What is one of the signs of hypoxic hypoxia?

Cyanosis is a classic sign of hypoxic hypoxia, which occurs when there is inadequate oxygen available to the tissues. This condition leads to a bluish discoloration of the skin and mucous membranes, particularly evident in areas with thin skin such as the lips or fingertips. The bluish tint arises from the deoxygenation of hemoglobin—the protein in red blood cells that carries oxygen. As oxygen levels drop, the blood takes on a darker red hue, which becomes visible externally.

In the context of hypoxic hypoxia, the body is unable to utilize oxygen efficiently due to low partial pressure of oxygen in the environment—such as at high altitudes or in situations of impaired breathing. The presence of cyanosis serves as a visual indicator that the body is experiencing oxygen deprivation, making it an important sign for recognizing the condition.

Other options indicate physiological responses that are not consistent with the effects of hypoxia. For instance, increased muscle strength, improved reaction time, and enhanced judgment are associated with optimal oxygen levels and aerobic metabolism, not a deficiency. In contrast, hypoxia typically leads to decreased cognitive and physical performance, underscoring why cyanosis is the correct choice.