西安交通大学医学院呼吸系统疾病课件 ASTHMA.pptVIP

ASTHMA Respiratory department Chen Mingwei Essentials of Diagnosis Episodic or chronic symptoms of airflow obstruction: breathlessness, cough, wheezing, and chest tightness. Prolonged expiration and diffuse wheezes on physical examination. Limitation of airflow on pulmonary function testing or positive bronchial provocation challenge. Complete or partial reversibility of airflow obstruction, either spontaneously or following bronchodilator therapy. General Considerations approximately 5% of the population. Men and women appear to be equally affected. Pathophysiology Airway obstruction in asthma is due to a combination of factors that include spasm of airway smooth muscle, edema of airway mucosa, increased mucus secretion, cellular (especially eosinophilic and lymphocytic) infiltration of the airway walls, and injury and desquamation of the airway epithelium. The number of eosinophils in peripheral blood and airway ecretions correlates closely with the degree of bronchial hyperresponsiveness. The degree of hyperresponsiveness is closely linked to the extent of inflammation, and both correlate closely with the severity of the disease and the need for drugs. Another possible cause of airway hyperresponsiveness is airway remodeling resulting in a small increase in airway thickness. T-cell activation of the allergic response is a key event in the inflammation that characterizes asthma. T cells and their secretory products (cytokines) perpetuate airway inflammation. The pathophysiologic changes described above lead to varying degrees of airway obstruction and to ventilation that is typically nonuniform. Symptoms and Signs Symptoms The frequency and severity of symptoms vary greatly from person to person and from time to time in the same person. Some asthmatics have occasional episodes that are mild and brief. Others have mild coughing and wheezing much of the time, Usually, an attack begins acutely with paroxysms of wheezing, coughing, and shortne