INCREASED CARBON-MONOXIDE IN EXHALED AIR OF SUBJECTS WITH UPPER RESPIRATORY-TRACT INFECTIONS

Viral infection may induce the expression of heme oxygenase, resulting in increased carbon monoxide (CO) formation. CO may be produced by va rious cells of the upper and tower respiratory tract and may be detect ed in the exhaled air. Therefore, exhaled CO concentrations were measu red on a CO monitor by vital capacity maneuver in subjects with upper respiratory tract infections (URTIs) and in nonsmoking and smoking hea lthy control subjects. At the time of symptoms of URTI, exhaled CO con centrations were 5.6 +/- 0.4 ppm and decreased to 1.0 +/- 0.1 ppm duri ng recovery. Recovery values of exhaled CO were similar to those in ag e-matched nonsmoking healthy control subjects (1.2 +/- 0.3 ppm). Smoki ng healthy control subjects had the highest levels of exhaled CO conce ntration among the groups (18.5 +/- 2.5 ppm). These findings suggest t hat symptomatic URTIs increase the concentration of CO in exhaled air. This may reflect the induction of heme oxygenase that has an antivira l effect in the airways.