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Chapter 40 — 5
PSA Oxygen Concentrator
These devices use a molecular sieve to filter nitrogen from air and deliver high
concentrations of oxygen. They are available in a portable size and can be battery powered.
Bag–Valve–Mask Respirator
These devices comprise a self inflating rubber or plastic bag and a valve system which allows
the patient to be ventilated with air through a mask by squeezing the bag. Oxygen can be
piped into the circuit to increase the inspired O
2
concentration. If a reservoir bag is attached
to the inflation bag, the inspired O
2
concentration can be increased to almost 100% by using a
large O
2
flow (approx. 12–14 litres per minute), providing a good seal is achieved and the
patient's respiratory volume is not excessive. The valve system also allows the patient to
breath spontaneously from the device. Details of the operation of these devices vary between
manufacturers and are outlined in the instruction manual supplied.
Fig. 40.3
A resuscitator showing anaesthetic-type mask, hand-squeezed breathing bag, oxygen
reservoir bag and head strap to secure mask to diver's face.
Multiple Systems
Most countries have a variety of multi-purpose near 100% O
2
delivery systems available.
Aga, AG, CIG, Ambu, LSP, Drager and Laerdal and DAN manufacture such units. Self-
contained O
2
therapy units and resuscitation devices are now available with a demand valve
allowing the patient to either breathe spontaneously out of the device, be given positive
pressure ventilation by manual pressure, or use a breathing bag. A flow meter can be fitted to
another part of the system, to allow O
2
to be delivered to a mask at a high continuous flow
rate. The details vary between resuscitators and are explained in instructions supplied with
them. The entire device should be contained in a sturdy rustproof metal or heavy duty plastic
box which is compact, water resistant and easy to carry. It should have an adaptor and be able
to be supplemented by connection to a larger O
2
cylinder, if necessary.