Exhaled nitric oxide levels during treatment of pediatric acute asthma exacerbations and association with the need for hospitalization.

OBJECTIVES

To examine how exhaled nitric oxide (eNO) levels measured before and after treatment of asthma exacerbations relate to emergency department (ED) disposition.

METHODS

We enrolled children 6 to 17 years old treated for asthma exacerbations in a pediatric ED. Using an offline single-breath eNO sampling technique, we collected replicate initial samples before treatment and replicate final samples when disposition was decided. We determined correlations and coefficients of variability of eNO values (parts per billion, ppb) of samples and compared by disposition (hospitalization or discharge) mean initial and final eNO levels and initial-to-final change.

RESULTS

Eighty-one subjects had initial and final eNO values; 24 subjects with more severe presentations had final values only. Replicate eNO samples were correlated (initial r = 0.98, final r = 0.99) and had low coefficients of variability (initial, 0.059 ± 0.057; final, 0.061 ± 0.070). For subjects with initial and final values, initial eNO levels were similar by disposition (mean difference, -8.0 ppb; 95% confidence interval [CI], -24.8 to 8.9 ppb), as were final levels (mean difference, -2.8 ppb; 95% CI, -23.8 to 18.2 ppb). Overall, final eNO was higher than initial (36.3 ± 29.7 vs 31.5 ± 23.9 ppb), but only 63% of subjects had any increase. Change in eNO was similar by disposition (mean difference, 4.6 ppb; 95% CI, -3.4 to 12.6). For more severe subjects with final eNO only, eNO was similar by disposition (P = 0.47).

CONCLUSIONS

For children aged 6 to 17 years with asthma exacerbations, eNO levels can be reliably measured. However, eNO levels measured before treatment or when disposition was determined did not distinguish children needing hospitalization.