National League for Nursing (NLN PAX) Practice Exam

Why does a person's respiratory rate increase during exercise?

1. Decrease in oxygen levels

2. Increase in lactate concentration

3. Increase in CO2 concentration in the blood

4. Increase in heart rate

The correct answer is: Increase in CO2 concentration in the blood

The increase in respiratory rate during exercise is primarily due to the increase in carbon dioxide (CO2) concentration in the blood. When a person exercises, the muscles require more oxygen for energy production, which leads to an increase in metabolic activity. This metabolic activity generates more carbon dioxide as a byproduct. As CO2 levels rise in the bloodstream, this change in concentration affects the body's acid-base balance and stimulates chemoreceptors located in the brain and in blood vessels. These receptors are sensitive to the levels of carbon dioxide and respond by signaling the respiratory center in the brain to increase the rate and depth of breathing. This compensatory mechanism aims to expel the excess CO2 and bring in more oxygen, ensuring that the body can continue to meet the heightened demands of exercise. While other factors, such as a decrease in oxygen levels, increased lactate concentration, and an increase in heart rate, can also affect respiratory patterns during exercise, the direct and immediate stimulus for the increase in breathing rate is primarily linked to the rising concentrations of carbon dioxide in the blood.