Hypoxia refers to a low concentrations of oxygen in the body or body part. The condition arises from a mismatch between the amount of oxygen demanded by the body and the amount of oxygenated blood that is supplied.

The symptoms of hypoxia depend on the severity of the condition and the rate at which it becomes a more severe hypoxia or anoxia (no oxygen present). Some of the symptoms of hypoxia include:

• Headaches
• Fatigue or tiredness
• Breathlessness or shortness of breath
• Palpitations may be seen in the initial phases of hypoxia. As hypoxia progresses, the heart rate may quickly fall by a significant degree. In severe cases, abnormal heart rhythms or arrhythmias may develop.
• Raised blood pressure in initial phases of hypoxia is followed by lowered blood pressure as the condition progresses.
• Light headedness
• Nausea and vomiting
• Skin and nail beds may turn bluish, a condition called cyanosis. Cyanosis is one of the most common signs of hypoxia. The tips of the fingers, toes, ears and nose may become cold and bluish in colour. Cyanosis arises because blood that is low in oxygen is a dark bluish-red colour that can change the appearance of the skin from a pinky red to a bluish colour.
• Euphoria or sensation of dissociation from self
• Confusion, memory loss and cognitive problems
• Disorientation and uncoordinated movement
• Severe hypoxia can lead to loss of consciousness, seizures or convulsions, coma and even death. Breathing may become slow and shallow and the pupils of the eyes may not be responsive when light is shone on them.

Long-term hypoxia

People who have suffered from hypoxia for a long time may have swollen tips of the fingers. In addition, their blood can become concentrated with a higher number of red blood cells (polycythemia). Other disorders in long-term hypoxia include right ventricular hypertrophy or enlargement of the heart and chronic pulmonary hypertension.