Excessive polycythemia occurs in young high-altitude (3600 M) residents in the absence of lung disease

Abstract

Objective: Chronic Mountain Sickness occurs in , 8% of the La Paz population. We asked whether its primary diagnostic sign, excessive polycythemia (EP), occurred in youngeraged persons without lung disease. Methods: In the 6200 persons referred to IBBA over the past 5 yrs, male hemoglobin (hgb) averages 17.5 gm/dL; we considered EP as values above this mean. From this population, we selected 26 younger- and 31 older-aged persons with EP (YEP, age = 20+1 yr; OEP, age = 36+1 yr) and 30 younger controls (C, age = 22+1 yr). Results: Height was similar but OEP weighed more (68.8+1.1 kg) than C or YEP (60.7+1.4, 63.7+1.4 kg, both p,<05 vs C). YEP and OEP had lower PaO2 and SaO2 than C, but PaCO2 was higher only in OEP. Higher hgb was associated with lower PaO2 (R2 = 0.55) and higher PaCO2 (R2 = 0.36) in all subjects. The increase in ventilation following 3 breaths of 10% O2 in N2 was reduced in YEP and OEP vs C. Forced vital capacity (FVC) and the FEV1/FVC ratio were similar in YEP and C but reduced in OEP. Diffusing capacity for CO was lower in YEP and OEP vs C but similar when controlled for hgb. Conclusion: EP occurs in younger-aged men in the absence of apparent lung disease but in the presence of a blunted ventilatory response to hypoxia and a suggestion of hypoventilation. (Supported by the French Cooperation and Universidad Mayor de San Andrés, La Paz, BO).