The Value of Impulse Oscillometric Parameters and Quantitative HRCT Parameters in Differentiating Asthma-COPD Overlap from COPD

Differential Clinical Significance of FENO200 and CANO in Asthma, Chronic Obstructive Pulmonary Disease (COPD), and Asthma-COPD Overlap (ACO)

Purpose

To investigate the differential clinical significance of fractional concentration of exhaled nitric oxide measured at a flow rate of 200 mL/s (FENO200) and concentration of nitric oxide in alveolar (CANO) in asthma, chronic obstructive pulmonary disease (COPD) or asthma-COPD Overlap (ACO).

Methods

A total of 178 patients were included, with 82 patients in asthma group, 47 patients in COPD group and 49 patients in ACO group. Data for demographic data, spirometry and exhaled nitric oxide were collected for comparative analysis, correlation analysis and discriminant canonical analysis.

Results

The values of FENO200 in asthma, COPD and ACO groups were 11.0(7.0-22.3), 8.0(6.0-11.0) and 9.0(6.5-19.5) ppb, respectively. In the asthma group, FENO200 exhibited negative correlations with FEV1/FVC, MMEF and MEF50. No significant correlation was observed between CANO and pulmonary function parameters. In the COPD group, both FENO200 and CANO showed negative correlation with pulmonary function parameters including FVC, FEV1, PEF, MMEF, MEF75, MEF50. In the ACO group, FENO200 demonstrated no significant correlation with pulmonary function parameters, while CANO was correlated with FEV1, PEF, MMEF and MEF50. In COPD group, ΔFEV1 in the bronchodilator test was correlated with FENO200. As for the ACO group, ΔFEV1 was correlated with CANO. In the discriminant canonical analysis, four parameters including gender, age, MEF75 and FENO50 discriminated between the three groups of asthma, COPD and ACO.

Conclusion

In asthma, COPD and ACO, FENO200 has demonstrated a robust correlation with CANO. Elevated FENO200 levels are predominantly indicative of pulmonary function impairment in asthma and COPD, whereas elevated CANO levels are mainly correlated with pulmonary function impairment in COPD and ACO. Compared with FENO200 and CANO, FENO50 may have a better discriminatory ability in distinguishing asthma, COPD and ACO.

Clinical Value of Impulse Oscillometry in Chronic Obstructive Pulmonary Disease: A Systematic Review and Meta-Analysis

INTRODUCTION

Impulse oscillometry (IOS) is an effortless test compared to spirometry. Numerous studies explored the role of IOS in spirometry-based chronic obstructive pulmonary disease (COPD), but most of them had limited sample sizes with poor statistical power. This systematic review and meta-analysis aimed to pool the individual data and quantitatively analyze the clinical value of IOS in COPD.

METHODS

PubMed, Web of Science, Ovid, Cochrane Library, China National Knowledge Internet, and Wanfang were searched for studies with comparisons of IOS indicators between COPD patients and healthy controls, including respiratory resistance at 5 Hz (R5) and 20 Hz (R20), difference between R5 and R20 (R5-R20), respiratory reactance at 5 Hz (X5), resonant frequency (Fres), and area of reactance (Ax). Meta-analyses were conducted to calculate the weighted mean differences (WMDs) and 95% confidence intervals (CIs).

RESULTS

39 eligible studies were enrolled, involving 6,144 COPD patients and 4,611 healthy controls. Relative to healthy controls, COPD patients had significantly higher R5 (WMD: 0.17, 95% CI: 0.14, 0.20), R5-R20 (WMD: 0.13, 95% CI: 0.11, 0.15), Fres (WMD: 9.04, 95% CI: 7.66, 10.42), Ax (WMD: 1.24, 95% CI: 0.86, 1.61), and lower X5 (WMD: -0.15, 95% CI: -0.18, -0.11), and such differences became even greater as the Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage escalated. Pooled correlation coefficients presented that R5, R5-R20, Fres, and X5 were significantly related to post-bronchodilator forced expiratory volume in the first second (FEV1)/forced vital capacity ratio (meta r = -0.37, -0.45, -0.53, and 0.42, respectively) and FEV1 as a percentage of predicted value (meta r = -0.43, -0.54, -0.59, and 0.56, respectively).

CONCLUSION

IOS may be a supplement to spirometry in diagnosing and assessing COPD, especially when spirometry is inappropriate. More well-designed, large sample-sized, prospective studies are warranted to establish an IOS-based criterion for COPD management.

Window of opportunity for respiratory oscillometry: A review of recent research

Oscillometry has been around for almost 70 years, but there are still many unknowns. The test is performed during tidal breathing and is therefore free from patient-dependent factors that could influence the results. The Forced Oscillation Technique (FOT), which requires minimal patient cooperation, is gaining ground, particularly with elderly patients and children. In pulmonology, it is a valuable tool for assessing obstructive conditions (with a distinction between central and peripheral obstruction) and restrictive disorders (intrapulmonary and extrapulmonary). Its sensitivity allows the assessment of bronchodilator and bronchoconstrictor responses. Different lung diseases show different patterns of changes in FOT, especially studied in asthma and chronic obstructive pulmonary disease. Because of these differences, many studies have analysed the usefulness of this technique in different areas of medicine. In this paper, the authors would like to present the basics of oscillometry with the areas of its most recent clinical applications.

Comparative assessment of small airway dysfunction by impulse oscillometry and spirometry in chronic obstructive pulmonary disease and asthma with and without fixed airflow obstruction

Background

Small airways play a major role in the pathogenesis and prognosis of chronic obstructive pulmonary disease (COPD) and asthma. More data on small airway dysfunction (SAD) using spirometry and impulse oscillometry (IOS) in these populations are required. The objective of this study was to compare the two methods, spirometry and IOS, for SAD detection and its prevalence defined by spirometry and IOS in subjects with COPD and asthma with and without fixed airflow obstruction (FAO).

Design

This is a cross-sectional study.

Methods

Spirometric and IOS parameters were compared across four groups (COPD, asthma with FAO, asthma without FAO, and healthy subjects). SAD defined by spirometry and IOS criteria were compared.

Results

A total of 262 subjects (67 COPD, 55 asthma with FAO, 101 asthma without FAO, and 39 healthy controls) were included. The prevalence of SAD defined by using IOS and spirometry criteria was significantly higher in patients with COPD (62.7 and 95.5%), asthma with FAO (63.6 and 98.2%), and asthma without FAO (38.6 and 19.8%) in comparison with healthy control (7.7 and 2.6%). IOS is more sensitive than spirometry in the detection of SAD in asthma without FAO (38.6% vs. 19.8%, p = 0.003) However, in subjects with FAO (COPD and asthma with FAO), spirometry is more sensitive than IOS to detect SAD (95.5% vs. 62.7%, p < 0.001 and 98.2% vs. 63.6%, p < 0.001, respectively).

Conclusion

Small airway dysfunction was significantly detected in COPD and asthma with and without FAO. Although IOS shows more sensitivity than spirometry in the detection of SAD in asthma without FAO, spirometry is more sensitive than IOS in patients with FAO including COPD and asthma with FAO.