A simple and hopefully not too technical explanation of the working of a high dose oxygen chamber.
Air is a mixture of nitrogen (78%) and oxygen (21%) and this is where we get our source of oxygen from - we don't have big banks of cylinders or anything like that and of course air is free. So what happens ?
Air is drawn into a compressor where it is compressed and dried. This air, now at a higher pressure, is fed into a filter which effectively filters the nitrogen out of the air leaving only compressed oxygen. If you want to know more about this process (known as Pressure Swing Adsorption) follow this link. If you're at the therapy centre you'll hear an occasional escape of gas. This is the unwanted nitrogen from the filter being exhausted into the atmosphere. The oxygen which is now about 94% pure is stored in a large pressure container.
Not all the compressed air is filtered to remove the nitrogen, some of it is used to pressurise the chamber. Our barochambers only use oxygen for the occupants to breathe during their therapy. The atmosphere of the chamber itself is pressurised air. A simple but very effective valve arrangement (similar to that used by scuba divers) allows oxygen to be fed to the breathing system at the same pressure as the ambient chamber pressure (the pressure inside the chamber). As the chamber operator increases or decreases the chamber pressure the oxygen delivered to the occupants is automatically adjusted thus avoiding discomfort and breathing difficulties.
Is breathing difficult?
The occupants use a closely fitting mask or sometimes a hood which is fed with oxygen. A valve in each occupant's breathing supply delivers the oxygen as soon as the person starts to inhale. So sensitive is this mechanism that most people don't realise that the oxygen isn't flowing continuously . However, If a hood is used, the oxygen does flow continuously.
By using individual tubes for exhaled breath from each occupant and exhausting these outside the chamber, no one breathes another person's exhaled breath.
If the mask is uncomfortable or needs to be removed for some reason, as the occupants are surrounded by air in the chamber, they'll simply breath air instead of oxygen when they remove the mask. Putting the mask back on will resume the oxygen delivery.
An operator is present at all times and can both see and talk to the occupants using the small windows, video monitors and intercom.
The pressure is increased and decreased slowly to minimise any discomfort to the chamber's occupants typical of that experienced when in an aircraft as it takes off or lands.
We mentioned earlier that the air and oxygen is dried and some people may wish to take a cup of water to drink into the chamber with them.
The risk of fire inside the chamber is very low because a) the chamber is designed that way and has its own sprinkler system and amongst the list of prohibited items is any item that is considered to be flammable .
High Dose Oxygen Therapy is often confused with diving however this is not the case and the treatment protocols used cannot cause any diving related complications.
Grateful thanks are extended to David Downie MBE for his assistance in producing this article. David Downie is Honorary Technical Advisor to the Wolfson Hyperbaric Medicine Unit of the University of Dundee, and Honorary Technologist to the UK National M.S. Therapy Chambers.
