Hypoxia, hypocapnia and spirometry at altitude

Area of Science:

• Environmental Physiology
• Respiratory Medicine
• Altitude Medicine

Background:

• Hypoxia and hypocapnia at high altitude can induce bronchoconstriction, potentially impacting performance and causing altitude sickness.
• Understanding these effects is crucial for individuals ascending to high elevations.

Purpose of the Study:

• To investigate the relationship between spirometry, arterial oxygen saturation, and end-tidal carbon dioxide (ETCO2) in healthy adults at high altitude.
• To evaluate the effects of supplementary oxygen and a beta-2 agonist on respiratory function at 5300m.

Main Methods:

• Spirometric data collected from 51 healthy adults at sea level and 5300m (Mount Everest Base Camp).
• Measurements included forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and peak expiratory flow (PEF).
• Evaluated responses to 5-minute oxygen inhalation and salbutamol administration; ETCO2 measured in 30 subjects.

Main Results:

• Lower oxygen saturation at 5300m correlated with reduced FEV1 and FVC, but not PEF.
• Oxygen administration increased saturation but did not significantly alter FEV1 or FVC; PEF decreased.
• Salbutamol did not significantly change PEF, FEV1, or FVC in non-asthmatic subjects.
• Mean ETCO2 was 26 mmHg; lower ETCO2 weakly associated with greater FVC drop at altitude.

Conclusions:

• No evidence of hypoxic bronchoconstriction was found in acclimatized individuals at 5300m.
• Respiratory function, particularly FVC, declined at altitude, with greater declines in those with lower oxygen saturation and ETCO2.
• Neither supplementary oxygen nor salbutamol improved FEV1 or PEF in this context.