In Canada passengers who travel and obviously need an attendant can declare that they are self reliant (even a quadriplegic) and the airline is forced to transport them.
Quote from the regulations: "Accepting a passenger's judgement
Sometimes, people with disabilities are perceived as needing extra services when in fact they do not. An air carrier is obliged to accept a person's word that he or she does not require any extra assistance or other service. Unquote
There is understanding at the Transport level (of course not in writting) that in an emergency those folks could be left behind but I suspect the public does not understand this.
At no time can we expect cabin crew to put their lives in jeopardy to evacuate a passenger with disabilities, while at the same time ensuring the safe evacuation of the other passengers and themselves. Passengers who need this type of assistance should be forced to travel with attendants who can provide them with the necessary assistance if using commercial transport or travel on medivac type of aircraft that can provide for their needs.