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

Background Fraction of exhaled nitric oxide (FE NO ) measurements performed on patients with acute asthma in the emergency department (ED) have previously shown poor reproducibility. Objectives 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. Methods 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. Results 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). Conclusions 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.