I was passingly acquainted with two quadriplegics from my corporate job. They were both employees of the company.
Quadriplegic just means all four limbs are impaired. The degree of impairment can vary substantially. One of these men had use of his arms, but did not have full use of his hands. He drove himself to work, had a full time job, wife and kid. He broke his neck in a pool accident in his teens. He used a manual wheelchair. He was able to use a manual wheelchair because he had use of his arms. He chose it over an automatic wheelchair to get in regular exercise.
The other was substantially more impaired. He broke his neck in a riding accident later in life. He had been a brilliant surgeon. He used an automated wheelchair. I think he had partial use of one arm and maybe a couple of fingers, which allowed him to navigate a smartphone with that hand. He came in once a week for a few hours to review surgical reports for the company. When ordinary claims processors (like I was) could not figure out if the surgery was covered and their boss with more training couldn't either, we printed off the entire file and hand delivered the paper version to this man on Friday afternoon. I had one claim go to him and hand walked my papers to the meeting.
I also attended an educational talk given by the two of them. This is how I know how they each broke their neck and other details.
Since your father was a consultant, he may be able to return to doing consulting work at some point in the future. The specialized knowledge in his head does not stop being valuable just because of his physical limitations. I am mentioning this because new quadriplegics are often suicidal. They feel that life is simply over. It's not. He was a professor and consultant, like this former surgeon, his knowledge and expertise still has value. Even though the former surgeon could no longer work as a surgeon, his knowledge of surgery was valuable and he had a unique very part time job at a world class company.
Depending on the exact details of your father's limitations, he may also benefit from the use of ordinary things like smart phones with apps. There are also a lot of non-tech assistive devices, like chairs to help them shower and spoons that can be strapped to their hand so they can feed themselves if they have arm movement but limited hand control.
Best.