Final answer:
Metabolic or histotoxic hypoxia occurs when tissues cannot utilize oxygen despite normal oxygen delivery through the blood. This can happen due to cellular machinery malfunction, often caused by toxins or metabolic diseases, which impair the cells' ability to use oxygen.
Step-by-step explanation:
The type of hypoxia where oxygen delivery is normal, but the tissues cannot utilize it, is known as metabolic or histotoxic hypoxia. In this condition, the percent saturation of hemoglobin may be normal, indicating adequate oxygen being transported in the blood. However, due to various factors such as toxins or certain metabolic diseases, the cells are unable to use the oxygen effectively.
Particularly, the issue arises within the cellular machinery, typically the mitochondria, where oxygen consumption occurs. Even though oxygen arrives at the cellular level, if the cells are poisoned or otherwise incapable of metabolizing it, symptoms of hypoxia will manifest, despite the presence of adequate oxygen in the bloodstream.
An example of histotoxic hypoxia can occur with cyanide poisoning, where despite having normal oxygen levels in the blood, cells are unable to utilize that oxygen to produce ATP because cyanide inhibits the cytochrome oxidase complex within the mitochondria. As a result, the tissue experiences hypoxia and cannot function properly.