Relationship between exhaled nitric oxide and airway hyperresponsiveness following experimental rhinovirus infection in asthmatic subjects
Abstract
Exhaled nitric oxide (NO) is elevated in asthmatics, and varies with disease severity. We postulated that a respiratory virus infection increases exhaled NO levels in asthma, and examined the relationship between the virus-induced changes in exhaled NO and in airway hyperresponsiveness to histamine. In a parallel study, seven patients underwent experimental rhinovirus 16 (RV16) inoculation at days 0 and 1, whilst seven patients received placebo. Exhaled NO was measured at baseline (day 0) and at days 1, 2 and 3 after inoculation. Histamine challenges were performed prior to (day -7) and after inoculation (day 3), and were expressed as provocative concentration causing a 20% fall in forced expiratory volume in one second (FEV1) (PC20). Following RV16 infection there was a significant increase in NO at days 2 and 3 as compared to baseline (median change (range): 4.2 (7.5) parts per billion (ppb), p=0.03, and 3.0 (10.1) ppb, p=0.02, respectively). Furthermore, PC20 decreased significantly following RV16 infection (mean+/-SD change in doubling dose: -0.65+/-0.54, p=0.02), whereas PC20 did not change in the placebo group (p=0.1). There was a significant correlation between the RV16-induced changes in exhaled NO levels at day 2 and t...Continue Reading
Citations
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