Small-airway disease in asthma: pharmacological considerations

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.

Increased Resistance of the Peripheral Airways in Patients with Unexplained Chronic Cough

INTRODUCTION

Troublesome coughing that persists for more than 8 weeks without evident aetiology or effective therapy is termed unexplained chronic cough (UCC). Using impulse oscillometry (IOS) and spirometry, we assessed the functionalities of the large and small airways, respectively, in patients with UCC and in healthy control subjects.

METHODS

On a single occasion, 50 patients with UCC (mean age, 61 years; 82% women) and 23 subjectively healthy controls (mean age, 58.9 years; 95.7% women) underwent IOS and spirometry. Patients with UCC were also subjected to fractional exhaled nitric oxide (FeNO) measurement, and they answered a local questionnaire, a visual analogue scale (VAS) for cough and cough-related symptoms, and a health-related quality of life questionnaire.

RESULTS

Forty-nine (98%) patients with UCC reported cough symptoms from exposure to chemicals, 39 (78%) had problems with cold air, and 38 (76%) had cough symptoms following exercise. The mean VAS cough score was 62 mm in the patient group. FeNO was measured in 25 patients, showing a mean value of 16.6 ppb. Women with UCC had significantly greater airway resistance and reactance than men with UCC. The UCC group showed significantly increased peripheral airway resistance and reactance, and lower FEV1% predicted values (albeit within the normal range), as compared with the healthy control group.

CONCLUSION

Patients with UCC show increased peripheral airway resistance and significantly lower FEV1% predicted values compared with healthy control subjects. Routine measurements of lung function with both IOS and spirometry could have added value to the diagnosis of UCC.

Identification and treatment of persistent small airway dysfunction in paediatric patients with asthma: a retrospective cohort study

BACKGROUND

Asthma is a common respiratory disease. In asthma, the small airways have more intensive inflammation and prominent airway remodelling, compared to the central airways. We aimed to investigate the predictive value of risk factors and the fractional concentration of exhaled nitric oxide (FeNO) for persistent small airway dysfunction (p-SAD), and compare the effects of different treatment modalities.

METHODS

This retrospective cohort study included 248 children with asthma (aged 4-11 years). Binary logistic regression was used to analyse the risk factors for p-SAD. Correlations among FEV1/FVC, small airway function parameters, and FeNO levels in patients with asthma were analysed using Spearman's rank correlation. The receiver operating characteristic curve and the Delong test were used to analyse the predictive value of FeNO for p-SAD. Differences in the treatment effects of inhaled corticosteroids (ICS) and ICS with a long-acting beta-agonist (ICS/LABA) on p-SAD were analysed using Fisher's exact test.

RESULTS

Asthmatic children with older age of receiving the regular treatment (OR 1.782, 95% CI 1.082-2.935), with younger age at the time of onset of suspected asthma symptoms (OR 0.602, 95% CI 0.365-0.993), with longer duration of using ICS or ICS/LABA (OR 1.642, 95% CI 1.170-2.305) and with worse asthma control (OR 3.893, 95% CI 1.699-8.922) had increased risk for p-SAD. Significant negative correlations of small airway function parameters with FeNO at a 200 mL/s flow rate (FeNO200), and the concentration of nitric oxide in the alveolar or acinar region (CaNO) were observed. The areas under the curve of FeNO200 (cut-off:10.5ppb), CaNO (cut-off:5.1ppb), and FeNO200 combined with CaNO were 0.743, 0.697, and 0.750, respectively, for asthma with p-SAD. After using ICS or ICS/LABA, switching to ICS/LABA was easier than continuing with ICS to improve small airway dysfunction (SAD) in the 8th month.

CONCLUSIONS

Paediatric asthma with p-SAD is associated with older age at receiving regular treatment, younger age at the time of onset of suspected asthma symptoms, longer duration of using ICS or ICS/LABA, worse asthma control, and higher FeNO200 and CaNO levels, all of which can be combined with small airway function indicators to distinguish p-SAD from asthma. ICS/LABA improves SAD better than ICS alone.

Small airways in asthma: Pathophysiology, identification and management

Background

The aim of this review is to summarize the current evidence regarding small airway disease in asthma, focusing on recent advances in small airway pathophysiology, assessment and therapeutic implications.

Methods

A search in Medline was performed, using the keywords "small airways", "asthma", "oscillometry", "nitrogen washout" and "imaging". Our review was based on studies from adult asthmatic patients, although evidence from pediatric populations is also discussed.

Results

In asthma, inflammation in small airways, increased mucus production and airway wall remodelling are the main pathogenetic mechanisms of small airway disease. Small airway dysfunction is a key component of asthma pathophysiology, leading to increased small airway resistance and airway closure, with subsequent ventilation inhomogeneities, hyperresponsiveness and airflow limitation. Classic tests of lung function, such as spirometry and body plethysmography are insensitive to detect small airway disease, providing only indirect measurements. As discussed in our review, both functional and imaging techniques that are more specific for small airways, such as oscillometry and the multiple breath nitrogen washout have delineated the role of small airways in asthma. Small airways disease is prevalent across all asthma disease stages and especially in severe disease, correlating with important clinical outcomes, such as asthma control and exacerbation frequency. Moreover, markers of small airways dysfunction have been used to guide asthma treatment and monitor response to therapy.

Conclusions

Assessment of small airway disease provides unique information for asthma diagnosis and monitoring, with potential therapeutic implications.

No-shaking and shake-fire delays affect respirable dose for suspension but not solution pMDIs

It has long been accepted that suspension pressurized metered-dose inhalers (pMDIs) must be shaken if a correct dose is to be delivered, if not, it will usually be higher than the label claim. The purpose of this work was to investigate the influence of the device being unshaken, shaken and after a period of delay in pMDI actuation on the Fine Particle Mass (<5 µm), Extra Fine Particle Mass (<2 µm) and MMAD. Solution and suspension commercial pMDIs containing one, two or three components were used in the study. Most of the suspension pMDIs produced variable amounts of respirable size drug following the shake-fire delays tested in terms of the label claim dose. The effect was even more critical if the inhaler was not shaken and the FPM was found to be between -82 % for Symbicort and 363 % for Ventolin compared with the control values. In the case of MMAD measurements, Seretide and Serzyl inhalers showed the largest change from around 3 µm to 4.2-5.1 µm when not shaken. Conversely, the FPM and MMAD for the solution aerosols remained unchanged whether or not they were shaken or when a progressive increase in the delay in actuation after shaking was employed.

Potential Drawbacks of ICS/LABA/LAMA Triple Fixed-Dose Combination Therapy in the Treatment of Asthma: A Quantitative Synthesis of Safety Profile

Introduction

Methods

Results

Conclusion

Impact of long-acting muscarinic antagonists on small airways in asthma and COPD: A systematic review

Small airway disease is recognized as a cardinal pathological process of chronic obstructive pulmonary disease (COPD), and recently small airways have been recognized as a major site of airflow obstruction also in asthmatic patients. The transversal involvement of small airways in COPD and asthma has warranted research efforts to identify therapeutic strategies able to unlock the small airway compartment. The mainstay of COPD treatment is represented by long-acting β₂-adrenoceptor agonists (LABAs) and long-acting muscarinic antagonists (LAMAs). In asthma, the efficacy of LAMAs administered add-on to inhaled corticosteroids (ICSs) or ICS/LABA combinations has been investigated only in recent years. The aim of this systematic review was to examine the current literature concerning the impact of LAMAs on small airways and their lung deposition in both COPD and asthma. LAMAs administered either alone or in combination induced an effective bronchorelaxant effect of small airways, however the effectiveness of respiratory medications not only relies on the selected drug, but also on the employed inhalation device and patient's adherence. Tiotropium delivered via Respimat® SMI achieved a superior drug deposition in the peripheral lung compared to HandiHaler® dry powder inhaler and metered-dose inhalers (MDIs). The use of co-suspension™ delivery technology for MDIs and the introduction of the eFlow® nebulizer to deliver glycopyrronium improved aerosol drug delivery to the peripheral lung, by achieving uniform distribution of drug particles. This systematic review provides a synthesis of current literature concerning the impact of LAMAs on small airways and an insight on LAMAs distribution within the lung.

Enhanced alveo pulmonary deposition of nebulized ciclesonide for attenuating airways inflammations: a strategy to overcome metered dose inhaler drawbacks

Ciclesonide (CIC), an inhaled corticosteroid for bronchial asthma is currently available as metered dose inhaler (CIC–MDI) which possesses a major challenge in the management of the elderly, critically ill patients and children. In this work, nebulized CIC nano-structure lipid particles (CIC-NLPs) were prepared and evaluated for their deep pulmonary delivery and cytotoxicity to provide additional clinical benefits to patients in controlled manner and lower dose. The bio-efficacy following nebulization in ovalbumin (OVA) induced asthma Balb/c mice compared to commercial (CIC–MDI) was also assessed. The developed NLPs of 222.6 nm successfully entrapped CIC (entrapment efficiency 93.3%) and exhibited favorable aerosolization efficiency (mass median aerodynamic diameter (MMAD) 2.03 μm and fine particle fraction (FPF) of 84.51%) at lower impactor stages indicating deep lung deposition without imparting any cytotoxic effect up to a concentration of 100 μg/ml. The nebulization of 40 µg dose of the developed CIC-NLPs revealed significant therapeutic impact in the mitigation of the allergic airways inflammations when compared to 80 µg dose of the commercial CIC–MDI inhaler (Alvesco^®). Superior anti-inflammatory and antioxidative stress effects characterized by significant decrease (p< .0001) in inflammatory cytokines IL-4 and 13, serum IgE levels, malondialdehyde (MDA), nitric oxide (NO), TNF-α, and activated nuclear factor-κB (NF-κB) activity were obvious with concomitant increase in superoxide dismutase (SOD) activity. Histological examination with inhibition of inflammatory cell infiltration in the respiratory tract was correlated well with observed biochemical improvement.

Small Airway Dysfunction in Asthma Is Associated with Perceived Respiratory Symptoms, Non-Type 2 Airway Inflammation, and Poor Responses to Therapy

BACKGROUND

Emerging evidence has indicated that small airway dysfunction (SAD) contributes to the clinical expression of asthma.

OBJECTIVES

The aim of the study was to explore the relationships of SAD assessed by forced expiratory flow between 25 and 75% (FEF25-75%), with clinical and inflammatory profile and treatment responsiveness in asthma.

METHOD

In study I, dyspnea intensity (Borg scale), chest tightness, wheezing and cough (visual analog scales, VASs), and pre- and post-methacholine challenge testing (MCT) were analyzed in asthma patients with SAD and non-SAD. In study II, asthma subjects with SAD and non-SAD underwent sputum induction, and inflammatory mediators in sputum were detected. Asthma patients with SAD and non-SAD receiving fixed treatments were prospectively followed up for 4 weeks in study III. Spirometry, Asthma Control Questionnaire (ACQ), and Asthma Control Test (ACT) were carried out to define treatment responsiveness.

RESULTS

SAD subjects had more elevated ΔVAS for dyspnea (p = 0.027) and chest tightness (p = 0.032) after MCT. Asthma patients with SAD had significantly elevated interferon (IFN)-γ in sputum (p < 0.05), and Spearman partial correlation found FEF25-75% significantly related to IFN-γ and interleukin-8 (both having p < 0.05). Furthermore, multivariable regression analysis indicated SAD was significantly associated with worse treatment responses (decrease in ACQ ≥0.5 and increase in ACT ≥3) (p = 0.022 and p = 0.032).

CONCLUSIONS

This study indicates that SAD in asthma predisposes patients to greater dyspnea intensity and chest tightness during bronchoconstriction. SAD patients with asthma are characterized by non-type 2 inflammation that may account for poor responsiveness to therapy.

Changes in airway diameter and mucus plugs in patients with asthma exacerbation

Background

Airway obstruction due to decreased airway diameter and increased incidence of mucus plugs has not been directly observed in asthma exacerbation. We studied the changes in the inner diameter of the airway (Din) and the frequency of mucus plugs by airway generation in patients with asthma exacerbation. We compared these patients to those in a stable phase using high-resolution computed tomography (HRCT).

Methods and findings

Thirteen patients with asthma were studied by HRCT during asthma exacerbation and in a stable period. The HRCT study was performed on patients who could safely hold their breath for a short while in a supine position 1 hour after initial treatment for asthma exacerbation. Using a curved multiplanar reconstruction (MPR) software, we reconstructed the longitudinal airway images and the images exactly perpendicular to the airway axis to measure the Din and mucus plugs from the second- (segmental) to sixth-generation bronchi in all segments of the lungs.The ratios of Din (exacerbation/stable) were 0.91(P = 0.016), 0.88 (P = 0.002), 0.83 (P = 0.001), 0.80 (P = 0.001), and 0.87 (NS) in the second-, third-, fourth-, fifth-, and sixth-generation bronchi, respectively. The percentages of airway obstruction due to mucus plugs were notably higher in the fourth- and fifth-generation bronchi (17.9%/18.1% in stable phase and 43.2%/45.9% in the exacerbation phase, respectively) than in the other generations of bronchi.

Conclusions

Among the bronchi examined, the fourth- and fifth-generation bronchi were significantly obstructed during asthma exacerbation compared with the stable phase in terms of a decreased airway diameter and mucus plugs.

Effects of Particle Size of Inhaled Corticosteroid on the Voice

OBJECTIVES

The purpose of this study was to determine if inhaled corticosteroid (ICS) particle size influences the development of laryngitis including candida laryngitis, dysphonia, or vocalis muscle atrophy in asthmatic patients.

STUDY DESIGN

Retrospective analysis.

METHODS

Medical records of patients from a quaternary care laryngology practice who have asthma were reviewed retrospectively. Subjects were divided into two groups determined by the particle size of their ICS, small or standard. Each patient only used one type of inhaler. All subjects had been seen in the office for dysphonia evaluation. Statistical analysis was performed on the collected data using χ2 analysis with Yate's Correction for categorical data and a student t-test for means. A P value of less than 0.05 was considered significant.

RESULTS

There was a significant difference in vocal fold atrophy rate between groups.

CONCLUSION

Routine use of standard particle size ICS is associated with more atrophy than small size ICS.

ERS International Congress, Madrid, 2019: highlights from the Airway Diseases, Asthma and COPD Assembly

The European Respiratory Society (ERS) International Congress 2019 in Madrid, Spain, was a platform for scientific discussion of the highest quality scientific research, cutting-edge techniques and innovative new therapies within the respiratory field. This article discusses some of the high-quality research studies presented at that Congress, with a focus on airway diseases, including asthma, COPD, small airways, bronchiectasis and cough, presented through the Airway Diseases, Asthma and COPD Assembly (Assembly 5) of the ERS. The authors establish the key take-home messages of these studies, compare their findings and place them into context of current understanding.

Choosing the right inhaler for your asthma or COPD patient

Appropriate selection and correct use of inhalation devices is an integral component in the management of asthma and chronic obstructive pulmonary disease (COPD). It is well known that there are many challenges with the use of inhalers, and no one device suits all patients. Challenges can range from difficulties related to lung disease severity and pulmonary function to physical considerations, including manual dexterity and comorbidities such as arthritis. In terms of device selection and adherence, patient engagement and satisfaction are also important factors to consider. Furthermore, problems with inhaler use can be most evident in children and older patients. Here, we discuss aspects for consideration with commonly used devices, including nebulizers, pressurized metered-dose inhalers, dry powder inhalers, and the soft mist inhaler. As each inhaler offers varying technical properties, a tailored and personalized approach to the selection of the most appropriate device for the patient is highly recommended in order to increase the likelihood of achieving improved disease outcomes and enhance persistence with device adherence. Importantly, education and support is crucial, not only to enable patients to recognize the need for optimal disease management, but also to help them develop good inhaler technique. In addition, health care professionals should also aim to increase their knowledge of the devices they prescribe, and develop systems to ensure that they offer comprehensive support to patients in clinical practice. Considering these aspects, this review discusses potential strategies to help address the challenges of inhaler use in asthma and COPD.

Small airway dysfunction may be an indicator of early asthma: findings from high-resolution CT

BACKGROUND

Increasing attention is now focused on the role of the small airways in asthma. Patients with small airway asthma typically have a preserved forced expiratory volume in 1 second, with disproportionate small airway dysfunction.

OBJECTIVE

The aim of this study was to determine whether there are structural changes in the large airways in patients with small airway asthma.

METHODS

Nine patients with small airway asthma and 20 healthy controls underwent high-resolution computed tomography (HRCT) scan. The apicoposterior segmental bronchus in the left upper lobe (LB1+2) and the posterior basal segmental bronchus in the left lower lobe (LB10) were identified on HRCT images. The luminal area (LA), wall area (WA), and wall area percentage (WA%) of each bronchus were measured from the 2nd (lobar) to the 6th generation and compared between the patients with small airway asthma and the healthy controls.

RESULTS

The WA% of the 6th generation in the patients with small airway asthma was higher than that in the healthy controls; the difference was statistically significant (LB1 + 2, P = .040; LB10, P = .033).

CONCLUSION

Structural changes in the large airways of patients with small airway asthma may represent an early stage of asthma.

Is there room for further innovation in inhaled therapy for airways disease?

Inhaled medication is the cornerstone in the treatment of patients across a spectrum of respiratory diseases including asthma and chronic obstructive pulmonary disease. The benefits of inhaled therapy have long been recognised but the most important innovations have occurred over the past 60 years, beginning with the invention of the pressurised metered dose inhaler. However, despite over 230 different device and drug combinations currently being available, disease control is far from perfect. Here we look at how innovation in inhaler design may improve treatments for respiratory diseases and how new formulations may lead to treatments for diseases beyond the lungs. We look at the three main areas where innovation in inhaled therapy is most likely to occur: 1) device engineering and design; 2) chemistry and formulations; and 3) digital technology associated with inhalers. Inhaler design has improved significantly but considerable challenges still remain in order to continually innovate and improve targeted drug delivery to the lungs. Healthcare professionals want see innovations that motivate their patients to achieve their goal of improving their health, through better adherence to treatment. Patients want devices that are easy to use and to see that their efforts are rewarded by improvements in their condition.

KEY POINTS

The dictionary definition of innovation is the introduction of new things, ideas or ways of doing something. We show how this definition can be applied to inhaled therapy.We take a look at the past to see what drove innovation in inhaler design and how this has led to the current devices.We look at the current drivers of innovation in engineering, chemistry and digital technology and predict how this may translate to new devices.Can innovation help the healthcare professional manage their patients better?What does the patient expect from innovation in their device?

EDUCATIONAL AIMS

To understand the importance of inhaled medication in the treatment of lung diseases.To understand how innovation has helped advance some of the devices patients use today from basic and inefficient designs.To understand the obstacles that prevent patients from receiving optimal treatment from their inhalers.To understand how innovation in inhaler design can lead to improved treatment for patients and widen the range of diseases that can be treated via the inhaled route.

Drug delivery to the lungs: challenges and opportunities

Pulmonary drug delivery is relatively complex because the respiratory tract has evolved defense mechanisms to keep inhaled drug particles out of the lungs and to remove or inactivate them once deposited. In addition to these mechanical, chemical and immunological barriers, pulmonary drug delivery is adversely affected by the behavioral barriers of poor adherence and poor inhaler technique. Strategies to mitigate the effects of these barriers include use of inhaler devices and formulations that deliver drug to the lungs efficiently, appropriate inhaler technique and improved education of patients. Owing to the advantages offered by the pulmonary route, the challenges that the route poses are worth addressing, and if successfully addressed, the pulmonary route offers huge opportunities, often fulfilling unmet clinical needs.

Continued Innovation in Respiratory Care: The Importance of Inhaler Devices

When it comes to the use in inhalers in the management of chronic obstructive pulmonary diseases, there are many options, considerations and challenges, which health care professionals need to address. Considerations for prescribing and dispensing, administering and following up, education, and adherence; all of these factors impact on treatment success and all are intrinsically linked to the device selected. This review brings together relevant evidence, real-life data and practice tools to assist health care professionals in making decisions about the use of inhalers in the management of chronic obstructive pulmonary diseases. It covers some of the key technical device issues to be considered, the evidence behind the role of inhalers in disease control, population studies which link behaviors and adherence to inhaler devices as well as practice advice on inhaler technique education and the advantages and disadvantages in selecting different inhaler devices. Finally, a list of key considerations to aid health care providers in successfully managing the use of inhaler devices are summarized.

Positive correlation of airway resistance and serum asymmetric dimethylarginine (ADMA) in bronchial asthma patients lacking evidence for systemic inflammation

Background

Contribution of nitric-oxide (NO) pathway to the pathogenesis of bronchial asthma (asthma) is ambiguous as NO may confer both protective and detrimental effects depending on the NO synthase (NOS) isoforms, tissue compartments and underlying pathological conditions (e.g. systemic inflammation). Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor and uncoupler of NOS with distinct selectivity for NOS isoforms. In a cross-sectional study, we assessed whether ADMA is an independent predictor of airway resistance (R_aw) in therapy-controlled asthma.

Methods

154 therapy-controlled asthma patients were recruited. ADMA, symmetric dimethylarginine and arginine were quantitated by HPLC with fluorescent detection. Pulmonary function test was done using whole-body plethysmography, quality of life via St. George’s Respiratory questionnaire (SGRQ). Multiple linear regression was used to identify independent determinants of R_aw. The final model was stratified based on therapy control.

Results

Evidence for systemic inflammation indicated by CRP and procalcitonin was lacking in our sample. Log R_aw showed significant positive correlation with log ADMA in the whole data set and well-controlled but not in the not well-controlled stratum (Spearman correlation coefficients: 0.27, p < 0.001; 0.30, p < 0.001; 0.12, p = 0.51 respectively). This relationship remained significant after adjusting for confounders by multiple linear regression (β = 0.22, CI 0.054, 0.383 p = 0.01). FEF 25–75% % predicted and SGRQ Total score showed significant negative while SGRQ Activity score showed significant positive correlation with R_aw in the final model.

Conclusions

Positive correlation between R_aw and ADMA in the absence of systemic inflammation implies that higher ADMA has detrimental effect on NO homeostasis and can contribute to a poor outcome in asthma.

Extrafine Versus Fine Inhaled Corticosteroids in Relation to Asthma Control: A Systematic Review and Meta-Analysis of Observational Real-Life Studies

BACKGROUND

The particle size of inhaled corticosteroids (ICSs) may affect airway drug deposition and effectiveness.

OBJECTIVE

To compare the effectiveness of extrafine ICSs (mass median aerodynamic diameter, <2 μm) versus fine-particle ICSs administered as ICS monotherapy or ICS-long-acting β-agonist combination therapy by conducting a meta-analysis of observational real-life asthma studies to estimate the treatment effect of extrafine ICSs.

METHODS

MEDLINE and EMBASE databases were reviewed for asthma observational comparative effectiveness studies from January 2004 to June 2016. Studies were included if they reported odds and relative risk ratios and met all inclusion criteria (Respiratory Effectiveness Group/European Academy of Allergy and Clinical Immunology quality standards, comparison of extrafine ICSs with same or different ICS molecule, ≥12-month follow-up). End-point data (asthma control, exacerbations, prescribed ICS dose) were pooled. Random-effects meta-analysis modeling was used. The study protocol is published in the PROSPERO register CRD42016039137.

RESULTS

Seven studies with 33,453 subjects aged 5 to 80 years met eligibility criteria for inclusion. Six studies used extrafine beclometasone propionate and 1 study used both extrafine beclometasone propionate and extrafine ciclesonide as comparators with fine-particle ICSs. The overall odds of achieving asthma control were significantly higher for extrafine ICSs compared with fine-particle ICSs (odds ratio, 1.34; 95% CI, 1.22-1.46). Overall exacerbation rate ratios (0.84; 95% CI, 0.73-0.97) and ICS dose (weighted mean difference, -170 μg; 95% CI, -222 to -118 μg) were significantly lower for extrafine ICSs compared with fine-particle ICSs.

CONCLUSIONS

This meta-analysis demonstrates that extrafine ICSs have significantly higher odds of achieving asthma control with lower exacerbation rates at significantly lower prescribed doses than fine-particle ICSs.

Small airways disease and severe asthma

The small airways of the lungs are commonly affected in pediatric and adult asthma. Small airways disease has been related to asthma control, severity, and risk of exacerbation. Diagnosis of small airways disease can be best made through evaluation of surgical lung specimens. Noninvasive techniques including spirometry, plethysmography, nitrogen washout, impulse oscillometry, and cross-sectional imaging have been utilized to assess and infer the extent of small airways disease in asthma and can be used longitudinally to assess response to treatment. Patients with small airways disease seem to benefit from inhaled asthma medications that have improved capacity to reach the distal lung compartment. This is especially important for patients with severe asthma, who rely upon high doses of inhaled corticosteroid and bronchodilators for asthma control. This review will describe the techniques which may be utilized to assess small airways disease, discuss the prevalence and characteristics of small airways disease in severe asthma, and highlight how small airway disease may complicate severe asthma treatment.

Determinants of peripheral airway function in adults with and without asthma

BACKGROUND AND OBJECTIVE

Peripheral airway involvement in asthma remains poorly understood. We investigated impulse oscillometry (IOS) measures of peripheral airway function in a population-based birth cohort.

METHODS

Pre- and post-bronchodilator spirometry and IOS measures of respiratory resistance and reactance were measured in 915 participants at age 38 years.

RESULTS

Current asthma was associated with impairments in both spirometry and IOS parameters. These impairments were greater in men and in those with childhood persistent asthma. Spirometry and IOS values for those whose asthma was in remission were not different to non-asthmatic participants. There were significant changes in IOS in both asthmatic and non-asthmatic participants after bronchodilator, but between-group differences persisted. Higher BMIs were associated with impairments in IOS but not spirometry. Cumulative tobacco use was associated with spirometric airflow obstruction in both sexes, whereas cannabis use was associated with impairments in IOS in women. Despite higher lifetime exposure, there were few associations between cannabis and IOS in men.

CONCLUSION

Asthma is associated with abnormalities in IOS measures of peripheral airway dysfunction. This association is stronger in men and in those with asthma persisting since childhood. Tobacco and cannabis use are associated with different patterns of spirometry and IOS abnormalities and may affect the bronchial tree at different airway generations with differences in susceptibility between sexes.

Effect of inhaled corticosteroid particle size on asthma efficacy and safety outcomes: a systematic literature review and meta-analysis

Background

Inhaled corticosteroids (ICS) are the primary treatment for persistent asthma. Currently available ICS have differing particle size due to both formulation and propellant, and it has been postulated that this may impact patient outcomes. This structured literature review and meta-analysis compared the effect of small and standard particle size ICS on lung function, symptoms, rescue use (when available) and safety in patients with asthma as assessed in head-to-head randomized controlled trials (RCTs).

Methods

A systematic literature search of MEDLINE was performed to identify RCTs (1998–2014) evaluating standard size (fluticasone propionate-containing medications) versus small particle size ICS medication in adults and children with asthma. Efficacy outcomes included forced expiratory volume in 1 s (FEV₁), morning peak expiratory flow (PEF), symptom scores, % predicted forced expiratory flow between 25 and 75% of forced vital capacity (FEF_25–75%)_, and rescue medication use. Safety outcomes were also evaluated when available.

Results

Twenty-three independent trials that met the eligibility criteria were identified. Benefit-risk plots did not demonstrate any clinically meaningful differences across the five efficacy endpoints considered and no appreciable differences were noted for most safety endpoints. Meta-analysis results, using a random-effects model, demonstrated no significant difference between standard and small size particle ICS medications in terms of effects on mean change from baseline FEV₁ (L) (−0.011, 95% confidence interval [CI]: −0.037, 0.014 [N = 3524]), morning PEF (L/min) (medium/low doses: −3.874, 95% CI: −10.915, 3.166 [N = 1911]; high/high-medium doses: 5.551, 95% CI: −1.948, 13.049 [N = 749]) and FEF_{25–75% predicted} (−2.418, 95% CI: −6.400; 1.564 [N = 115]).

Conclusions

Based on the available literature, no clinically significant differences in efficacy or safety were observed comparing small and standard particle size ICS medications for the treatment of asthma.

Trial registration

GSK Clinical Study Register No: 202012.

Manifesto on small airway involvement and management in asthma and chronic obstructive pulmonary disease: an Interasma (Global Asthma Association - GAA) and World Allergy Organization (WAO) document endorsed by Allergic Rhinitis and its Impact on Asthma (ARIA) and Global Allergy and Asthma European Network (GA2LEN)

Evidence that enables us to identify, assess, and access the small airways in asthma and chronic obstructive pulmonary disease (COPD) has led INTERASMA (Global Asthma Association) and WAO to take a position on the role of the small airways in these diseases.

Starting from an extensive literature review, both organizations developed, discussed, and approved the manifesto, which was subsequently approved and endorsed by the chairs of ARIA and GA²LEN. The manifesto describes the evidence gathered to date and defines and proposes issues on small airway involvement and management in asthma and COPD with the aim of challenging assumptions, fostering commitment, and bringing about change.

The small airways (defined as those with an internal diameter <2 mm) are involved in the pathogenesis of asthma and COPD and are the major determinant of airflow obstruction in these diseases. Various tests are available for the assessment of the small airways, and their results must be integrated to confirm a diagnosis of small airway dysfunction.

In asthma and COPD, the small airways play a key role in attempts to achieve disease control and better outcomes. Small-particle inhaled formulations (defined as those that, owing to their size [usually <2 μm], ensure more extensive deposition in the lung periphery than large molecules) have proved beneficial in patients with asthma and COPD, especially those in whom small airway involvement is predominant.

Functional and biological tools capable of accurately assessing the lung periphery and more intensive use of currently available tools are necessary. In patients with suspected COPD or asthma, small airway involvement must be assessed using currently available tools. In patients with subotpimal disease control and/or functional or biological signs of disease activity, the role of small airway involvement should be assessed and treatment tailored. Therefore, the choice between large- and small-particle inhaled formulations must reflect the physician’s considerations of disease features, phenotype, and response to previous therapy.

This article is being co-published in Asthma Research and Practice and the World Allergy Organization Journal.

Manifesto on small airway involvement and management in asthma and chronic obstructive pulmonary disease: an Interasma (Global Asthma Association - GAA) and World Allergy Organization (WAO) document endorsed by Allergic Rhinitis and its Impact on Asthma (ARIA) and Global Allergy and Asthma European Network (GA2LEN)

Evidence that enables us to identify, assess, and access the small airways in asthma and chronic obstructive pulmonary disease (COPD) has led INTERASMA (Global Asthma Association) and WAO to take a position on the role of the small airways in these diseases.

Starting from an extensive literature review, both organizations developed, discussed, and approved the manifesto, which was subsequently approved and endorsed by the chairs of ARIA and GA²LEN. The manifesto describes the evidence gathered to date and defines and proposes issues on small airway involvement and management in asthma and COPD with the aim of challenging assumptions, fostering commitment, and bringing about change.

The small airways (defined as those with an internal diameter <2 mm) are involved in the pathogenesis of asthma and COPD and are the major determinant of airflow obstruction in these diseases. Various tests are available for the assessment of the small airways, and their results must be integrated to confirm a diagnosis of small airway dysfunction.

In asthma and COPD, the small airways play a key role in attempts to achieve disease control and better outcomes. Small-particle inhaled formulations (defined as those that, owing to their size [usually <2 μm], ensure more extensive deposition in the lung periphery than large molecules) have proved beneficial in patients with asthma and COPD, especially those in whom small airway involvement is predominant.

Functional and biological tools capable of accurately assessing the lung periphery and more intensive use of currently available tools are necessary. In patients with suspected COPD or asthma, small airway involvement must be assessed using currently available tools. In patients with subotpimal disease control and/or functional or biological signs of disease activity, the role of small airway involvement should be assessed and treatment tailored. Therefore, the choice between large- and small-particle inhaled formulations must reflect the physician’s considerations of disease features, phenotype, and response to previous therapy. This article is being co-published in Asthma Research and Practice and the World Allergy Organization Journal.

Dilemmas, Confusion, and Misconceptions Related to Small Airways Directed Therapy

During the past decade, there has been increasing evidence that the small airways (ie, airways < 2 mm in internal diameter) contribute substantially to the pathophysiologic and clinical expression of asthma and COPD. The increased interest in small airways is, at least in part, a result of innovation in small-particle aerosol formulations that better target the distal lung and also advanced physiologic methods of assessing small airway responses. Increasing the precision of drug deposition may improve targeting of specific diseases or receptor locations, decrease airway drug exposure and adverse effects, and thereby increase the efficiency and effectiveness of inhaled drug delivery. The availability of small-particle aerosols of corticosteroids, bronchodilators, or their combination enables a higher total lung deposition and better peripheral lung penetration and provides added clinical benefit, compared with large-particle aerosol treatment. However, a number of questions remain unanswered about the pragmatic approach relevant for clinicians to consider the role of small airways directed therapy in the day-to-day management of asthma and COPD. We thus have tried to clarify the dilemmas, confusion, and misconceptions related to small airways directed therapy. To this end, we have reviewed all studies on small-particle aerosol therapy systematically to address the dilemmas, confusion, and misconceptions related to small airways directed therapy.

Clinical characteristics of adult asthma associated with small airway dysfunction

Suboptimal asthma control is common despite modern asthma therapy. The degree of peripheral airway involvement remains unclear and poor medication delivery to these regions might be a contributing reason for this failure in obtaining adequate symptom control. A cohort of 196 adults (median (range) age 44 (18-61) years, 109 females, 54 ex-smokers, six current smokers) with physician-diagnosed asthma were recruited from primary care. Subjects were characterized clinically by interviews, questionnaires, skin prick tests (SPT) and blood eosinophil counts. Lung function was assessed by spirometry, impulse oscillometry (IOS) and nitrogen multiple breath washout (N2 MBW). IOS assessed peripheral airway resistance (FDR, frequency dependence of resistance). N2 MBW assessed global ventilation inhomogeneity (LCI, lung clearance index), specific indices of peripheral airway function (Scond × VT and Sacin × VT; VT, tidal volume), and inter-regional inhomogeneity (specific ventilation ratio). Never-smoking healthy cohorts of 158 and 400 adult subjects provided local reference values for IOS and N2 MBW variables, respectively. Peripheral airway dysfunction was detected in 31% (FDR or specific ventilation ratio) to 47% (Scond x VT) of subjects. Risk factors for peripheral airway dysfunction were identified. Among subjects with low FEV1 and either positive smoking history and/or blood eosinophilia (>4.0%), 63% had abnormality across all peripheral airway outcomes, whilst only one subject was completely normal. Abnormal peripheral airway function was present in a large proportion of adult asthmatics at baseline. Reduced FEV1, a positive smoking history, and/or blood eosinophilia identified "a small airway asthma subtype" that might benefit from peripheral airway targeted therapy.

The prevalence of small airways disease in adult asthma: A systematic literature review

BACKGROUND

Small airways dysfunction and inflammation contribute significantly to the clinical impact of asthma, yet conventional methods of assessing airways function in the clinic cannot reliably evaluate its presence. However, most recently, promising methods of assessment are being utilised.

METHODS

We conducted a systematic literature review, using PubMed, with the aim of determining the prevalence of small airways disease in adult patients with asthma. We ascertained how small airways disease prevalence compared between different studies when measured using distinct techniques of small airways assessment.

RESULTS

Fifteen publications were identified determining the prevalence of small airways disease in asthma. Methods of assessments included impulse oscillometry, spirometry, body plethysmography, multiple-breath nitrogen washout, and high-resolution computed tomography. These studies used differing inclusion characteristics and recruited patients with a broad range of asthma severity, yet collectively they reported an overall prevalence of small airways disease of 50-60%. Small airways disease was present across all asthma severities, with evidence of distal airway disease even in the absence of proximal airway obstruction.

CONCLUSIONS

Small airways disease is highly prevalent in asthma, even in patients with milder disease. Given the clinical impact of small airways disease, its presence should not be underestimated or overlooked as part of the daily management of patients with asthma.

Bridging the Gap Between Science and Clinical Efficacy: Physiology, Imaging, and Modeling of Aerosols in the Lung

Development of a new drug for the treatment of lung disease is a complex and time consuming process involving numerous disciplines of basic and applied sciences. During the 2015 Congress of the International Society for Aerosols in Medicine, a group of experts including aerosol scientists, physiologists, modelers, imagers, and clinicians participated in a workshop aiming at bridging the gap between basic research and clinical efficacy of inhaled drugs. This publication summarizes the current consensus on the topic. It begins with a short description of basic concepts of aerosol transport and a discussion on targeting strategies of inhaled aerosols to the lungs. It is followed by a description of both computational and biological lung models, and the use of imaging techniques to determine aerosol deposition distribution (ADD) in the lung. Finally, the importance of ADD to clinical efficacy is discussed. Several gaps were identified between basic science and clinical efficacy. One gap between scientific research aimed at predicting, controlling, and measuring ADD and the clinical use of inhaled aerosols is the considerable challenge of obtaining, in a single study, accurate information describing the optimal lung regions to be targeted, the effectiveness of targeting determined from ADD, and some measure of the drug's effectiveness. Other identified gaps were the language and methodology barriers that exist among disciplines, along with the significant regulatory hurdles that need to be overcome for novel drugs and/or therapies to reach the marketplace and benefit the patient. Despite these gaps, much progress has been made in recent years to improve clinical efficacy of inhaled drugs. Also, the recent efforts by many funding agencies and industry to support multidisciplinary networks including basic science researchers, R&D scientists, and clinicians will go a long way to further reduce the gap between science and clinical efficacy.

Impulse oscillometry identifies peripheral airway dysfunction in children with adenosine deaminase deficiency

Adenosine deaminase-deficient severe combined immunodeficiency (ADA-SCID) is characterized by impaired T-, B- and NK-cell function. Affected children, in addition to early onset of infections, manifest non-immunologic symptoms including pulmonary dysfunction likely attributable to elevated systemic adenosine levels. Lung disease assessment has primarily employed repetitive radiography and effort-dependent functional studies. Through impulse oscillometry (IOS), which is effort-independent, we prospectively obtained objective measures of lung dysfunction in 10 children with ADA-SCID. These results support the use of IOS in the identification and monitoring of lung function abnormalities in children with primary immunodeficiencies.

Small airway dysfunction and bronchial asthma control : the state of the art

According to national and international guidelines, achieving and maintaining asthma control is a major goal of disease management. In closely controlled clinical trials, good asthma control can be achieved , with the medical treatments currently available, in the majority of patients , but large population-based studies suggest that a significant proportion of patients in real-life setting experience suboptimal levels of asthma control and report lifestyle limitations with a considerable burden on quality of life. Poor treatment adherence and persistence, failure to use inhalers correctly, heterogeneity of asthma phenotypes and associated co-morbidities are the main contributing factors to poor disease control. Now, it is widely accepted that peripheral airway dysfunction , already present in patients with mild asthma, is a key contributor of worse control. The aim of this paper is to investigate the association between small-airways dysfunction and asthma symptoms/control. We therefore performed a PubMed search using keywords : small airways; asthma (limits applied: Humans, English language) and selected papers with a study population of asthmatic patients, reporting measurement of small-airways parameters and clinical symptoms/control.

Can 'extrafine' dry powder aerosols improve lung deposition?

There is increasing interest in the use of so-called 'extrafine' aerosols to target the small airways in the management of asthma and COPD. Using previously presented deposition data, we assessed whether submicron (<1μm) particles can improve central and deep lung deposition. Our data show instead that particles in the range 1-3μm are much more relevant in this respect. Based on this finding the Symbicort Turbuhaler, Seretide Diskus, Rolenium Elpenhaler and Foster (Fostair) NEXThaler ICS/LABA combination DPIs were tested in vitro as a function of the pressure drop (2, 4 and 6kPa) across the inhaler. Obtained fine particle fractions (FPFs) <5μm (as percent of label claim) were divided into subfractions <1, 1-3 and 3-5μm. Differences of up to a factor of 4 were found between the best (Turbuhaler) and worst performing DPI (Elpenhaler), particularly for the FPF in the size range 1-3μm. The NEXThaler, described as delivering 'extrafine' particles, did not appear to be superior in this size range. The marked differences in amount and size distribution of the aerosols between the devices in this study must cause significant differences in the total lung dose and drug distribution over the airways.

The role of the small airways in the pathophysiology of asthma and chronic obstructive pulmonary disease

Chronic respiratory diseases, such as asthma and chronic obstructive pulmonary disease (COPD), represent a major social and economic burden for worldwide health systems. During recent years, increasing attention has been directed to the role of small airways in respiratory diseases, and their exact contribution to the pathophysiology of asthma and COPD continues to be clarified. Indeed, it has been suggested that small airways play a distinct role in specific disease phenotypes. Besides providing information on small airways structure and diagnostic procedures, this review therefore aims to present updated and evidence-based findings on the role of small airways in the pathophysiology of asthma and COPD. Most of the available information derives from either pathological studies or review articles and there are few data on the natural history of small airways disease in the onset or progression of asthma and COPD. Comparisons between studies on the role of small airways are hard to draw because both asthma and COPD are highly heterogeneous conditions. Most studies have been performed in small population samples, and different techniques to characterize aspects of small airways function have been employed in order to assess inflammation and remodelling. Most methods of assessing small airways dysfunction have been largely confined to research purposes, but some data are encouraging, supporting the utilization of certain techniques into daily clinical practice, particularly for early-stage diseases, when subjects are often asymptomatic and routine pulmonary function tests may be within normal ranges. In this context further clinical trials and real-life feedback on large populations are desirable.