ASTHMA

Asthma:

Asthma is a reactive airway disease with a characteristic presentation of dry cough, shortness of breath, and expiratory wheezing. It shares these characteristics with other obstructive lung diseases such as emphysema and chronic bronchitis, howeer it is not traditionally classified under the umbrella term COPD like these other two.

Pathophysiology:

Asthma results from a triad of bronchial inflammation, increased mucous secretion, and bronchoconstriction/bronchospasm. These manifestations are the result of either intrinsic factors or extrinsic factors.

In EXTRINSIC asthma, an IgE mediated reaction occurs in response to exposure to certain environmental allergens. This is more common in childhood and often resolves with age.

INTRINSIC asthma does not result from IgE activity, and is instead driven by the action of mast cells in the body. Triggers may still include allergens, however attacks more commonly result from triggers such as stress, exercise, or cold exposure.

Clinical presentation:

Asthma is a disease that occurs with symptom free periods, and episodic exacerbations. Most mild to moderate exacerbations present with dyspnea, cough, and constriction of the lower airways (hence wheezing). Severe exacerbations may occur in some patients, resulting in severe dyspnea, hypoxia, and potentially a silent chest on auscultation. Any patient who is in severe distress, whose condition does not respond to medications, is said to be in status asthmaticus. This is a serious, life-threatening, situation that requires rapid intervention. Another red flag to be aware of is tripod breathing with “head bobbing”. These patients are recruiting accessory muscles to attempt to allow for improved airflow. This is an energy expensive strategy, and often precipitates respiratory failure.

Common pharmacological treatments include:

 Beta 2 agonists: Trigger bronchodilation by stimulating beta 2 adrenergic receptors.

 Epinephrine: Stimulates rapid bronchodilation in severe asthma. Also mediates the

inflammatory effect of histamines, and overrides parasympathetic bronchoconstriction caused

by stimulation of cholinergic receptors.

 Anticholinergic medications: Block parasympathetic bronchoconstriction, and inhibit mucous

production in the bronchioles.

 Magnesium: Acts on the calcium channels, causing smooth muscle relaxation in the airways.

Prehospital treatment plan:

 If severe asthma or status asthmaticus, provide PPV and administer IM epinephrine.

 Provide supplemental O2.

 Salbutamol MDI or nebulized.

Consider use of steroids if authorized.