[QUOTE=Karina_KV;11944080]
Originally Posted by
justapax
I work in the gas industry and would strongly recommend that you first discuss with your doctor or your oxygen supplier whether or not to bring oxygen on board. They will be best able to advise you on how much oxygen your condition may require and what type of cylinder, if any, will be appropriate. It certainly won't be a scuba-sized cylinder.
Hospitals use large oxygen cylinders, but these are usually reserved for critical patients who may have a continuous oxygen consumption of around 10-15 L/min. This is quite a lot, to compare - a healthy person in a calm condition consumes about 1.5–2 liters of oxygen per minute. In most cases, heavy patients are connected to a central oxygen supply; when cylinders are used, they are not always large. Smaller cylinders and lightweight composite cylinders are also widespread. Larger cylinders are more common, mainly because they are cheaper, so they are common in hospitals (and elsewhere).
I would suggest that you use a cylinder of around 0.5 L at a pressure of around 150 bar. This will give you around 15-30 minutes or more of continuous breathing, depending on the condition. However, if you only need oxygen for occasional inhalation rather than continuous breathing, a small cylinder may be sufficient. But again - you need to speak with your doctor at first.
From my ongoing research into oxygen supply on commercial aircraft, I know that there are usually several medical oxygen cylinders (usually 1–2L size) on board. They are designed to provide sufficient breathing support in case of breathing difficulties during the flight.
Bringing your own oxygen cylinder on board can be tricky, as compressed gas cylinders are considered dangerous. If something happens, such as a valve failure, the cylinder will fly around the cabin like a rocket. All oxygen cylinders carried on board an aircraft are regularly checked according to strict protocols, and larger cylinders are always securely fastened. This does not guarantee 100% safety, but it significantly reduces the risks. At the same time, the staff does not know where you bought your cylinder and what condition it is in - so it is difficult for them to agree to allow you on the plane with a bottle of gas under high pressure.
I get a doctor's letter for my cylinder(s) of 22l of oxygen, I guess these are at low pressure as they are about the size of a bottle of wine, so roughly 22/.75 = just under 30 bar, far less than the pressure used in hospital bottles of O2. This seems to do the trick checking in. I don't think my doctor has ever seen one of these little cylinders, I just sent him a photograph, but he's a pretty tame doctor and usually does what he's told, e.g., prescribing oxycodone when I broke my arm without quibbling.