Pulmonary Vascular Function and Aerobic Exercise Capacity at Moderate Altitude

Area of Science:

• Cardiovascular Physiology
• Altitude Physiology
• Exercise Science

Background:

• Pulmonary vascular reserve, characterized by low pulmonary vascular resistance (PVR) and high lung diffusing capacity (DL), is suggested to enhance aerobic exercise capacity.
• The effect of pulmonary vascular reserve on exercise capacity at moderate altitudes remains unclear.

Purpose of the Study:

• To investigate how pulmonary vascular reserve influences aerobic exercise capacity at moderate altitude.
• To compare the effects of pulmonary vascular reserve on exercise capacity at sea level versus moderate altitude.

Main Methods:

• Thirty-eight healthy subjects underwent exercise stress echocardiography and cardiopulmonary exercise testing at sea level and 2250 m.
• Measurements included diffusing capacity for nitric oxide (DLNO) and carbon monoxide (DLCO), and arterial oxygen content (CaO2).

Main Results:

• Moderate altitude reduced maximum oxygen uptake (V˙O2max) and CaO2, but did not alter cardiac output, PVR, or pulmonary vascular distensibility during exercise.
• DLNO showed an inverse correlation with the ventilatory equivalent of CO2 (V˙E/V˙CO2).
• Independent predictors of V˙O2max included the pulmonary artery pressure-cardiac output relationship, resting stroke volume, and resting DLNO at both altitudes. Exercise-induced decrease in CaO2 predicted the reduction in V˙O2max at altitude.

Conclusions:

• Pulmonary vascular reserve modulates aerobic exercise capacity similarly at sea level and moderate altitude.
• The primary driver of reduced aerobic exercise capacity at moderate altitude is exercise-induced hypoxemia (decreased arterial oxygenation).