Comparison of exhalation time methods (6 sec vs. 10 sec) of a hand-held exhaled nitric oxide analyzer

Standard exhalation time for measuring fractional exhaled nitric oxide (FeNO) is 10 sec, but this is not easy for younger children. We aimed to investigate the agreement between FeNO values during 10‐sec (FeNO‐10) and 6‐sec (FeNO‐6) exhalation and the feasibility of measuring FeNO‐6, using a hand‐held analyzer, NIOX‐MINO®. FeNO values measured during 10‐ and 6‐sec (random order) were compared. Success rates of the two different time modes were also evaluated. In 119 asthmatic children (median age 8 years [range 4–15]) who had been already accustomed to NIOX‐MINO®, median FeNO‐10 (29 ppb [IQR 15.2–42.0]) and FeNO‐6 (27 ppb [IQR 16.0–43.5]) did not differ significantly (P = 0.90), and there was a good correlation between both values (r = 0.984, P