Ventilatory function and oxygen delivery at high altitude in the Himalayas

Area of Science:

• Physiology
• Altitude Medicine
• Respiratory Science

Background:

• High-altitude environments present physiological challenges due to reduced oxygen availability.
• Understanding respiratory adaptations and potential impairments is crucial for safe high-altitude expeditions.

Purpose of the Study:

• To evaluate changes in lung function (spirometry) and arterial blood gas content in healthy individuals during a Himalayan trek.
• To assess the impact of high altitude on respiratory parameters and oxygen saturation.

Main Methods:

• 19 healthy Italian adults trekked in Nepal, with measurements taken at baseline (Kathmandu, ~1400m) and peak altitude (~5000m).
• Spirometry and arterial blood gas analysis were performed, alongside daily acetazolamide administration.
• Data were collected at rest and after acclimatization at each altitude.

Main Results:

• Arterial hemoglobin saturation, O2 and CO2 partial pressures, and bicarbonate levels decreased significantly (p < 0.001).
• Forced vital capacity (FVC) remained stable, but forced expiratory volume in 1s (FEV1) decreased, lowering the FEV1/FVC ratio (p < 0.001).
• Partial pressure of oxygen was the best predictor of acute mountain sickness (p = 0.004). Finger pulse oximetry overestimated arterial saturation.

Conclusions:

• High-altitude hypoxia alters respiratory function and arterial oxygen saturation.
• Reduced air density and temperature may contribute to hypoxic bronchoconstriction.
• Pulse oximetry alone may be insufficient for medical decision-making at high altitudes.