Could be related to his lack of oxygen, could be something demonic in nature, oppressing him.

If your father is a Christian, I suggest he leaves a light on, prays for peace, and plays the word of God via recording in the room.

If it is demonic, as a Christian he can come against it by prayer and ordering the presence to depart in Christ's name.

Display a cross in the room as well.

These things won't help if he is not of the faith.

He should probably be checked for a UTI as well, as they can lead to visions and people seeing things.