Alteration in Carboxyhemoglobin Concentrations During Exposure to 9 ppm Carbon Monoxide for 8 Hours at Sea Level and 2134 m Altitude in a Hypobaric Chamber

Inhaled whole exhaust and its effect on exercise performance and vascular function

“…While elevated COHb concentrations may impair oxygen delivery to the working muscles, the CO levels in the present study (4.75 ppm ± 3.12) were well below the National Ambient Air Quality Standard (NAAQS) of 9 ppm and 35 ppm for the 8 h and 1 h average, respectively (EPA, 2010). COHb concentrations of 4-6% have resulted in decreased exercise performance (Adir et al, 1999), however, exposure to 9 ppm has resulted in a gradual increase in COHb which peaked at only 0.7% after 5 h of continuous exposure (Horvath & Bedi, 1989), therefore, it does not appear as though elevated COHb levels contributed to the decreased performance observed in the present study. Ghofrani et al (2004) has previously shown that elevated PP in response to acute hypoxia at high-altitude may decrease exercise capacity on a cycle ergometer and while elevated PP may also contribute to decreased exercise performance in HPM conditions, this is not supported by the present study in which the comparatively lower PP's were not related to changes in exercise performance and unlikely to be responsible for decreased cardiac output like that observed by Ghofrani et al (2004).…”