• Vydehi R Murthy, Hugo Escobar, Mike Norberg, Charisse I Lachica, Linda L Gratny, Ashley K Sherman, William E Truog, and Winston M Manimtim.
• Children's Mercy Hospitals and Clinics, University of Missouri-Kansas City School of Medicine, Kansas City, Missouri.
• Respir Care. 2017 May 1; 62 (5): 595-601.

BackgroundThe lower airway concentration of fractional exhaled nitric oxide (FENO) is unknown in children with chronic lung disease of infancy who have tracheostomy for long-term mechanical ventilation. We aimed to evaluate an online method of measuring FENO in a cohort of ventilator-dependent children with a tracheostomy and to explore the relationship between the peak FENO concentration (FENO peak) and the degree of respiratory support using the respiratory severity score.MethodsWe conducted a prospective cross-sectional study in 31 subjects who were receiving long-term respiratory support through a tracheostomy. We measured the FENO peak and FENO plateau concentration from the tip of the tracheostomy tube using a nitric oxide analyzer in subjects during a quiet state while being mechanically ventilated. We obtained 2 consecutive 2-min duration measurements from each subject. The FENO peak, exhaled NO output (equal to the FENO peak × minute ventilation), and pulmonary NO excretion (exhaled NO output/weight) were calculated and correlated with the respiratory severity score.ResultsThe median FENO peak was 2.69 ppb, and the median FENO plateau was 1.57 ppb. The coefficients of repeatability between the 2 consecutive measurements for FENO peak and FENO plateau were 0.74 and 0.59, respectively. The intraclass coefficient between subjects within the cohort was 0.988 (95% CI 0.975-0.994, P < .001) for FENO peak and 0.991 (95% CI 0.982-0.996, P < .001) for FENO plateau. We found that the FENO peak was directly correlated with minute ventilation, but we did not find a direct relationship between the FENO peak concentration, exhaled NO output, or pulmonary NO excretion and respiratory severity score.ConclusionsFENO peak and plateau concentration can be measured online easily with a high degree of reliability and repeatability in infants and young children with a tracheostomy. FENO peak concentration from the lower airway is low and influenced by minute ventilation in children receiving mechanical ventilation.Copyright © 2017 by Daedalus Enterprises.

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