What is happening when just 15 min. prior to death, the patients face flushes a bright crimson from neck up entire face. patient the resumes breathin?

Low oxygen level: These are incredibly difficult moments to observe. As death approaches, the drive to breathe coming from the brain stem becomes weaker. If there are pauses in breath, the natural, physiologic response is for the heart to beat more rapidly/strongly in order to compensate for reduced oxygen in the blood. This temporarily causes increased blood flow and flushing. Resolves when breathing resumes.

?Cheyne-Stokes: Cheyne–Stokes respiration is an abnormal pattern of breathing characterized by progressively deeper and sometimes faster breathing, followed by a gradual decrease that results in a temporary stop in breathing called an apnea. With the lack of Proper and normal oxygen to the body, a flushing or change in color can occur. This is often at the very last, late stages of death.