LATE-BREAKING ABSTRACT: Extended NO analysis is useful to modify anti-inflammatory treatment in asthmatic children with intermediate FENO50

Exhaled NO (F E NO 50 ) is elevated in asthma and clinical practice guidelines are published. A F E NO 50 above 35 ppb in children indicate eosinophilic inflammation and the response to inhaled corticosteroids (ICS) is likely. Intermediate F E NO 50 should be interpreted cautiously. Children with ICS provided exhaled breath samples for off line NO measurement with Sievers NOA 280. Three flow rates 16, 90 and 230 mL/s were used for the extended NO analysis (Hogman-Merilainen algorithm, HMA) to determine the alveolar concentration-C A NO, diffusion rate of the airway wall-D aw NO and airway wall content-C aw NO. For accuracy of the HMA, calculations of F E NO 50 were compared with measured F E NO 50 . Five children with F E NO 50 35 ppb with allergy had F E NO 50 56 (47;60) ppb and C aw NO 140 (121;172) ppb. In 13 children, with intermediate F E NO 50 20-35 ppb, with allergy had F E NO 50 27 (25;30) ppb with a wide range of C aw NO. In 5 children C aw NO is comparable to healthy children, 44 (43;50) ppb, but 8 children have increased C aw NO of 108 (95;129) ppb. Using the F E NO 50 > 35 ppb, the response to ICS is likely. However, in the children with F E NO 50 20-35 ppb more than half of them could possibly benefit of an adjustment of ICS if the C aw NO is considered. These results needs to be confirmed in a larger study where anti-inflammatory treatment is guided either by F E NO 50 as in the clinical practice guidelines or with the use of extended NO analysis where a personal target value of F E NO 50 can be calculated. 1 NO values given in geometrical mean (25;75 percentile).