AEMCA Practice Exam

How can chronic bronchitis lead to cor pulmonale?

1. By increasing arterial oxygen levels

2. By inducing chronic low CO2 levels

3. By causing pulmonary vasoconstriction due to high CO2 levels

4. By reducing heart rate to maintain blood flow

The correct answer is: By causing pulmonary vasoconstriction due to high CO2 levels

Chronic bronchitis is characterized by inflammation of the bronchial tubes and excessive mucus production, which leads to airway obstruction and difficulty in breathing. This condition commonly results in low oxygen levels (hypoxemia) and high carbon dioxide levels (hypercapnia) in the bloodstream. When the levels of carbon dioxide in the blood increase, it creates a situation where the body needs to compensate for the impaired gas exchange occurring in the lungs. One of the compensatory mechanisms is pulmonary vasoconstriction, which is the constriction of blood vessels in the lungs. The body's response to an increase in CO2 and persistent low oxygen levels is to redirect blood flow away from poorly ventilated areas of the lungs to more functional areas, but this can lead to increased pressure in the pulmonary arteries. Over time, this increased pressure causes the right side of the heart to work harder to pump blood through the narrowed and constricted pulmonary vessels, leading to the development of cor pulmonale, which is right heart failure resultant from lung disease. In essence, chronic bronchitis causes a series of physiological changes, including pulmonary vasoconstriction due to high carbon dioxide levels, which culminates in cor pulmonale.