Reversible airway obstruction

Sympathomimetics (drugs that mimic the sympathetic nervous system) are used primarily to treat reversible airway obstruction caused by bronchospasm associated with acute and chronic bronchial asthma, exercise-induced bronchospasm, bronchitis, emphysema, bronchiectasis (abnormal condition of the bronchial tree), or other obstructive pulmonary diseases. 

Bronchial asthma is defined as a chronic inflammatory disease of the lungs it affects an estimated 9 to 12 million individuals in the U.S. Furthermore, its prevalence has been increasing in recent years. Asthma is characterized by reversible airway obstruction (in particular, bronchospasm), airway inflammation, and increased airway responsiveness to a variety of bronchoactive stimuli. Many factors may induce an asthmatic attack, including allergens respiratory infections hyperventilation cold air exercise various drugs and chemicals emotional upset and airborne pollutants (smog, cigarette smoke). 

The desired outcome in the pharmacological treatment of asthma is to prevent or relieve the reversible airway obstruction and airway hyperresponsiveness caused by the inflammatory process. Therefore, categories of medications include bronchodilators and anti-inflammatory drugs. 

An inhalable medication that relaxes the muscles in the airways (bron-chodilator) is frequently administered when airways obstruction is identified. In this bronchodilator trial test, the spirometry test is subsequently repeated and compared to the results from the initial spirometry test. If there is substantial improvement in lung function with the administration of the bronchodilator, the airways obstruction is reversible. An example of a lung disease with reversible airways obstruction is asthma, in which s)nnptoms occur episodically when airways obstruction occurs. If there is little or no improvement after the administration of the bronchodilator, the airways obstruction is fixed. An example of a limg disease with fixed airways obstruction is BO, where there is scarring of the airways. 

Rajan KG, Davies BH Reversible airways obstruction and interstitial pneumonitis due to acetic acid. BrJ Ind Med 46 67-68, 1989... 

To gain full therapeutic benefit, administer twice daily (morning and evening) in the treatment of reversible airway obstruction. 

Asthma is a chronic inflammatory condition characterized by bronchial hyper-responsiveness and reversible airway obstruction. Cytokine release from a variety of cell types such as eosinophils, lymphocytes and other inflammatory cells produces epithelial sloughing, plasma protein extravasation from the tracheobronchial microcirculation and airway remodeling. Bronchial mucosal inflammation is present in all patients. The primary goal of asthma management is to maintain control of the disease process by reducing symptoms and improving lung function. 

Xanthine derivatives are a group of chemically similar compounds that exert a variety of pharmacologic effects. Common xanthine derivatives include theophylline, caffeine, and theobromine (Fig. 26-2) these compounds are frequently found in various foods and beverages (tea, coffee, soft drinks). Theophylline and several theophylline derivatives are also administered therapeutically to produce bronchodilation in asthma and other forms of reversible airway obstruction (bronchitis, emphysema).65,79 Theophylline and caffeine are also potent CNS stimulants, and some of the more common side effects of these drugs are related to this CNS excitation (see Adverse Side Effects, later in this chapter). 

Simple spirometric testing with a bronchodilator challenge can identify patients with reversible airway obstruction, such as asthma (Figure A.3). The patient fills his or her lungs maximally and then expels the air as rapidly as possible. First a baseline reading is taken for this forced expiratory volume in the first second (FEV. Next, an aerosol bronchodilator, such as albuterol, is administered and the test is repeated after 15 minutes. Airway obstruction is considered to be reversible when the FEVi improves by more than... 

Salbutamol (Ventolin Accuhaler) - management of asthma, bronchospasm and/or reversible airways obstruction (also terbutaline, formoterol, salmeterol, etc.). 

Smooth muscle (other than vascular muscle, which is discussed above) is relaxed. The only important clinical use for this action is in reversible airways obstruction (asthma), when the action of theophylline can be a very valuable addition to therapy. 

Whereas asthma is characterised by reversible airways obstruction and bronchial hyperreactivity, COPD is characterised by incompletely reversible airways obstruction and mucus hypersecretion it is predominantly a disease of the smaller airways. Nevertheless, distinguishing the two can be difficult in some patients and one view is that asthma predisposes smokers to COPD (Dutch hypothesis). In practice, even though — indeed precisely because — most of the airway obstruction is fixed in COPD, it is important to maximise the reversible component. This can be assessed by measuring FEVj before and after a course of oral prednisolone, e.g. at least 30 mg/day for 2 weeks reversibility is arbitrarily defined as > 15% rise (and > 200 ml) in... 

Asthma is a disease characterized by reversible airways obstruction and increased responsiveness of the airways to specific and nonspecific bronchocon-strictor stimuli. Indeed, the latter feature may be used in diagnosis of asthma (vide infra). Obstruction to the flow of air in asthma is the product of three factors smooth muscle contraction, mucosal edema, and augmented mucus secretion. Pathological features, such as infiltration of the airway walls with inflammatory cells (e.g., eosinophils, neutrophils), and the efficacy of antiinflammatory steroids in treating the disease have pointed to an important role of inflammation in the disease process. 

Keeley DJ, Neill P, Gallivan S Comparison of the prevalence of reversible airways obstruction in... 

Reversible airway obstruction is common in asthma and chronic obstructive pulmonary disease (COPD). An increase in FEVi after an inhaled/f-agonist of 12% and greater than 0.2 L suggests an acute bronchodilator response. 

The worldwide incidence, morbidity, and mortality of allergic asthma are increasing. Asthma has become an epidemic, affecting 155 million individuals throughout the world. It is a complex disorder characterized by local and systemic allergic inflammation, mucus hypersecretion, and reversible airway obstruction [88]. The pathogenesis of asthma reflects the activity of cytokines from Th2 cells. Without these cells there is no asthma. Animal models support important roles for the cytokines IL-4, IL-5, and the recent IL-13 [89]. The latter is closely related to IL-4 they both bind to the same IL-4 receptor, to the a-chain of that receptor, particularly. 

Observations of relief of bronchoconstriction without cardiovascular side effects suggest that prostaglandins have a potential clinical role in conditions such as asthma. Cuthbert [273] compared the effect of aerosol-administered PGEi on airways resistance in healthy and asthmatic volunteers with reversible airways obstruction. In the healthy subjects, the forced expiratory volume in one second (FEVi) was unaffected by the prostaglandin when administered as the free acid or as the triethanolamine salt. However, in the asthmatics, inhalation of 55 pg of the triethanolamine salt produced an increase in FEVi comparable in both degree and duration with that produced by an inhalation of 550 jig of isoprenaline sulphate. The triethanolamine salt was employed in the asthmatic trials since it was better tolerated, the free acid being irritant to the upper respiratory tract. Similar results were obtained with PGE2 [274]. 

In patients with reversible airway obstruction (81), the greatest bronchodi-latation was obtained when the pMDI containing terbutaline was actuated during a slow inhalation (25 to 30 L/min) and actuation is followed by a breath-hold lasting 10 s. A significant correlation between mean bronchodilator response for the different inhalation modes and pulmonary deposition of labeled Teflon particles obtained in the aforementioned studies was reported (77). Studies with other Pj-agonists inhaled via pMDI have given similar results (82) and confirmed the clinical relevance of flow dependency of pulmonary deposition for pMDIs. 

Carlsson LG, Arwestrom E, Friberg K, Kallen A, Lunde H, Lofdahl CG. Efficacy of cumulative doses of salbutamol administered via Turbuhaler or Diskhaler in patients with reversible airway obstruction. Allergy 1998 53 712-715. 

Lofdahl CG, Andersson L, Bondesson E, Carlsson LG, Friberg K, Hedner J. Differences in bronchodUating potency of salbutamol in Turbuhaler as compared with a pressurized metered-dose inhaler formulation in patients with reversible airway obstruction. EurRespir J 1997 10 2474—2478. 

Asthma is defined by three characteristic features airway inflammation, intermittent reversible airway obstruction and airway hyperresponsiveness [67]. This results in the... 

Asthma is a common disease affecting approx 10% of the population in developed countries, and the prevalence and mortality are rising. The disease has characteristic symptoms, namely intermittent airway obstruction, airway hyperresponsiveness, and increased numbers of activated inflammatory cells and airway structural changes as a result of chronic airway inflammation. The primary underlying abnormality in bronchial asthma is thought to be the unique form of airway inflammation, including particularly eosinophils and mast cells, that gives rise to reversible airway obstruction and hyperresponsiveness. 

Keeley DJ, NeiU P, GaUivan S. Comparison of the prevalence of reversible airways obstruction in rural and urban Zimbabwean children. Thorax 1991 46(8) 549-553. Strachan DP. Lifestyle and atopy. Lancet 1999 353(9163) 1457-1458. 

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