Conjunctival oxygen tension at high altitude.

Area of Science:

• Physiology
• Altitude Medicine
• Respiratory System

Background:

• Assessing oxygen levels is crucial for understanding physiological responses to altitude.
• Non-invasive monitoring methods are preferred for continuous assessment during hypoxia.
• Transcutaneous oxygen tension (PtcO2) is one such method, but its accuracy at altitude requires further investigation.

Purpose of the Study:

• To investigate transconjunctival oxygen tension (PcjO2) as a non-invasive indicator of arterial oxygen tension (PaO2) under hypobaric conditions.
• To compare PcjO2 measurements with PaO2 during simulated altitude exposure and actual mountaineering.
• To evaluate the precision and sensitivity of PcjO2 compared to transcutaneous oxygen tension (PtcO2).

Main Methods:

• Measurements of PcjO2 were taken in a hypobaric chamber at simulated altitudes from sea level to 4267 m (14,000 ft).
• PcjO2 was also measured in 16 subjects during mountaineering excursions at various altitudes.
• PcjO2 values were compared with arterial blood oxygen tension (PaO2) and transcutaneous oxygen tension (PtcO2).

Main Results:

• PcjO2 decreased significantly with increasing altitude in both chamber and mountaineering studies.
• PcjO2 was consistently around 74% of PaO2 across different altitudes.
• Conjunctival measurements demonstrated greater precision and sensitivity compared to transcutaneous measurements.

Conclusions:

• Transconjunctival oxygen tension (PcjO2) serves as a reliable, non-invasive reflection of arterial oxygen tension (PaO2).
• PcjO2 monitoring is suitable for continuous assessment during hypoxia and altitude studies.
• The conjunctival site offers a more precise measurement of oxygen tension than the transcutaneous site.