What condition refers to the deficiency of oxygen reaching the tissues?

The condition that refers to the deficiency of oxygen reaching the tissues is hypoxia. Hypoxia specifically denotes a state where there is inadequate oxygen supply to the cells, which can result in cellular damage or dysfunction. This can occur even when the blood oxygen levels are normal if the oxygen cannot be adequately delivered to the tissues due to various factors, such as impaired circulation or environmental conditions.

In contrast, hypoxemia refers to low levels of oxygen in the blood specifically, which may or may not lead to tissue hypoxia. Hyperoxia, conversely, refers to an excess of oxygen in the tissues, which is not relevant to this question. Ischemia involves reduced blood flow to an organ or tissue, which can lead to hypoxia, but it does not specifically refer to the oxygen deficiency itself. This makes hypoxia the correct answer as it directly aligns with the description of oxygen deficiency at the tissue level.