Is a 24/7 oxygen considered critical care?
There is much discussion going on about proper reimbursement for oxygen therapy. Some say that the lobbyist who lobby congress for insurance are not informed enough about the real needs of patients.
Write down what your need is. Why are you on the concentrator instead of the critical care venitlator? You need to make your needs known both to the insurers and to the people who deliver and maintain the equipment.
Also, get on the web and find chat rooms where people are discussing this topic. You can become an expert in your own condition and perhaps can help others as well. The very best wishes for you to succeed are coming your way from me to you.