Measurement of FeNO with a portable, electrochemical analyzer using a 6-second exhalation time in 7-10-year-old children with asthma: comparison to a 10-second exhalation.

Objective: Fractional exhaled nitric oxide (FeNO) is a valuable tool for assessing Th2 inflammation in children with asthma. Exhalation times of 6 and 10 s meet the current recommendations for assessing FeNO. The 6-s exhalation provides an alternative for 7-10 year olds not able to complete the 10-s exhalation. Methods: We performed a sub-analysis on data from 7-10-year-old children who participated in a previous study which evaluated the agreement of the 6 and 10-s exhalation times in 6-10 year olds with asthma. Agreement between observed FeNO results obtained by both modes was assessed by weighted Deming regression analysis and Bland-Altman plots. Repeatability was also assessed. Results: Repeatability and agreement of the 6 and 10-s exhalations was demonstrated in 7-10 year olds with two measurements in each mode. Mean observed FeNO measurements were 33.59 ppb (SD = 25.804) for 6 s and 32.46 ppb (SD = 25.302) for 10-s exhalation. Paired differences were centered close to 0 ppb (median = 0.50). Conclusions: Children aged 7-10 years can successfully perform FeNO measurements using a portable, electrochemical FeNO analyzer. Measurements from the 6 and 10-s exhalations were repeatable and consistent with a high degree of agreement between one another. Thus, in young children successful FeNO measurements can be obtained in either the 6-s or 10-s mode, providing physicians valuable information on airway inflammation to aid in the diagnosis and treatment of asthma.