What is the pathophysiology of asthma?

Asthma is a very common respiratory disorder that paramedics attend and are particularly capable of making difference to the health outcomes of a person suffering a medical emergency. In young male patients severe asthma is one of the most common medical causes of sudden death and it is for this reason that paramedics must be diligent when attending asthmatic patients.

What is the pathophysiology of asthma?

Asthma is a disease that leads to a  chronic disorder involving inflammation of the bronchial airways as an allergic reaction to a pollutant or irritant, which may be both internal (stress) or external (pollutant). During the normal progression of asthma, the inflammatory response causes a narrowing of the bronchial airways which allow a decreased amount of airflow. During the expiratory phase the exhaled air naturally causes the bronchial airways to close, and can be heard in the form of a wheeze. In severe cases, a wheeze may be heard on the inspiratory phase as well as the expiratory phase. This results in an increased difficulty getting rid of the pollutants (often which caused the problem in the first place) and therefore great inflammation. This leads to increased mucous production and increased formation of a mucosal plug.

In an attempt to resolve all of this, the body may develop a broncho-spasm, which further narrows the airways and results in an audible wheeze. This results in a difficulty in getting rid of the air that a patient has inhaled. If the patient is young and otherwise healthy, he or she should still be able to compensate well up until this point. However, as the course of asthma progresses the patient will no longer be able to compensate. As the muscles of respiration become fatigued (such as the diagaphram and accessory muscles: sternocloidomastoid, pectoralis major, intercostal muscles) the body will start to decompensate and will eventually result in the patient suffering a respiratory arrest. This is a life-threatening emergency and should be treated as such because of the risk of sudden decompensation leading to respiratory arrest and death.

Treatment includes preventative medicine such as avoiding irritants and pollutants in the first place which stimulate the inflammatory response, bronchodilators (such as salbutamol), anticholinergic bronchodilators (such as atrovent) cortico steroids (such as hydrocortisone), and a very good asthma care plan.

As a paramedic, reassurance is paramount for these patients because they will literally feel as though they are suffocating. A calm, competent response by paramedics is the best reassurance available.

In severe cases of asthma (asthmatic in extremis) I/M or IV adrenaline is the front-line treatment. This is because nebulised salbutamol will not be able to reach the bronchioles where they can cause bronchodilation and effect a change. Consequently Adrenaline should be used as your first line of treatment in severe asthma. Don’t forget to get help running on the way (you will most likely need help extricating these patients as they will not be able to help themselves). Don’t wait on scene for the patient to get better, get going to hospital.

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