Asthma Pathophysiology | Nursing School Notes

Updated: May 24

Asthma is a chronic inflammatory disease of the airways, that causes hyperresponsiveness, increased mucus production and mucosal oedema.


What this means is that Asthma is a long-term condition where the body has an extreme allergic reaction to environmental factors such as dust, pollen or animal dander. When triggered, this reaction causes inflammation in the airways which in turn causes excessive mucus production and swelling of the airways.


The interesting thing about asthma though is that these extreme episodes come and go. When on the right treatment, an asthmatic patient can live a normal life without any breathing issues, but when it is triggered the symptoms can quickly become severe and cause other complications. As a condition, asthma is not curable but we can treat its symptoms and in most cases, all symptoms can be reversed without any permanent damage.


In these notes, we’ll be going over the:

  1. Pathophysiology of Asthma

  2. Risk Factors of Asthma

  3. Symptoms of Asthma

But before diving into this topic, you must first understand the basics. So start off by reading the Anatomy and Physiology of the Respiratory System, and then come back to understand Asthma and its manifestations.

 

The Pathophysiology of Asthma

Before we being, it is important to understand that we can not pinpoint one single cause for Asthma. The condition is brought on by several environmental and genetic factors, which make it difficult to track exactly how and why it develops. What we know for sure, is that some people are allergic to dust, pollen and animal dander.


When our bodies come across harmful particles in the air, they try to block them from entering the lungs, and they do this by quickly contracting the bronchial smooth muscle (aka. Bronchoconstriction). But in Asthmatic people, this contraction happens extremely quickly as they are much more sensitive to environmental allergens, and we call this Hyperresponsiveness.


When bronchoconstriction occurs, the body starts to produce Immunoglobin-E (IgE) which are a group of antibodies that will fight off the allergen. Think of them as soldiers who are trying to protect their lungs.  Once produced, the IgE will settle onto the surface of Mast Cells (aka. Immune Cells) which are found in the connective tissues throughout the body and stand on guard ready for the allergen to arrive.


Unless removed, the allergen will continue to invade the airways and eventually come up to the IgE antibodies that are guarding the Mast Cells. At this point, the allergen will attack the IgE antibodies and stick to them, causing the release of Inflammatory Mediators such as Histamine, Tryptase, Leukotrienes and Prostaglandins.


These mediators will try to block the allergen and in doing so, they contract the airways causing Bronchospasm and triggering an Asthma Attack. They also contribute to epithelium cell injury, mucus hypersecretion and airway hyperresponsiveness. If no treatment is given to stop this Asthma Attack, more and more structures start to get involved all wanting to fight off the allergen. But the more they fight it, the more they block off the airways.


The Goblet cells for example start to produce excessive amounts of mucus which plug the airways. The Eosinophils which are a type of disease-fighting white blood cells release proteins that damage the epithelial cells of the airway and secrete more Inflammatory Mediators which ultimately lead to Airway Remodelling. This means that the structure of the airways will be damaged permanently and the change in shape affects lung function.


The Symptoms of Asthma

In most cases, Asthmas presents with a:

  1. Cough

  2. Wheezing

  3. Dyspnoea

But just like every other illness its manifestations are specific to the individual and some people might only have one of the symptoms. The cough could be dry and persistent or with mucus production, and the thickness of the mucus will vary depending on the severity of the illness. The wheezing is a sign that the airways have narrowed down, and it generally starts only on expiration but as the attack progresses it can also be heard during inspiration.


Since the patient’s airways are narrower and cough might be present, they will start to have difficulty breathing which is often accompanied by a feeling of choking or chest tightness. Expiration will no longer be a passive movement, but it will require effort and become prolonged. Moreover, as the exacerbation continues complications start to arise including diaphoresis, tachycardia, hypoxemia and lastly central cyanosis.


Even though the onset of an exacerbation is quick, most people would have had mild symptoms for a couple of days before the asthma attack occurs. And those with exercise-induced asthma would only have symptoms during exercise.


The Risk Factors of Asthma

Asthma can be triggered by many factors; however, Allergens and prolonged exposure to airway irritants are the most common cause. In fact, the most common allergens are


Seasonal

Perennial

Grass

Mould

Trees

Dust

Pollen

Roaches

Animal Dander


Asthma can also be triggered by:


Airway Irritants

Food

Others

Air Pollution

Shellfish

Exercise

Cold/Hot Temperatures

Nuts

Stress

Strong Odour/ Perfumes

Hormonal Changes

Smoke

Medications

Occupational Exposure

Respiratory Tract Infections

Gastroesophageal Reflux


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References

  1. Mubarak, B., Shakoor, H., & Masood, F. (2019). Eosinophilic Asthma. In (Ed.), Asthma – Biological Evidences. IntechOpen. https://doi.org/10.5772/intechopen.84297

  2. Lloyd, C. M., & Hawrylowicz, C. M. (2009). Regulatory T cells in asthma. Immunity31(3), 438–449. https://doi.org/10.1016/j.immuni.2009.08.007

  3. https://pharmaceutical-journal.com/article/ld/asthma-pathophysiology-causes-and-diagnosis

  4. Hinkle, Janice. Brunner & Suddarth’s Textbook of Medical-Surgical Nursing. Wolters Kluwer Health. Kindle Edition.

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