Abstract Introduction Spirometry is widely recognized as the gold standard for assessing airway disease in clinical practice. However, its effectiveness is often limited in advanced disease by the requirement for forceful respiratory manoeuvres. In recent years, Oscillometry has emerged as an alternative for pulmonary function evaluation for clinical and research purposes. Oscillometry also offers high sensitivity in the detection of small airways disease and changes in airway mechanics. Methods We aim to evaluate the comparative utility of oscillometry versus spirometry in the routine assessment of individuals with Alpha-1 antitrypsin deficiency. In particular, we evaluate if oscillometry may offer greater sensitivity than spirometry in detecting airway obstruction and small airway disease. Forced oscillation technique (FOT) was performed using the Resmon Pro Full device as per the European Respiratory Society technical standards. Spirometry was performed using ERS/ATS guidelines. The FOT parameters (R5, R19, R5-R19, X5, Ax) were compared with traditional spirometry parameters (FEV1, FVC, FEV1/FVC). Results We analysed oscillometry data from 100 Alpha-1 antitrypsin deficient individuals with matched spirometry data. This cohort consists of 30% moderately deficient (MZ) individuals and 70% severe deficiency (ZZ) individuals with a range of severity classified by GOLD stages from 0-4. We also evaluate if FEV1/FVC correlates with R5 and X5 and the association between FEV1, FEV1%, FVC, FVC% with R5, R19, R5% R19% and Ax. Our results suggest a beneficial role for FOT in detecting small airway disease in the setting of normal spirometry.Oscillometry parameters demonstrated progressive deterioration with increasing GOLD stage. Area of reactance (Ax) increased significantly across GOLD stages (p 0.0001), indicating worsening small airway dysfunction. Airway resistance (R5 z-scores and R5 % predicted) rose with increasing disease severity (p 0.0001 and p = 0.0030, respectively), reflecting worsening airway mechanics. In contrast, Airway reactance (X5) z-scores declined with GOLD severity (p 0.0001), consistent with reduced lung compliance and greater peripheral airway obstruction. These findings align with expected pathophysiological changes in COPD and support the utility of oscillometry indices as sensitive markers of disease progression and small airway impairment beyond conventional spirometric measures. Conclusions This real world study demonstrates consistency between spirometry and oscillometry measurements in AATD. Oscillometry is a good adjunct to spirometry, specifically for evaluation of those with normal spirometry and also advanced disease with fixed obstruction. The main factor limiting its widespread use in clinical practice is the paucity of data on reference values which is currently being addressed. This abstract is funded by: Alpha-1 Foundation Ireland
Roche et al. (Fri,) studied this question.