Application value of the impulse oscillometry system in the airway evaluation of patients with chronic obstructive...

The impulse oscillometry system (IOS) uses a tidal-breathing method requiring considerably less patient cooperation than conventional spirometry, thereby more accurately reflecting normal respiratory physiology.

To investigate the application value of the IOS in evaluating the airways of patients with chronic obstructive pulmonary disease (COPD) across different age groups in China.

This retrospective cohort study enrolled 115 COPD patients and 103 healthy volunteers, categorised into young/middle-aged (≤60 years) and elderly (>60 years) groups. Participants underwent IOS and conventional pulmonary function tests. Logistic regression and receiver operating characteristic (ROC) curves were used to evaluate the sensitivity, specificity and optimal cut-off values of key IOS parameters - including resonance frequency (Fres), low-frequency reactance area (AX) and resistance percentage (R5-R20%R5) - to distinguish COPD patients within each age stratum.

For young and middle-aged patients, the area under the curve (AUC) of AX was 0.838 (95% confidence interval (CI): 0.756-0.921, P < 0.001); a cut-off value of 1.36 kPa/L yielded 83.7% sensitivity and 75.0% specificity. For elderly patients, the AUC of R5-R20%R5 was 0.849 (95% CI: 0.775-0.924, P < 0.001); a cut-off value of 48.68% achieved 76.4% sensitivity and 97.9% specificity. Additionally, the AUC of Fres in the elderly was 0.734 (95% CI: 0.646-0.823, P < 0.001; cut-off: 22.75 Hz; sensitivity: 56.9%; specificity: 87.2%).

Changes in AX are sensitive indicators for early COPD screening in young and middle-aged individuals. Furthermore, R5-R20%R5 and Fres serve as highly specific and reliable diagnostic parameters for elderly patients, particularly those unable to cooperate with conventional spirometry.