Late Breaking Abstract - Conversion of FENO: from different flows to the standard flow.

Background: Clinicians commonly utilize expiratory nitric oxide (FENO) in diagnostics of asthma or other pulmonary diseases, as a useful biomarker of airway inflammation. FENO levels are influenced by the expiratory flow rate and therefore presently standardised at 50 mL/s. Data acquired preceding the standardisation is difficult to compare with standard flow data, due to differences in flow rates. To facilitate the comparison of former FENO results, we purposed to establish a method for converting FENO to the standard flow and to validate the model in five external populations. Methods: We obtained FENO from 30 participants (mixed adult population) at the flow rates 30, 50 100 and 300 mL/s. Results: In healthy adults and children, the deviation between estimated FENO from 100 mL/s and measured FENO at 50 mL/s was the lowest: -0.38 ppb and 0.3 ppb respectively. The deviation in the mixed adults was -0.39 ppb, in COPD and asthma patients -0.81 ppb and -1.5 ppb, respectively. The deviation was the highest in patients with alveolitis: 1.55 ppb. Conclusions: We proposed a model to convert FENO in healthy or mixed populations, as well in subjects with obstructive pulmonary diseases, using a multiple flow FENO equipment. In conclusion, the model is reliable in converting mean FENO in large epidemiological data, but not on individual level.