. 176, 177)	Higher (= 32a) (Ref. 176)	Same (= 30) (Ref. 176)	Higher (= 38) (Ref. 32)	(AN = T) < A < E
A-aDO2c, mmHg	7c–11d (Refs. 150, 177)	Lower (= 4c) (Ref. 150)	Lower (= 7c)	?	AN > (A = T)
$S{a}_{O_2}$, %	92 (Refs. 24, 27, 137)	Same (= 91) (Refs. 10, 70, 137, 176)	Lower (= 88) (Refs. 10, 70, 137, 176)	Higher (= 95) (Ref. 8) or Same (= 92) (Ref. 58)	(AN = A) > T
Hemoglobin, gm/dl	17.6 (Refs. 24, 27)	Same (= 17) (Refs. 8, 83)	Lower (= 15e–18f) (Refs. 8, 133, 160, 176)	Lower? (= 15g–16h (Refs. 10, 129)	(AN = A) > (T = E)
${\text{Ca}}_{\text{O}}{}_{{}_2}$, vol%i	21 (Refs. 24, 27)	Same (= 21)	Same (= 21)	Lower (= 19, 20)	(AN = A = T) > E
Cardiac output		Same	Same	?	?
Ppa hypoxic response	Present	Intermediate (Ref. 52)	Absent (Ref. 52)	Intermediate (Ref. 58)	AN > (A = E) > T
Brain blood flow, cm/s	27j (Ref. 62)	Lower (−18%k) (Ref. 70)	Higher (= 29j,+6.2%k) (Refs. 62, 70)	?	(AN < T) > A
Uterine blood flow, ml/min	269 (Ref. 101)	Higher (= 452) (Ref. 101)	Higherl	?	AN < (T = A)
O2 metabolismm		Higher	Higher	?	AN < (T = A)

A-aDO₂,  alveolar-to-arterial O₂ diffusion gradient; AN, acclimatized newcomers of various populations; ${Ca}_o{}_{{}_2}$, arterial O₂ content; ${\text{Pa}}_{\text{CO}}{}_{{}_2}$ or $\mathrm{P}\mathrm{E}{\mathrm{T}}_{\mathrm{C}{\mathrm{O}}_{\mathrm{2}}}$, arterial or end-tidal Pco₂, respectively; Ppa, pulmonary arterial pressure; ${Sa}_{\text{O}}{}_{{}_2}$, arterial O₂ saturation.

^a${\text{Pa}}_{\text{CO}}{}_{{}_2}$ or $\mathrm{P}\mathrm{E}{\mathrm{T}}_{\mathrm{C}{\mathrm{O}}_{\mathrm{2}}}$ are inversely related to alveolar ventilation.

^bValues are averaged from multiple studies whose original reference appears in reference(s) cited.

^cMeasured at moderate exercise (~140 W) at 5,260 m.

^dMeasured at moderate exercise (~140 W) at 3,658 m.

^eHemoglobin concentration reported in Refs. 7, 159.

^fHemoglobin concentration reported in Refs. 132, 175.

^gHemoglobin concentration reported in Ref. 9.

^hHemoglobin concentration reported in Ref. 128.

ⁱEstimated from above $S{a}_{O_2}$ and hemoglobin values (without incorporation of dissolved O₂).

^jMeasured as internal carotid artery flow velocity at moderate exercise (~140 W) at 3,658 m.

^kExpressed as a percent of sea-level values measured using Doppler in Tibetans and the arterial-jugular difference in O₂ content in Andeans.

^lVolumetric flow not reported, but Tibetans had greater flow velocity in Refs. 29, 107.

^mSummary numbers not available due to different study designs and methods in Refs. 58, 59.