Relationships among bronchodilator reversibility, the fraction of exhaled nitric oxide, and the parameters of the forced oscillation technique in adult asthma treated with inhaled corticosteroids and long-acting 2 agonists combination

In bronchial asthma, both airway inflammation and reversible airway narrowing require assessment and treatment. These two pathologies are treated primarily with inhaled corticosteroids (ICS) and long-acting beta 2 agonists (LABA), respectively. Therefore, ICS-LABA combinations are widely used to treat asthma. Airway inflammation and reversible airway narrowing are assessed primarily with fraction of exhaled nitric oxide (FENO) and bronchodilator reversibility (BDR). The forced oscillation technique (FOT) has recently attracted attention as a method for assessing obstructive respiratory disturbance. However, little is known about the relationships among these assessments. Therefore, we investigated the relationships among BDR, FENO, and FOT during ICS-LABA combination therapy. The subjects comprised 87 patients (25 men and 62 women) with asthma undergoing ICS/LABA combination therapy from July to September 2017. We applied the FENO test, FOT, and BDR testing without the patients stopping their therapy. The rates of change in FEV1 (Delta FEV1%) was correlated with FENO (r = 0.278). Among the FOT parameters, X5 (r = -0.263), Fres (r = 0.292), and AX (r = 0.245) were significantly correlated with Delta FEV1%. FENO, Fres and %FEV1 at baseline in these stable asthmatics were significantly assosiated with Delta FEV1% independently of the effects of age, atopy and body mass index (BMI). These results suggest that FENO and the results of respiratory function testing and FOT reflect different aspects of asthma and should be combined and comprehensively evaluated.