Lung function in adults with stable but severe asthma: Air trapping and incomplete reversal of obstruction with bronchodilation

Univ. of Wisconsin, 777 Highland Ave., Madison, WI 53705, USA.
Journal of Applied Physiology (Impact Factor: 3.06). 03/2008; 104(2):394-403. DOI: 10.1152/japplphysiol.00329.2007
Source: PubMed


Five to ten percent of asthma cases are poorly controlled chronically and refractory to treatment, and these severe cases account for disproportionate asthma-associated morbidity, mortality, and health care utilization. While persons with severe asthma tend to have more airway obstruction, it is not known whether they represent the severe tail of a unimodal asthma population, or a severe asthma phenotype. We hypothesized that severe asthma has a characteristic physiology of airway obstruction, and we evaluated spirometry, lung volumes, and reversibility during a stable interval in 287 severe and 382 nonsevere asthma subjects from the National Heart, Lung, and Blood Institute Severe Asthma Research Program. We partitioned airway obstruction into components of air trapping [indicated by forced vital capacity (FVC)] and airflow limitation [indicated by forced expiratory volume in 1 s (FEV(1))/FVC]. Severe asthma had prominent air trapping, evident as reduced FVC over the entire range of FEV(1)/FVC. This pattern was confirmed with measures of residual lung volume/total lung capacity (TLC) in a subgroup. In contrast, nonsevere asthma did not exhibit prominent air trapping, even at FEV(1)/FVC <75% predicted. Air trapping also was associated with increases in TLC and functional reserve capacity. After maximal bronchodilation, FEV(1) reversed similarly from baseline in severe and nonsevere asthma, but the severe asthma classification was an independent predictor of residual reduction in FEV(1) after maximal bronchodilation. An increase in FVC accounted for most of the reversal of FEV(1) when baseline FEV(1) was <60% predicted. We conclude that air trapping is a characteristic feature of the severe asthma population, suggesting that there is a pathological process associated with severe asthma that makes airways more vulnerable to this component.

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Available from: William J Calhoun
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    • "It is recognized that the majority of asthmatics may be controlled by regular treatment with ICS/LABA. However there remains a small proportion of patients who do not respond to this treatment [1] [2]. Severe asthma accounts for a major part of financial burden to health care system posed by asthma [3]. "
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    ABSTRACT: The Belgian severe asthma registry is a web-based registry encompassing demographic, clinical, functional and inflammatory data of severe asthmatics (SA), aiming at improving awareness, knowledge on its natural history and subphenotypes, and offering tools to optimize care of this asthma population. The cross-sectional analyses of this registry included 350 SA as defined by the ATS (2000) from 9 Belgian centres, with at least one year follow up. Mean age was 55 ± 14 yrs. SA were more frequently female (57%) and atopic (70%). Late-onset asthma (≥40 yr) was observed in 31% of SA. Current smokers represented 12% while 31% were ex-smokers. In addition to high doses ICS + LABA, 65% of patients were receiving LTRA, 27% anti-IgE and 24% maintenance oral corticosteroids (8 mg (Interquartile range-IQR:4-8) methylprednisolone). Despite impaired airflow (median FEV1:67%; IQR: 52-81) only 65% had a post-bronchodilator FEV1/FVC ratio <70%. The median blood eosinophil count was 240/mm³. The median FENO was 26 ppb (IQR: 15-43) and 22% of SA had FENO ≥ 50 ppb. Induced sputum was successful in 86 patients. Eosinophilic asthma (sputum Eos ≥ 3%) was the predominant phenotype (55%) while neutrophilic (sputum Neu ≥ 76%) and paucigranulocytic asthma accounted for 22% and 17% respectively. Comorbidities included rhinitis and chronic rhinosinusitis (49%), nasal polyposis (19%), oesophageal reflux (36%), overweight and obesity (47%) and depression (19%). In addition, 8% had aspirin-induced asthma and 3% ABPA. Asthma was not well-controlled in 83% according to ACT < 20 and 77% with ACQ > 1.5. In this cohort of patients with severe asthma, the majority displayed indices of persistent airflow limitation and eosinophilic inflammation despite high-dose corticosteroids, suggesting potential for eosinophil-targeted biotherapies. Copyright © 2014 Elsevier Ltd. All rights reserved.
    Full-text · Article · Dec 2014 · Respiratory Medicine
    • "The majority of asthmatic patients suffer mild to moderate disease that can be well controlled with standard therapy [3] allowing clinical stability. However, 5e10% of asthmatics suffer from a severe disease characterized by frequent exacerbations and poor clinical control being often refractory to usual treatment [4] [5]. The principal causes of asthma exacerbations are considered the viral infections [6e8] possibly accounting for 80% of exacerbations in children and 50% in adults [9] (respiratory syncitial virus in infancy [10] and rhinovirus in adults [11]). "
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    ABSTRACT: Background Limited information is available about clinical outcomes and microbiology of community-acquired pneumonia in asthma. Methods We prospectively studied 4079 CAP patients over a 12-years period and found 139 (3.4%) asthmatic patients. Results Asthmatics showed younger age (57±19 vs. 66±19 years), less males (32% vs. 68%) and less active smokers (15% vs. 25%). Moreover, they had used more frequently inhaled corticosteroids (ICs, 53% vs. 17%, p<0.001) and antibiotics (32% vs. 24%, p=0.041). In comparison with non asthma-CAP, asthmatics showed at admission more pleuritic pain and dyspnoea but less severe pneumonia (PSI, CURB-65, PaO2/FiO2 ratio; p<0.05). No differences were observed in CAP microbiology, being Streptococcus pneumoniae the most frequent isolate. Clinical outcomes in asthmatic patients were similar to the general population (mortality, mechanical ventilation, etc.) but with a shorter median length of stay (6 [3; 9] vs. 7 [4; 10] days, p=0.023). The chronic use of ICs did not influence clinical presentation and outcomes among asthmatic patients. Conclusions Asthmatics were younger and showed similar clinical presentation. Consistently with PSI, asthmatics showed similar outcomes than the general population. The microbial aetiology of CAP in asthma did not differ from the general population and antibiotic therapy should follow current guidelines.
    No preview · Article · Sep 2014 · Respiratory Medicine
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    • "Similarly, Perez and colleagues have demonstrated the presence of small airways impairment (defined primarily by body plethysmography measures of lung hyperinflation such as functional residual capacity (FRC), residual volume (RV) and the ratio of RV/total lung capacity) in nearly 40% of clinically stable moderate-to-severe asthmatics treated with ICS/LABA who had a normal FEV1, supporting the observation that conventional physiological measurements are unable to sensitively evaluate this airway region.45 The forced vital capacity (FVC) is gaining support as an indirect marker of air trapping, where in the severe asthma research programme, the FVC as a percentage of predicted was shown to be highly inversely correlated to the ratio of residual volume to total lung capacity (RV/TLC) as a percentage of predicted46 Indeed, Papi and colleagues have shown that improvements in FVC may reflect reduction in air trapping and small airways obstruction.47 The authors investigated the effects of 3 months of treatment with small particle (~1.5 microns) combination ICS/LABA aerosols (beclomethasone dipropionate [BDP] with formoterol [Form], 400/24 µg daily) delivered via an hydrofluoroalkane (HFA)-solution pressurised metered dose inhaler (pMDI) and compared this to large particle (~2.7 microns) combination ICS/LABA aerosols (fluticasone propionate (FP) with salmeterol (Salm), 500/100 µg daily) administered as an HFA-suspension pMDI, and observed a significant improvement in FVC with the small particle aerosols. "
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    ABSTRACT: 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.
    Full-text · Article · Sep 2014 · Allergy, asthma & immunology research
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