[Determination of pulmonary arterial pressure and pulmonary vasoconstrictive responses to hypoxia in healthy Tibetan men].

Elevated pulmonary arterial pressures have been observed in persons after acute or chronic exposure to high altitude. Five normal lifelong male of Tibet descents, 22 +/- 1 years old residents, at the altitudes of over 3658 m were studied in Lhasa (3658 m, 65.3 kPa PB) at rest and during near-maximal exercise. The resting PAM (2 +/- 0.3 kPa, 15 +/- 1 mmHg) and PVR (1.8 +/- 0.2 Wood units) were within sea-level norms and were little changed while breathing a hypoxic gas mixture (PaO2 = 4.80 kPa, 36 +/- 2 mmHg). Near-maximal exercise (87 +/- 13% VO2 max) increased cardiac output more than three-fold to attain values of 18.3 +/- 1.2 L/min but did not elevate PVR. Breathing 100% O2 during near-maximal exercise did not reduce PAM and PVR. We suggested that Tibetan had resting pulmonary arterial pressure that was normal as sea-level standard and exhibited minimal hypoxic pulmonary vasoconstriction both at rest and exercise. These findings are consistent with remarkable cardiac performances and high altitude adaptation in Tibetan. Those with pulmonary arterial hypertension might be a maladaptative response to chronic hypoxia.