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

Domiciliary measurements of airflow obstruction and inflammation may assist healthcare teams and patients in determining asthma control and facilitate self-management.To evaluate parameters derived from domiciliary spirometry and fractional exhaled nitric oxide (Feno) in monitoring asthma exacerbations and control.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.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 characteristic curve, 0.71) at the end of the monitoring period.Compliance with domiciliary spirometry and Feno varied widely among patients even in the setting of a research study. However, despite significant missing data, Feno and FEV1 were associated with asthma exacerbations and control, making these measurements potentially clinically valuable if used.