Asthma Basics for the Physician Assistant Exam
Asthma is a chronic inflammatory process of the airway and is covered on the Physician Assistant Exam. An asthma attack can be stimulated by a hyperresponsiveness to environmental exposures or other triggers. Asthma is reversible, and it can resolve either on its own or with treatment. Asthma is very common in the younger population, especially African-Americans. During the teenage years, males are more likely than females to have asthma.
Insights on asthma
Triggers for asthma can include seasonal allergies, environmental allergens (mold, dust, and so on), salicylic acid derivatives, exercise, changes in weather or temperature, and gastroesophageal reflux disease (GERD).
Allergic rhinitis, GERD, and/or cough-variant asthma are the three primary differential diagnoses for chronic cough in the outpatient setting. GERD can sometimes present solely as a cough without any symptoms of heartburn at all, appearing predominantly at night. This is great information for a PANCE question.
Here are key points about asthma:
Clinical presentation includes rapid onset of shortness of breath, tightness in the chest, and/or cough during an acute asthma exacerbation. You may hear an audible wheeze.
Physical examination can demonstrate tachypnea, wheezing, and decreased air movement on lung auscultation. Accessory muscle use is a bad sign — it indicates that the person is tiring and may need to be intubated for airway protection.
Labs can show a CBC demonstrating a mild eosinophilia. Although bronchial thickening, hyperinflation, and focal atelectasis suggest asthma when they’re present, the chest radiograph can be normal.
The diagnosis is made by spirometry — an FEV1/FVC < 0.8 is diagnostic. But a more important measurement for asthma is the peak flow. During an asthma exacerbation, the peak flow, as measured by a peak flow meter, is usually substantially reduced from the patient’s baseline.
The peak flow is vital both in the early evaluation of an asthma attack and also chronically to assess efficacy of treatment. Different calculations, based on a person’s height, weight, and gender, can determine what a normal peak flow should be. Variations from this can determine how reduced the peak flow is from normal during an asthma exacerbation.
If you obtain an ABG that’s normal during an acute asthma exacerbation, that’s a very bad prognostic sign that the patient is tiring and is having trouble getting rid of the excess carbon dioxide. During an acute asthma episode, you should see a respiratory alkalosis characterized by an elevated pH and low pCO2. There may or may not be a low PaO2 as well.
During an acute asthma exacerbation, treatment includes intravenous steroids and beta-2 agonists (for example, albuterol sulfate). After the acute exacerbation is over, the treatment depends on the type and severity of asthma.
Asthma classifications and treatments
Asthma has different classifications. It can be either intermittent or persistent. The only type of intermittent asthma is mild intermittent asthma. Here, the asthma exacerbations are infrequent, and they usually resolve through treatment with a short-acting beta-2 agonist such as albuterol.
The three kinds of persistent asthma are mild, moderate, and severe. The differences have to do with the frequency and severity of symptoms:
Mild persistent asthma: The person has fewer than two asthma exacerbations in a 7-day period. He or she also never has more than one exacerbation per day. Usually the treatment involves an inhaled corticosteroid.
Moderate persistent asthma: The person has daily asthma symptoms and nighttime symptoms more than once per week. The treatment usually involves an inhaled corticosteroid plus a long-acting beta-2 agonist.
Severe persistent asthma: The person is exhibiting nearly continuous symptoms with frequent nocturnal exacerbations. Other medications, such as montelukast (Singulair) may be used. Steroids may be needed for an acute exacerbation.
Understand that treating asthma requires a stepwise approach that depends on the frequency and severity of symptoms.
When you’re answering test questions about asthma, the classification and treatment are big topics. You repeatedly see questions in which a patient diagnosed with a certain classification of asthma is failing prescribed medical therapy. You may then be asked which classification of asthma he or she has now or how you should change his or her therapy.
You’re evaluating a 45-year-old woman with a history of recurrent asthma exacerbations. She’s admitted with severe shortness of breath. The patient has limited audible wheezing, is tachypneic, and is using accessory muscles. An ABG is pH 7.18, pCO2 69, and pO2 56. What is your next step?
(A) Do bilevel positive airway pressure (BiPAP).
(B) Put the patient on a 100% nonrebreathing mask.
(C) Do emergent intubation.
(D) Give a stat dose of methylprednisolone (Solu-Medrol).
(E) Give a stat nebulizer treatment with albuterol.
The answer is Choice (C), emergent intubation. This patient has status asthmaticus, a severe asthmatic attack that doesn’t respond to usual therapy. The first thing you assess for any patient is the ABCs. You need to stabilize the airway. Limited wheezing indicates decreased air movement and is also an ominous sign. This patient is getting tired and needs help. BiPAP won’t work because the patient is too fatigued.