Final answer:
Elevated CO₂ levels in the atmosphere due to human activities cause the ETCO₂ to rise in spite of increases in Ve. This is because the increased atmospheric CO₂ affects the acid-base balance in the body, leading to an increase in CO₂ levels in the blood, which is detected by chemoreceptors in the brain and results in an increase in ventilation.
Step-by-step explanation:
Elevated CO₂ levels in the atmosphere have been steadily rising due to human activities, mainly the burning of fossil fuels. This increase in CO₂ concentration is causing the Earth's average temperature to rise, a phenomenon known as global warming. As a result of this increase in atmospheric CO₂, the concentration of CO₂ in exhaled breath (ETCO₂) is also rising, even though there may be increases in Ve (minute ventilation).
The reason for this is that the elevated CO₂ levels in the atmosphere can cause a shift in the acid-base balance in the body, leading to an increase in the partial pressure of CO₂ in the blood. This increase in CO₂ in the blood is detected by chemoreceptors in the respiratory center of the brain, which then signal the respiratory muscles to increase ventilation and remove the excess CO₂. So, the Ve (minute ventilation) increases, but the ETCO₂ also rises due to the elevated atmospheric CO₂.