Quality assessment pathway for respiratory oscillometry

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.

Quality control in respiratory oscillometry: reproducibility measures ignoring reactance?

This study demonstrates the inadequacy of the current technical standards of oscillometry that are based on the within-trial reproducibility of the lowest-frequency R_rs, and suggests the use of a simple variability measure encompassing both R_rs and X_rs https://bit.ly/3AYRid6.

Clinical characteristics of airway impairment assessed by impulse oscillometry in patients with chronic obstructive pulmonary disease: findings from the ECOPD study in China

BACKGROUND

The role of airway impairment assessed by impulse oscillometry (IOS) in patients with chronic obstructive pulmonary disease (COPD) remains unclear. Therefore, this study aimed to analyze the proportion and clinical characteristics of airway impairment assessed by IOS across COPD severities, and explore whether airway impairment is a subtype of COPD.

METHODS

This study was based on cross-sectional data from the ECOPD cohort in Guangdong, China. Subjects were consecutively recruited from July 2019 to August 2021. They filled out questionnaires and underwent lung function tests, IOS and computed tomography (CT). COPD was defined as post-bronchodilator forced expiratory volume in one second/forced vital capacity < lower limit of normal (LLN). Meanwhile, airway impairment was defined as IOS parameters > upper limit of normal or < LLN. On the one hand, Poisson regression was employed to analyze the associations between acute exacerbations of COPD (AECOPD) in the previous year and airway impairment. On the other hand, logistic regression was used to assess differences in CT imaging between patients with IOS parameters' abnormalities and patients with normal IOS parameters.

RESULTS

768 COPD subjects were finally enrolled in the study. The proportion of airway impairment assessed by R₅, R₂₀, R₅-R₂₀, X₅, AX, and F_res was 59.8%, 29.7%, 62.5%, 52.9%, 60.9% and 67.3%, respectively. Airway impairment assessed by IOS parameters (R₅, R₅-R₂₀, X₅, AX, and F_res) in patients with COPD was present across all severities of COPD, particularly in GOLD 3-4 patients. Compared with patients with normal IOS parameters, patients with IOS parameters' abnormalities had more respiratory symptoms, more severe airway obstruction and imaging structural abnormalities. Patients with IOS parameters' abnormalities assessed by R₅ [risk ratio (RR): 1.58, 95% confidential interval (CI): 1.13-2.19, P = 0.007], R₅-R₂₀ [RR: 1.73, 95%CI: 1.22-2.45, P = 0.002], X₅ [RR: 2.11, 95%CI: 1.51-2.95, P < 0.001], AX [RR: 2.20, 95%CI: 1.53-3.16, P < 0.001], and F_res [RR: 2.13, 95%CI: 1.44-3.15, P < 0.001] had a higher risk of AECOPD in the previous year than patients with normal IOS parameters.

CONCLUSIONS

Airway impairment assessed by IOS may be a subtype of COPD. Future studies are warranted to identify the underlying mechanisms and longitudinal progression of airway impairment.

Airwave oscillometry and spirometry in children with asthma or wheeze

OBJECTIVE

Lung function testing is used in diagnosing asthma and assessing asthma control. Spirometry is most commonly used, but younger children can find performing this test challenging. Non-volitional tests such as airwave oscillometry (AOS) may be helpful in that population. We compared the success of spirometry and AOS in assessing bronchodilator responsiveness in children.

METHODS

AOS was conducted alongside routine lung function testing. Resistance at 5 Hz (R5), the difference between the resistance at 5 and 20 Hz (R5-20) and the area under the reactance curve (AX) were assessed. Patients between 5 and 16 years old attending clinic with wheeze or asthma were assessed. Patients performed AOS, followed by spirometry and were then given 400 µg salbutamol; the tests were repeated 15 minutes later.

RESULTS

Lung function testing was performed in 47 children of whom 46 (98%) and 32 (68%) performed acceptable baseline oscillometry and spirometry, respectively (p < 0.001). Children unable to perform acceptable spirometry were younger (7.35, range: 5.4-10.3 years) than those who could (10.4, range: 5.5-16.9 years), p < 0.001. The baseline z-scores of AOS R5 correlated with FEV₁ (r = 0.499, p = 0.004), FEF₇₅ (r = 0.617, p < 0.001), and FEV₁/FVC (r = 0.618, p < 0.001). There was a positive bronchodilator response assessed by spirometry (change in FEV₁ ≥ 12%) in eight children which corresponded to a change in R5 of 36% (range: 30%-50%) and a change in X5 of 39% (range: 15%-54%).

CONCLUSIONS

Oscillometry is a useful adjunct to spirometry in assessing young asthmatic children's lung function. The degree of airway obstruction, however, might affect the comparability of the results of the two techniques.

Comparison between impulse oscillometry parameters and spirometry for the diagnosis of exercise-induced bronchoconstriction in asthmatic children and adolescents

INTRODUCTION

Impulse oscillometry (IOS) parameters are obtained more easily and effortlessly in comparison to forced expiratory volume in the first second (FEV1).

OBJECTIVE

To compare IOS parameters to FEV1 in exercise-induced bronchoconstriction (EIB) diagnosis.

METHODS

Seventy-four (60.8% male; 39.2 female) young asthmatics aged between 7 and 17 years (mean 12.6 ± 2.8 years) were evaluated. EIB was defined as a reduction in FEV1 ≥ 10% compared with basal after standardized challenge by treadmill running (TR). IOS parameters and FEV1 were obtained at baseline and 5,15, and 30 min after TR. The area under the receiver operator characteristic curve (AUC) was calculated from the reduction in FEV1 ≥ 10% to evaluate the best psychometric characteristics of IOS parameters.

RESULTS

Twenty-four individuals (32.4%) were diagnosed with EIB. A moderate inverse correlation was found between the IOS and FEV1 variables immediately after the TR, with resistance at 5 Hz (R5Hz), resonant frequency (Fres), and reactance area (AX), (r = -0.64, r = -0.53 and r = -0.69, respectively, all with p < 0.05). An increase of 25 kPa/l/s in R5 Hz, of 19k Pa/l/s in AX and 21 Hz in Fres were found to best correlate with EIB diagnosis by FEV1 (sensitivity 67% and specificity 62%, sensitivity 84% and specificity 50%, and sensitivity 84% and specificity 60%, respectively).

CONCLUSION

IOS parameters have a significant inverse correlation with FEV1. This study presents cut-off points for EIB diagnosis for R5Hz, AX, and Fres, however, the findings in IOS parameters should be used and interpreted carefully if the goal is to replace spirometry.