Clinical application value of impulse oscillometry in geriatric patients with COPD

Abstract

Background: The diagnosis and assessment of COPD rely mainly on the use of spirometry, which is an effort-dependent test and requires good patient cooperation. Impulse oscillometry (IOS) is a non-volitional method that requires less effort and cooperation and presents advantages for geriatric patients. However, the clinical application value of IOS in geriatric patients with COPD remains unclear.

Aim: The aim of this study was to investigate the clinical application value of IOS in geriatric patients with COPD.

Subjects and methods: A total of 234 subjects were retrospectively enrolled in this study, including 133 patients with COPD and 101 healthy volunteers. All the participants underwent IOS and spirometry examination. The data were collected and analyzed in the overall group, the geriatric group (aged ≥65 years), and the advanced elderly group (aged ≥80 years).

Results: 1) In COPD patients, a significant increase in respiratory impedance (Z5), resonant frequency (Fres), and respiratory resistance (R5, R20, R5-R20) and a decrease in respiratory reactance (X5) were observed in the overall group, the geriatric group, and the advanced elderly group compared with the healthy control subjects. 2) The IOS parameters correlated well with spirometry in COPD. In particular, R5-R20 showed the best correlation with forced expiratory volume in 1 second (FEV₁) in the different age groups. 3) Fres and R5-R20 had the best diagnostic efficiency for COPD. The area under the curve (AUC) values for Fres, expressed by the receiver operating characteristic (ROC) curve, were 0.905, 0.909, and 0.914, for the different age groups, respectively. 4) The optimal cutoff values for Fres to diagnose airflow obstruction from ROC curves was 17.715 in the COPD patients. Its sensitivity and specificity were 0.789 and 0.931, respectively, and the cutoff values were similar in geriatric and advanced elderly patients.

Conclusion: IOS demonstrated good relevance compared with spirometry for geriatric patients with COPD. IOS may serve as an alternative method for spirometry in elderly subjects for the evaluation of the state of COPD.

Keywords: COPD; geriatric patients; impulse oscillometry; spirometry.

Figure 1

Changes in IOS parameters with increasing airflow limitation. Notes: ^aP<0.05 compared with the healthy controls. ^bP<0.05 compared with COPD 1. ^cP<0.05 compared with COPD 2. Abbreviations: IOS, impulse oscillometry; R5–R20, respiratory resistance; Fres, resonant frequency; X5, respiratory reactance; Z5, respiratory impedance.

Figure 2

ROC curves for COPD in the overall subjects (A), geriatric subjects (B), and advanced elderly subjects (C). Abbreviations: ROC, receiver operating characteristic; X5, respiratory reactance; R5–R20, respiratory resistance; Fres, resonant frequency; Z5, respiratory impedance.