The Impact of Carbon Monoxide and Altitude on Vascular Function

Each year, millions of people make journeys from low altitude regions to high altitude for recreation, travel, and religious pilgrimage. Carbon monoxide (CO) is commonly associated with cigarette smoke, exhaust fumes, and is viewed as a life-threatening toxic gas. Exposure to CO occurs during travel to and during activities common in high-altitude travel and pilgrimage including vehicle fumes, incense, and second-hand smoke exposure. High altitude exposure and CO exposure have been observed independently to have complex and opposing effects on vascular endothelial function. Observation of these stimuli together in a controlled environment may allow for further understanding of the underlying mechanisms of vascular physiology and adaptations to both high-altitude and CO exposure. The CarMA (Carbon Monoxide and Altitude) Study aims to observe the vascular effects of carbon monoxide exposure at low and high altitudes. Recently, other studies have showed a significant improvement in flow mediated dilation (FMD) with acute exposure to low levels of CO To date, no research has been presented concerning the effect of CO on vascular function at altitude. The present study aims to observe the effect of acute carbon monoxide exposure on 1) flow mediated dilation, 2) conduit artery flow in exercise induced reactive hyperemia at sea level and at altitude, and 3) the effect of CO on vascular function in a high altitude dwelling (sherpa) population.

Inclusion criteria

• Between the ages of 18-50 years
• No medical history of cardiovascular, respiratory, nervous system, or metabolic disease.
• Women must be pre-menopausal.

Exclusion criteria

• Participants with any known cardiovascular, respiratory, nervous system, or metabolic disease.
• Having travelled above 2,000m within 1 month of testing at low and high altitude.
• Women who are pregnant, confirmed by a pregnancy test.
• Women who are post-menopausal.
• Participants that are classified as obese (body mass index > 30 kg/m2).
• Participants who are current daily smokers.
• Participants that are currently taking monoamine (MAO) inhibitors, or tricyclic antidepressants.