Introduction.

Human adaptation to high altitude involves evolutionary changes leading adaptive responses, such as to hypoxia. Andeans developed different erythroid phenotypes in relation to other populations at high altitude, which can vary depending on the altitude.

Objective.

To determine the phenotypic variations of hemoglobin (Hb), oxygen saturation (SpO2), P50 and lactate in Bolivian Andeans residing between 400, 4000 or 5000 masl.

Material and methods.

Prospective cross-sectional descriptive study. Peripheral venous blood from Bolivian Andeans (n=124) born at 4000 m, but residing at different altitudes (400 m, 4000 m, 5000 m), likewise from those with pathological erythrocytosis were collected. Additionally, samples from Europeans residing at 4000 m (n=11) were collected. CBC, oximetry and blood gas studies were performed. P50 was calculated using the Lichtman formula.

Results.

Healthy Andeans, compared between different altitudes, reflected an increased Hb (p: 0.001), but a decreased SpO2 (p: 0.001) and P50 (p: 0.001) as the altitude was higher; without variations in lactate. Europeans at 4000 m, related to Andeans at the same altitude, presented increased Hb (p: 0.01), SpO2 and P50 without variations, but significantly increased lactate (p: 0.001). Patients with erythrocytosis compared to healthy subjects, at 4000 m and 5000 m respectively, depicted increased Hb (p: 0.001); decreased SpO2 (p: 0.001); P50 without changes, but increased lactate (p: 0.01). Increased lactate in subjects with erythrocytosis at 5000 m was remarkable (1.7 mmol/L).

Conclusion.

The phenotypic variations observed among Andeans residing at different altitudes constitute an expression of partial adaptation to altitude.

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