stylistic:tone
Differential diagnosis

Treatment will depend on severity and may also depend on the cause, as some cases are due to external causes and removing them and treating acute symptoms may be sufficient, but where the symptoms are due to underlying pathology, treatment of the obvious symptoms may only provide temporary or partial relief, so differential diagnosis can be important in selecting definitive treatment.

Hypoxemic hypoxia: Low oxygen tension in the arterial blood (P) is generally an indication of inability of the lungs to properly oxygenate the blood. Internal causes include hypoventilation, impaired alveolar diffusion, and pulmonary shunting. External causes include hypoxic environment, which could be caused by low ambient pressure or unsuitable breathing gas. Both acute and chronic hypoxia and hypercapnia caused by respiratory dysfunction can produce neurological symptoms such as encephalopathy, seizures, headache, papilledema, and asterixis. Obstructive sleep apnea syndrome may cause morning headaches

Circulatory Hypoxia: Caused by insufficient perfusion of the affected tissues by blood which is adequately oxygenated. This may be generalised, due to cardiac failure or hypovolemia, or localised, due to infarction or localised injury.

Anemic Hypoxia is caused by a deficit in oxygen-carrying capacity, usually due to low hemoglobin levels, leading to generalised inadequate oxygen delivery.

Histotoxic Hypoxia (Dysoxia) is a consequence of cells being unable to utilize oxygen effectively. A classic example is cyanide poisoning which inhibits the enzyme cytochrome C oxidase in the mitochondria, blocking the use of oxygen to make ATP.

Critical illness polyneuropathy or myopathy should be considered in the intensive care unit when patients have difficulty coming off the ventilator.