Human airway smooth muscle

The function of airway smooth muscle in normal subjects is not evident. Possible physiological roles include maintenance of optimal regional ventilation/perfusion ratios, reduction of anatomic dead space, stabilisation of cartilaginous bronchi, defense against impurities and, less likely, squeezing mucus out of mucous glands and pulling open the alveoli next to the airways1 . Any role of airway smooth muscle is necessarily limited, because an important degree of contraction will lead to airway narrowing and to an increased work of breathing. There is, however, no doubt that in asthma the acute bronchoconstriction following exposure to nonspecific or allergic stimuli is due to airway smooth muscle contraction. Most research on airway smooth muscle function has therefore concentrated on clarifying its role in bronchial hyperresponsiveness, airway obstruction and allergy. From the foregoing chapters it can be concluded that many factors may be involved in the pathogenesis of the abnormal responsiveness of airway smooth muscle in patients with asthma or chronic bronchitis. One of these factors is an intrinsic abnormality of the airway smooth muscle cells. In order to examine this, several animal models have been developed, most of which have features in common with human allergic bronchoconstriction2 • Because of important differences between species, and because there is no satisfactory animal model of spontaneous, non-allergic asthma, it is crucial to study human airway smooth muscle from subjects with and without airway hyperresponsiveness. The research on human lung tissue in vitro has been limited by the supply, and by difficulties in obtaining stable and reproducible responses of airway smooth muscle in vitro. Moreover, it is very difficult to obtain lung tissue from asthmatic subjects. This chapter will give a summary of the research on airway smooth muscle hyperresponsiveness in experimental animals and man. From these data, the aims of the studies to be presented in parts II and III will be derived and briefly outlined

Exhaled nitric oxide measurements in the first 2 years of life: methodological issues, clinical and epidemiological applications

Fractional exhaled nitric oxide (FeNO) is a useful tool to diagnose and monitor eosinophilic bronchial inflammation in asthmatic children and adults. In children younger than 2 years of age FeNO has been successfully measured both with the tidal breathing and with the single breath techniques. However, there are a number of methodological issues that need to be addressed in order to increase the reproducibility of the FeNO measurements within and between infants. Indeed, a standardized method to measure FeNO in the first 2 years of life would be extremely useful in order to meaningfully interpret FeNO values in this age group. Several factors related to the measurement conditions have been found to influence FeNO, such as expiratory flow, ambient NO and nasal contamination. Furthermore, the exposure to pre- and postnatal risk factors for respiratory morbidity has been shown to influence FeNO values. Therefore, these factors should always be assessed and their association with FeNO values in the specific study population should be evaluated and, eventually, controlled for

Stand van zaken:Treating asthma in children successfully: 10 tips

Although clinical studies show that childhood asthma can be controlled well with inhaled corticosteroids, many children with asthma remain symptomatic despite maintenance treatment with inhaled corticosteroids. In this article, we present 10 tips for successfully treating childhood asthma using only an inhaled corticosteroid and a short-acting bronchodilator. These 10 tips are: make the diagnosis based on the history; do not emphasize the role of lung function studies in the diagnostic process; treat asthma with appropriate medications once you have made the diagnosis; collaborate with the patient and his or her parents; pay attention to the non-drug aspects of therapy; choose an inhaler the child is able to use, train correct use; make follow-up appointments; monitor symptoms, exacerbations and impact on daily life; when children remain symptomatic despite the use of inhaled steroids: investigate potential causes; invest in mutual collaboration between primary and secondary care.</p