Alterations in exhaled gas profile during allergen-induced asthmatic response

The source of exhaled carbon monoxide (CO) and the relationship to airway inflammation are not clear. If CO is produced by the inflamed airway, we hypothesized that inflammation induced by allergen challenge would increase exhaled CO of atopic asthmatics. Eight atopic asthmatics underwent whole lung allergen challenge. CO, nitric oxide (NO), oxygen, and carbon dioxide (CO(2)) were measured simultaneously in exhaled breath which was collected into Mylar balloons before (baseline), immediately after, and at subsequent times after allergen. NO was higher in asthmatics than control subjects at baseline, increased further in seven of the eight asthmatics after allergen, and was inversely correlated to specific conductance. In contrast, exhaled CO of asthmatics was not higher than that of control individuals at baseline, decreased immediately after allergen, and returned to baseline levels during the late asthmatic response. Thus, allergen-induced airway inflammation did not lead to increased exhaled CO in asthma.