Expired nitric oxide and airway reactivity in infants at risk for asthma

Background

Family histories of atopy, as well as histories of atopic dermatitis and food allergy, are important risk factors for an infant to have asthma. Although atopic sensitization appears to contribute to the development of asthma, it is unclear when the airways become involved with the atopic process and whether airway function relates to the atopic characteristics of the infant.

Objective

We sought to evaluate whether atopic infants without prior episodes of wheezing have increased expired nitric oxide (eNO) levels and heightened airway reactivity.

Methods

Infants with eczema were recruited, and atopic status was defined by specific IgE levels to foods or aeroallergens and total IgE levels. eNO, forced expiratory flow at 75% exhaled volume (FEF₇₅), and airway reactivity to inhaled methacholine were measured in sedated infants. Airway reactivity was quantified by using the provocative concentration to decrease FEF₇₅ by 30%.

Results

Median age for the 114 infants evaluated was 10.7 months (range, 2.6–19.1 months). Infants sensitized to egg or milk compared with infants sensitized to neither egg nor milk had lower flows (FEF₇₅: 336 vs 285 mL/s, P < .003) and lower lnPC₃₀ (mg/mL) provocative concentrations to decrease FEF₇₅ by 30% (−0.6 vs −1.2, P < .02) but no difference in eNO levels. Infants with total serum IgE levels of greater than 20 IU/mL had higher eNO levels compared with infants with IgE levels of 20 IU/mL or less (14.6 vs 11.2 ppb, P < .023) but no difference in forced flows or airway reactivity.

Conclusions

Our findings suggest that atopic characteristics of the infant might be important determinants of the airway physiology of forced expiratory flows, airway reactivity, and eNO.

Key words: Atopy, eczema, airway reactivity

Abbreviations used: eNO, Expired nitric oxide, FEF₇₅, Forced expiratory flow at 75% exhaled volume, NO, Nitric oxide, PC₃₀, Provocative concentration to decrease FEF₇₅ by 30%