Oxygen therapy

A common use of supplementary oxygen is in patients with chronic obstructive pulmonary disease (COPD), a common long term effect of smoking, who may require additional oxygen to breathe either during a temporary worsening of their condition, or throughout the day and night. It is indicated in COPD patients with PaO2 ≤ 55mmHg or SaO2 ≤ 88% and has been shown to increase lifespan.
Use in acute conditions

Oxygen is widely used in emergency medicine, both in hospital and by emergency medical services or advanced first aiders.

In the pre-hospital environment, high flow oxygen is definitively indicated for use in resuscitation, major trauma, anaphylaxis, major haemorrhage, shock, active convulsions and hypothermia.

It may also be indicated for any other patient where their injury or illness has caused hypoxaemia, although in this case oxygen flow should be moderated to achieve target oxygen saturation levels, based on pulse oximetry (with a target level of 94-98% in most patients, or 88-92% in COPD patients).

Oxygen therapy is the administration of oxygen as a medical intervention, which can be for a variety of purposes in both chronic and acute patient care.

Oxygen is essential for cell metabolism, and in turn, tissue oxygenation is essential for all normal physiological functions.

Room air only contains 21% oxygen, and increasing the fraction of oxygen in the breathing gas increases the amount of oxygen in the blood.

It is often only required to raise the fraction of oxygen delivered to 30–35% and this is done by use of a nasal cannula.

When 100% oxygen is needed, it may be delivered via a tight-fitting face mask, or by supplying 100% oxygen to an incubator in the case of infants.

Oxygen can be administered in other ways, including specific treatments at raised air pressure, such as hyperbaric oxygen therapy.

High blood and tissue levels of oxygen can be helpful or damaging, depending on circumstances and oxygen therapy should be used to benefit the patient by increasing the supply of oxygen to the lungs and thereby increasing the availability of oxygen to the body tissues, especially when the patient is suffering from hypoxia and/or hypoxaemia.