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where possible. It is important to recognize that this may result from interruption to any part of respiration; for example, the patient may be in severe pain and appropriate pain management may improve their respiratory function, or conversely an opioid overdose may result in decreased or absent respiration and the antidote to the opioid will then need to be given. There may be a mechanical obstruction to respiration, such as an infective obstruction like epiglottitis, and the treatment is therefore directed at treating the infection whilst also oxygenating the patient.

Respiratory therapy therefore covers a wide area and will include any manipulation or management of alteration to any part of the respiratory tree. It may include pharmacological management including pain management, antidotes to drug toxicity, support and guidance on smoking cessation, antimicrobials for infections of the respiratory tract, respiratory stimulants, surgery to repair a ruptured diaphragm or to manage trauma, the insertion of a tracheostomy or chest drains, or a thoracoabdominal shunt for superior vena cava obstruction. Finally, positioning and physiotherapy play a major role in improving respiratory function.

Any person who is unable to maintain tissue oxygenation will need to receive supplemental oxygen until they are able to manage again on room air. This oxygen may be delivered in different ways depending on the severity of the condition and the level of hypoxia.

Oxygen therapy

Definition

Oxygen therapy is the administration of oxygen at concentrations greater than that in ambient air with the intention of treating or preventing the symptoms and manifestations of hypoxia.

Evidence-based approaches

Rationale

Indications

Respiratory failure, of which there are two types, is characterized by problems with some or all of the four functions listed earlier Guyton and Hall 2006, Marieb et al. 2010, Tortora and Derrickson 2009).

— Type 1, referred to as hypoxaemic respiratory failure (failure to oxygenate the tissues). The PaO2 is <8 kPa (60 mmHg) while the carbon dioxide (PCO2) is normal or low. Common causes include infectious conditions, pneumonia, pulmonary oedema and adult respiratory distress syndrome.

— Type 2, referred to as hypercapnic (raised carbon dioxide) or respiratory pump failure. Alveolar ventilation is insufficient to excrete carbon dioxide accompanied by hypoxaemia (deficiency of oxygen in the arterial blood). The PCO2 is >6 kPa (45 mmHg). Common causes include chronic obstructive pulmonary disease (COPD), chest wall deformities, drug overdose and chest injury.

Acute myocardial infarction.

Cardiac failure.

Shock – haemorrhagic, bacteraemic and cardiogenic.

Conditions in which there is a reduced ability to transport oxygen, for example anaemia.

During anaesthesia.

Postoperatively.

Sleep apnoea.

Severe pain.

Asthma.

Pulmonary embolus.

Conditions that affect the neuromuscular control of breathing such as muscular dystrophy, Guillain–Barré.

Severe trauma affecting the diaphragm, ribs, lungs or trachea.

Tension pneumothorax.

Pleural effusion.

Contraindications

No specific contraindications to oxygen therapy exist, but the following precautions or possible contraindications need to be considered.

With increased PaO2 ventilatory depression may occur in spontaneously breathing patients with elevated PaCO2.

With high flow of fractional inspired oxygen (FiO2), absorption atelectasis, oxygen toxicity and/or depression of ciliary and/or leucocytic function may occur.

Supplemental oxygen should be administered with caution to patients suffering from paraquat poisoning and those receiving bleomycin.

During laser bronchoscopy, minimal levels of supplemental oxygen should be used to avoid intratracheal ignition.

Fire hazard is increased in the presence of increased oxygen concentrations.

Bacterial contamination associated with certain nebulization and humidification systems is a possible hazard.

Anticipated patient outcomes

Outcome is determined by clinical and physiological assessment to establish adequacy