Effect of mannitol dry powder challenge on exhaled nitric oxide in children.
BACKGROUND
Fractional exhaled nitric oxide (FENO), a non-invasive marker of eosinophilic airway inflammation, is increasingly used for diagnostic and therapeutic decisions in adult and paediatric asthma. Standardized guidelines for the measurement of FENO recommend performing FENO measurements before rather than after bronchial provocation tests.


OBJECTIVE
To investigate whether FENO levels decrease after a Mannitol dry powder (MDP) challenge in a clinical setting, and whether the extent of the decrease is influenced by number of MDP manoeuvres, baseline FENO, atopy and doctor diagnosed asthma.


METHODS
Children aged 6-16 years, referred for possible reactive airway disease to a respiratory outpatient clinic, performed an MDP challenge (Aridol®, Pharmaxis, Australia). FENO was measured in doublets immediately before and after the challenge test using the portable NIOX MINO® device (Aerocrine, Stockholm, Sweden). We analysed the data using Kruskal-Wallis rank tests, Wilcoxon signed rank tests and multivariable linear regressions.


RESULTS
One hundred and seven children completed both tests (mean±SD age 11.5±2.8 years). Overall, median (interquartile range) FENO decreased slightly by -2.5 ppb (-7.0, -0.5), from 18.5 ppb (10.5, 45.5) before the MDP challenge to 16.5 ppb thereafter (8.5, 40.5; p<0.001). In all participants, the change in FENO was smaller than one standard deviation of the baseline mean. The % fall in FENO was smaller in children with less MDP manoeuvres (e.g. higher bronchial responsiveness; p = 0.08) but was not influenced by levels of baseline FENO (p = 0.68), atopy (p = 0.84) or doctor diagnosed asthma (p = 0.93).


CONCLUSIONS
MDP challenge test influences FENO values but differences are small and clinically barely relevant.
Department of Paediatric Pulmonology & Allergology, Children's Hospital, St. Gallen, Switzerland. juerg.barben@kispisg.ch
Juerg
J
Barben
Marie-Pierre F
MP
Strippoli
Daniel
D
Trachsel
Barbara
B
Schiller
Juerg
J
Hammer
Claudia E
CE
Kuehni
D000293:Adolescent; D001249:Asthma / Q000150:complications / Q000175:diagnosis / Q000188:drug therapy* / Q000503:physiopathology; D001944:Breath Tests; D002648:Child; D058995:Dry Powder Inhalers; D045853:Exhalation; D005260:Female; D006801:Humans; D008297:Male; D008353:Mannitol / Q000008:administration & dosage*; D009569:Nitric Oxide / Q000378:metabolism*; D011014:Pneumonia / Q000150:complications / Q000175:diagnosis / Q000188:drug therapy* / Q000503:physiopathology
D009569:Nitric Oxide; D008353:Mannitol