Erythrocytosis is not associated with decreased pulmonary nitric oxide in healthy Bolivian high‐altitude dwellers

Pulmonary exhaled nitric oxide (NOex) plays a role in the regulation of pulmonary‐artery tone during hypoxia. Bolivian high‐altitude dwellers develop erythrocytosis as an adaptive mechanism, which when excessive, may be associated with pulmonary hypertension, but the underlying mechanism is not known. We hypothesized that erythrocytosis may impair pulmonary NO bioavailability, because pulmonary NO is scavenged by hemoglobin. We therefore measured NOex (Niox Mino ®)) and hemoglobin concentration in 179 healthy high‐altitude dwellers in La Paz, Bolivia (3600 m). Smokers, and subjects with asthma, allergic rhinitis or recent airway viral infection were excluded from the study. The main new finding was that, in contrast to our expectations, NOex increased with increasing hemoglobin concentration, and that there existed a highly significant relationship between the two variables (r=0.42, p<0.001). These findings suggest, that erythrocytosis is not associated with decreased NOex in healthy Bolivian high‐altitude dwellers. We speculate that pulmonary hypertension in high‐altitude dwellers developing erythrocytosis is not related to impaired pulmonary NO availability.