Factors that can contribute to asthma or airway hyperreactivity may include any of the following:

• Environmental allergens (eg, house dust mites; animal allergens, especially cat and dog; ****roach allergens; and fungi);

• Viral respiratory tract infections;

• Exercise, hyperventilation;

• GERD;

• Chronic sinusitis or rhinitis;

• Aspirin or nonsteroidal anti-inflammatory drug hypersensitivity, sulfite sensitivity;

• Use of beta-adrenergic receptor blockers (including ophthalmic preparations);

• Obesity;

• Environmental pollutants, tobacco smoke;

• Occupational exposure;

• Irritants (eg, household sprays, paint fumes);

• Various high- and low-molecular-weight compounds (eg, insects, plants, latex, gums, diisocyanates, anhydrides, wood dust, and fluxes; associated with occupational asthma);

• Emotional factors or stress; and

• Perinatal factors (prematurity and increased maternal age; maternal smoking and prenatal exposure to tobacco smoke; breastfeeding has not been definitively shown to be protective).

For more on the etiology of asthma, read here.

Acute episodes of asthma can be mild, moderately severe, or severe, or characterized by imminent respiratory arrest.

During a mild episode, patients may be breathless after physical activity, such as walking; they can talk in sentences and lie down; and they may be agitated. Patients with mild acute asthma are able to lie flat.

In a mild episode, the respiratory rate is increased, and accessory muscles of respiration are not used. The heart rate is < 100 beats/min, and pulsus paradoxus (an exaggerated fall in systolic blood pressure during inspiration) is not present. Auscultation of the chest reveals moderate wheezing, which is often end-expiratory. Rapid forced expiration may elicit wheezing that is otherwise inaudible, and the oxyhemoglobin saturation on room air is > 95%.

In a moderately severe episode, the respiratory rate is also increased. Typically, accessory muscles of respiration are used. In children, also look for supraclavicular and intercostal retractions and nasal flaring, as well as abdominal breathing. The heart rate is 100-120 beats/min. Loud expiratory wheezing can be heard, and pulsus paradoxus may be present (10-20 mm Hg). The oxyhemoglobin saturation on room air is 91%-95%.

Patients experiencing a moderately severe episode are breathless while talking, and infants have feeding difficulties and a softer, shorter cry. In more severe cases, the patient assumes a sitting position.

In a severe episode, patients are breathless during rest, are uninterested in eating, sit upright, talk in words rather than sentences, and are usually agitated. The respiratory rate is often > 30 breaths/min. Accessory muscles of respiration are usually used, and suprasternal retractions are commonly present. The heart rate is > 120 beats/min. Loud biphasic (expiratory and inspiratory) wheezing can be heard, and pulsus paradoxus is often present (20-40 mm Hg). The oxyhemoglobin saturation on room air is < 91%. As the severity increases, the patient increasingly assumes a hunched-over sitting position with the hands supporting the torso, termed the "tripod position."

When children are in imminent respiratory arrest, in addition to manifesting symptoms of a severe asthma episode, they are drowsy and confused; in contrast, adolescents may not appear drowsy or confused until they are in frank respiratory failure. In status asthmaticus with imminent respiratory arrest, paradoxical thoracoabdominal movement occurs. Wheezing may be absent (associated with most severe airway obstruction), and severe hypoxemia may manifest as bradycardia. Pulsus paradoxus noted earlier may be absent; this finding suggests respiratory muscle fatigue.

As the episode becomes more severe, profuse diaphoresis occurs, with the diaphoresis presenting concomitantly with a rise in PCO₂ and hypoventilation. In the most severe form of acute asthma, patients may struggle for air; act confused and agitated; and remove their oxygen mask, stating, "I can't breathe." These are signs of life-threatening hypoxia. With advanced hypercapnia, bradypnea, somnolence, and profuse diaphoresis may be present; almost no breath sounds may be heard; and the patient is willing to lie recumbent.

For more on the presentation of asthma, read here.

Blood eosinophilia > 4% or 300-400 cells/μL supports the diagnosis of asthma, but the absence of this finding is not exclusionary. Total serum immunoglobulin E levels > 100 IU/mL are frequently observed in patients experiencing allergic reactions, but this finding is not specific for asthma and may be observed in patients with other conditions (eg, allergic bronchopulmonary aspergillosis, Churg-Strauss syndrome).

Venous PCO₂ levels have been tested as a substitute for arterial measurements, and a venous PCO₂ value > 45 mm Hg may serve as a screening test but cannot substitute for arterial blood gas evaluation of respiratory function. Sinus CT may be useful to help exclude acute or chronic sinusitis as a contributing factor.

For more on the workup of asthma, read here.

The pharmacologic treatment of asthma is based on stepwise therapy. Asthma medications should be added or discontinued as the frequency and severity of the patient's symptoms change.

• Step 1—Intermittent asthma: A controller medication is not indicated. The reliever medication is a short-acting beta-agonist as needed for symptoms.

• Step 2—Mild persistent asthma: The preferred controller medication is a low-dose inhaled corticosteroid. Alternatives include sodium cromolyn, nedocromil, or a leukotriene receptor antagonist.

• Step 3—Moderate persistent asthma: The preferred controller medication is either a low-dose inhaled corticosteroid plus a long-acting beta-agonist (combination medication is the preferred choice to improve adherence) or an inhaled medium-dose corticosteroid. Alternatives include an inhaled low-dose corticosteroid plus either a leukotriene receptor antagonist, theophylline, or zileuton (Zyflo®).

• Step 4—Moderate to severe persistent asthma: The preferred controller medication is an inhaled medium-dose corticosteroid plus a leukotriene receptor antagonist (combination therapy). Alternatives include an inhaled medium-dose corticosteroid plus either a leukotriene receptor antagonist, theophylline, or zileuton.

• Step 5—Severe persistent asthma: The preferred controller medication is an inhaled high-dose corticosteroid plus a leukotriene receptor antagonist. Consider omalizumab for patients who have allergies.

• Step 6—Severe persistent asthma: The preferred controller medication is a high-dose inhaled corticosteroid plus a leukotriene receptor antagonist plus an oral corticosteroid. Consider omalizumab for patients who have allergies.

For more on the treatment of asthma, read here.

Indications for hospitalization are based on findings from the repeat assessment of a patient after he or she has received three doses of an inhaled bronchodilator. The decision whether to admit is based on the following:

• Duration and severity of asthma symptoms;

• Severity of airflow obstruction;

• Course and severity of prior exacerbations;

• Medication use and access to medications;

• Adequacy of support and home conditions; and

• Presence of psychiatric illness.

Admit the patient to the intensive care unit for close observation and monitoring in certain situations, such as the following:

• Rapidly worsening asthma, or a lack of response to the initial therapy in the emergency department;

• Confusion, drowsiness, signs of impeding respiratory arrest, or loss of consciousness;

• Impending respiratory arrest, as indicated by hypoxemia (PO₂ < 60 mm Hg) despite supplemental oxygen and/or hypercapnia with PCO₂ > 45 mm Hg; and

• Intubation is required because of the continued deterioration of the patient's condition despite intervention

Status asthmaticus, or an acute severe asthmatic episode that is resistant to appropriate outpatient therapy, is a medical emergency that requires aggressive hospital management. This may include admission to an intensive care unit for treatment of hypoxia, hypercapnia, and dehydration and possibly for assisted ventilation because of respiratory failure.

For more about the treatment of asthma, read here.

Related Resources Asthma Pediatric Asthma Allergic and Environmental Asthma

 

Medscape © 2015  WebMD, LLC

Cite this article: Zab Mosenifar. Quiz: How Much Do You Know About Asthma? Medscape. Jun 10, 2015.