MEDICAL OXYGEN (OXYGEN PH EUR)

High concentration oxygen therapy, with concentrations up to 60% for short periods is safe for conditions like pneumonia, pulmonary thrombo-embolism and fibrosing alveolitis. Low concentration (controlled) oxygen therapy should be used in patients with ventilatory failure due to chronic obstructive airways disease and other causes.

The concentration should not exceed 28% and even 24% may be excessive in some patients. Oxygen may be administered at concentrations of up to and including 100% though with most delivery systems inspired concentrations over 60% (80% in children) are unlikely to be achieved.

In practice 30% is usually taken as the lower limit, with allowance for a safety margin. The dosage is adapted to the patient on the basis of the clinical course of the illness and generally ranges from 1 to 10 litres of gas per minute.

Systems for longer-term oxygen therapy usually rely on a mixture of air and additional oxygen being supplied. Masks, nasal cannulae, etc. can provide fixed or variable mixtures depending on their design. g. anaesthetics and analgesics) then it is essential that the proportion of oxygen in the inspired mixture never falls bellow the concentration in air.

In practice 30% is usually taken as a lower limit, with allowance for a safety margin. Care should be taken to prevent rebreathing of expired carbon dioxide. With vented face masks and flow rates over 4 litres/minute this should rarely be a problem.

In an emergency a doctor may need to administer doses considerably higher to patients with severe breathing difficulties. Such doses may be up to 60 litres per minute, controlled by special flowmeters. Other systems of administration include face tents, headboxes, cot hoods and supply to a tracheotomy.

In severe hypoxia the use of a positive pressure mask may be valuable. This technique should only be used by experienced practitioners.

In patients with chronic severe airway disease, who rely on hypoxic drive of respiration, the administration of high levels of oxygen, will result in further under- ventilation, and further accumulation of carbon dioxide and acidosis.

In the premature neonate, exposure to excessive oxygen concentrations may be associated with the following conditions: retrolental fibroplasia, bronchopulmonary dysplasia, sub-ependymal and intraventricular haemorrhage and necrotising enterocolitis.

CNS oxygen toxicity only occurs when the partial pressure of inspired oxygen exceeds 2 atmospheres (203 kPa), that is in hyperbaric oxygen therapy. Reporting of suspected adverse reactions Reporting suspected adverse reactions after authorisation of the medicinal product is important.

It allows continued monitoring of the benefit/risk balance of the medicinal product. uk/yellowcard or search for MHRA Yellow Card in Google Play or Apple App Store.

4. Special Warnings and Special Precautions for Use Patients with chronic severe obstructive airways disease rely on hypoxic drive for respiration. When such patients are given oxygen therapy it must be administered at a relatively low concentration and must be accurately metered and titrated against arterial concentrations and clinical observation.

Note that contact with liquid oxygen can cause burns. Avoid such contact by wearing protective clothing. Eye protection and suitable gloves should be worn with full-length outer garments [full-length trousers without turn-ups and full length rolled down sleeves] so as to facilitate safe and correct usage and handling.

Connections for hoses, valves etc. must be clean and dry. If necessary, clean only with plain water. Do not use solvents. Use clean, lint free cloths for cleaning and drying off. Use no oil or grease on valve or associated equipment. Do not allow naked flames near the container.

Do not smoke when using oxygen. Do not breathe oxygen at pressures in excess of atmospheric.

3. Contra-Indications 1 High concentrations of oxygen are contra-indicated in chronic severe airways disease and premature neonates. 2 Patients should not smoke while on oxygen therapy because of the fire risks.