Adding oscillometry to spirometry in guidelines better identifies uncontrolled asthma, future exacerbations, and potential targeted therapy

Oscillometry-defined small airways dysfunction as a treatable trait in asthma

The small airways, also referred to as the lung's silent zone, are closely associated with poor symptom control and more frequent asthma exacerbations. The oscillometry technique superimposes sound or airwaves onto normal tidal breathing and provides information on resistance and reactance, that is, obstacles to airflow occurring inside and outside of the bronchi. More recently, a management paradigm based on so-called "treatable traits" has been proposed to personalize and improve asthma care for individuals by proactively identifying and targeting modifiable pulmonary, extrapulmonary, and behavioral traits affecting asthma control. In this review article, we evaluate the literature on small airways dysfunction as a potential treatable trait in persistent asthma. In particular, we discuss whole- and intrabreath oscillometry and the impact of extrafine inhaled corticosteroids and systemic biologics on the peripheral airways.

Impulse Oscillometry Combined to FeNO in Relation to Asthma Control Among Preschool Children

Objective

We aimed to observe and analyze the differences in impulse oscillometry (IOS) and fractional expiratory nitric oxide (FeNO) in relation to asthma control among preschool children, and to explore the predictive value of IOS combined with FeNO for uncontrolled asthma.

Methods

This study enrolled 171 preschool children with asthma and 30 healthy preschool children between June 2022 and June 2023. We categorized the asthmatic children as having controlled asthma (n=85) and uncontrolled asthma (n=86) after a 3-month follow-up. IOS and FeNO were collected on the first visit at baseline. Differences in metrics were compared between controlled asthma, uncontrolled asthma and healthy control groups. The area under the receiver operating characteristic curve (AUROC) was utilized to explore the discriminative ability of IOS and FeNO, alone or in combination, against uncontrolled asthma.

Results

Compared to the controlled asthma group, the IOS values of R5, X5, R5-R20, and Fres were significantly higher in the uncontrolled asthma group, except for R20. R5 and R5-R20 had the highest area under the curve (AUC), which could reach 0.74 (95% CI 0.66-0.82) and 0.72 (95% CI 0.64-0.80). R20 had the lowest AUC of 0.59. The AUC for FeNO alone was 0.88 (95% CI 0.84-0.93) with a cutoff value of 17.50 ppb, sensitivity and specificity of 0.73 and 0.89. The AUCs of all IOS metrics combined with FeNO were significantly higher, with the highest AUC of 0.92 (95% CI 0.87-0.96) for R5-R20+FeNO, and with a sensitivity and specificity of 0.88 and 0.84.

Conclusion

There were significant differences in IOS and FeNO in relation to asthma control among preschooler children. FeNO might be the best predictor of asthma control, and adding any of IOS metrics increased moderately the predictive value.

Small airway dysfunction measured by impulse oscillometry is associated with exacerbations and poor symptom control in patients with asthma treated in a tertiary hospital subspecialist airways disease clinic

Introduction

Small airways dysfunction contributes to asthma pathophysiology and clinical outcomes including exacerbations and asthma control. Respiratory oscillometry is a simple, non-invasive and effort independent lung function test that provides vital information about small airway function. However, interpretation and clinical utility of respiratory oscillometry has been in part limited by lack of agreed parameters and the respective cutoffs. The aim of this study was to determine the prevalence of small airways dysfunction based on published impulse oscillometry (IOS) definition in patients with asthma referred to a tertiary asthma clinic and the extent to which it correlates with asthma clinical outcomes.

Methods

We retrospectively reviewed the medical records of all patients with asthma managed in the severe asthma clinic between January 2019 and December 2022 who underwent routine lung function tests with oscillometry and spirometry. Small airways dysfunction was determined from various published IOS parameter cutoffs, and the data were analysed to determine correlations between IOS parameters and asthma outcomes.

Results

Amongst the 148 patients, the prevalence of small airways dysfunction ranged from 53% to 78% depending on the defining oscillometry parameter. All oscillometry parameters correlated with the severity of airflow obstruction (FEV1% predicted, p < 0.001). Several oscillometry parameters correlated with asthma symptom burden, the strongest correlation was seen for frequency dependent resistance (R5-R20) with scores of Asthma Control Questionnaire (ACQ6) (Spearman's rank coefficient 0.213, p = 0.028) and Asthma Control Test (ACT) (Spearman's rank coefficient -0.248, p = 0.012). R5-R20 was predictive of poor asthma control defined by ACQ6 >1.5 (OR 2.97, p = 0.022) or ACT <20 (OR 2.44, p = 0.055). Small airways dysfunction defined by R5-R20 and area under the reactance curve (AX) also significantly increases asthma exacerbation risk (OR 2.60, p = 0.02 and OR 2.31, p = 0.03 respectively).

Conclusion

Respiratory oscillometry is a sensitive measure of small airways dysfunction that should complement spirometry in the routine assessment of asthma. Small airways dysfunction is highly prevalent in patients with asthma referred to a tertiary asthma clinic. R5-R20 was the metric most predictive in identifying patients at risk of asthma exacerbations and poor asthma control.

Predictive Value of Impulse Oscillometry Combined with Fractional Expiratory Nitric Oxide Test for Asthma in Preschool Children

Objective

Prediction of asthma in preschool children is challenging and lacks objective indicators. The aim is to observe and analyze the variances between impulse oscillometry (IOS) and fractional expiratory nitric oxide (FeNO) in preschool children with wheezing, establish a joint prediction model, and explore the diagnostic value of combining IOS with FeNO in diagnosing asthma among preschool children.

Patients and methods

This study enrolled children aged 3-6 years with wheezing between June 2021 and June 2022. They were categorized as asthmatic (n=104) or non-asthmatic (n=109) after a 1-year follow-up. Clinical data, along with IOS and FeNO measurements from both groups, underwent univariate regression and multiple regression analyses to identify predictive factors and develop the most accurate model. The prediction model was built using the stepwise (stepAIC) method. The receiver operating characteristic curve (ROC), calibration curve, Hosmer-Lemeshow test, and decision curve analysis (DCA) were employed to validate and assess the model.

Results

During univariate analysis, a history of allergic rhinitis, a history of eczema or atopic dermatitis, and measures including FeNO, R5, X5, R20, Fres, and R5-R20 were found to be associated with asthma diagnosis. Subsequent multivariate analysis revealed elevated FeNO, R5, and X5 as independent risk factors. The stepAIC method selected five factors (history of allergic rhinitis, history of eczema or atopic dermatitis, FeNO, R5, X5) and established a prediction model. The combined model achieved an AUROC of 0.94, with a sensitivity of 0.89 and specificity of 0.88, surpassing that of individual factors. Calibration plots and the HL test confirmed satisfactory accuracy.

Conclusion

This study has developed a prediction model based on five factors, potentially aiding clinicians in early identification of asthma risk among preschool children.

The role of oscillometry in asthma

PURPOSE OF REVIEW

Oscillometry is a noninvasive pulmonary function test that has gained significant interest in the evaluation of lung disease. Currently, oscillometry is primarily a research tool, but there is a growing body of evidence supporting its clinical use. This review describes the recent work evaluating the role of oscillometry in the diagnosis and treatment of asthma.

RECENT FINDINGS

A large body of observational data supports the ability of oscillometry to distinguish healthy individuals from those with respiratory symptoms or lung disease. Oscillometry may not be as useful as an isolated diagnostic test in asthma, but the combination with other pulmonary function tests may improve its diagnostic ability. Oscillometry can detect peripheral airways dysfunction in asthma, which is associated with symptoms and the risk for exacerbations. To help guide future research, minimal clinically important differences for specific oscillometry variables have been developed. Oscillometry may be useful in monitoring the response to biological therapy and has potential for personalizing treatment for individual patients. Oscillometry also has potential in uncovering unique aspects of the pathophysiology of asthma in obesity.

SUMMARY

Oscillometry is a promising tool in the diagnosis and management of asthma. More research is needed to support its routine clinical use.