The Relevance of Small Airway Dysfunction in Asthma with Nocturnal Symptoms

Small airway disease (SAD) in asthma in pregnancy evaluated by impulse oscillometry: A cross-sectional study

BACKGROUND AND OBJECTIVE

Asthma is a common respiratory disease in pregnancy, with approximately 18% of cases worsening. Small airway disease (SAD) with a reported prevalence of up to 70% is now recognised as a principal indicator of poor asthma control. Impulse oscillometry (IOS) is a non-invasive, technically easier, and patient-friendly tool for detecting SAD. We aimed to assess the prevalence of SAD in pregnant women with asthma and the acceptance of the IOS across different trimesters of pregnancy.

METHODS

This cross-sectional study was conducted among pregnant women aged ≥18 years with clinically diagnosed asthma. All patients underwent IOS following manufacturer and European Respiratory Society guidelines. A questionnaire was used to assess their satisfaction with the technique.

RESULTS

Out of 78 patients who underwent IOS, SAD was present in 55.1% (95% CI = 43.4 to 66.4%). Post-bronchodilator reversibility was observed in 37.2% of patients. Abnormal total (R5) and larger (R20) airway resistance were found in 79.5% and 64.1% of patients, respectively. Other IOS parameters (Fres, AX, and X5) were abnormal in 58.9%, 30.7%, and 39.7% of patients, respectively. Bivariate and multivariate logistic regression analyses indicated longer duration of asthma (OR = 1.1; 95% CI = 1.05-1.18; P < 0.001) and passive smoking (OR = 4.2; 95% CI = 1.58-11.1; P = 0.004) were significantly associated with SAD. All participants tolerated the IOS well, with a satisfaction score of 4.75 ± 0.72.

CONCLUSION

The IOS is a helpful tool for the evaluation of SAD, a significant comorbidity in pregnant women with asthma. Factors such as longer disease duration and exposure to passive smoking, akin to risk factors for chronic airflow obstruction, are significantly associated with SAD. Future research should explore SAD's impact on clinical management and overall asthma outcomes.

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.

Small airways response to bronchodilators as the marker of the uncontrolled asthma in children

OBJECTIVE

Aim: To develop the criteria of small airways response to bronchodilators (by spirometry indices maximal expiratory flow (MEF50 and MEF25) as the markers of uncontrolled asthma course.

PATIENTS AND METHODS

Materials and Methods: The study involved 92 participants (64 boys and 28 girls) aged 6 to 17 years (60 were less than 12 years old) with diagnosed asthma. Asthma control was assessed with the use of Asthma Control Test and Asthma Control Questionnaire. Spirometry and bronchodilator responsiveness testing were performed for all participants.

RESULTS

Results: Mostly, the studied children had a normal level of forced expiratory volume in the first second (FEV1), even at unsatisfactory symptoms control. The indicators of the medium and small airways patency were significantly worse in uncontrolled asthma children even in normal FEV1. Among children, the lack of asthma control can be caused by small airways obstruction in up to 80% cases. Among children who need the high dose inhaled corticosteroids treatment 93.3% have uncontrolled asthma with small airways obstruction. We found out that MEF50 and MEF25 could be the signs of the reversibility of bronchial obstruction and uncontrolled asthma with high sensitivity and specificity.

CONCLUSION

Conclusions: Indices MEF50 and MEF25 allow detecting the small airways obstruction and their reversibility as a mark of uncontrolled asthma (MEF25 has a higher diagnostic value). In case of MEF50 and/or MEF25 increasing for 22% or 25% accordingly in bronchodilator test in children, the asthma should be considered uncontrolled.

Impulse oscillometry defined small airway dysfunction in asthmatic patients with normal spirometry: Prevalence, clinical associations, and impact on asthma control

BACKGROUND

The small-airway dysfunction (SAD), detected with impulse oscillometry (IOS) methods, has been recently better characterized in patients with asthma. However, little is known about SAD in asthmatic patients with normal spirometry (NS).

OBJECTIVE

In this study, we aimed to investigate, in an unselected sample of 321 patients with physician-diagnosed asthma and NS, prevalence, clinical characterization, and impact on asthma control of IOS-defined SAD. As a secondary objective of the study, we focused on comparing the difference between IOS- and spirometry-defined SAD.

METHODS

Consecutive patients with a previous diagnosis of asthma but normal spirometry at the moment of the enrollment were stratified by the presence of IOS-defined SAD (difference in resistance at 5 Hz and at 20 Hz [R5-R20] greater than 0.07 kPa x s x L-1). We have also assessed the presence of SAD defined by spirometry, according to FEF 25-75 < 65% of the predicted. Clinical and laboratory features were collected, and univariable and multivariable analyses were used to analyze cross-sectional associations between clinical variables and outcomes (SAD).

RESULTS

IOS-defined SAD was present in 54.1% of the cohort. In contrast, spirometry-defined SAD was present in only 10% of patients. Subjects with IOS-defined SAD showed less well-controlled asthma and a higher mean inhaled corticosteroid dosage use compared with subjects without SAD (both P < .001). Overweight (odds ratio [OR], 1.14; 95% CI, 1.05-1.23), exacerbation history (OR, 3.06; 95% CI, 1.34-6.97), asthma-related night awakenings (OR, 6.88; 95% CI, 2.13-22.23), exercise-induced asthma symptoms (OR, 33.5; 95% CI, 9.51-117.8), and controlled asthma (OR, 0.22; 95% CI, 0.06-0.84) were independently associated with SAD.

CONCLUSIONS

Asthmatic patients with IOS-defined SAD showed less well-controlled asthma, more severe exacerbations and higher mean inhaled corticosteroid dosage. We confirmed exercise-induced asthma, asthma-related night awakenings, exacerbation history, and overweight as independently associated with SAD, while showing well-controlled asthma as inversely associated. SAD may be overlooked by standard spirometry.

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.

Detection of Small Airway Dysfunction in Asthmatic Patients by Spirometry and Impulse Oscillometry System

BACKGROUND

There is no gold standard in diagnosing SAD. Indicators of SAD are considered: (a) a value <65% of predicted values of two of three measures, FEF25-75, FEF50 e FEF75 (FEF+); (b) a value of FEV3/FEV6 < LLN (FEV3/FEV6+); (c) an IOS value of R5-R20 >0.07 kPa·s·L-1 (R5-R20+).

AIM AND OBJECTIVES

The aim of the study was to ascertain, in asthmatic patients, whether spirometry and IOS indicators agree in detecting SAD. We also assessed the relationship between spirometry and IOS indicators and clinical features of asthma.

METHODS

We prospectively recruited adult asthmatic patients. Anthropometric and clinical characteristics were recorded. All patients performed spirometry and IOS tests.

RESULTS

We enrolled 301 asthmatic patients (179 females; mean age 50 ± 16 years) with normal to moderately severe degree of airway obstruction; 91% were non-smokers, 74% were atopic, 28% had an exacerbation in the previous year, and 18% had a poor asthma control by ACT. SAD was diagnosed in 62% of patients through FEF+, in 40% through FEV3/FEV6+ and in 41% through R5-R20+. κ values were 0.49 between FEF+ and FEV3/FEV6+, 0.20 between FEF+ and R5-R20+, 0.07 between FEV3/FEV6+ and R5-R20+. R5-R20+ but not FEF+ and FEV3/FEV6+ was significantly associated with ACT score (p < 0.05).

CONCLUSIONS

Our study shows that in mild to moderately severe asthmatic patients, spirometry and IOS indicators are complementary in diagnosing SAD. Additionally, IOS indicator, but not spirometry ones, was related to asthma control.

Small airway dysfunction in asthmatic patients treated with as-needed SABA monotherapy: A perfect storm

BACKGROUND

Short-acting beta agonist (SABA)-only treatment is associated with poor asthma control and adverse clinical outcomes. The importance of small airway dysfunction (SAD) is increasingly recognized in asthma, but less is known in patients using SABA-only therapy. We aimed to investigate the impact of SAD on asthma control in an unselected cohort of 60 adults with physician-diagnosed intermittent asthma treated with as-needed SABA monotherapy.

METHODS

All patients underwent standard spirometry and impulse oscillometry (IOS) at the first visit and were stratified by the presence of SAD defined by IOS (fall in resistance 5-20 Hz [R5-R20]>0.07 kPa × s*L^-1). Univariable and multivariable analyses were used to analyze cross-sectional relationships between clinical variables and SAD.

RESULTS

SAD was present in 73% of the cohort. Compared with patients without SAD, adults with SAD had a higher number of severe exacerbations (65.9% versus 25.0%, p < 0.05), higher use of annual SABA canisters (median (IQR), 3 (1.75-3) versus 1 (1-2), p < 0.001), and significantly less well-controlled asthma (11.7% versus 75.0%, p < 0.001). Spirometry parameters were similar between patients with IOS-defined SAD and those without SAD. The multivariable logistic regression analysis showed that exercise-induced bronchoconstriction symptoms (EIB, odds ratio [OR] 31.18; 95%CI:4.85-365.00) and night awakenings due to asthma (OR 30.30; 95%CI:2.61-1141.00) were independent predictors of SAD, with a high predictive power of the model incorporating these baseline predictors (AUC 0.92).

CONCLUSIONS

EIB and nocturnal symptoms are strong predictors of SAD in asthmatic patients using as-needed SABA-monotherapy, helping to distinguish subjects with SAD among patients with asthma when IOS cannot be performed.

Who and how, DNA sensors in NETs-driven inflammation

During infections, neutrophil extracellular traps act like a meshwork of molecules that captures microbes. In contrast, during sterile inflammation the presence of NETs is usually associated with tissue damage and uncontrolled inflammation. In this context, DNA acts both as activator of NETs formation and immunogenic molecule fueling inflammation within the injured tissue microenvironment. Pattern recognition receptors that specifically bind to and get activated by DNA such as Toll-like receptor-9 (TLR9), cyclic GMP-AMP synthase (cGAS), Nod-like receptor protein 3 (NLRP3) and Absence in Melanoma-2 (AIM2) have been reported to play a role in NETs formation and detection. However, how these DNA sensors contribute to NETs-driven inflammation is not well understood. Whether these DNA sensors have unique roles or on the contrary they are mostly redundant is still elusive. In this review, we summarize the known contribution of the above DNA sensors to the formation and detection of NETs in the context of sterile inflammation. We also highlight scientific gaps needed to be addressed and propose future direction for therapeutic targets.

BMAL1/FOXA2-induced rhythmic fluctuations in IL-6 contribute to nocturnal asthma attacks

The circadian clock is closely associated with inflammatory reactions. Increased inflammatory cytokine levels have been detected in the airways of nocturnal asthma. However, the mechanisms that contribute to the nocturnal increase in inflammatory responses and the relationship with circadian clock remain unknown.

Methods

Inflammatory cytokine levels were measured in asthma patients with and without nocturnal symptoms. Allergic airway disease was induced in mice by ovalbumin (OVA), and different periods of light/dark cycles were used to induce circadian rhythm disorders. Serum shock was used to stimulate the rhythmic expression in human bronchial epidermal cells (16HBE). The expression and oscillation of circadian clock genes and inflammatory cytokines in 16HBE cells subjected to brain and muscle ARNT-like protein-1 (BMAL1) and Forkhead Box A2 (FOXA2) knockdown and treatment with a FOXA2 overexpression plasmid were assessed.

Results

Serum IL-6 was found to be significantly higher in asthmatic patients with nocturnal symptoms than those without nocturnal symptoms. The OVA-induced asthma model with a circadian rhythm disorder and 16HBE cells treated with serum shock showed an increase in IL-6 levels and a negative correlation with BMAL1 and FOXA2. The knockdown of BMAL1 resulted in a lower correlation between IL-6 and other rhythm clock genes. Furthermore, knockdown of the BMAL1 and FOXA2 in 16HBE cells reduced the expression and rhythmic fluctuations of IL-6.

Conclusions

Our findings suggest that there are increased IL-6 levels in nocturnal asthma resulting from inhibition of the BMAL1/FOXA2 signalling pathway in airway epithelial cells.

Daytime and Nighttime Visual Analog Scales May Be Useful in Assessing Asthma Control Levels Before and After Treatment

PURPOSE

Few questionnaires evaluate daytime and nighttime symptoms separately, although these assessments could contribute to the improvement of disease control levels and prevention of future risks in asthma. The purpose of this retrospective study was to investigate whether daytime and nighttime visual analog scales (VAS) are useful in measuring the perception of symptoms, assessing disease control levels, and evaluating the treatment effects in asthma.

PATIENTS AND METHODS

Self-reporting asthma control tests (ACT) before and after treatment are standardized tests used to determine disease control levels. A multiple regression analysis was performed to determine the correlation between daytime and nighttime VAS and the characteristics of patients before treatment, as well as the changes in VAS and lung functions and fractional exhaled nitrogen oxide after treatment in 55 treatment-naïve symptomatic adult patients with asthma.

RESULTS

Both daytime (r = -0.57, P < 0.0001) and nighttime (r = -0.46, P < 0.0001) VAS correlated well with ACT scores, and there was a correlation between daytime and nighttime VAS (r = 0.33, P = 0.0148) before treatment. In addition, the changes in daytime (r = -0.65, P < 0.0001) and nighttime (r = -0.44, P < 0.0001) VAS were significantly associated with changes in the ACT scores. The multiple regression analysis (β [95% confidence interval]) revealed that improvements in the daytime (-2.33 [-4.55 to -0.11], P = 0.0405) and nighttime (-3.09 [-6.25 to 0.07], P = 0.0505) VAS were associated with an increased forced vital capacity after treatment, although there was no correlation between the VAS and characteristics before treatment.

CONCLUSION

Our study demonstrated that daytime and nighttime VAS were useful in assessing disease control levels and evaluating the treatment effects in asthma.

Monoclonal antibodies targeting small airways: a new perspective for biological therapies in severe asthma

Small airway dysfunction (SAD) in asthma is characterized by the inflammation and narrowing of airways with less of 2 mm in diameter between generations 8 and 23 of the bronchial tree. It is now widely accepted that small airways are involved in the pathogenesis of asthma and are a major determinant of airflow obstruction in this disease. 

In recent years, specialized tests have been developed, such as Impulse Oscillometry (IOS) and Multiple Breath Nitrogen Washout (MBNW) tests, which have been deemed more accurate in detecting SAD than conventional spirometry. Clinical studies show that SAD is associated with more severe bronchial hyperresponsiveness, worse asthma control, and a higher risk of exacerbations. Recent data from a large cohort study showed that the prevalence of SAD in asthma patients increases with asthma severity. Overall, SAD seems to represent a treatable trait, which makes it appealing for asthma control optimization and exacerbation rate reduction, especially in moderate-to-severe asthma.

Biologic agents are now available for the treatment of different severe asthma phenotypes and endotypes. However, the effect of these therapies on SAD remains poorly characterized. Literature showing that biologic agents can also favorably improve small airway function is accumulating. In particular, anti-IL5 agents (mepolizumab and benralizumab) seems to have a greater impact on SAD as compared to other biological agents, but direct comparisons in prospective randomized controlled trials are lacking.

In this mini-review article, we address the latest evidence on the effect of biological therapies on SAD in patients with severe asthma.

Longitudinal Impact of Sputum Inflammatory Phenotypes on Small Airway Dysfunction and Disease Outcomes in Asthma

BACKGROUND

Little is known about the relationship between airway inflammatory phenotypes and some important asthma features such as small airway dysfunction (SAD).

OBJECTIVE

To describe the longitudinal impact of airway inflammatory phenotypes on SAD and asthma outcomes.

METHODS

We measured eosinophil and neutrophil counts in induced sputum at baseline and 1 year later to stratify 197 adult patients with asthma into 4 inflammatory phenotypes. We conducted a comprehensive assessment of lung function using spirometry, body plethysmography, impulse oscillometry, and inert gas single and multiple breath washouts. We compared lung function, asthma severity, exacerbation frequency, and symptom control between the phenotypes. We studied the longitudinal impact of persistent sputum inflammatory phenotypes and the change of sputum cell counts on lung function.

RESULTS

Patients were stratified into eosinophilic (23%, n = 45), neutrophilic (33%, n = 62), mixed granulocytic (22%, n = 43), and paucigranulocytic (24%, n = 47) phenotypes. Patients with eosinophilic and mixed granulocytic asthma had higher rates of airflow obstruction and severe exacerbation as well as poorer symptom control than patients with paucigranulocytic asthma. All SAD measures were worse in patients with eosinophilic and mixed asthma than in those with paucigranulocytic asthma (all P values <.05). Eosinophilic asthma also indicated worse distal airflow obstruction, increased ventilation inhomogeneity (all P values <.05), and higher tendency for severe exacerbation (P = .07) than neutrophilic asthma. Longitudinally, persistent mixed granulocytic asthma was associated with the worst follow-up measures of SAD compared with persistent neutrophilic, persistent paucigranulocytic, or nonpersistent asthma phenotypes. In patients with stable forced expiratory volume in 1 second (FEV1), the mean increase in small airway resistance (R5-20) was greater in patients with persistent mixed granulocytic asthma (+103%) than in patients with persistent neutrophilic (+26%), P = .040, or persistent paucigranulocytic asthma (-41%), P = .028. Multivariate models adjusted for confounders and treatment with inhaled or oral corticosteroids or antieosinophilic biologics indicated that the change of sputum eosinophil rather than neutrophil counts is an independent predictor for the longitudinal change in FEV1, forced expiratory flow at 25% to 75% of forced vital capacity, specific effective airway resistance, residual lung volume, and lung clearance index.

CONCLUSIONS

In asthma, airway eosinophilic inflammation is the main driver of lung function impairment and poor disease outcomes, which might also be aggravated by the coexistence of airway neutrophilia to confer a severe mixed granulocytic asthma phenotype. Persistent airway eosinophilia might be associated with dynamic SAD even in patients with stable FEV1.

Small Airways: The “Silent Zone” of 2021 GINA Report?

Asthma is a chronic disease, affecting approximately 350 million people worldwide. Inflammation and remodeling in asthma involve the large airways, and it is now widely accepted that the small airways (those with an internal diameter <2 mm) are involved in the pathogenesis of asthma and are the major determinant of airflow obstruction in this disease. From a clinical perspective, small airways dysfunction (SAD) is associated with more severe bronchial hyperresponsiveness, worse asthma control and more exacerbations. Unlike the GOLD guidelines which, in their definition, identify COPD as a disease of the small airways, the Global Initiative for Asthma (GINA) guidelines do not refer to the prevalence and role of SAD in asthmatic patients. This decision seems surprising, given the growing body of compelling evidence accumulating pointing out the high prevalence of SAD in asthmatic patients and the importance of SAD in poor asthma control. Furthermore, and remarkably, SAD appears to possess the characteristics of a treatable pulmonary trait, making it certainly appealing for asthma control optimization and exacerbation rate reduction. In this mini-review article, we address the most recent evidence on the role of SAD on asthma control and critically review the possible inclusion of SAD among treatable pulmonary traits in international guidelines on asthma.

Prognosis of bronchial asthma in children with different pulmonary function phenotypes: A real-world retrospective observational study

OBJECTIVE

To follow up on the changes in pulmonary function phenotypes in children with asthma in the first year after diagnosis, and explore the risk factors of poor control in children with good treatment compliance.

METHODS

Children who were diagnosed with asthma in the Respiratory Department of Shanghai Children's Medical Center from January 1, 2019 to December 31, 2020 and were re-examined every 3 months after diagnosis for 1 year were continuously included, regardless of gender. We collected the clinical data, analyzed clinical characteristics of the different pulmonary function phenotypes at baseline and explored risk factors of poor asthma control after 1 year of standardized treatment.

RESULTS

A total of 142 children with asthma were included in this study, including 54 (38.0%) with normal pulmonary function phenotype (NPF), 75 (52.8%) with ventilation dysfunction phenotype (VD), and 13 (9.2%) with small airway dysfunction phenotype (SAD) in the baseline. Among them, there were statistically significant differences in all spirometry parameters, age, and course of disease before diagnosis (P < 0.05), and a negative correlation between age (r ² = -0.33, P < 0.001), course of disease before diagnosis (r ² = -0.23, P = 0.006) and FEV₁/FVC. After 1-year follow-up, large airway function parameters and small airway function parameters were increased, fractional exhaled nitric oxide (FeNO) was decreased, the proportion of NPF was increased, the proportion of VD was decreased (P < 0.05), while there was no significant difference in the proportion of SAD. After 1 year of standardized treatment, 21 patients (14.8%) still had partly controlled or uncontrolled asthma. Our results showed that the more asthma attacks occurred within 1 year (OR = 6.249, 95% CI, 1.711-22.818, P = 0.006), the more times SAD presented at baseline and Assessment 1-4 (OR = 3.092, 95% CI, 1.222-7.825, P = 0.017), the higher the possibility of incomplete control of asthma.

CONCLUSION

About 15% of the children with good treatment compliance were still not completely controlled after 1 year of treatment, which is closely associated with persistent small airway dysfunction.