What is Hypoxia

Hypoxia is a pathological condition where the body or a region is deprived of oxygen supply in adequacy. These variations in the supply of oxygen depend on normal physiology or involvement in strenuous physical exercises.  The mismatch in supply of oxygen at the cell level results in hypoxia.  In cases where the oxygen supply is deprived completely, this is termed to as anoxia.  Many people tend to confuse hypoxia with hypoxemia. There however exists a difference.   In the case of hypoxemia, arterial oxygen supply is just low abnormally. You may experience hypoxia and still maintain a high level of oxygen pressure.  Ideally, hypoxemia is one of the causes of hypoxia.

Hypoxia occurs mainly in healthy people especially when they ascend high altitudes.  In this case, it causes altitude sickness. This can lead to conditions that can transform to fatal complications.  Hypoxia can also occur to people who are healthy after breathing mixed gases that have low oxygen concentrations.  Mild or non damaging hypoxia is also used in altitude training in order to improve athletic performance down to the cellular level.  Hypoxia is detected in humans through chemoreceptors.

Classifications

Hypoxemic hypoxia

This is ideally generalized hypoxia.  This is characterized by inadequacy of oxygen supply in the whole body.  This is hypoxia that is caused by low oxygen pressure in arterial blood.  This condition occurs due to hypoventilation, shunts in pulmonary circulation, pulmonary fibrosis, and decreased oxygen concentrations in inspired air and anemia among many other causes.  Hypoventilation is characterized by inadequate pulmonary ventilation.  Shunts in pulmonary circulation may be a big cause of this. These are caused by collapsed alveoli that are perfused.

Histotoxic hypoxia

In this case, the amount of oxygen that reaches the cells is normal.  The cells however are not able to use the oxygen they get much effectively. This is due to the inability of the oxidative enzymes to perform their synthesis job.

Signs and symptoms

The symptoms of hypoxia depend on acceleration of onset and the severity of the condition.  The cause of hypoxia may be altitude sickness. In this case the affected person would experience headaches, breath shortness, fatigue, nausea and also some feelings of euphoria.

In case of severe hypoxia, or otherwise hypoxia that has rapid onset, the patient experiences seizures,, priapism, unconsciousness, and death may also occur.  Severe hypoxia involves the discoloration of the skin. This condition is also referred to as cyanosis.  In some instances of oxygen supply inadequacy, the skin may turn cherry red.

Pathophysiology

Oxygen diffuses after it has mixed with vapor and expired carbon dioxide in the lungs. It then enters arterial blood. In this case, the partial pressure is 100mmHg. The arterial blood flow then delivers oxygen to peripheral tissues. It then again diffuses a pressure gradient to the cells and then enters the mitochondria.

If at all the delivery of oxygen to cells is not sufficient, hydrogen is the shifted to pyruvic acid which then converts it into lactic acid.  This is referred to as anaerobic metabolism and allows the release of small amounts of energy. The buildup of lactic acid in blood and tissues is a sign of inadequate supply of oxygen to the mitochondria.

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