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

Abstract

Objectives and hypothesis: 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.

Methods: 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.

Results: 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.

Conclusions: 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.