Asthma: Diagnosis and Treatment

Diagnosis

A characteristic history of periodic bronchospasm and variable airflow obstruction, occurring with or without stimuli that provoke an attack, is usually present. During acute attacks, symptoms such as tachypnea, chest tightness, wheezing, shortness of breath, and cough, with or without sputum production, are common. Difficulty taking deep breaths, difficulty finishing sentences, and/or lethargy indicate greater severity, and, possibly, status asthmaticus.

Physical examination often reveals use of accessory respiratory muscle, a prolonged expiratory phase with diffuse wheezing, and sometimes hyper-resonant lung fields with diminished breath sounds due to air trapping. Severe attacks may have less wheezing (due to reduced air flow), cyanosis, and signs of mental obtundation.

Routine pulmonary function tests during asymptomatic periods may be entirely normal. During exacerbations or in patients who have had asthma for many years, spirometry typically shows reduced FEV1 (forced expiratory volume in 1 second), a reduced FEV1/FVC (forced vital capacity) ratio, and/or reduced peak flows, and may also demonstrate increased total lung capacity (TLC), residual volume (RV), and functional residual capacity (FRC).

Blood testing may reveal eosinophilia and elevated serum IgE levels in asthma patients with atopy.

Skin testing can identify allergens that may be environmentally controlled.

Treatment

With optimal asthma management, patients should have no symptoms or exercise limitation, no exacerbations or need for oral steroids, no albuterol requirement, and, overall, minimal medications and side effects.

Types of Asthma

Mild intermittent asthma is treated on an as-needed basis with inhaled beta-2-selective agonists, such as albuterol. Beta-adrenergic medications are bronchodilators and can be used before exercise or when symptoms occur; these are sometimes called "rescue medications".⁷ An alternative for exercise-induced asthma is cromolyn, a mast cell stabilizer. It is beneficial only if taken before exercise.

Mild persistent asthma usually requires daily inhalation of a corticosteroid, along with a short-acting beta-agonist for breakthrough symptoms. Inhaled corticosteroids decrease the risk of exacerbations and reduce the need for rescue medication. Common steroid preparations include budesonide, fluticasone, triamcinalone, beclomethasone, and flunisolide.

Moderate persistent asthma calls for an increased dose of inhaled corticosteroid and/or the addition of a long-acting beta agonist or leukotriene antagonist. Examples of leukotriene antagonists are zileuton, montelukast, pranlukast, and zafirlukast. Sustained-release theophylline or cromolyn preparations are alternatives. Failure to control symptoms with the use of 2 of the above medications suggests the patient may have severe asthma or perhaps another diagnosis.

Severe asthma requires high-dose inhaled corticosteroids or oral corticosteroids, along with other controller medicines.

Other Considerations

Leukotriene antagonists are no substitute for inhaled corticosteroids,⁸ but in patients who make an excess of leukotrienes, they may complement the above therapies. Patients with exercise-induced bronchoconstriction, nasal polyposis, and aspirin sensitivity (triad asthma) tend to respond well to leukotriene antagonists.

Long-acting beta-agonists, such as salmeterol, are not to be used as monotherapy,⁹ as they have no significant anti-inflammatory effects. Indeed, they cause prolonged bronchodilation, which may mask a progressive inflammatory process that may eventually lead to a severe attack.

A recent study showed a small increase in risk of death among patients, particularly for African Americans, using salmeterol in addition to typical asthma drugs.¹⁰

Cromolyn and theophylline are rarely considered as first-line agents. However, in combination with inhaled corticosteroids, any of the above may be beneficial.

Omalizumab is a new monoclonoal antibody directed to human IgE. For patients with refractory asthma or for whom inhaled and/or oral steroids cause major side effects, anti-IgE therapy may reduce steroid requirements and side effects, and provide improved control for allergic asthmatics.

Emergency Treatment

Immediate bronchodilation with inhaled albuterol is the mainstay of emergency treatment. In the emergency room, the delivery method for albuterol is most often continuous nebulization (approximately 10 mg/hr), or 2.5 mg every 20 minutes for 3 doses. However, data show that using a metered-dose inhaler (with a spacer) for 4 to 6 successive inhalations is approximately equal to 1 nebulizer. This method has the advantages of reducing the total amount of albuterol administered and shortening the length of stay in the emergency department, without increasing hospital admissions.¹¹

Systemic corticosteroids, such as prednisone, prednisolone, and methylprednisolone, should be started concurrently in a patient who does not adequately respond to albuterol therapy. Their effect is often delayed up to 6 hours. Inhaled ipratropium bromide (an anticholinergic agent) is indicated if a person has moderate to severe airway obstruction that is unresponsive to beta agonists alone.

Heliox can benefit patients with severe airflow obstruction and mild hypoxemia in the acute setting. In patients with severe hypoxemia, the helium concentration needs to be decreased to a level less than what has been shown to be effective for improving airflow obstruction (70-80% helium) in order to deliver oxygen concentrations needed to maintain normoxia. Therefore heliox is contraindicated in severe hypoxemia.