Pathological Mechanisms of Chronic and Acute Asthma Exacerbations

Asthma has a complicated pathophysiology that includes bronchial inflammation with airway constriction and resistance that causes coughing, shortness of breath and wheezing. The trachea, bronchi and bronchioles may become inflamed also. The inflammation may not cause obvious symptoms of asthma even if there is inflammation. Bronchospasms, edema, excessive mucus and epithelial and muscle damage can also led to bronchoconstriction and spasms. These symptoms can cause a narrowing of the airway. Another symptom of asthma is increased mucus secretions, which can cause mucus plugs to buildup and block the airway. Vasileiadis, Alevrakis, and Koutsoukou (2019) of the Journal of Clinical Medicine say, “The consequent narrowing of airway diameter leads to increases in airway resistance and limitation of expiratory flow, and hence to air trapping and dynamic hyperinflation. As tidal breathing then starts taking place within the flat portion of the pressure-volume curve, the elastic work of breathing is dramatically increased” (Vasileiadis, Alevrakis, & Koutsoukou, 2019, p. 1). This makes breathing harder to perform and can lead to hypoxemia with PaO2 levels of less than 60 mmHg even in patients without severe asthma.

Hyperresponsiveness in Asthma

If injury occurs to the epithelium, extreme airway impairment may also occur and that can allow allergens to penetrate and cause hyperresponsive airways, which is one of the major symptoms of asthma. To what extent a patient may be hyperresponsive depends on how much inflammation occurs and the patient’s immunologic response to the allergens. Hypocapnia, or reduced CO2 in the blood, can be attributed to airway hyperresponsiveness. However, Vasileiadis, Alevrakis, and Koutsoukou (2019) studied hyperresponsiveness in asthmatic patients and patients without asthma and found that “while the fall of PCO2 increased airway resistance in asthmatic patients, it did not significantly change the respiratory resistance in normal individuals. It was suggested that hypocapnia is probably associated with the airway obstruction observed in asthmatics, thus having an important role in the pathophysiology of asthma” (Vasileiadis, Alevrakis, & Koutsoukou, 2019, p. 3). PCO2 is partial pressure of carbon dioxide. It reflects the amount of carbon dioxide gas dissolved in the blood. The PCO2 reflects the exchange of this gas through the lungs to the outside air. High PCO2 values cause bronchodilation and reduce airway resistance in both asthma patients and patients without asthma.

Acute Asthma Exacerbation vs. Chronic Asthma Exacerbation

Acute asthma exacerbations are episodes of increased airway disturbances in a person with chronic asthma. A person with chronic asthma may go for months without an exacerbation as long as they follow the treatment plan for their condition, but they can encounter allergens or climatic or environmental conditions that cause an exacerbation. Hyperresponsiveness leads to the increase in the severity of symptoms that may be present to a lesser degree in a patient with chronic asthma. The severity of symptoms brings on the acute asthma exacerbation which may include airway obstruction, wheezing, chest tightness, and coughing—the common symptoms of asthma.

Diagnosis and Treatment

Symptoms of asthma are not enough to diagnose a patient with asthma. Lynn (2015) of American Nurse Today says that to diagnose asthma pulmonary function tests and peak expiratory volume measurements are done. These tests measure blood gases and air exchange rates among other things. When these measurements fall below a specific level, asthma is the diagnosis. Acute asthma exacerbation is treated with fast-acting beta 2 agonist, such as albuterol, which helps the measurements of blood gases and air exchanges to reach the acceptable levels (Lynn, 2015, p. 50). The measurements that help to diagnose asthma are also used to manage the disease.

For acute exacerbations fast acting medications are usually prescribed. These include ipratropium bromide inhalers such as Atrovent or short-acting beta 2 agonists or oral corticosteroids. These medications cause bronchodilation and begin working within minutes. For long term management of chronic asthma, inhaled corticosteroids, leukotriene modifiers, long-acting beta agonists (LABAs), theophylline, and combination inhalers that include an inhaled corticosteroid and LABA may be prescribed. These medications must be used for weeks or months to reach their optimum effect (Lynn, 2015, pp. 50-51).

Conclusion

Asthma was once thought to be specific disease that could be diagnosed and treated basically in the same way for every patient. However, that thinking has changed and now asthma is viewed as a spectrum of diseases that cause common symptoms. Hyperresponsiveness that leads to acute exacerbations can