Domiciliary monitoring of exhaled nitric oxide in the management of asthma: a pilot study

Whether asthma patients could benefit from home monitoring for fractional exhaled nitric oxide (flow of 50 mL/s, Fe_NO50) is unknown. We explore the application value of home monitoring Fe_NO50 in daily asthma management.

Twenty-two untreated, uncontrolled asthma patients were selected. Medical history, blood and sputum samples, pulmonary function, Asthma Control Test (ACT), and other clinical data of the subjects were collected. All subjects underwent daily monitoring for four weeks using a Fe_NO50 monitor and mobile spirometry (mSpirometry). The diurnal differences and dynamic changes were described. Compare the effect-acting time and the relative plateau of treatment between Fe_NO50 and mSpirometry monitoring.

In the first two weeks, the morning median (IQR) level of Fe_NO50 was 44 (35, 56) ppb, which was significantly higher than the evening median level [41 (32, 53) ppb, P = 0.028]. The median (IQR) effect-acting time assessed by Fe_NO50 was 4 (3, 5) days, which was significantly earlier than each measure of mSpirometry (P < 0.05). Fe_NO50 reached the relative plateau significantly earlier than FEV₁ (15 ± 2 days vs. 21 ± 3 days, P < 0.001). After treatment, the daily and weekly variation rates of Fe_NO50 showed a gradually decreasing trend (P < 0.05). The ACT score, sputum eosinophils, and blood eosinophils also significantly improved (P ≤ 0.01).

The daily home monitoring of Fe_NO50 in asthmatic patients showed significant circadian rhythm, and the sensitivity of Fe_NO50 in evaluating the response to treatment was higher than mSpirometry. The daily and weekly variation rates of Fe_NO50 change dynamically with time, which may be used to assess the condition of asthma.