My 80 yo father awake many times during nights asking for oxygen while there is no apparent sign of difficult breathing .. but he always grunt .... I do not know if he is really in medical problem ... or it is manifestation of depression.
The hard part is over.
I'm matching you with one of our specialists who will be calling you in the next few minutes.
This should be discussed with his doctor.
If you are not sure whether or not this is a physical issue or a depression issue the only way to find out is through a medical diagnosis.