Let us briefly consider the methods of administering oxygen:
I find nasal cannula easy to use. Even with a transnasal bronchoscopy, you can maintain sufficient oxygenation. I do not recall any circumstance when I had to resort to a mask. Even if nasal passages are completely blocked by nasal polyps, I can use the cannula in the mouth.
Two facts are well established:
The oxygen saturation and pulse rate can be monitored with ease using a finger transcutaneous oximeter. We use it routinely. It has helped us avert serious hypoxemia in a few cases. However, routine use of oximeter may not be necessary.