Asthma is a disorder of the tracheobronchial tree characterized by mild to severe obstruction to airflow. Symptoms vary from coughing to dyspnea, and are generally episodic or paroxysmal, but may be persistent.
The clinical hallmark is wheezing, but cough may be the predominant symptom.
Acute symptoms are characterized by narrowing of large and small airways due to spasm of bronchial smooth muscle, edema and inflammation of the bronchial mucosa, and production of mucus.
Asthma is common in children, and is a leading cause of missed school days.
Asthma can be caused by: allergic factors (airborne pollens, molds, house dust - mites, animal dander, or feather pillows), Smoke and other pollutants, Infections (especially viral), Aspirin, tartrates, Exercise, Sinusitis, Gastroesophageal reflux, or Sleep (peak expiratory flow rate is lowest at 4 am). Current research focuses on the inflammatory response (including abnormal release of chemical mediators, eosinophil chemotactic factor, neutrophil chemotactic factor, and others).
Risk factors for asthma include: a positive family history, and viral lower respiratory infection during infancy.
Leukotrienes are potent bronchoconstrictors: Phospholipids -> arachadonic acid -> leukotrienes
enzymes: phospholipase, 5-lipoxygenase and HPETE
HPETE -> HETE via glutathione peroxidase with selenium
HPETE is toxic and inhibits prostacycline (PGI2); HETE is not toxic
Standard labs include CBC (which is usually normal), Nasal eosinophils, Immunoglobulins, and a screen for immunodeficiency. IgE is elevated in allergic bronchopulmonary aspergillosis (ABPA). A sweat test may be ordered in chronic childhood asthmatics. Arterial blood gases are ordered in status asthmaticus.
Additional tests include: Pulmonary function tests, Allergy testing, PPD yearly, and Exercise tolerance testing. A Chest x-ray is usually ordered once.
A sputum culture shows eosinophils, Charot-Leyden crystals, Curschman spirals.
ABGs show respiratory alkalosis (increased pH and HCO3)
PFTs - typical obstructive dysfunction with increased FRC
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