Question

A 25-year-old previously well woman presents to doctor’s office with complaints of episodic shortness of breath and chest tightness. She has had the symptoms on and off for about 2 years but states that the have worsened lately, occurring two to three times a month. She notes that the symptoms are worse during the spring months. She has no exercise-induced or nocturnal symptoms. The family history is notable for a father with asthma. She is single and works as an administrative assistant in a high-tech firm. She lives with a roommate, who moved approximately two months ago. The roommate has a cat. The patient smokes occasionally when out with friends and drinks socially, but has not history of illicit drug use. Examination is notable for mild end-expiratory wheezing. The history and physical examination are consistent with a diagnosis of asthma. Pulmonary function tests are ordered to confirm the diagnosis.

1. What are three categories of provocative agents that can trigger asthma? What are some possible triggers in this patient?

2. Describe the early events responsible for the pathogenesis of asthma. How does this result in chronic airway inflammation and airway hyperresponsiveness.

3. Define wheezing. What pathogenetic mechanisms are responsible for this patient’s symptoms of wheezing, shortness of breath, and chest tightness?

4. What might you expect the results of her pulmonary function tests to be? Why?

Answer 1

1) Provocative agents for Asthma :

- Physiological mediators like histamine which cause contraction of respiratory smooth muscles.

- Physical agents like cold exposure or exercise.

- Allergy inducing mediators like pollen or pests.

The possible triggers in this patient are:

- Exposure to pets like cat.

- Smoking habit.

2) Pathogenesis of Asthma :

After inhalation triggers of Asthma cause mast cell degranulation and release of histamine which will induce production of leukotrienes and other inflammatory mediators. Cytokines released by mast cells enhance infiltration by other inflammatory cells.

Early events responsible for Asthma are : airway inflammation, increased permeability of vascular endothelium, enhanced secretion of mucus. These processes leads to bronchospasm and leads to wheezing.

These changes when untreated leads to hypertrophy of airway smooth muscle, hyperplasia of airway epithelium and connective tissue deposition and leads to chronic airway inflammation and airway hyperresponsiveness.

3) Wheezing : is defined as a high pitched whistling like sound produced while breathing due to the constriction of the airways.

Mechanism of :

a) Wheezing : Constriction of air ways.

b ) Shortness of breath : due to Constriction of air ways as well as impaired gas exchange.

c) Chest tightness : is due to blocking of airways resulting in failure to expire after inspiration.

4) Pulmonary function test in Asthma Patients :

- Low FEV1/ FVC ratio because of obstruction to airflow. Lung volumes and gas exchange are obstruction to airflow is due to Bronchoconstriction.