Physiological measurement of the small airways

Clinical characterization and outcomes of impulse oscillometry-defined bronchodilator response: an ECOPD cohort-based study

BACKGROUND

The clinical significance of the impulse oscillometry-defined small airway bronchodilator response (IOS-BDR) is not well-known. Accordingly, this study investigated the clinical characteristics of IOS-BDR and explored the association between lung function decline, acute respiratory exacerbations, and IOS-BDR.

METHODS

Participants were recruited from an Early Chronic Obstructive Pulmonary Disease (ECOPD) cohort subset and were followed up for two years with visits at baseline, 12 months, and 24 months. Chronic obstructive pulmonary disease (COPD) was defined as a post-bronchodilator forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) ratio < 0.70. IOS-BDR was defined as meeting any one of the following criteria: an absolute change in respiratory system resistance at 5 Hz ≤ - 0.137 kPa/L/s, an absolute change in respiratory system reactance at 5 Hz ≥ 0.055 kPa/L/s, or an absolute change in reactance area ≤ - 0.390 kPa/L. The association between IOS-BDR and a decline in lung function was explored with linear mixed-effects model. The association between IOS-BDR and the risk of acute respiratory exacerbations at the two-year follow-up was analyzed with the logistic regression model.

RESULTS

This study involved 466 participants (92 participants with IOS-BDR and 374 participants without IOS-BDR). Participants with IOS-BDR had higher COPD assessment test and modified Medical Research Council dyspnea scale scores, more severe emphysema, air trapping, and rapid decline in FVC than those without IOS-BDR over 2-year follow-up. IOS-BDR was not associated with the risk of acute respiratory exacerbations at the 2-year follow-up.

CONCLUSIONS

The participants with IOS-BDR had more respiratory symptoms, radiographic structural changes, and had an increase in decline in lung function than those without IOS-BDR.

TRIAL REGISTRATION

Chinese Clinical Trial Registry, ChiCTR1900024643. Registered on 19 July, 2019.

Small airways in asthma: From inflammation and pathophysiology to treatment response

Small airways are characterized as those with an inner diameter less than 2 mm and constitute a major site of pathology and inflammation in asthma disease. It is estimated that small airways dysfunction may occur before the emergence of noticeable symptoms, spirometric abnormalities and imaging findings, thus characterizing them as "the quiet or silent zone" of the lungs. Despite their importance, measuring and quantifying small airways dysfunction presents a considerable challenge due to their inaccessibility in usual functional measurements, primarily due to their size and peripheral localization. Several pulmonary function tests have been proposed for the assessment of the small airways, including impulse oscillometry, nitrogen washout, body plethysmography, as well as imaging methods. Nevertheless, none of these methods has been established as the definitive "gold standard," thus, a combination of them should be used for an effective assessment of the small airways. Widely used asthma treatments seem to also affect several parameters of the small airways. Emerging biologic treatments show promising results in reducing small airways inflammation and remodelling, providing evidence for potential alterations in the disease's progression and outcomes. These novel therapies have implications not only in the clinical aspects of asthma but also in its inflammatory and functional aspects.

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.

TEV/FEV₃ as a coherent metric of small airway dysfunction in childhood asthma

Background: Spirometry is an unrivalled tool for determining asthma and asthma severity. The ratio of forced expiratory volume (FEV) in 1 second (FEV₁) to forced vital capacity (FVC) and the forced expiratory flow between 25% and 75% of FVC (FEF_25-75) are well-known markers of airway obstruction, but they are limited by low reproducibility, particularly in children. In this study, we defined terminal expiration volume (TEV) as FEV in 3 seconds forced expiratory volume in 3 seconds (FEV₃) minus forced expiratory volume in 1 seconds (FEV₁) and investigate whether TEV/FEV₃ can function as a coherent marker to compensate for existing markers. Methods: This retrospective study comprised 980 children ages ≤ 18 years who underwent spirometry and the bronchial provocation testing. TEV/FEV₃ was compared with regard to asthma presence and severity. The findings were verified with an external validation group (n = 105). Results: FEV₃ was obtained in 837 children (85.4%). TEV/FEV₃ was significantly higher in patients with asthma than in patients who did not have asthma (17.1 ± 5.5 versus 12.0 ± 4.4, p < 0.001). External validation with 73 patients showed similar results (18.0 ± 5.9 in asthma versus 10.2 ± 5.1 in non-asthma, p < 0.001). The discriminatory power of TEV/FEV₃ for asthma was comparable with that of FEF_25-75 (p = 0.804). TEV/FEV₃ significantly increased with asthma severity (mild, 16.1 ± 5.4; moderate, 17.7 ± 5.4; severe, 22.0 ± 5.3; p < 0.001). For patients who could not achieve FEV₃, FEF_25-75 demonstrated no significant difference between mild and moderate asthma, and could not discriminate asthma or asthma severity. Conclusion: TEV/FEV₃ is a new metric that may help diagnose and determine asthma severity by using conventional spirometry by assessing small airway dysfunction. TEV/FEV₃ promotes a reassessment of the reliability of other spirometric parameters, particularly in young children. Caution is needed in interpreting the result of spirometry in children who cannot achieve FEV₃.

Small airway function measured using forced expiratory flow between 25% and 75% of vital capacity and its relationship to airflow limitation in symptomatic ever-smokers: a cross-sectional study

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is diagnosed and its severity graded by traditional spirometric parameters (forced expiratory volume in 1 s (FEV₁)/forced vital capacity (FVC) and FEV₁, respectively) but these parameters are considered insensitive for identifying early pathology. Measures of small airway function, including forced expiratory flow between 25% and 75% of vital capacity (FEF_25-75), may be more valuable in the earliest phases of COPD. This study aimed to determine the prevalence of low FEF_25-75 in ever-smokers with and without airflow limitation (AL) and to determine whether FEF_25-75 relates to AL severity.

METHOD

A retrospective analysis of lung function data of 1458 ever-smokers suspected clinically of having COPD. Low FEF_25-75 was defined by z-score<-0.8345 and AL was defined by FEV₁/FVC z-scores<-1.645. The severity of AL was evaluated using FEV₁ z-scores. Participants were placed into three groups: normal FEF_25-75/ no AL (normal FEF_25-75/AL-); low FEF_25-75/ no AL (low FEF_25-75/AL-) and low FEF_25-75/ AL (low FEF_25-75/AL+).

RESULTS

Low FEF_25-75 was present in 99.9% of patients with AL, and 50% of those without AL. Patients in the low FEF_25-75/AL- group had lower spirometric measures (including FEV₁ FEF_25-75/FVC and FEV₃/FVC) than those in the normal FEF_25-75/AL- group. FEF_25-75 decreased with AL severity. A logistic regression model demonstrated that in the absence of AL, the presence of low FEF_25-75 was associated with lower FEV₁ and FEV₁/FVC even when smoking history was accounted for.

CONCLUSIONS

Low FEF_25-75 is a physiological trait in patients with conventional spirometric AL and likely reflects early evidence of impairment in the small airways when spirometry is within the 'normal range'. FEF_25-75 likely identifies a group of patients with early evidence of pathological lung damage who warrant careful monitoring and reinforced early intervention to abrogate further lung injury.

A positive effect of a short period stay in Alpine environment on lung function in asthmatic children

Lung function is a central issue in diagnosis and determination of asthma severity and asthma control has been previously reported to improve after a stay in mountain environment for at least 2 weeks. No data are available for shorter periods of stay, in particular for small airways during a stay at altitude. The aim of this study is to focus on changes in respiratory function, regarding both the central airways and the peripheral airways in the first 2 weeks of stay in a mountain environment in asthmatic children. In this study, 66 asthmatic children (age: 14 ± 2.8 years) were evaluated through spirometric and oscillometric tests at the time of arrival at the Istituto Pio XII, Misurina (BL), Italy, 1756 m above sea level (T0), after 24 h (T1), and 168 h (T2) of stay. FEV1%, FEF25%-75%, and FEV1/FVC increased significantly from T0 value both at T1 and T2 (respectively, p = 0.0002, p < 0.0001, p = 0.0002). Oscillometry showed a significant improvement in R5, R20, and R5-20 at both T1 and T2 as compared to T0 (respectively, p = 0.0001, p = 0.0002, and p = 0.049). Reactance at 5 Hz (X5) improved significantly at T2 versus T0, p = 0.0022. The area under reactance curve between Fres and 5 Hz (AX) was significantly reduced (p = 0.0001) both at T1 and T2 as compared to T0. This study shows an improvement in respiratory indices as soon as after 24 h of stay at altitude, persisting in the following week.

Spirometry parameters used to define small airways obstruction in population-based studies: systematic review protocol

INTRODUCTION

In recent years, there has been increasing interest in the use of spirometry for the assessment of small airways obstruction (SAO) driven by the idea that these changes occur prior to development of established obstructive lung disease. Maximal mid-expiratory and distal flow rates have been widely used despite a lack of agreement regarding parameter selection or definition of an abnormal result. We aim to provide evidence from population-based studies, describing the different parameters, definitions of normal range and the resulting impact on prevalence estimates for SAO. Summarising this evidence is important to inform development of future studies in this area.

METHODS AND ANALYSIS

A systematic review of population-based studies will be conducted. MEDLINE, Web of Science and Google Scholar will be searched from database inception to May 2021. Primary outcomes will include the spirometry parameter used to define SAO, and the definition of an abnormal result. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines will be followed for study selection. Study methods will be assessed using the Newcastle-Ottawa scale and the Grading of Recommendations Assessment, Development and Evaluation working group methodology. Narrative synthesis will be conducted for all included studies. Meta-analysis will also be conducted for prevalence estimates and associated risk factors where data quality and availability allow. Random effects models will be used to conduct the meta-analysis and I² statistics will be used to assess heterogeneity across studies. Where appropriate subgroup analysis will be conducted to explore heterogeneity.

ETHICS AND DISSEMINATION

There is no requirement for ethical approval for this project. Findings will be disseminated via peer-reviewed publications and other formats, for example, conferences, congresses or symposia.

PROSPERO REGISTRATION NUMBER

CRD42021250206.

Prediction of COPD by the single-breath nitrogen test and various respiratory symptoms

Early identification of subjects running an increased risk of contracting COPD enables focus on individual preventive measures. The slope of the alveolar plateau of the single-breath nitrogen washout test (N₂-slope) is a sensitive measure of small-airway dysfunction. However, its role remains unexplored in predicting hospital admission or death related to COPD, i.e. incident COPD events, in relation to the presence of various respiratory symptoms.

A random population sample of 625 men, aged 50 (n=218) or 60 years (n=407), was followed for 38 years for incident COPD events. At baseline, a questionnaire on respiratory symptoms and smoking habits was collected, spirometry and the single-breath nitrogen test were performed, and the N₂-slope was determined. Proportional hazard regression (Cox regression) analysis was used for the prediction model.

The N₂-slope improved the prediction of COPD events significantly beyond that of respiratory symptoms weighted all together and other covariates (hazard ratio 1.63, 95% CI 1.20–2.22; p<0.005), a prediction applicable to subjects without (p=0.001) and with (p<0.05) airway obstruction. Dyspnoea and wheezing were the most predictive symptoms. The combination of the N₂-slope and number of respiratory symptoms notably resulted in an effective prediction of incident COPD events even in nonobstructive subjects, as evidenced by a predicted incidence of ∼70% and ∼90% for a very steep N₂-slope combined with many respiratory symptoms in subject without and with airway obstruction, respectively.

The alveolar N₂-slope should be considered in the critical need for further research on early diagnosis of COPD.

The N₂ slope of the single-breath nitrogen test predicts incident COPD events as well as or better than respiratory symptoms among subjects without and with airway obstruction. Combining N₂ slope and symptoms results in effective prediction.https://bit.ly/3dYJdu1

Small airway dysfunction and poor asthma control: a dangerous liaison

Asthma is a common chronic condition, affecting approximately 339 million people worldwide. The main goal of the current asthma treatment guidelines is to achieve clinical control, encompassing both the patient symptoms and limitations and the future risk of adverse asthma outcomes. Despite randomized controlled trials showing that asthma control is an achievable target, a substantial proportion of asthmatics remain poorly controlled in real life. The involvement of peripheral small airways has recently gained greater recognition in asthma, and many studies suggest that the persistent inflammation at these sites leads to small airway dysfunction (SAD), strongly contributing to a worse asthma control. Overall, the impulse oscillometry (IOS), introduced in the recent years, seems to be able to sensitively assess small airways, while conventional spirometry does not. Therefore, IOS may be of great help in characterizing SAD and guiding therapy choice. The aim of this article is to review the literature on SAD and its influence on asthma control, emphasizing the most recent evidence.

Ventilation Heterogeneity in Asthma and COPD: The Value of the Poorly Communicating Fraction as the Ratio of Total Lung Capacity to Alveolar Volume

BACKGROUND

The ventilation heterogeneity (VH) is reliably assessed by the multiple-breath nitrogen washout (MBNW), which provides indices of conductive (Scond) and acinar (Sacin) VH as well as the lung clearance index (LCI), an index of global VH. VH can be alternatively measured by the poorly communicating fraction (PCF), that is, the ratio of total lung capacity by body plethysmography to alveolar volume from the single-breath lung diffusing capacity measurement.

OBJECTIVES

Our objective was to assess VH by PCF and MBNW in patients with asthma and with COPD and to compare PCF and MBNW parameters in both patient groups.

METHOD

We studied 35 asthmatic patients and 45 patients with COPD. Each patient performed spirometry, body plethysmography, diffusing capacity, and MBNW test.

RESULTS

Compared to COPD patients, asthmatics showed a significantly lesser degree of airflow obstruction and lung hyperinflation. In asthmatic patients, both PCF and LCI and Sacin values were significantly lower than the corresponding ones of COPD patients. In addition, in both patient groups, PCF showed a positive correlation with LCI (p < 0.05) and Sacin (p < 0.05), but not with Scond. Lastly, COPD patients with PCF >30% were highly likely to have a value ≥2 of the mMRC dyspnea scale.

CONCLUSIONS

These results showed that PCF, a readily measure derived from routine pulmonary function testing, can provide a comprehensive measure of both global and acinar VH in asthma and in COPD patients and can be considered as a comparable tool to the well-established MBNW technique.

Small-airway dysfunction in paediatric asthma

PURPOSE OF REVIEW

Asthma is a chronic inflammatory airway disorder that can involve the entire bronchial tree. Increasing evidence shows that ventilation heterogeneity and small airway dysfunction are relevant factors in the pathogenesis of asthma and represent a hallmark in adults with persistent asthma. Little is known about the contribution of peripheral airway impairment in paediatric asthma, mainly due to the inaccessibility to evaluation by noninvasive techniques, which have only been widely available in recent years.

RECENT FINDINGS

Emerging evidence suggests that small airways are affected from the early stages of the disease in childhood-onset asthma. Conventional lung function measurement, using spirometry, is unable to sensitively evaluate small airway function and may become abnormal only once there is a significant burden of disease. Recent studies suggest that chronic inflammation and dysfunction in the small airways, as detected with new advanced techniques, are risk factors for asthma persistence, asthma severity, worse asthma control and loss of pulmonary function with age, both in adults and children. Knowing the extent of central and peripheral airway involvement is clinically relevant to achieve asthma control, reduce bronchial hyper-responsiveness and monitor response to asthma treatment.

SUMMARY

This review outlines the recent evidence on the role of small airway dysfunction in paediatric asthma development and control, and addresses how the use of new diagnostic techniques available in outpatient clinical settings, namely impulse oscillometry and multiple breath washout, could help in the early detection of small airway impairment in children with preschool wheezing and school-age asthma and potentially guide asthma treatment.

Ventilation heterogeneity in children with severe asthma

Small airway disease, characterised by ventilation heterogeneity (VH), is present in a subgroup of patients with asthma. Ventilation heterogeneity can be measured using multiple breath washout testing. Few studies have been reported in children. We studied the relationship between VH, asthma severity, and spirometry in a cross-sectional observational cohort study involving children with stable mild-moderate and severe asthma by GINA classification and a group of healthy controls. Thirty-seven participants aged 5-16 years completed multiple breath nitrogen washout (MBNW) testing (seven controls, seven mild-moderate asthma, 23 severe asthma). The lung clearance index (LCI) was normal in control and mild-moderate asthmatics. LCI was abnormal in 5/23 (21%) of severe asthmatics. The LCI negatively correlated with FEV₁ z-score.Conclusion: VH is present in asthmatic children and appears to be more common in severe asthma. The LCI was significantly higher in the cohort of children with severe asthma, despite no difference in FEV₁ between the groups. This supports previous evidence that LCI is a more sensitive marker of airway disease than FEV₁. MBNW shows potential as a useful tool to assess children with severe asthma and may help inform clinical decisions. What is Known: • Increased ventilation heterogeneity is present in some children with asthma • Spirometry is not sensitive enough to detect small airway involvement in asthma What is New • Lung clearance index is abnormal in a significant subgroup of children with severe asthma but rarely in children with mild-moderate asthma • Our data suggests that LCI monitoring should be considered in children with severe asthma.

Interrelationships Among Small Airways Dysfunction, Neutrophilic Inflammation, and Exacerbation Frequency in COPD

BACKGROUND

Small airways disease (SAD) is a key component of COPD and is a main contributing factor to lung function decline.

RESEARCH QUESTION

Is SAD a key feature of frequent COPD exacerbators and is this related to airway inflammation?

STUDY DESIGN AND METHODS

Thirty-nine COPD patients defined as either frequent exacerbator (FE) group (≥ 2 exacerbations/y; n = 17) and infrequent exacerbator (IFE) group (≤ 1 exacerbation/y; n = 22) underwent the forced oscillation technique (resistance at 5 Hz minus 19 Hz [R5-R19], area of reactance [AX]), multiple breath nitrogen washout (conducting airways ventilation heterogeneity, acinar ventilation heterogeneity [S_acin]), plethysmography (ratio of residual volume to total lung capacity), single-breath transfer factor of the lung for carbon monoxide, spirometry (FEV₁, FEV₁/FVC), and paired inspiratory-expiratory CT scans to ascertain SAD. A subpopulation underwent bronchoscopy to enable enumeration of BAL cell proportions.

RESULTS

S_acin was significantly higher in the COPD FE group compared with the IFE group (P = .027). In the FE group, markers of SAD were associated strongly with BAL neutrophil proportions, R5-R19 (P = .001, r = 0.795), AX (P = .049, ρ = 0.560), residual volume to total lung capacity ratio (P = .004, r = 0.730), and the mean lung density of the paired CT scans (P = .018, r = 0.639).

INTERPRETATION

Increased S_acin may be a consequence of previous exacerbations or may highlight a group of patients prone to exacerbations. Measures of SAD were associated strongly with neutrophilic inflammation in the small airways of FE patients, supporting the hypothesis that frequent exacerbations are associated with SAD related to increased cellular inflammation.

A retrospective analysis of usefulness of impulse oscillometry system in the treatment of asthma

BACKGROUND

Bronchial asthma (BA) has different phenotypes, and it requires a clinically effective subtype classification system. The impulse oscillometry system (IOS) is an emerging technique device used in respiratory functional tests. However, its efficacy has not been validated. Therefore, this study aimed to assess the relationship between BA and the IOS parameters, and the difference in the therapeutic effects of inhaled corticosteroids (ICSs) among the subtype classifications was evaluated using the IOS.

METHODS

Of the 245 patients with bronchial asthma who were screened, 108 were enrolled in this study. These patients were divided based on three subtypes according to the IOS result as follows: central predominant type (n = 34), peripheral predominant type (n = 58), and resistless type (n = 16). Then, the following ICSs were randomly prescribed in daily medical care: coarse-particle ICS (fluticasone propionate [FP]), fine-particle ICS (mometasone furoate [MF]), and moderate-particle ICS (budesonide [BUD]). The treatment effects were assessed using the Asthma Health Questionnaire (AHQ) and the Asthma Control Test (ACT) and were compared among the three subtypes.

RESULTS

In the central predominant type, the AHQ score of the MF group was significantly higher than that of the FP group (15.4 vs. 3.6, p < 0.01) and the BUD group (15.4 vs. 8.8, p < 0.05); the ACT score of the FP group was significantly higher than that of the MF and BUD groups (24.3 vs. 21.7, 22.3, respectively, p < 0.05) at 4 weeks after treatment. In the peripheral predominant type, the AHQ score of the FP group was significantly higher than that of the MF group (14.1 vs. 3.4, p < 0.05); the ACT score of the FP group was lower than that of the MF and BUD groups (22.8 vs. 24.6, 24.4, respectively, p < 0.01) at 4 weeks after treatment.

CONCLUSIONS

An association was observed between IOS subtype classification and ICS particle size in terms of therapeutic efficacy in BA. This result indicates that the IOS could be an effective tool in the selection of ICS and the evaluation of the BA phenotype.

Ventilation heterogeneity in smokers: role of unequal lung expansion and peripheral lung structure

Smoking-induced ventilation heterogeneity measured at the mouth via established washout indices [lung clearance index (LCI) and alveolar mixing efficiency (AME)] potentially results from unequal expansion, which can be quantified by computer tomography (CT), and structural changes down to the lung periphery, characterized by CT parametric response mapping indices [percentage of lung affected by functional small airway disease (PRM^fSAD) and emphysema (PRM^Emph)]. By combining CT imaging and nitrogen (N₂) washout tests in smokers, we specifically examined the roles of unequal lung expansion and peripheral structure. We first extracted three-dimensional maps of local lung expansion from registered inspiratory/expiratory CT images in 50 smokers (GOLD 0-IV) to compute for each smoker the theoretical N₂ washout concentration curve solely attributable to unequal local expansion. By a head-on comparison with washout N₂ concentrations measured at the mouth in the same smokers supine, we observed that 1) LCI increased from 4.8 ± 0.2 (SD) to 6.6 ± 0.8 (SD) due to unequal lung expansion alone and further increased to 9.0 ± 1.5 (SD) independent of local expansion and 2) AME decreased (from 100% by definition) to 95 ± 2 (SD)% due to unequal expansion alone and further decreased to 75 ± 7(SD)% independent of local expansion. In a multiple regression between the washout indices and CT-derived PRM^fSAD and PRM^Emph, LCI was related to PRM^fSAD (r = +0.58; P < 0.001), whereas AME was related to both PRM^fSAD (r_partial = -0.44; P = 0.002) and PRM^Emph (r_partial = -0.31; P = 0.033), in line with AME being dominated by alterations in peripheral structure. We conclude that smokers showing an increased LCI without corresponding AME decrease are predominantly affected by unequal lung expansion, whereas an AME decrease with a commensurate LCI increase indicates a smoking-induced alteration of peripheral structure.NEW & NOTEWORTHY A head-on comparison between imaging and multiple breath washout in supine smokers shows that computer tomography-measured unequal local lung expansion accounts for 50% or less of smoking-induced increase in ventilation heterogeneity. The contributions from unequal lung expansion and peripheral structure to the two main washout indices also explain their respective association with parametric response mapping indices.

Smoking and lung function among adults with newly onset asthma

Introduction

Smoking increases the risk of asthma and reduces lung function among subjects with and without asthma. We assessed the effects of smoking on lung function reflecting both central and small airways among adults with newly onset asthma.

Methods

In a population-based study, 521 (response rate 86%) working-aged adults with clinically defined newly diagnosed asthma answered a questionnaire on personal smoking and other factors potentially influencing lung function, and performed spirometry. We applied multiple linear regression analysis to estimate the relations between smoking and lung function adjusting for confounding.

Results

Among asthmatics, FEV₁ level was reduced significantly, on average 208 mL, related to regular smoking (adjusted effect estimate −0.208, 95% CI −0.355 to −0.061) and 245 mL in relation to former smoking, that is, among those who quit less than a year ago (−0.245, 95% CI −0.485 to −0.004). In contrast, FEV₁ was not significantly related to occasional smoking or former smoking among those who quit over a year ago. Forced expiratory flow (FEF) levels (L/s) were also significantly reduced among regular smokers (FEF_25–75%: −0.372, 95% CI −0.607 to −0.137; FEF_50%: −0.476, 95% CI −0.750 to −0.202). An exposure–response pattern related to both daily smoking rate and lifetime cumulative smoking was seen both among men and women.

Conclusions

This study provides new evidence that among working-aged adults with new asthma, regular smoking and former smoking reduce lung function levels with a dose–response pattern. The lung function parameters applied as outcomes reflect both larger and smaller airways.

Exhaled particles and small airways

BACKGROUND

Originally, studies on exhaled droplets explored properties of airborne transmission of infectious diseases. More recently, the interest focuses on properties of exhaled droplets as biomarkers, enabled by the development of technical equipment and methods for chemical analysis. Because exhaled droplets contain nonvolatile substances, particles is the physical designation. This review aims to outline the development in the area of exhaled particles, particularly regarding biomarkers and the connection with small airways, i e airways with an internal diameter < 2 mm.

MAIN BODY

Generation mechanisms, sites of origin, number concentrations of exhaled particles and the content of nonvolatile substances are studied. Exhaled particles range in diameter from 0.01 and 1000 μm depending on generation mechanism and site of origin. Airway reopening is one scientifically substantiated particle generation mechanism. During deep expirations, small airways close and the reopening process produces minute particles. When exhaled, these particles have a diameter of < 4 μm. A size discriminating sampling of particles < 4 μm and determination of the size distribution, allows exhaled particle mass to be estimated. The median mass is represented by particles in the size range of 0.7 to 1.0 μm. Half an hour of repeated deep expirations result in samples in the order of nanogram to microgram. The source of these samples is the respiratory tract ling fluid of small airways and consists of lipids and proteins, similarly to surfactant. Early clinical studies of e g chronic obstructive pulmonary disease and asthma, reported altered particle formation and particle composition.

CONCLUSION

The physical properties and content of exhaled particles generated by the airway reopening mechanism offers an exciting noninvasive way to obtain samples from the respiratory tract lining fluid of small airways. The biomarker potential is only at the beginning to be explored.

Alternate gas washout indices: Assessment of ventilation inhomogeneity in mild to moderate pediatric cystic fibrosis lung disease

INTRODUCTION

Normalized phase III slope (Sn_III ) indices from multiple breath washout (MBW) estimate ventilation inhomogeneity. Alternate (*) protocols for Sn_III indices exist, however the utility of these outcomes in children with mild-to-moderate cystic fibrosis (CF) is unknown.

METHODS

We measured nitrogen MBW and spirometry in 135 children (43 controls) aged 4-18 years. We assessed validity, practicability, and reliability of Sn_III protocols. Outcomes included the ability to detect abnormal lung function, test agreement, measurement duration, intra-test repeatability, and quality.

RESULTS

Lung clearance index (LCI) was abnormal in 80 (87%), Scond in 55 (60%), Scond* in 17 (19%), Sacin in 10 (11%), Sacin* in 11 (12%), and FEV₁ in 28 (30%). Alternate protocols reduced measurement duration. Agreement of indices to detect abnormal lung function was poor. The quality of analysis and repeatability deteriorated with the alternate technique compared to standard.

CONCLUSION

In children with mild-to-moderate CF lung disease, alternate protocols seem practical but clinimetric properties of standard Sn_III protocols are preferable.

Correcting for tissue nitrogen excretion in multiple breath washout measurements

Nitrogen excreted from body tissues impacts the calculation of multiple breath nitrogen washout (MBWN2) outcomes. The aim of this study was to determine the effect of tissue N2 on MBWN2 outcomes in both healthy subjects and patients with CF and to assess whether it is possible to correct for tissue N2. The contribution of tissue N2 to MBWN2 outcomes was estimated by comparing MBWN2-derived functional residual capacity (FRCN2) to FRC measured by body plethysmography (FRCpleth) and by comparing MBW outcome measures derived from MBWN2 and sulfur hexafluoride MBW (MBWSF6). Compared to plethysmography and MBWSF6, MBWN2 overestimated FRC and lung clearance index (LCI). Application of mathematical tissue N2 corrections reduced FRCN2 values closer to FRCpleth in health and reduced LCIN2 in both health and CF, but did not explain all of the differences observed between N2-dependent and -independent techniques. Use of earlier washout cut-offs could reduce the influence of tissue N2. Applying tissue N2 corrections to LCIN2 measurements did not significantly affect the interpretation of treatment effects reported in a previously published interventional trial. While tissue N2 excretion likely has an impact on MBWN2 outcomes, better understanding of the nature of this phenomenon is required before routine correction can be implemented into current MBWN2 protocols.

Ventilation distribution and small airway function in patients with systemic sclerosis

BACKGROUND

Despite the importance of traditional pulmonary function tests (PFTs) in managing systemic sclerosis (SSc), many patients with pulmonary disease diagnosed by computed tomography (CT) present with normal PFTs.

OBJECTIVE

To evaluate the efficacy of the nitrogen single-breath washout (N₂SBW) test in diagnosing SSc and to correlate N₂SBW parameters with the PFT indexes used in the follow-up of these patients, clinical data, and CT findings.

METHODS

Cross-sectional study in which 52 consecutive SSc patients were subjected to spirometry, body plethysmography, analysis of the diffusing capacity for carbon monoxide (DLCO), analysis of respiratory muscle strength, N₂SBW testing, and CT analysis.

RESULTS

Twenty-eight patients had a forced vital capacity (FVC) that was <70% of the predicted value. In the N₂SBW test, 44 patients had a phase III slope (Phase III slope_N2SBW) that was >120% of the predicted value, while 15 patients had a closing volume/vital capacity (CV/VC) that was >120% of the predicted value. A significant difference in Phase III slope_N2SBW was observed when the patients with predominant traction bronchiectasis and honeycombing were compared to the patients with other CT patterns (p<0.0001). The Phase III slope_N2SBW was correlated with FVC (r_s=-0.845, p<0.0001) and DLCO (r_s=-0.600, p<0.0001), and the CV/VC was correlated with FVC (r_s=-0.460, p=0.0006) and residual volume/total lung capacity (r_s=0.328, p=0.017).

CONCLUSION

Ventilation heterogeneity is a frequent finding in SSc patients that is associated with restrictive damage, changes in pulmonary diffusion, and CT patterns. In addition, approximately one-third of the patients presented with findings that were compatible with small airway disease.

Sex and the lung: Observations, hypotheses, and future directions

Sex-related differences in a variety of lung diseases in infants and young children are reviewed, including respiratory distress syndrome, and chronic lung disease of prematurity, lower respiratory tract illnesses and wheezing, asthma, diffuse, and interstitial lung diseases, and cystic fibrosis. Differences in anatomy and physiology, such as airway size, airway muscle bulk, airway reactivity, airway tone, and cough reflexes may explain much of these sex differences. Better understanding of sex-related lung differences could help personalize respiratory treatment.

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.

Transfer factor, lung volumes, resistance and ventilation distribution in healthy adults

Monitoring of chronic lung disease requires reference values of lung function indices, including putative markers of small airway function, spanning a wide age range.We measured spirometry, transfer factor of the lung for carbon monoxide (TLCO), static lung volume, resistance and ventilation distribution in a healthy population, studying at least 20 subjects per sex and per decade between the ages of 20 and 80 years.With respect to the Global Lung Function Initiative reference data, our subjects had average z-scores for forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC) and FEV1/FVC of -0.12, 0.04 and -0.32, respectively. Reference equations were obtained which could account for a potential dependence of index variability on age and height. This was done for (but not limited to) indices that are pertinent to asthma and chronic obstructive pulmonary disease studies: forced expired volume in 6 s, forced expiratory flow, TLCO, specific airway conductance, residual volume (RV)/total lung capacity (TLC), and ventilation heterogeneity in acinar and conductive lung zones.Deterioration in acinar ventilation heterogeneity and lung clearance index with age were more marked beyond 60 years, and conductive ventilation heterogeneity showed the greatest increase in variability with age. The most clinically relevant deviation from published reference values concerned RV/TLC values, which were considerably smaller than American Thoracic Society/European Respiratory Society-endorsed reference values.

Acinar ventilation heterogeneity in COPD relates to diffusion capacity, resistance and reactance

The aim of this study was to investigate heterogenic ventilation in the acinar (Sacin) and conductive (Scond) airways of patients with varying chronic obstructive pulmonary disease (COPD) severity and how these relates to advanced lung function parameters, primarily measured by impulse oscillometry (IOS). A secondary aim was to investigate the effects of a short acting beta2-agonist and a muscarinic antagonist on the heterogenic ventilation. Eleven never smoking controls, 12 smoking controls, and 57 COPD patients (7 GOLD 1, 25 GOLD 2, 14 GOLD 3 and 11 GOLD 4) performed flow-volume spirometry, IOS, body plethysmography, single breath carbon monoxide diffusion, and N2-multiple breath washout. Six smoking controls and 13 of the COPD patients also performed double reversibility test by using salbutamol and its combination with ipratropium. Sacin was significantly higher in GOLD 2-4 compared to never smoking controls and smoking controls, but showed similar levels in GOLD 3 and 4. A factor analysis identified 4 components consisting of; 1) IOS parameters, 2) volume parameters, 3) diffusion parameters, Sacin and some IOS parameters and 4) Scond with central obstruction/air trapping. Salbutamol and its combination with ipratropium had no effect on Sacin and Scond. Increased Sacin in COPD was strongly related to diffusion capacity and lung volumes, but also weakly to resistance and reactance, showing a link between ventilation heterogeneity in the acinar airways and parameters measured by IOS.

Feasibility of automated slope III and Scond analysis in children

BACKGROUND

Multiple breath washout (MBW) derived Scond is an established index of ventilation inhomogeneity. Time-consuming post hoc calculations of the expirogram's slope of alveolar phase III (SIII) and the lack of available software hampered widespread application of Scond.

METHODS

Seventy-two school-aged children (45 with cystic fibrosis; CF) performed 3 nitrogen MBW. We tested a new automated algorithm for Scond analysis (Scondauto ) which comprised breath selection for SIII detection, calculation and reporting of test quality. We compared Scondauto to (i) standard Scond analysis (Scondmanual ) with manual breath selection and to (ii) pragmatic Scond analysis including all breaths (Scondall ). Primary outcomes were success rate and agreement between different Scond protocols, and Scond fitting quality (linear regression R(2) ).

RESULTS

Average Scondauto (0.06 for CF and 0.01 for controls) was not different from Scondmanual (0.06 for CF and 0.01 for controls) and showed comparable fitting quality (R(2) 0.53 for CF and 0.13 for controls vs. R(2) 0.54 for CF and 0.13 for controls). Scondall was similar in CF and controls but with inferior fitting quality compared to Scondauto and Scondmanual .

CONCLUSIONS

Automated Scond calculation is feasible and produces robust results comparable to the standard manual way of Scond calculation. This algorithm provides a valid, fast and objective tool for regular use, even in children.

Small-airway disease in asthma: pharmacological considerations

PURPOSE OF REVIEW

To review the pharmacological considerations and rationale for treating small-airway disease in asthma via the inhaled and systemic route, and to also directly address the comparison between small vs. large aerosol particles in the management of asthmatic patients.

RECENT FINDINGS

Airway inflammation in patients with asthma is predominantly present within the small airways and this region is the main contributor to airflow limitation. Assessing small-airway dysfunction has advanced in the last decade, allowing us to compare this region in disease to health and also in response to treatment. Recent pharmaceutical developments have led to inhaler devices with smaller aerosols and systemic biologic treatments, enabling therapeutic drug delivery to the distal lung regions. The question therefore is does targeting the small airways directly translate into health benefits for asthmatic patients with respect to an improvement in their disease control and quality of life?

SUMMARY

Studies now show that treating the peripheral airways with smaller drug particle aerosols certainly achieve comparable efficacy (and some studies show superiority) compared with large particles, a reduction in the daily inhaled corticosteroid dose, and greater asthma control and quality of life in real-life studies. Hence, the small airways should not be neglected when choosing the optimal asthma therapy.

Assessment of Small Airways with Computed Tomography: Mosaic Attenuation or Lung Density?

BACKGROUND

Computed tomography (CT) assessment of air trapping has been considered useful as a measure of small airway disease. Mean lung density (MLD) and the percentage of the lung field occupied by low attenuation area (LAA%) can be evaluated automatically, and their expiratory/inspiratory (E/I) ratios correlate with asthma severity and spirometry parameters. However, mosaic attenuation, another indicator of air trapping, has been assessed visually, and its functional relevance remains controversial.

OBJECTIVES

This retrospective study was conducted to correlate mosaic attenuation, which was assessed visually and automatically, and the E/I ratios of MLD and LAA% (defined as areas <-960 Hounsfield units) with clinical and physiological variables, including impulse oscillometry (IOS) indices.

MATERIAL AND METHODS

In 36 nonsmoking patients with stable asthma, the lungs were scanned at full inspiration and full expiration. Mosaic attenuation was measured visually and automatically, by counting areas with CT values higher than the surrounding areas. MLD and LAA% were measured using our validated method. Spirometry, IOS, exhaled NO and the sputum eosinophil count were evaluated.

RESULTS

The automatic results and visual scores of mosaic attenuation correlated well on expiratory scans (r = 0.894) and to a lesser degree on inspiratory scans (r = 0.629; p < 0.0001 for both). However, only the E/I ratios of MLD and LAA% correlated with forced expiratory volume in 1 s/forced vital capacity of spirometry and the IOS indices of resistance from 5 to 20 Hz and the integrated area of low-frequency reactance.

CONCLUSIONS

Our automatic method for analysis of mosaic attenuation is likely useful, but the results themselves may not be reflecting small airway involvement of asthma, unlike the E/I ratios of MLD and LAA%.

Unlocking the quiet zone: the small airway asthma phenotype

The small airways in the distal lung have been called the quiet zone because they are difficult to assess and treat in patients with asthma who have disproportionate impairment of small airway function. Evidence is accumulating to support a distinct clinical phenotype for patients with asthma who have impaired small airway function. The small airway asthma phenotype, which is prevalent in patients at all steps of management guidelines, seems to be associated with poor disease control. Alternatively, small airway dysfunction might be a sensitive indicator of early disease rather than a phenotype. Conventional coarse-particle inhalers, which emit particles larger than 2 μm, might not address persistent small airway dysfunction in patients with asthma. To target the entire lung with extra-fine particle formulations (smaller than 2 μm) of inhaled corticosteroids alone or in combination with long-acting β-agonists might result in improved long-term asthma control along with a commensurate improvement in small airway function. Prospective randomised controlled trials with extra-fine-particle inhaled drugs are now needed for patients with the small airway asthma phenotype.

Techniques of assessing small airways dysfunction

The small airways are defined as those less than 2 mm in diameter. They are a major site of pathology in many lung diseases, not least chronic obstructive pulmonary disease (COPD) and asthma. The small airways are frequently involved early in the course of these diseases, with significant pathology demonstrable often before the onset of symptoms or changes in spirometry and imaging. Despite their importance, they have proven relatively difficult to study. This is in part due to their relative inaccessibility to biopsy and their small size which makes their imaging difficult. Traditional lung function tests may only become abnormal once there is a significant burden of disease within them. This has led to the term 'the quiet zone' of the lung. In recent years, more specialised tests have been developed which may detect these changes earlier, perhaps offering the possibility of earlier diagnosis and intervention. These tests are now moving from the realms of clinical research laboratories into routine clinical practice and are increasingly useful in the diagnosis and monitoring of respiratory diseases. This article gives an overview of small airways physiology and some of the routine and more advanced tests of airway function.

Irreversible acinar airway abnormality in well controlled asthma

RATIONALE

Even in stable asthma patients, acinar ventilation distribution can be abnormal, and we aimed to specifically maximize its reversibility by switching patients from a standard inhaled corticosteroid (iCS) to a fine particle iCS formulation.

METHODS

For this prospective double-blind double-dummy randomized study, 66 stable asthma patients under maintenance iCS (equivalent budesonide ≤ 800 μg/day) were screened for abnormal baseline acinar ventilation heterogeneity (Sacin). After a 3-week run-in period, 35 eligible patients were randomized to fine particle beclomethasone (HFA-BDP; Qvar Autohaler) or to budesonide (DPI-BUD; Pulmicort Turbohaler). Asthma Control Test (ACT) score and various lung function indices reflecting the small airways were obtained at baseline, after 6 and 12 weeks.

RESULTS

Thirty one patients [age:52 ± 17(SD) years; FEV1:76 ± 19(SD)%pred] completed the study (DPI-BUD:n = 16; HFA-BDP:n = 15). After 6 and 12 weeks, there were no significant changes in acinar or conductive ventilation heterogeneity, nor in mid-expiratory flow, RV/TLC, closing capacity, impulse oscillometry indices (resistance, reactance), bronchial NO production or alveolar NO, in either treatment arm. Asthma control was maintained in both arms.

CONCLUSION

In stable asthma patients with small airways dysfunction under maintenance therapy, there is a residual functional abnormality in the lung periphery which is probably not eosinophilic in origin and cannot be normalized with the iCS formulations under study. ISRCTN17195095.

Alveolar and exhaled NO in relation to asthma characteristics--effects of correction for axial diffusion

BACKGROUND

Inflammation in the small airways might contribute to incomplete asthma disease control despite intensive treatment in some subgroups of patients. Exhaled NO (FeNO) is a marker of inflammation in asthma and the estimated NO contribution from small airways (CalvNO ) is believed to reflect distal inflammation. Recent studies recommend adjustments of CalvNO for trumpet model and axial diffusion (TMAD-adj). This study aimed to investigate the clinical correlates of CalvNO , both TMAD-adjusted and unadjusted.

METHODS

Asthma symptoms, asthma control, lung function, bronchial responsiveness, blood eosinophils, atopy and treatment level were assessed in 410 subjects, aged 10-35 years. Exhaled NO was measured at different flow-rates and CalvNO calculated, with TMAD-adjustment according to Condorelli.

RESULTS

Trumpet model and axial diffusion-adjusted CalvNO was not related to daytime wheeze (P = 0.27), FEF50 (P = 0.23) or bronchial responsiveness (P = 0.52). On the other hand, unadjusted CalvNO was increased in subjects with daytime wheeze (P < 0.001), decreased FEF50 (P = 0.02) and with moderate-to-severe compared to normal bronchial responsiveness (P < 0.001). All these characteristics correlated with increased FeNO (all P < 0.05). Unadjusted CalvNO was positively related to bronchial NO flux (J'awNO ) (r = 0.22, P < 0.001) while TMAD-adjCalvNO was negatively related to J'awNO (r = -0.38, P < 0.001).

CONCLUSIONS

Adjusted CalvNO was not associated with any asthma characteristics studied in this large asthma cohort. However, both FeNO and unadjusted CalvNO related to asthma symptoms, lung function and bronchial responsiveness. We suggest a potential overadjustment by current TMAD-corrections, validated in healthy or unobstructed asthmatics. Further studies assessing axial diffusion in asthmatics with different degrees of airway obstruction and the validity of proposed TMAD-corrections are warranted.

Advances in airway clearance technologies for chronic obstructive pulmonary disease

Techniques to promote clearance of sputum from the airways (airway clearance techniques; ACTs) have existed in clinical practice for more than a century. This review examines current evidence and clinical recommendations regarding ACTs for individuals with chronic obstructive pulmonary disease. Comparisons between this literature and reports of current practice suggest that discrepancies may exist in relation to the clinical management of sputum in individuals with COPD. The novel application of newer technologies has enhanced our ability to assess the complex physiological processes underpinning airway clearance therapy. The potential for physiologically tailored ACT prescription may, however, depend on the capacity for translation of such technology from the research setting into the clinical environment. Future directions regarding this common form of therapy will be discussed, including identification of the key research priorities to optimize evidence-based practice in this area.

Respiratory impedance and response to salbutamol in healthy individuals and patients with COPD

BACKGROUND

Recent studies suggested that the bronchodilator response depends on airway obstruction. The forced oscillation technique (FOT) may help improve our understanding of the changes in respiratory mechanics that occur after the application of a bronchodilator.

OBJECTIVES

We aimed to (1) assess the response to salbutamol and to compare the impedance changes in healthy individuals and COPD patients, (2) investigate the effects of airway obstruction on this response and (3) evaluate the utility of the FOT as a complementary measurement to assess the response to the bronchodilator.

METHODS

Twenty-five healthy individuals and 82 patients with COPD were assessed with the FOT followed by spirometry before and after the use of salbutamol.

RESULTS

The changes exhibited by the COPD subgroups were greater than in the healthy individuals (p < 0.05). Increased obstruction resulted in decreased reductions in mean resistance and increased improvements in mean reactance (p < 0.001). In addition, the bronchodilation reduced the ventilation heterogeneity and the impedance modulus in all COPD stages (p < 0.05). The correlation coefficients for the spirometric and FOT changes were low (0.21-0.38).

CONCLUSIONS

In the initial phases of COPD (stage I), the effects of bronchodilation are greater than in healthy volunteers. The bronchodilator use improved the oscillatory mechanics in all of the studied groups of COPD patients. These improvements are reduced in more advanced phases of airway obstruction (II, III and IV). The FOT provides information that complements the data supplied by spirometry, contributing to an improvement in the evaluation of the bronchodilator response in COPD.

Small airways dysfunction in asthma: evaluation and management to improve asthma control

The small airways have been neglected for many years, but interest in the topic has been rekindled with recent advances in measurement techniques to assess this region and also the ability to deliver therapeutics to the distal airways. Current levels of disease control in asthmatic patients remain poor and there are several contributory factors including; poor treatment compliance, heterogeneity of asthma phenotypes and associated comorbidities. However, the proposition that we may not be targeting all the inflammation that is present throughout the whole respiratory tree may also be an important factor. Indeed decades ago, pathologists and physiologists clearly identified the importance of small airways dysfunction in asthmatic patients. With improved inhaler technology to deliver drug to target the whole respiratory tree and more sensitive measures to assess the distal airways, we should certainly give greater consideration to treating the small airway region when seeing our asthmatic patients in clinic. The aim of this review is to address the relevance of small airways dysfunction in the daily clinical management of patients with asthma. In particular the role of small particle aerosols in the management of patients with asthma will be explored.

Predictors of phase III slope of nitrogen single-breath washout in COPD

The nitrogen (N₂) single-breath washout (SBW) test is a measure of ventilation distribution inhomogeneity and also a small airway function that offers complementary information to spirometry; however, the relevance to the forced oscillation technique (FOT) and pulmonary emphysema in COPD is not fully understood. We hypothesized that pulmonary functions, forced oscillatory parameters, and emphysema extent would contribute independently to the results of the SBW test. In this cross-sectional study we assessed the relationship between the phase III slope (delta N₂) derived from N₂ SBW and these parameters. Spirometry, lung volumes, N₂ SBW, and the broadband frequency FOT were performed in 56 patients with COPD. Emphysema extent was measured by high-resolution computed tomography and scored. In multiple regression analyses, the delta N₂ was independently predicted by forced vital capacity, resonant frequency, and emphysema score (R(2)=0.57, p<0.0001). The degree of ventilation inhomogeneity derived from N₂ SBW is independently predicted by spirometry, lung mechanics, and the degree of emphysema.

Positive expiratory pressure via mask does not improve ventilation inhomogeneity more than huffing and coughing in individuals with stable chronic obstructive pulmonary disease and chronic sputum expectoration

BACKGROUND

Positive expiratory pressure (PEP) has been used to promote airway clearance in individuals with chronic obstructive pulmonary disease (COPD) for many years; however, its mechanism of action and benefits are unclear. Previous authors have suggested that PEP improves collateral ventilation via changes in lung volumes.

OBJECTIVES

It was the aim of this study to determine whether PEP improves ventilation inhomogeneity more than controlled huffing and coughing in individuals with stable COPD.

METHODS

Twelve participants with COPD (mean forced expiratory volume in 1 s 45% predicted) and chronic sputum expectoration performed PEP therapy (10-20 cm H2O) or controlled huffing and coughing in random order on alternate study days with a 48-hour washout. Measures of acinar and conductive airway ventilation (S(acin), S(cond)), lung volumes, spirometry and sputum wet weight were recorded before, immediately after and 90 min following treatment. Ease of expectoration [visual analogue scale (VAS)] and oxyhaemoglobin saturation were assessed immediately following treatment.

RESULTS

There were no significant differences between the effect of either test condition at any time point for any test parameter. Mean Sacin immediately following PEP and control conditions was 0.465 and 0.438 litre(-1), respectively (p = 0.45 for comparison between conditions) and mean S(cond) was 0.042 and 0.039 litre(-1) (p = 0.55). PEP therapy did not significantly enhance total mean sputum expectoration compared to controlled huffing and coughing (7.06 vs. 6.15 g; p = 0.51) and did not improve ease of expectoration (VAS PEP 4.8 cm vs. control 4.1 cm; p = 0.53).

CONCLUSION

Any therapeutic benefits of PEP in individuals with COPD and chronic sputum expectoration are unlikely to be mediated by improvements in ventilation or lung volumes.

Novel functional imaging of changes in small airways of patients treated with extrafine beclomethasone/formoterol

BACKGROUND

Inhaled formulations using extrafine particles of long-acting β2-agonists and corticosteroids were developed to optimize asthma treatment. Findings that these combinations reach and treat smaller airways more effectively are predominantly based on general non-specific outcomes with little information on regional characteristics.

OBJECTIVES

This study aims to assess long-term effects of extrafine beclomethasone/formoterol on small airways of asthmatic patients using novel functional imaging methods.

METHODS

Twenty-four stable asthma patients were subdivided into three groups (steroid naive, n = 7; partially controlled, n = 6; well controlled, n = 11). Current treatment was switched to a fixed combination of extrafine beclomethasone/formoterol (Foster®; Chiesi Pharmaceuticals, Parma, Italy). Patients underwent lung function evaluation and thorax high-resolution computerized tomography (HRCT) scan. Local airway resistance was obtained from computational fluid dynamics (CFD).

RESULTS

After 6 months, the entire population showed improvement in pre-bronchodilation imaging parameters, including small airway volume (p = 0.0007), resistance (p = 0.011), and asthma control score (p = 0.016). Changes in small airway volume correlated with changes in asthma control score (p = 0.004). Forced expiratory volume in 1 s (p = 0.044) and exhaled nitric oxide (p = 0.040) also improved. Functional imaging provided more detail and clinical relevance compared to lung function tests, especially in the well-controlled group where only functional imaging parameters showed significant improvement, while the correlation with asthma control score remained.

CONCLUSIONS

Extrafine beclomethasone/formoterol results in a significant reduction of small airway obstruction, detectable by functional imaging (HRCT/CFD). Changes in imaging parameters correlated significantly with clinically relevant improvements. This indicates that functional imaging is a useful tool for sensitive assessment of changes in the respiratory system after asthma treatment.

Treating the small airways

The final article in this series evaluates the approaches undertaken to treating the small-airway region of the lungs and the clinical implications of inhaled therapy targeting the periphery in patients with asthma and chronic obstructive pulmonary disease.