During flight, what part of the body is most affected by stagnant hypoxia?

Stagnant hypoxia occurs when there is inadequate blood flow to various parts of the body, which can be due to factors like reduced heart output or excessive G-forces. Among the options, the heart is indeed critical as it is responsible for pumping oxygenated blood throughout the body. If the heart is not functioning effectively, it can lead to reduced blood circulation, meaning that the heart itself becomes heavily impacted by stagnant hypoxia.

While the brain can experience severe consequences from stagnant hypoxia due to its high sensitivity to oxygen levels, the heart's role in maintaining overall circulation makes it particularly vulnerable when blood flow is impaired. This explains why the heart is highlighted in the context of stagnant hypoxia. Other parts, like the lungs and red blood cells, are less directly involved in the stagnant process compared to the heart's crucial function in maintaining adequate blood flow to the body's tissues.