Symptom-pattern phenotype and pulmonary function in preschool wheezers.
BACKGROUND
Pulmonary function in preschool wheezing phenotypes based on wheeze onset and duration and atopic status has been extensively described but has not been studied in symptom-pattern phenotypes of episodic (viral) and multiple-trigger wheeze.


OBJECTIVE
We investigated whether multiple-trigger wheezers were more likely to have abnormal pulmonary function and increased fraction of exhaled nitric oxide (FeNO) than episodic (viral) wheezers and whether multiple-breath wash-out was more sensitive at detecting abnormal pulmonary function than specific airways resistance (sR(aw)) in preschool wheezers.


METHODS
FeNO, multiple-breath wash-out indices (lung clearance index [LCI] and conductive airways ventilation inhomogeneity [S(cond)]) and sR(aw) were measured in healthy children and those with recurrent wheeze aged 4 to 6 years. Subgroup analysis was performed according to current symptom-pattern (multiple-trigger vs episodic [viral]), atopic status (atopic vs nonatopic), and wheeze status (currently symptomatic vs asymptomatic).


RESULTS
Seventy-two control subjects and 62 wheezers were tested. Multiple-trigger wheezers were associated with an average increase of 11% (95% CI, 7% to 18%; P < .001) in LCI, 211% (95% CI, 70% to 470%; P < .001) in S(cond), and 15% (95% CI, 3% to 28%; P = .01) in sR(aw) compared with episodic (viral) wheezers. Pulmonary function in episodic (viral) wheezers did not differ significantly from control subjects. The presence of current atopy or wheeze was associated with higher FeNO (P = .05) but did not influence pulmonary function significantly. On average, LCI was abnormal in 39% (95% CI, 32% to 45%), S(cond) was abnormal in 68% (95% CI, 61% to 74%), and sR(aw) was abnormal in 26% (95% CI, 16% to 35%) of multiple-trigger wheezers.


CONCLUSIONS
Multiple-trigger wheeze is associated with pulmonary function abnormalities independent of atopic and current wheeze status. S(cond) is the most sensitive indicator of abnormal pulmonary function in preschool wheezers.
Sonnappa
Samatha
S
Portex Unit, Respiratory Medicine and Physiology, UCL Institute of Child Health, London, United Kingdom.
Bastardo
Cristina M
CM
Wade
Angela
A
Saglani
Sejal
S
McKenzie
Sheila A
SA
Bush
Andrew
A
Aurora
Paul
P
D017668:Age of Onset; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D016014:Linear Models; D008171:Lung Diseases / Q000150:complications* / Q000503:physiopathology*; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism; D010641:Phenotype; D012015:Reference Standards; D012129:Respiratory Function Tests; D012130:Respiratory Hypersensitivity / Q000821:virology; D012135:Respiratory Sounds / Q000209:etiology; D012680:Sensitivity and Specificity
D009569:Nitric Oxide