(1989; 60 pages) [French]
Group: inhalational gas
Pressurized oxygen cylinders for industrial use that contain gas at about 13 000 kPa are acceptable for use in anaesthesia. Cylinders intended for anaesthetic use are supplied with pin-index valves. They contain more than 99% oxygen by volume with small residues of nitrogen or argon. Cylinders should always be connected to anaesthetic apparatus by a suitable pressure-reducing valve and they should be replaced as soon as the cylinder pressure falls below 800 kPa.
Oxygen concentrators have recently been developed that offer a more economical source of oxygen and avert the need for frequent delivery and storage of cylinders.
To maintain an adequate oxygen tension in inhalational anaesthesia.
Dosage and administration
The concentration of oxygen in inspired anaesthetic gases should never be less than 21%.
It may be administered with the anaesthetic gases, or from a face mask or via a nasal catheter.
Combustion or sparking creates a danger of fire or explosion at high oxygen tensions. Use of cautery is contraindicated whenever oxygen is used in combination with ether. Reducing valves should not be greased, since this creates a danger of explosion.
Oxygen should not be used for longer or at a greater concentration than is necessary to prevent hypoxaemia.
After prolonged administration, concentrations greater than 80% at atmospheric pressure have a toxic effect on the lungs, which presents initially as a mild substernal irritation progressing to pulmonary congestion, exudation and atelectasis.
Use of unnecessarily high concentrations of oxygen in incubators has led to the development of retrolental fibroplasia and permanent blindness in premature infants.
Oxygen is supplied under pressure in cylinders, which must be kept below 25°C.
Cylinders containing premixed oxygen 50% and nitrous oxide 50% are available for analgesia in some countries. However, the constituents separate out at -6°C, in which case adequate mixing must be assured before use. When the two components are supplied from separate cylinders a safety device must be installed that cuts off the flow of nitrous oxide should the oxygen pressure fall.
Identification of cylinders
An ISO standard1 requires that cylinders containing oxygen intended for medical use should bear the name of the contents in legible and permanent characters and, preferably, also the chemical symbol O2. The neck, from the valve to the shoulder, should be coloured white. Cylinders containing nitrous oxide and oxygen mixtures should be similarly labelled, and the neck coloured white and blue.
1International Standard 32. Gas cylinders for medical use - marking for identification of content. Switzerland, International Organization for Standardization, 1977.