Increased metabolism contributes to increased resting ventilation at high altitude

Area of Science:

• Physiology
• Altitude Medicine
• Respiratory Physiology

Background:

• Ventilatory acclimation to high altitude involves increased minute ventilation and decreased alveolar PCO2 (hyperventilation).
• The relative contributions of metabolic rate changes versus alveolar hyperventilation to this increased ventilation are not fully understood.

Purpose of the Study:

• To investigate the role of metabolic rate changes in augmenting minute ventilation during high-altitude exposure.
• To differentiate the drivers of increased ventilation at rest versus during exercise at altitude.

Main Methods:

• Twelve healthy males were studied at low altitude (Denver, 1600 m) and high altitude (Pikes Peak, 4300 m) for 5 days.
• Resting and exercise measurements included minute ventilation, metabolic rate (VO2, VCO2), and arterialized PCO2.
• Correlations between ventilation, CO2 production, and oxygen saturation were analyzed.

Main Results:

• Resting minute ventilation increased by 26% and metabolic rate by 16% at high altitude.
• Increased metabolic rate accounted for over half of the rise in resting minute ventilation.
• At high altitude, exercise ventilation increased by 58%, but this was not explained by increased CO2 production.

Conclusions:

• At rest, an elevated metabolic rate significantly contributes to increased minute ventilation during high-altitude acclimation.
• During exercise at high altitude, the rise in minute ventilation is primarily driven by factors other than increased metabolic rate.