Forced Oscillometry: A New Tool for Assessing Airway Function-Is It Ready for Prime Time?

Oscillometry in severe asthma: the state of the art and future perspectives

INTRODUCTION

Approximately 3-10% of people with asthma have severe asthma (SA). Patients with SA have greater impairment in daily life and much higher costs. Even if asthma affects the entire bronchial tree, small airways have been recognized as the major site of airflow limitation. There are several tools for studying small airway dysfunction (SAD), but certainly the most interesting is oscillometry. Despite several studies, the clinical usefulness of oscillometry in asthma is still in question. This paper aims to provide evidence supporting the use of oscillometry to improve the management of SA in clinical practice.

AREAS COVERED

In the ATLANTIS study, SAD was strongly evident across all severity. Various tools are available for evaluation of SAD, and certainly an integrated use of these can provide complete and detailed information. However, the most suitable method is oscillometry, implemented for clinical routine by using either small pressure impulses or small pressure sinusoidal waves.

EXPERT OPINION

Oscillometry, despite its different technological implementations is the best tool for determining the impact of SAD on asthma and its control. Oscillometry will also be increasingly useful for choosing the appropriate drug, and there is ample room for a more widespread diffusion in clinical practice.

Differences in respiratory oscillometry measurements using mouthpiece, mouth, and nasal mask in healthy adults

Airway resistance measurements using oscillometry provide a potential alternative to spirometry in assessing airway obstruction and dynamics due to measurements taken during tidal breathing. Oscillometry typically requires participants to form a tight seal around a mouthpiece that can prove challenging for some people. To address this challenge, we conducted a prospective study to evaluate the effect of different interfaces like mouthpiece, mouth mask, and nasal mask on respiratory impedance results from oscillometry in a cohort of healthy adults. Ten healthy adults [7 females; mean age: 38.9 yr (SD ±15.5)] underwent oscillometry using each of the three interfaces. We measured resistance at 5 Hz (Rrs₅), frequency dependence of resistance at 5-20 Hz (Rrs_5-20), and reactance area (Ax). Rrs₅ was not different when using the mouthpiece compared with the mouth mask [mean 2.98 cmH₂O/L/s (SD ±0.68) vs. mean 3.2 cmH₂O/L/s (SD ±0.81); P = 0.92; 95% CI -0.82 to +0.38], respectively. Nasal mask Rrs₅ measurements were significantly higher than mouthpiece measurements (mean 7.31 cmH₂O/L/s; SD ±2.62; P < 0.01; 95%CI -6.91 to -1.75). With Ax₅, we found a mean of 4.01 cmH₂O/L (SD ±2.04) with the mouth mask compared with a mean of 4.02 cmH₂O/L (SD ±1.87; P = 1.0 95% CI -1.86 to +1.87) for the mouthpiece, however, we found a significant difference between the mouthpiece and nasal mask for Ax (mean = 10.71; SD ±7.0 H₂O/L; P = 0.04, 95% CI -12.96 to -0.43). Our findings show that oscillometry using a mouth mask may be just as effective as using a mouthpiece in assessing airway dynamics and resistance.NEW & NOTEWORTHY This is the first study to compare the use of different interfaces: mouthpiece, mouth mask, and nasal mask, for oscillometry in an adult population. We report that using a mouth mask in oscillometry may provide a valid alternative to a mouthpiece in cohorts who may struggle to form the required tight seal that is typically required in oscillometry or spirometry.

Lung Function Reference Equations for Indian Ethnic Groups Based on a Handheld Forced Oscillation Device for Age 9-19 Years

OBJECTIVE

To develop regression equations to predict forced oscillation technique (FOT) parameters in Indian children and adolescents.

METHODS

Lung function was assessed in a multigeographic cohort of residential school children using a portable FOT-based device (PulmoScan) and spirometry. FOT measurements were performed in 1497 study participants, aged 9-19 y, from 8 Indian districts. Bland-Altman analysis was performed for additional 32 adult subjects to compare the results of PulmoScan to a standard IOS device in an outpatient setting. Reference equations were developed for R_rs and X_rs from the data of healthy subjects with normal spirometry using multivariate regression model for Indo-European, Dravidian, and mixed ethnic groups.

RESULTS

X5 (bias = 0.02) showed a better agreement than resistance parameters (R5 bias = 0.75, R20 bias =  -0.22) in IOS/PulmoScan comparison. Anthropometric variables (age, height, and weight) were positively correlated with reactance (X5) and negatively with resistance parameters (R5, R10, R15, and R20), with most associations being stronger in boys. Final regression model considered ethnicity as a key determinant along with anthropometry.

CONCLUSION

Multiethnic reference equations were developed for Indian children aged 9-19 y based on a novel handheld FOT device.

Airway smooth muscle function in asthma

Known to have affected around 340 million people across the world in 2018, asthma is a prevalent chronic inflammatory disease of the airways. The symptoms such as wheezing, dyspnea, chest tightness, and cough reflect episodes of reversible airway obstruction. Asthma is a heterogeneous disease that varies in clinical presentation, severity, and pathobiology, but consistently features airway hyperresponsiveness (AHR)—excessive airway narrowing due to an exaggerated response of the airways to various stimuli. Airway smooth muscle (ASM) is the major effector of exaggerated airway narrowing and AHR and many factors may contribute to its altered function in asthma. These include genetic predispositions, early life exposure to viruses, pollutants and allergens that lead to chronic exposure to inflammatory cells and mediators, altered innervation, airway structural cell remodeling, and airway mechanical stress. Early studies aiming to address the dysfunctional nature of ASM in the etiology and pathogenesis of asthma have been inconclusive due to the methodological limitations in assessing the intrapulmonary airways, the site of asthma. The study of the trachealis, although convenient, has been misleading as it has shown no alterations in asthma and it is not as exposed to inflammatory cells as intrapulmonary ASM. Furthermore, the cartilage rings offer protection against stress and strain of repeated contractions. More recent strategies that allow for the isolation of viable intrapulmonary ASM tissue reveal significant mechanical differences between asthmatic and non-asthmatic tissues. This review will thus summarize the latest techniques used to study ASM mechanics within its environment and in isolation, identify the potential causes of the discrepancy between the ASM of the extra- and intrapulmonary airways, and address future directions that may lead to an improved understanding of ASM hypercontractility in asthma.

Forced Oscillation Measurements in Patients with Idiopathic Interstitial Pneumonia Subjected to Pulmonary Rehabilitation

(1) Background: Pulmonary rehabilitation (PR) plays a significant therapeutic role for patients with idiopathic interstitial pneumonia (IIP). The study assessed the impact of physical activity on lung function measured by forced oscillation technique (FOT). (2) Methods: The study involved 48 patients with IIP subjected to a 3-week inpatient PR. The control group included IIP patients (n = 44) on a 3-week interval without PR. All patients were assessed at baseline and after 3 weeks of PR by FOT, spirometry, plethysmography, grip strength measurement and the 6-minute walk test. (3) Results: There were no significant changes in FOT measurements in the PR group, except for reduced reactance at 11 Hz, observed in both groups (p < 0.05). Patients who completed PR significantly improved their 6-min walk distance (6MWD) and forced vital capacity (FVC). The change in 6MWD was better in patients with higher baseline reactance (p = 0.045). (4) Conclusions: Patients with IIP benefit from PR by an increased FVC and 6MWD; however, no improvement in FOT values was noticed. Slow disease progression was observed in the study and control groups, as measured by reduced reactance at 11 Hz. Patients with lower baseline reactance limitations achieve better 6MWD improvement.

Non-human primate models of human respiratory infections

Respiratory pathogens represent a great burden for humanity and a potential source of new pandemics, as illustrated by the recent emergence of coronavirus disease 2019 (COVID-19). In recent decades, biotechnological advances have led to the development of numerous innovative therapeutic molecules and vaccine immunogens. However, we still lack effective treatments and vaccines against many respiratory pathogens. More than ever, there is a need for a fast, predictive, preclinical pipeline, to keep pace with emerging diseases. Animal models are key for the preclinical development of disease management strategies. The predictive value of these models depends on their ability to reproduce the features of the human disease, the mode of transmission of the infectious agent and the availability of technologies for monitoring infection. This review focuses on the use of non-human primates as relevant preclinical models for the development of prevention and treatment for human respiratory infections.

Lung Function Assessment by Impulse Oscillometry in Adults

Over the past decades, impulse oscillometry (IOS) has gained ground in the battery of pulmonary function tests. Performing the test requires minimal cooperation of the patient; therefore, it is a useful tool, especially in evaluating lung mechanics in children, elderly patients, and those who cannot perform spirometry. Oscillometry has also been used in both clinical and research departments. Studies were published mainly in asthma regarding detection of bronchodilator response and the therapeutic response to different drugs. Furthermore, it has been shown to be a sensitive technique to evaluate disease control. Other studied diseases were COPD, interstitial lung diseases, small airway disease, impairment of lung function due to exposure to occupational hazards or smoking, central airways obstruction, cystic fibrosis, monitoring lung mechanics during mechanical ventilation and sleep, neuromuscular diseases, lung transplant, and graft function. The aim of this review is to present the utility of oscillometry on the previously mentioned clinical fields.