Domiciliary Fractional Exhaled Nitric Oxide and Spirometry in Monitoring Asthma Control and Exacerbations

BACKGROUND: Domiciliary measurements of airflow obstruction and inflammation may assist healthcare teams and patients in determining asthma control and facilitate self-management. OBJECTIVE: To evaluate parameters derived from domiciliary spirometry and fractional exhaled nitric oxide (FENO) in monitoring asthma exacerbations and control.METHODS: Patients with asthma were provided with hand-held spirometry and FENO devices in addition to their usual asthma care. Patients were instructed to perform twice-daily measurements for 1 month. Daily symptoms and medication change were reported through a mobile health system. The Asthma Control Questionnaire was completed at the end of the monitoring period.RESULTS: One hundred patients had spirometry, of which 60 were given additional FENO devices. Compliance rates for twice-daily measurements were poor (median [interquartile range], 43% [25%-62%] for spirometry; 30% [3%-48%] for FENO); at least 15% of patients took little or no spirometry measurements and 40% rarely measured FENO. The coefficient of variation (CV) values in FEV1 and FENO were higher, and the mean % personal best FEV1 lower in those who had major exacerbations compared with those without (P < .05). FENO CV and FEV1 CV were associated with asthma exacerbation during the monitoring period (area under the receiver-operating characteristic curve, 0.79 and 0.74, respectively). Higher FENO CV also predicted poorer asthma control (area under the receiver-operating char-acteristic curve, 0.71) at the end of the monitoring period.