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A 'Good' muscle in a 'Bad' environment: The importance of airway smooth muscle force adaptation to airway hyperresponsiveness.

Asthma is characterized by airway inflammation, with a consequent increase in spasmogens, and exaggerated airway narrowing in response to stimuli, termed airway hyperresponsiveness (AHR). The nature of any relationship between inflammation and AHR is less clear. Recent ex vivo data has suggested a novel mechanism by which inflammation may lead to AHR, in which increased basal ASM-tone, due to the presence of spasmogens in the airways, may "strengthen" the ASM and ultimately lead to exaggerated airway narrowing.

This phenomenon was termed "force adaptation" [Bossé, Y., Chin, L.Y., Paré, P.D., Seow, C.Y., 2009. Adaptation of airway smooth muscle to basal tone: relevance to airway hyperresponsiveness. Am. J. Respir. Cell Mol. Biol. 40, 13-18].

However, it is unknown whether the magnitude of the effect of force adaptation ex vivo could contribute to exaggerated airway narrowing in vivo. Our aim was to utilize a computational model of ASM shortening in order to quantify the potential effect of force adaptation on airway narrowing when all other mechanical factors were kept constant. The shortening in the model is dictated by a balance between physiological loads and ASM force-generating capacity at different lengths.

The results suggest that the magnitude of the effect of force adaptation on ASM shortening would lead to substantially more airway narrowing during bronchial challenge at any given airway generation.

We speculate that the increased basal ASM-tone in asthma, due to the presence of inflammation-derived spasmogens, produces an increase in the force-generating capacity of ASM, predisposing to AHR during subsequent challenge.

The interest of FEF(25-75) in evaluating bronchial hyperresponsiveness with the methacholine test.

BACKGROUND: Bronchial hyperresponsiveness is the pathogenic basis of asthma, and measurement of its intensity is investigated using the methacholine provocation test, which not only and particularly evaluates the reduction in FEV1 (PD20) but also takes forced mid-expiratory flow or FEF(25-75) (PD40) into account. The present study aims to evaluate the usefulness of both parameters.

MATERIAL AND METHODS: Provocation testing was carried out in 151 patients between 7 and 22 years of age diagnosed with asthma, tracheobronchitis and/or rhinitis, using a short method that allows quantification of the methacholine administered. The subjects were divided into three groups according to the amount of methacholine needed to obtain the mentioned parameters (group 1: ≤1000μg; group 2: 1001-2000μg; group 3: ≥2001μg).

RESULTS: Greater variability was recorded for FEF(25-75) than for FEV1. Paired comparison among the three groups for FEV1 proved significant, in the same way as for FEF(25-75) between groups 2 and 3, and 1 and 3, but not between groups 1 and 2. Calculation was made of the amount of methacholine required to obtain PD20 and PD40 from the same dose. Only the significant differences corresponded to the comparison of group 1 versus the rest, with no differences between the means of the total mean values.

CONCLUSIONS: The utility of PD20 is more evident, considering the variability of PD40; the latter may be useful in patients with rhinitis or tracheobronchitis when PD20 proves scantly demonstrative.

Asthma and risk of lung cancer.

Asthma is a very common chronic disease that occurs in all age groups. Its high prevalence has significant health costs, which are even higher in the most severe disease forms. Lung cancer has the highest incidence of all cancers in the developed world and is an important cause of mortality.

Patients with lung cancer are a big economic burden on health services, both in direct and indirect costs. Different authors suggest that atopic constitution, including different manifestations of allergy and asthma, are possible risk factors for lung cancer, above all in never-smokers. Given the high asthma prevalence and lung cancer incidence and mortality in developed countries, this association would have important public health implications.

Uncertainties about the association and the underlying physiopathological mechanisms, however, seem to require further studies.

Home-based educational interventions for children with asthma.

BACKGROUND: While guidelines recommend that children with asthma should receive asthma education, it is not known if education delivered in the home is superior to usual care or the same education delivered elsewhere. The home setting allows educators to reach populations (such as the economically disadvantaged) that may experience barriers to care (such as lack of transportation) within a familiar environment.

OBJECTIVES: To perform a systematic review on educational interventions for asthma delivered in the home to children, caregivers or both, and to determine the effects of such interventions on asthma-related health outcomes. We also planned to make the education interventions accessible to readers by summarising the content and components.
SEARCH STRATEGY: We searched the Cochrane Airways Group Specialised Register of trials, which includes the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, CINAHL, AMED and PsycINFO, and handsearched respiratory journals and meeting abstracts. We also searched the Education Resources Information Center database (ERIC), reference lists of trials and review articles (last search January 2011).
SELECTION CRITERIA: We included randomised controlled trials of asthma education delivered in the home to children, their caregivers or both. In the first comparison, eligible control groups were provided usual care or the same education delivered outside of the home. For the second comparison, control groups received a less intensive educational intervention delivered in the home.
DATA COLLECTION AND ANALYSIS: Two authors independently selected the trials, assessed trial quality and extracted the data. We contacted study authors for additional information. We pooled dichotomous data with fixed-effect odds ratio and continuous data with mean difference (MD) using a fixed-effect where possible.
MAIN RESULTS: A total of 12 studies involving 2342 children were included. Eleven out of 12 trials were conducted in North America, within urban or suburban settings involving vulnerable populations. The studies were overall of good methodological quality. They differed markedly in terms of age, severity of asthma, context and content of the educational intervention leading to substantial clinical heterogeneity. Due to this clinical heterogeneity, we did not pool results for our primary outcome, the number of patients with exacerbations requiring emergency department (ED) visit. The mean number of exacerbations requiring ED visits per person at six months was not significantly different between the home-based intervention and control groups (N = 2 studies; MD 0.04; 95% confidence interval (CI) -0.20 to 0.27). Only one trial contributed to our other primary outcome, exacerbations requiring a course of oral corticosteroids. Hospital admissions also demonstrated wide variation between trials with significant changes in some trials in both directions. Quality of life improved in both education and control groups over time.A table summarising some of the key components of the education programmes is included in the review.
AUTHORS' CONCLUSIONS: We found inconsistent evidence for home-based asthma educational interventions compared to standard care, education delivered outside of the home or a less intensive educational intervention delivered at home. Although education remains a key component of managing asthma in children, advocated in numerous guidelines, this review does not contribute further information on the fundamental content and optimum setting for such educational interventions.

Lung function increases with resveratrol, white wine intake

NEW YORK (Reuters Health) - Consumption of resveratrol and white wine is associated with higher levels of lung function, researchers from The Netherlands report online August 28 in the European Respiratory Journal Express. (Source: Modern Medicine)

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