Volume of Oxygen Produced By Electrolysis of Water
Thank you very much for your idea and help.
I think that your calculations are correct.
But I think you'd better to try other simpler choices to make oxygen.
One way is air separation. If you separate nitrogen from air, you gain oxygen.
This can be done by &quot;Zeolite oxygen generators&quot;. You can read these site about them.
1- https://www.zeochem.com/our-applications/medical-oxygen-generation
2- https://www.jalonzeolite.com/product-item/molecular-sieve-jlox-500/
There are many important factors that you have to consider about electrolysis of water that I know some of them:
First water has low conductivity. So, you have to add a strong inert electrolyte to make charge transfer between electrodes. This electrolyte could be any soluble salt, an acid or any substance that solves in water and then dissociates to ions. But, the electrolyte must not interacts to the main reaction and should be inert and surely it should be absolutely safe and not harmful for patient. Sodium or potassium sulfate or nitrate can be used.

Next, you have to choose an inert electrode to conduct electricity to the solution and then the gas be produced on it. Platin and gold can be use. But, they are expensive. Another choice can be carbon electrode.
And also take care about Hydrogen that produced on the negative electrode (cathode), that is flammable and can be exploded by spark.
And, so many other considerations to make oxygen efficiently and, next purify it to be suitable for hospital usage.
I wish you health.