Changes in fractional exhaled nitric oxide, forced expiratory volume in one second, and forced oscillation technique parameters over three years in adults with bronchial asthma managed under Yokohama Seibu Hospital’s coordinated care system

In western Yokohama, our hospital and primary care clinics manage adults with asthma via a coordinated care system. We investigated the changes in the fractional expired nitric oxide (FeNO), forced expiratory volume in 1 second (FEV₁), and forced oscillation technique (FOT) parameters over 3 years in a cohort of patients in our collaborative system.

From 288 adults with well controlled asthma managed under the Yokohama Seibu Hospital coordinated care system between January 2009 and May 2018, we selected 99 subjects to undergo spirometry, FeNO and FOT testing over 3 years and analyzed the changes in these parameters.

Of the 99 patients enrolled, 17 (17.2%) experienced at least one exacerbation (insufficiently controlled (IC)), whereas, 82 (82.8%) remained in well controlled during the 3-year study period. Of well-controlled patients, 54 patients (54.5%) met the criteria for clinical remission under treatment (CR); the remaining 28 patients did not meet the CR criteria (WC). There were no differences in FeNO, FEV₁, or FOT parameters at baseline among the IC, WC, and CR groups. The levels of FEV₁ decreased gradually, whereas the levels of FeNO decreased significantly over 3 years. The levels of percent predicted FEV₁ (%FEV₁) significantly increased. We also observed significant improvement in FOT parameters; reactance at 5 Hz (R₅), resonant frequency (Fres), and integral of reactance up to the resonant frequency (AX). The CR group demonstrated significant relationships between the change in FeNO and the change in FEV₁ and between the change in FEV₁ and the change in FOT parameters. No significant correlations emerged in the IC or WC group.

The decrease in FeNO and increase in %FEV₁, we observed in all study participants suggest that the coordinated care system model benefits patients with asthma. Although it is difficult to predict at baseline which patients will experience an exacerbation, monitoring changes in FeNO and FEV₁ is useful in managing patients with asthma. Furthermore, monitoring changes in R_5, Fres, and AX via forced oscillation technique testing is useful for detecting airflow limitation.