Asthma Pathophysiology: Study Guide and Overview for Medical Students

Asthma is an obstructive condition that affects millions of people around the world. That is exactly why it’s important to develop an understanding of the Asthma pathophysiology — especial as a Respiratory Therapy, nursing, or medical student.

The good news it, that is exactly what this study guide is all about. As you will see below, it provides an overview of most of the important concepts of learning the pathophysiology of asthma.

As I said, this is especially important for practicing medical professionals. So if you’re ready, let’s get into it. 

What is Asthma?

The disease is chronic, obstructive, inflammatory, and varies with different levels of severity. An episode can occur due to certain triggers, such as pollen, grass, dust, or smoke.

Signs and Symptoms of Asthma

• Coughing and wheezing
• Shortness of breath, pursed-lip breathing, chest tightness.
• Increased A-P diameter of the chest during an episode.
• Increased accessory muscle use
• Hyperresonant/tympanic chest percussion note
• Breath sounds will be diminished or wheezing
• Diaphoresis
• Vital signs include tachycardia, tachypnea, and pulsus paradoxus during severe episodes.

Diagnostic Testing for Asthma

• Arterial Blood Gas – An ABG will initially will show acute alveolar hyperinflation with hypoxemia, but may show hypercarbia in status asthmaticus.
• Chest X-ray – It will show an increased A-P diameter, dark (translucent) lung fields, and flattened diaphragms.
• Pulmonary Function Testing – The patient’s PFTs will show reduced flow rates.
• Post Bronchodilator Therapy – It will show a significant improvement in the FEV1. There will be an increase of at least 12%.

Asthma Pathophysiology

As mentioned earlier, asthma is a pulmonary condition that causes chronic inflammation of airways that causes the smooth muscle tissue to tighten up. This is referred to as bronchoconstriction.

According to the WHO, Asthma affects more that 330 million people across the world. Asthma stems from both allergic and non-allergic reactions. With that said, in this study guide, we’re focusing primarily on the allergic causes of Asthma.

Treatment for Acute Asthma Episodes

Here are the different treatments for an acute asthmatic episode:

• Oxygen
• Aerosol therapy with short-acting beta agonist and anticholinergic (Continuous treatment may be necessary for extreme cases)
• Corticosteroids
• Monitor the patient closely
• Intubation may be necessary if ventilatory failure or respiratory arrest occurs
• Adjunct therapies may be necessary, such as heliox, magnesium sulfate, or subcutaneous epinephrine

Management of Long-term Asthma Patient

• Eliminate asthma triggers, or minimize them at the very least.
• Use control medications such as long-acting beta-agonists, inhaled corticosteroids, mast cell stabilizers, and leukotriene inhibitors.
• Monitor peak flows to help develop an action plan.

Asthma Practice Questions:

1. What is the definition of Asthma?
A respiratory disorder characterized by recurring episodes of paroxysmal dyspnea, wheezing on expiration or inspiration caused by constriction of the bronchi, coughing, and viscous mucoid bronchial secretions. The episodes may be precipitated by inhalation of allergens or pollutants, infection, cold air, vigorous exercise, or emotional stress. It’s essentially hyperreactivity of the airways.

2. What does hyperractivity of the airways lead to?
Bronchoconstriction & bronchospasm, mucosal swelling, and increased production of thick tenacious mucus.

3. What are the two types of asthma?
Extrinsic and Intrinsic.

4. What kind of asthma is extrinsic?
It is considered type-one or allergenic asthma.

5. What kind of asthma is intrinsic?
It is considered type-two or non-allergenic asthma.

6. What can cause the onset of extrinsic asthma?
Pollen, mold, dander, or different foods.

7. What can cause the onset intrinsic asthma?
Stress, cold or dry air, smoke, anxiety, viruses, or infections.

8. What are signs, symptoms, and observations of asthma?
Increased respiratory rate, work of breathing, heart rate, cardiac output, and blood pressure. The patient may also have a prolonged (forceful) expiration and a decreased peak expiratory flow rate.

9. What are the breath sounds of a patient with asthma?
Wheezing – you will always hear on expiration. If heard on inspiration, it’s a more serious case of asthma.

10. What does it mean when you do not hear wheezes when listening to an asthma patient who is clearly in distress?
This means that there is no air movement and is amongst the most serious cases of asthma. This could be life-threatening and may require intubation and mechanical ventilation.

11. What are the ABG results associated with asthma?
Here are the ABG results that you will likely see for a patient having an asthma attack:

For a mild asthma attack, the pH may be increased with a low PaCO2 due to the patient hyperventilating.

For a moderate asthma attack, you the pH is normal and the patient’s oxygen level (PaO2) is starting to decrease, while the PaCO2 and HCO3 are still in the normal ranges.

For a severe asthma attack, the pH is decreased, the PaO2 is severely decreased, and the PaCO2 is increased. This is a case of impending respiratory failure.

13. If the PaCO2 rises drastically and suddenly during an asthma attack, what does that mean?
It likely means that the patient isn’t moving any air and may be going into respiratory failure. This is a very dangerous situation and may require intubation and mechanical ventilation.

14. What will a chest X-ray show with a patient with asthma?
You may see no significant changes. It may be slightly darkened. Also, you may see an increased capacity due to air trapping.

15. What happens to the systolic blood pressure during an asthma attack?
It will decrease during inspiration by 10-20 mmHg.

16. Which WBC increases during an asthma attack?
Eosinophils.

17. What will a PFT test show on an asthmatic?
Decreased airflow, low peak flows, and an increased residual volume. The FVC may be decreased due to air trapping, and the FEV1/FVC ratio is decreased.

18. What is the first treatment when it comes to asthma?
Prevention; avoid triggers if possible.

19. What are some medical treatments for patients that have asthma?
The patient will undergo a preventative asthma action plan and also immunotherapy.

20. What is Pulsus Paradoxus?
It is an abnormally large decrease in the patient’s stroke volume, systolic blood pressure and pulse wave amplitude during inspiration.

21. What is the 1st line of defense in asthma?
Maintenance with long-acting beta-2 agonists and inhaled corticosteroids.

22. What is the 2nd line of defense in asthma?
Fast-acting medication (Beta-2 agonists) such as: albuterol, xopenex, etc., as well as anticholinergic medications like ipratropium bromide.

23. What is the 3rd line of defense in asthma?
Emergency oral and intravenous steroids.

24. What is the 4th line of defense in asthma?
Xanthines such as aminophylline, magnesium sulfate via an IV, as well as Heliox.

25. What are some special medications used for asthma?
Luekotriene antagonist, Montelukast Sodium (Singulair).

26. What are some prophylactic medications used for asthma?
Cromolyn (intal) and Nedocromil (tilade).

27. When would you use Xolair (omalizumab) to treat asthma?
It can be used to treat patient that are 12 years of age and above. They must have a moderate to severe persistent asthma have asthma triggered by year-round allergens in the air, and continue to have asthma symptoms even though they are taking inhaled steroids.

28. What are other treatment considerations for asthma patient?
In the emergency department, back-to-back continuous short-acting bronchodilators may be given to the patient to help alleviate bronchospasm. This is often termed as a continuous breathing treatment. Also, if you’re looking for a home remedy, tumeric has been shown to naturally reduce the symptoms of asthma.

29. True or False: A methacholine challenge test can be used in the diagnoses of asthma.
True. A methacholine challenge test is performed to determine how reactive or responsive your lungs are to different asthma triggers in the environment. The test can help your doctor evaluate symptoms suggestive of asthma and help diagnose whether or not the patient has it.

30. What are some symptoms of asthma?
Cough, chest tightness, shortness of breath, and wheezing.

31. What are some triggers of asthma?
Allergens, irritants, weather changes, viral or sinus infection, exercise, herd, medications/food, emotional anxiety.

32. What are some allergens of asthma?
Pollens, molds, animal dander, house dust mites, and cockroach droppings.

33. What is an allergen?
They affect only people allergic to a specific substance.

34. What is an irritant?
The effect everyone if the dose is high enough.

35. What are some examples of irritants?
Tobacco smoke, wood smoke, chemicals in the air, ozone, perfumes, household cleaners, cooking fumes, paints, and varnishes.

36. What are some occupational irritants?
Vapors, dust, gases, and fumes.

37. What are some other common causes of asthma?
Viral and sinus infections, exercise, reflux disease herd, medications (NSAIDS), beta blockers, and emotional anxiety.

38. What are the types of medications that help with asthma symptoms?
Antihistamines, decongestants, anti-inflammatory agents, anti-leukotrienes, bronchodilators, and anticholinergics.

39. What are the 3 types of medications that are used as anti-inflammatory agents?
Mast cell stabilizers, corticosteroids, and bronchodilators.

40. What are the classes of bronchodilators available for asthma?
Beta-agonist bronchodilators, methylxanthines, and anticholinergics.

41. What are methylxanthines?
PDE inhibitors such as theophylline, aminophylline, and theobromide.

42. What are rescue medications?
They are there for when a patient has symptoms of an asthma attack.

43. What are maintenance medications?
They are there for when a patient doesn’t have symptoms and but are meant to help control the disease.

44. How do anticholinergics work?
They block the veal nerve in bronchoconstriction and can be used alone or along with bronchodilators. Some examples include Atrovent and Spiriva (tiotropium bromide). These are better for COPD rather than asthma.

45. What are the 6 goals for the effective management of asthma?
(1) To prevent chronic and troublesome symptoms, (2) to maintain normal breathing, (3) to maintain normal activity levels including exercise, (4) to prevent recurrent asthma flare-ups, (5) to minimize the need for emergency room, and (6) to provide optimal medication therapy with no or minimal effort.

46. What are the 4 categories of asthma?
(1) Mild intermittent, (2) mild persistent, (3) moderate persistent, and (4) severe persistent.

47. What are the rules of 2 for asthma medications that tell you that your asthma is not under control?
You use a rescue inhaler more than 2 times a week, you awaken at night with asthma symptoms more than 2 times a month, you use more than 2 canisters a year of rescue medications (inhaler).

48. What are quick-relief medications?
Short-acting beta-2 agonists, inhaled anticholinergics, short-acting theophylline, epinephrine/ adrenaline injection.

49. What are examples of long-term asthma medications?
Corticosteroids, tablets or syrup steroids, mast cell stabilizers, long-acting beta-2 agonist, sustained-release tablets, sustained release methylxanthines, anti-leukotrienes.

50. What is immunotherapy?
It’s a form of antigen extract to desensitize the patient to asthma triggers. It can help to reduce asthma symptoms, as well as the need for medications. It can also help reduce the risk of severe asthma attacks after future exposure to the allergen. It has been shown to possibly be as effective as inhaled steroids.

Final Thoughts

So there you have it. That’s wraps up this study guide on the pathophysiology of Asthma. Whether you’re a medical, nursing, or Respiratory Therapy student, hopefully this guide can help make the learning process much easier for you.

We also have a similar study guide that provides and Overview of COPD that I think you will enjoy. Thanks for reading and as always, breathe easy my friend.

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