Treating asthma requires a step-by-step approach in order to provide the correct medication. In general, therapy is initiated at a higher level to establish prompt control and is then "stepped down" to reduce the risk of adverse effects of medication. This "step therapy" also ensures that medication will be given in the proper dosage and that unnecessary medication will not be given. To prescribe the correct asthma medication, a physician must grade patients according to the severity of their condition. This Topic will define asthma in terms of its severity and proposes a strategy for treatment based on degree of severity.

Adult Asthma: Mild, Moderate and Severe

The National Institutes of Health has categorized asthma as "mild intermittent," "mild persistent," "moderate persistent," and "severe persistent" Mild intermittent asthma is defined as a condition in which attacks do not Occur more than twice a week and never during sleep. Between attacks, peak flow rates are maintained at more than 80 percent of normal. Mild persistent asthmatics have symptoms more than twice a week but less than once a day. Their peak flows are between 60 percent and 80 percent of normal. Moderate persistent asthmatics have daily symptoms. Severe persistent asthmatics require regular bronchodilator use, often need oral corticosteroid courses, have been hospitalized for severe attacks usually with assisted respiration, and often have night attacks. Peak flow measurements are less than 60 percent of normal. Steroid-dependent asthmatics form a subgroup of these severe patients. These patients are never with out oral corticosteroids due to almost continuous symptoms.

Use Severity Definitions Cautiously

These severity definitions are helpful but should not be employed rigidly. It should be emphasized that patients at any level may experience severe life-threatening asthmatic attacks. These severe attacks may occur suddenly after long symptom-free periods with normal lung function. Patients with allergic or extrinsic asthma may only be symptomatic during certain seasons depending on the amount of pollen to which they are exposed. Some allergic patients experience symptoms only when exposed to certain allergens such as cat dander; others may display symptoms only during an upper respiratory tract infection such as a sore throat or sinus infection. A few patients will be symptomatic only after exercise. All these patients could also be defined as mild asthmatics even though their attacks may sometimes be severe. Th be sure, asthma severity varies from patient to patient and strict definitions are not easily applied.