Circadian rhythm and variability of large and small airway spirometric variables in healthy individuals.

ABSTRACT

Objective: To assess the diurnal rhythm and variability of lung function in healthy individuals, encompassing both large and small airways. Methods: A prospective study enrolled 35 healthy adults without a history of smoking. Initial spirometry and a bronchodilation test were performed using the Jaeger spirometer, followed by a seven-day continuous home monitoring using the GOSPT2000. We evaluated repeatability using the intraclass correlation coefficient and agreement through linear regression and Bland-Altman analyses. Circadian rhythm and variability in spirometric measurements were analyzed using the coefficient of variation (CV) and daily variation rate. Results: The GOSPT2000 demonstrated strong repeatability and high agreement with the Jaeger spirometer. Notable findings included a decrease in nocturnal forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), and FEV3 by 44, 59, and 53 mL, respectively. In contrast, peak expiratory flow at noon showed an increase of 0.143L/min. Small-airway variables, including forced expiratory flow at 50% and 75% of the FVC and maximum midexpiratory flow, showed no significant diurnal variation. The nocturnal CV for large-airway variables was ≤ 4%, while for small-airway variables, it was ≤ 11.89%. Conclusion: This study has established a spectrum of variability for both large and small airways in healthy populations. The variability of small-airway variables is higher than that of large-airway variables. The investigation into the diurnal rhythms and variability characteristics of both large and small airway variables in the healthy population can serve as a foundation for diagnosing asthma or assessing the efficacy of asthma treatments.