Lack of protection against hypoxic pulmonary hypertension in Bolivian high altitude natives?

Abstract

Pulmonary artery pressure increases at high altitude. It has been speculated that augmented respiratory synthesis of the vasodilator nitric oxide (NO) protects high-altitude natives from pulmonary hypertension, but direct evidence for this speculation is lacking. We, therefore, measured systolic pulmonary artery pressure (right ventricular to right atrial pressure gradient, Doppler-echocardiography), exhaled NO (NIOX MINO®) and oxygen saturation in 34 healthy adult Bolivian high altitude natives and in 35 healthy age- and sex-matched, well acclimatized European low altitude natives living at high-altitude (3′600 m). Mean±SD systolic pulmonary artery pressure (29.3±5.9 mm Hg, range 16 to 40, vs. 29.6±4.9 mm Hg, range 22 to 42), exhaled NO (19.2±7.2 ppb, range 8 to 41, vs. 22.5±9.5 ppb, range 9 to 52) and arterial oxygen saturation (92.4±3.2, range 80 to 97, vs. 92.5±2.4, range 87 to 97) were similar in Bolivians and Europeans. There was no relationship between pulmonary artery pressure and respiratory NO neither in Bolivians (r=0.14, p=0.44), nor in Europeans (r=0.19, p=0.29). These findings provide the first evidence that at high altitude, pulmonary artery pressure in European low altitude natives is not elevated, but similar to the one measured in Bolivian high altitude natives. These findings challenge the concept that Bolivian high altitude natives are protected from hypoxic pulmonary hypertension.