What happens to blood flow and oxygen delivery to the brain during hyperventilation?

During hyperventilation, a person breathes rapidly and deeply, which leads to excessive exhalation of carbon dioxide (CO2) from the body. As CO2 levels drop, the bloodstream becomes more alkaline (a condition known as respiratory alkalosis). This change in blood chemistry affects cerebral circulation.

The reduction in CO2 causes cerebral vasoconstriction, meaning that the blood vessels in the brain narrow. As a result, blood flow to the brain decreases. Since oxygen delivery is closely tied to blood flow, a reduction in blood flow results in decreased oxygen delivery to the brain. Consequently, not only does the amount of blood reaching the brain decline, but the overall supply of oxygen that can be transported is also diminished. This process can lead to symptoms such as lightheadedness, tingling sensations, and even fainting because the brain is not receiving the adequate oxygen it needs.

In summary, hyperventilation leads to reduced blood flow and decreased oxygen delivery to the brain, explaining why this choice is accurate in the context of physiological responses to rapid breathing.