This appeared in Question 18.1 from the first paper of 2008.
The cylinders, according to a reputable source, can withstand a pressure of 24,000 kPa, but normally rest at around 12,000-17,000 (that is the "green zone" on the gauge). The standard (mandatory) wall gas pressure is 415 kPa (about 4 atmospheres). For the gas which powers surgical tools, the pressure is 1400 kPa.
This excellent lecture from the University of Sydney has a vast amount of obscure information (did you know oxygen tanks are aged at 175°C for 8 hours, and that their walls are only 3mm thick?)
Medical Gas Standard AS 2896-2011 is available online, but you have to pay over $200 to purchase it.
Dorsch and Dorsch have a chapter dedicated to medical gas supply and suction equipment, which can be accessed by Google Books.