Airways obstruction

W ithin the past few years a number of new drugs have been introduced to treat respiratory disorders, such as bronchial asthma and disorders that produce chronic airway obstruction. This chapter discusses the bronchodilators, dragp that have been around for a long time but are still effective in specific instances, and the newer antiasthma drugs that have proven to be highly effective in the prophylaxis (prevention) of breathing difficulty. 

Asthma is a reversible obstructive disease of the lower airway. With asthma there is increasing airway obstruction caused by bronchospasm and bronchoconstriction, inflammation and edema of the lining of the bronchioles, and the production of thick mucus that can plug the airway (see Pig. 37-1). There are three types of asthma ... 

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. 

Prophylactic treatment of Cl INH deficiency consists of Cl INH replacement infusions, androgens (danazol, stanozolol, oxymethalone) or antifibrinolytic agents. Acute treatment employs Cl INH replacement (where available), fresh-frozen plasma, and placement of an airway when significant airway obstruction is evident. Abdominal attacks require IV fluid, analgesics, and watchful waiting . 

Some physicians recommend epinephrine metered-dose inhalers as an alternative to epinephrine autoinjectors. While a few inhalations might relieve mild or moderate respiratory symptoms, for relief of life-threatening airway obstruction or shock, adults need to inhale 20-30 puffs and children need to inhale 10-20 puffs, which is hard to do [35]. Epinephrine metered-dose inhalers contain chlorofluorocarbon propellants. For environmental reasons, they might not be manufactured in the future. 

Inhaled short-acting fl2-agonists are the most effective agents for reversing acute airway obstruction caused by bronchoconstriction. 

Asthma is characterized by inflammation, airway hyperresponsiveness (AHR), and airway obstruction. Inhaled antigens... 

Airway obstruction manifests itself as symptoms such as chest tightness, cough, and wheezing. Airway obstruction can be caused by multiple factors including airway smooth muscle constriction, airway edema, mucus hypersecretion, and airway remodeling. Airway smooth muscle tone is maintained by an interaction between sympathetic, parasympathetic, and non-adrenergic mechanisms. Acute bronchoconstriction usually... 

Decreased FEVRFVC (less than 80%, but may be normal between exacerbations) demonstrates airway obstruction. 

A greater than or equal to 12% (at least 200 mL) improvement in FEV after an inhaled bronchodilator demonstrates a reversible obstruction. A 2- to 3-week course of oral corticosteroids may be necessary to demonstrate reversibility in airway obstruction. 

Lower airway obstruction Congestive heart failure... 

At blood levels from 0.4g%-0.6g% (86.8 to 130.2 mmol/L) alcoholic coma often occurs, accompanied by decreased respiration, blood pressure, and body temperature Blood levels between 0.6 g% and 0.8 g% (130.2 to 173.6 mmol/L) are often fatal resulting from respiratory arrest, aspiration of gastric contents, or airway obstruction due to flaccid tongue... 

Patients with airway obstruction may have shortness of breath. 

Radiation therapy is the treatment of choice for chemotherapy-resistant tumors such as non-small cell lung cancer (NSCLC) or in chemotherapy-refractory patients with SVCS. Between 70% and 90% of patients will experience relief of symptoms. Radiation therapy also may be combined with chemotherapy for chemotherapy-sensitive tumors such as SCLC and lymphoma. In the rare emergency situations of airway obstruction or elevated intracranial pressure, empirical radiotherapy prior to tissue diagnosis should be used. In most patients, symptoms resolve within 1 to 3 weeks. 

Angioedema Swelling similar to urticaria (hives), but the swelling occurs beneath the skin instead of on the surface. Angioedema is characterized by deep swelling around the eyes and lips, and sometimes of the hands and feet. If it proceeds rapidly, it can lead to airway obstruction and suffocation, and it should therefore be treated as a medical emergency. 

Explain the effects of airway obstruction and obstructed blood flow on ventilation-perfusion matching... 

Figure 17.3 Airway obstruction, (a) Normal, patent airway with radial traction offered to it by surrounding airways. Resistance in this airway is low and air flows through it freely, (b) The airway is obstructed by the presence of excess mucus and airway resistance is increased. Airflow is reduced, (c) Thickening of the airway wall due to inflammation or edema narrows the lumen of the airway. The decrease in airway radius increases airway resistance and decreases airflow, (d) Destruction of surrounding airways results in the loss of interdependence, or radial traction. Without the structural support offered by surrounding airways, the central airway collapses and airflow through it is reduced.

Airway obstruction. Airway obstruction may be caused by several factors including ... 

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. 

---