Florida State Paramedic Practice Exam

In patients with chronic obstructive pulmonary disease (COPD), what serves as the stimulus to breathe?

1. Increased CO2 levels

2. High blood pressure

3. Decreased O2 levels

4. Chest pain

The correct answer is: Decreased O2 levels

In patients with chronic obstructive pulmonary disease (COPD), the primary stimulus for breathing is a decrease in oxygen levels, also known as hypoxemia. In a healthy individual, the drive to breathe is mainly stimulated by rising levels of carbon dioxide (CO2) in the blood. However, individuals with COPD often develop a tolerance to elevated CO2 levels, resulting in their bodies relying more on oxygen levels to trigger the respiratory drive. Because patients with COPD frequently experience hypoxemia due to impaired gas exchange and airflow limitation, a significant drop in oxygen saturation becomes the primary factor that urges them to inhale. This mechanism differs from that of healthy individuals, where CO2 is the critical stimulus due to its role in maintaining acid-base balance. Understanding this shift in the respiratory stimulus is crucial for managing patients with COPD. This knowledge impacts treatment approaches, particularly when considering oxygen therapy, as administering high-flow oxygen may suppress their breathing stimulus further by alleviating hypoxemia, potentially leading to respiratory failure.