Can forced oscillation technique parameters predict airway hyperresponsiveness to histamine?

Background Measurement of airway hyperresponsiveness (AHR) is more sensitive than spirometry for diagnosing and monitoring asthma. However, because the measurement of AHR is invasive, safer and less invasive methods are needed. Forced oscillation technique (FOT) is a rapid, noninvasive method of measuring the resistance and reactance of the respiratory system at rest. Objective To assess whether FOT parameters predict the level of AHR to histamine in stable adult Japanese asthmatics. Methods We recruited 62 stable asthmatics that were being treated with inhaled corticosteroids and investigated the correlations between AHR to histamine and FOT parameters. For each patient, we determined fraction of exhaled nitric oxide (FeNO), forced expiratory volume in 1 s (FEV 1 ), and percentage predicted FEV 1 (%FEV 1 ) with standard techniques, and resistance at 5 Hz (R5) and 20 Hz (R20), the difference between R5 and R20 (R5 – R20), reactance at 5 Hz (X5), frequency of resonance (Fres), and low-frequency reactance area (ALX) with a MostGraph FOT machine (Chest Co., Ltd., Tokyo, Japan). We then determined the logarithm of the provocative concentration of histamine producing a 20% fall in FEV 1 (Log PC 20 ). Results R5, R20, X5, Fres, and ALX were significantly correlated with FEV 1 and %FEV 1 . Log PC 20 was significantly correlated with R5 ( r = –0.446, P r = –0.401, P = 0.001), and R5 – R20 ( r = –0.401, P = 0.001). There were no significant correlations between the FOT parameters and FeNO. Conclusion FOT parameters measured with a MostGraph FOT machine may predict the level of AHR to histamine in stable adult asthmatics.