Emergency Medical Technician (EMT) Intermediate Practice Exam

In cases of chronic carbon dioxide retention, patients typically breathe based on which of the following?

1. Decreased oxygen levels

2. Increased carbon dioxide levels

3. Blood pH levels

4. Lung capacities

The correct answer is: Decreased oxygen levels

In cases of chronic carbon dioxide retention, patients typically breathe based on increased carbon dioxide levels. In individuals with chronic respiratory conditions, such as COPD (Chronic Obstructive Pulmonary Disease), the body becomes accustomed to elevated levels of carbon dioxide. As a result, the primary drive to breathe shifts from responding to low oxygen levels to responding to high carbon dioxide levels. This physiological adaptation is known as respiratory acidosis, where the body compensates for the increased CO2 by adjusting its breathing pattern. Consequently, the respiratory centers in the brain become more sensitive to rising CO2 levels rather than low oxygen levels, to stimulate deeper or more frequent breathing to expel CO2 effectively. While decreased oxygen levels and blood pH levels can influence breathing in different contexts, in chronic carbon dioxide retention, the drive to breathe is most strongly associated with the levels of carbon dioxide present in the blood.