Fractional exhaled nitric oxide exchange parameters among 9-year-old inner-city children

To determine the feasibility of using a multiple flow offline fractional exhaled nitric oxide (FeNO) collection method in an inner-city cohort and determine this population's alveolar and conducting airway contributions of NO. We hypothesized that the flow independent NO parameters would be associated differentially with wheeze and seroatopy.

As part of a birth cohort study, 9-year-old children (n=102) of African-American and Dominican mothers living in low-income NYC neighborhoods had FeNO samples collected offline at constant flow rates of 50, 83, and 100 ml/sec. Seroatopy was defined as having measurable (≥ 0.35 IU/ml) specific IgE to any of the five inhalant indoor allergens tested. Current wheeze (last 12 months) was assessed by ISAAC questionnaire. Bronchial NO flux (J(NO) ) and alveolar NO concentration (C(alv)) were estimated by the Pietropaoli and Hogman methods.

Valid exhalation flow rates were achieved in 96% of the children. Children with seroatopy (53%) had significantly higher median J(NO) (522 pl/sec vs. 161 pl/sec, P<0.001) when compared to non-seroatopic children; however, median C(alv) was not significantly different between these two groups (5.5 vs. 5.8, P=0.644). Children with wheeze in the past year (21.6%) had significantly higher median C(alv) (8.4 ppb vs. 4.9 ppb, P<0.001), but not J(NO) (295 pl/sec vs. 165 pl/sec, P=0.241) when compared with children without wheeze. These associations remained stable after adjustment for known confounders/covariates.

The multiple flow method was easily implemented in this pediatric inner-city cohort. In this study population, alveolar concentration of NO may be a better indicator of current wheeze than single flow FeNO.