Two versions of all scenes of the coma patients in the coma clinic were filmed. One version had them semi-naked whilst the other, for television screenings, had them covered-up.
Producer Martin Erlichman first read the film's source novel when it was in galley form. Erlichman once said that for this movie he wanted to do for hospitals what Jaws (1975) had done to people with the ocean and sharks. He said: "People have a primal fear of the ocean and Jaws titillated that phobia. In a similar manner, Coma (1978) accents one's primal fears of hospitals. This is an even stronger phobia because a person can always refrain from going into the water, but cannot always avoid the necessity of going into hospital!"
In an interview with 'Millimeter' magazine, this film's director Michael Crichton said, "This is a story that contains many elements of reality: the fear people have of surgery, the fear of dying at the hands of your doctor, phobias about hospitals. Those are very real fears, and so to exaggerate them would not be much fun. My idea was to put the picture together in such a way that the fears are put in a safe perspective, and can be enjoyed as scares, without awakening deeper and more real anxieties."
Director Michael Crichton attended medical school while author Robin Cook is a doctor (surgeon and ophthalmologist).