My 82 Yr Old Father Has Developed A "rash" With

my 82 yr old father has developed a "rash" with all these purple spots. It began about a month ago on the calves of his legs, being extremely itchy. It has moved up his body and now covers his back. It has a sort of a pimple type head that opens and is kind of oozy. He is nearly beside himself with itching. First his dr thought is was folliculitis and prescribed antibiotics. The rash cleared some on his legs but then moved to his back. Then he took prednizone for 6 days which really helped, but of course his dr doesnt want to keep him on that so he is without any thing for that now. The dr took a biopsy about 2 wks ago and are waiting for the results.
My dad has atrial fibrillation and has a pacemaker. He is taking Warfarin and carvedilol. He also has a rare form of sleep apnea where his brain does not stimulate his breathing while sleeping. I think it is called central sleep apnea. He has been waiting for a special kind of machine which makes him breath while he is sleeping. The last few days he has been very tired and says his head feels heavy. Wondering what to do and feeling somewhat frustrated as to where to get help, or whether there is help.
Thanks for your time
Marilyn