Early detection of small airway dysfunction in smokers and people with COPD via forced oscillation technique and its association with biomarkers: a pilot study

Early airflow changes associated with tobacco smoking often occur without observable obstruction or symptoms. Spirometry, the gold standard, has limitations in detecting early disease highlighting the need for sensitive diagnostic methods. We aimed to evaluate the utility of the forced oscillation technique (FOT) and biomarkers in detecting early airway abnormalities in smokers and patients with chronic obstructive pulmonary disease (COPD), and to explore the correlation between FOT parameters, spirometry measures, and biomarkers of airway inflammation. A cross-sectional study was conducted on 71 participants divided into three groups: patients with COPD (CP, <i>n</i> = 27), normal lung function smokers (NS, <i>n</i> = 22), and healthy controls (HC, <i>n</i> = 22). Lung function was assessed using spirometry and FOT, with biomarkers of inflammation (MMP-9, TIMP-1, and TIMP-2) measured from venous blood samples. Statistical analyses included group comparisons and correlation between lung function parameters and biomarker levels. Patients with COPD had significantly lower spirometry and higher FOT values compared with NS and HC (<i>P</i> < 0.01). In contrast, NS participants had similar spirometry values to HC, except for FEF25-75% and peak expiratory flow (PEF). The NS group exhibited significantly higher values for R5 compared with HC (<i>P</i> < 0.05). FOT parameters, particularly R5, demonstrated comparable diagnostic accuracy with spirometry in smokers, and all other parameters showed excellent discriminatory ability in patients with COPD. MMP-9 correlated positively with percentage predicted FOT parameters, R5-R20 and AX, and X5 (<i>r'</i> = 0.29, 0.30, and 0.31; <i>P</i> = 0.02, 0.04, and 0.02, respectively) in the combined group of smokers and patients with COPD and positively with percentage predicted Fres (<i>r'</i> = 0.30; <i>P</i> = 0.01) when all groups were analyzed together. FOT may be a sensitive and complementary measure to detect early airway changes in smokers and patients with COPD. MMP-9 correlating with FOT further supports the role of FOT combined with biomarkers in detecting early airway abnormalities in smokers and earlier stages of COPD.<b>NEW & NOTEWORTHY</b> This study highlights the utility of the forced oscillation technique (FOT) and biomarkers in detecting early airway changes in smokers and patients with COPD. FOT, along with biomarkers for airway remodeling can provide a sensitive measure and insight into early airway dysfunction, complementing traditional spirometry. These findings underscore the importance of early detection of airway abnormalities and the potential of FOT as a clinical tool for managing at-risk populations.