A 74 year old female is admitted to the hospital with a diagnosis of 'wound infection.' She is non- verbal with a previous history of a stroke that has left her wheelchair bound. Her vital signs are: Temp 101.6 F, heart rate 100, respiratory rate 20, pulse ox 96%. On assessment her left arm is warm to the touch with fluid filled vesicles noted. Some of the vesicles appear to be excoriated. The right arm appears normal. When turning the patient her sacrum is noted to be red but blanches when touched. Her left heel is noted to be very soft, and mushy feeling, with a blood blister that is intact on it. The assessment findings that caused you the most concern lead you to a hypothesis that this patient's primary issue is: