Diagnosis Of Asthma

Asthma

DIAGNOSIS

Chronic asthma

Ø      The diagnosis of asthma is made primarily by a history of recurrent episodes of coughing, wheezing, chest tightness, or shortness of breath and confirmatory spirometry.

Ø      The patient may have a family history of allergy or asthma or have symptoms of allergic rhinitis. A history of exercise or cold air precipitating dyspnea or increased symptoms during specific allergen seasons also suggests asthma.

Ø      Spirometry demonstrates obstruction (forced expiratory volume in 1 second [FEV1]/forced vital capacity less than 80%) with reversibility after inhaled β2-agonist administration (at least a 12% improvement in FEV1). Failure of pulmonary function to improve acutely does not necessarily rule out chronic asthma. If baseline spirometry is normal, challenge testing with exercise, histamine, or methacholine can be used to elicit BHR.

Acute severe asthma

Ø      Peak expiratory flow (PEF) and FEV1 are less than 50% of normal predicted values. Pulse oximetry reveals decreased arterial oxygen and O2 saturations.

Ø      The best predictor of outcome is early response to treatment as measured by improvement in FEV₁ at 30 minutes after inhaled β2-agonists.

Ø      Arterial blood gases may reveal metabolic acidosis and a low PaO₂.

Ø      The history and physical examination should be obtained while initial therapy is being provided. A history of previous asthma exacerbations (e.g., hospitalizations, intubations) and complicating illnesses (e.g., cardiac disease, diabetes) should be obtained. The patient should be examined to assess hydration status; use of accessory muscles of respiration; and the presence of cyanosis, pneumonia, pneumothorax, pneumomediastinum, and upper airway obstruction. A complete blood count may be appropriate for patients with fever or purulent sputum.

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