Hypoxia is a pathogical condition in which the body as a whole (generalised) hypoxia) or a region of the body (tissue hypoxia) is deprived of an adequate oxygen supply. Variations in arterial oxygen concentrations can be part of normal physiology such as during strenuous exercise.


Generalised hypoxia occurs in healthy people when they ascend to high altitudes causing altitude sickness. It can also occur in healthy people due to breathing a mixture of gases with low oxygen content. For example when diving underwater defined as "Low Oxygen" in the blood. This medical condition may arise when insufficient oxygen reaches the bodies tissues.


But there are a number of causes to be considered also:



  • Drowning.
  • Lack of oxygen in the area, i.e. gas or smoke.
  • Carbon monoxide.
  • Suffocation.



  • Obstruction by the tongue.
  • Vomit.
  • Anaphylaxis.
  • Burns.
  • Hanging - Strangulation.



  • Asthma.
  • Poisoning.
  • Chest Injury.
  • Crush injury.
  • Collapsed Lung.
  • Lung Infections.



  • Heart attack.
  • Angina.
  • Anaemia.
  • Cardiac arrest.


Control Centre (Brain):

  • Head injury.
  • Strokes.
  • Overdose.
  • Electric shock.
  • Spinal injury


Low levels of oxygen can prove to be potentially fatal; it is therefore essential that first aiders can recognise this condition and treat the patient accordingly.


Signs & Symptoms:

The symptoms of generalised hypoxia depend on its severity and acceleration of onset. In altitude sickness for example the onset is gradual and as well as the symptoms below the individual may have feelings of euphoria.

  • Pale, cold, clammy skin.
  • Increased pulse rate.
  • Increased breathing rate.
  • Grey-blue skin (cyanosis).
  • Anxiety.
  • Restlessness.
  • Headache.
  • Nausea – Vomiting.
  • Because haemoglobin is darker red when not bound to oxygen, when seen through the skin it can reflect blue light back to the eye, so in cases where the oxygen has been displaced by carbon monoxide the skin may appear cherry red rather than cyanotic.



  • Remove the patient from the cause.
  • Monitor patient level of consciousness (AVPU).
  • Maintain patient's airway.
  • Unconscious patient to be placed in the recovery position.
  • If available use a pulse oximeter on patient's finger (a non invasive method of measuring the oxygenation of haemoglobin).
  • Sats below 94% give patient oxygen therapy using a 100% non-rebreathing mask at 15 liters per minute.
  • Monitor sats.



  • Do not allow your patient to eat, drink or smoke.


We hope you find this article useful. This is one in an alphabetical series of articles addressing various symptoms and their first aid treatments. If you would like more information on related resuscitation and first aid training, please get in touch.


You might also be interested in our blog 'How should we control bleeding?' by Tim Hart.


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