To determine the duration of flow for an oxygen cylinder, you subtract the safe residual pressure from the gauge pressure in psi (pounds per square inch) and multiply by the cylinder constant divided by the flow rate in liters per minute. the safe residual pressure is always:

The correct answer to the question: The safe residual pressure is always:___, would be: 200 psi.

Explanation:

Portable oxygen that is placed in cylinders has become a great resource for people who are oxygen dependent, but wish to maintain a certain level of independence. However, it is important to understand that these cylinders must be managed in accordance with series of factors, and variables, that will make the use of them safe por a patient. One such really important variable is the residual pressure within a cylinder, which means the pressure exerted by the oxygen available still in the cylinder as it flows. Universally it is accepted that the minimum level of this residual pressure must be 200 psi (pounds per square inch) and once it reaches here it means that once that levels has been reached, it is no longer safe to use that cylinder anymore.

frequency is the answer