Evaluation of exhaled nitric oxide measurements in the emergency department for patients with acute asthma

Abstract

Fraction of exhaled nitric oxide (FE(NO)) measurements performed on patients with acute asthma in the emergency department (ED) have previously shown poor reproducibility. To evaluate the reproducibility of FE(NO) measurements in the ED using a new monitoring device, to evaluate any factors that may correlate with FE(NO) measurements, and to investigate if FE(NO) levels predict the need for admission to the hospital. Thirty-five adult patients with asthma seen in the ED performed FE(NO), forced expiratory volume in 1 second, and peak expiratory flow rate maneuvers in triplicate. Reproducibility was evaluated using the intraclass correlation coefficient and the coefficient of variation. Associations between FE(NO), demographic, and traditional asthma measurements were investigated. The FE(NO) levels between patients admitted for further care and those discharged home were compared. The FE(NO) measurements showed acceptable intraclass correlation coefficient and coefficient of variation values (0.98 and 9.42%, respectively) for reproducibility. These values were superior to the values obtained for forced expiratory volume in 1 second and peak expiratory flow rate. No correlation was found between FE(NO) and traditional asthma factors, although length of the asthma attack trended toward statistical significance (P = .08). The FE(NO) levels did not differ between those admitted and those discharged home (P = .53). Fraction of exhaled nitric oxide measurements can be obtained in the ED setting with good reproducibility. These measurements may provide useful information not obtainable by other means. Further research is needed to determine how best to incorporate FE(NO) values into the ED setting.