“…In 1 of 2 recently published studies, FENO was not found to be useful in acute asthma because it could be measured only in 68% of the children presenting to the emergency department (ED) with acute asthma, 14 while in the second study, FENO failed to distinguish children requiring hospitalization from those who were discharged to home. 15 In neither study were FENO levels available at baseline, nor an attempt was made to determine what role viral infections played in FENO levels. The aims of this study were 2-fold: to determine whether the FENO level is elevated during an acute asthma exacerbation compared with baseline in children with persistent asthma and to determine the influence of viral infections on FENO levels in children presenting with an acute asthma exacerbation requiring prednisone therapy.…”