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Evidence‐based approaches

Rationale

Indications

Oxygen is indicated for any condition that causes hypoxaemia. For example:

during cardiac or respiratory arrest
for initial treatment during critical illness (anaphylaxis, shock, sepsis, carbon monoxide poisoning, major head injury, status epilepticus, major pulmonary haemorrhage, near drowning, etc.)
during serious illness when hypoxaemia is suspected or has been confirmed (e.g. acute asthma, pneumonia, pulmonary embolism, pulmonary oedema, pleural effusion lung cancer or worsening lung fibrosis)
during and after conscious sedation or anaesthesia if the patient is unable to maintain their own airway or maintain oxygen saturations between 94% and 98% (or 88–92% if at risk of hypercapnic respiratory failure) (O'Driscoll et al. [209]).

Any of the above conditions can lead to respiratory failure, of which there are two types (Brady [29]):

Type 1 is referred to as ‘hypoxaemic respiratory failure’ (failure to oxygenate the tissues), where the PaO₂ is less than 8 kPa (60 mmHg) while the carbon dioxide (PaCO₂) is normal or low.
Type 2 is referred to as ‘hypercapnic respiratory failure’ (raised carbon dioxide) or ‘respiratory pump failure’, where the PaCO₂ is greater than 6 kPa (45 mmHg). Alveolar ventilation is insufficient to excrete carbon dioxide and this is accompanied by hypoxaemia.

Table 12.1 outlines some of the common causes of the different types of respiratory failure.

Table 12.1 Common causes of respiratory failure

Type 1 respiratory failure (hypoxaemic)	Type 2 respiratory failure (hypercapnic)
COPD Pneumonia Pulmonary oedema Pulmonary fibrosis Asthma Pneumothorax Pulmonary embolism Pulmonary arterial hypertension Pneumoconiosis Granulomatous lung diseases Cyanotic congenital heart disease Bronchiectasis ARDS Fat embolism syndrome Kyphoscoliosis Obesity	COPD Severe asthma Drug overdose or sedative drugs Poisoning Myasthenia gravis Polyneuropathy Poliomyelitis Primary muscle disorders Porphyria Cervical cordotomy Head and cervical cord injury Primary alveolar hypoventilation Obesity hypoventilation syndrome Pulmonary oedema ARDS Myxoedema Tetanus

ARDS, acute respiratory distress syndrome; COPD, chronic obstructive pulmonary disease.

Source: Adapted from Feller‐Kopman and Schwartzstein ([78]), Kayner ([126]).

Contraindications

No specific contraindications to oxygen therapy exist (Bein et al. [19]), but the following precautions need to be considered (GOLD [91], Moore [166], NICE [194], O'Driscoll et al. [209]):

Patients at risk of hypercapnic respiratory failure (e.g. those with chronic obstructive pulmonary disease) should receive prescribed titrated oxygen to maintain oxygen saturations of 88–92%.
The administration of high concentrations of fractional inspired oxygen (FiO₂) for prolonged periods of time can cause absorption atelectasis (incomplete lung inflation) and oxygen toxicity.
Supplemental oxygen should be administered with caution to patients with paraquat poisoning and those who have previously received bleomycin chemotherapy due to the risk of pulmonary toxicity and bleomycin‐induced pneumonitis.
Bacterial contamination associated with certain nebulization and humidification systems is a possible hazard.
Fire hazard is increased in the presence of increased oxygen concentrations.

Anticipated patient outcomes

The patient will achieve the desired oxygen saturations with the least amount of supplementary oxygen necessary.