The AWARE study of cerebral oxygen
The monitoring and study of cerebral oxygen (rsO2) during cardiac arrest has been a planned aspect of the AWARE study from the outset of it’s conception, and has seen implementation through the completed first phase, and now into a second ongoing phase, it is under further scrutiny.
Dr Sam Parnia asserts this and refers to the monitoring in some detail in his book Erasing Death (The Lazarus Effect).
“To measure the changes in oxygen levels in the brain during cardiac arrest, we obtained a highly sophisticated brain monitoring device, called a cerebral oximeter, that could measure oxygen levels in the brain continuously and record the levels every few seconds during a cardiac arrest and allow us to see if any relationship exists.”
“The results so far have been very promising and have demonstrated that almost all the patients in our study who have suffered with cardiac arrests start out with very low brain oxygen levels.”
“Today, we are also continuing our efforts with respect to the use of cerebral oximetry, both in terms of the relationship that it may have with patient’s experiences and, more important, as a unique way to determine the quality of resuscitation; we hope to identify novel ways to improve oxygen delivery to the brain with a view to ensuring more people survive and have less brain injury.” *
The purpose of studying rsO2 in the first phase appears chiefly to have been investigating the relationship between oxygen levels during a cardiac arrest, and the longer term physiological outcome of the patient.
It may seem obvious that a better maintained bloodflow level is going to be conducive to better patient recovery, but exactly what level as the critical threshold during the resuscitation process has hitherto never been that extensively explored, with just one or two small scale studies in the published domain.
Dr Parnia is keen to set a standard of rsO2 monitoring and targeting as a routine element of the resuscitation process in emergency medicine, with a view as ever to improving the overall success and survival rate.
So what of NDEs?
In the UKCRN outline of the study’s second phase, and indeed in Erasing Death, it is suggested that there may be a similar relationship between better rsO2 levels during cardiac arrest, and the apparent patient recollections of experience during the arrest.
“Maybe patients were able to recall specific memories because physicians had achieved better blood and oxygen delivery to the brain without realising it.” *
Dr Parnia has previously asserted an accepted science that low level oxygen in cardiac arrest means brain functionality is lost, being in an EEG flatline state until the heart is restarted. He may now be reconsidering this assumption. It is worth remembering here that the one ‘verified’ case of interest described in the first study phase results paper discusses apparent recall from well after 30 seconds into the arrest.
“There have been many scientific studies that have examined what happens to the brain immediately after the heart goes into VF (ventricular fibrillation) and stops. These studies have all demonstrated that brain electrical activity stops and the brain itself flatlines” *
By suspecting higher rsO2 levels as a factor in NDEs, Dr Parnia and the team must be suggesting one of a few scenarios:
- In some cases of resuscitation, even though the heart is not pumping, there is enough blood flow and oxygen to cue a minimal level of brain activity, perhaps close to consciousness, that may even be measurable on an EEG, to give rise to experiences stimulated by environmental sensory input.
- There maybe possible activity levels that though allow no consciousness, not even being measurable by EEG, do however allow external stimuli data to be stored and retrieved later in recovery, that then give rise to memories.
- Higher blood flow and oxygen aids a better path of recovery and a quicker resumption of conscious awareness, but the patients’ recalled experiences are confused illusions based on external stimuli in the recovery stage, with a working heart and restored blood flow, rather than from during the actual arrest and resuscitation period.
Either way, it becomes apparent that connecting experiences with a part functioning brain implies that the visual aspect of any such recollection must be illusionary, perhaps as the brain makes sense of external audio stimuli.
So are the AWARE team by suggesting higher rsO2 therefore suggesting some level of functionality during the arrest / resuscitation period?
Is there an implied suggestion then that NDE recalls are in fact from explainable physical brain activity?
“This is a possibility that has to be considered. Although previous research had indicated that, in general, during cardiac arrest, doctors cannot get enough blood into the patient’s brain, there was no way to rule out the possibility that some individuals who had recalled specific experiences had not somehow received better resuscitation. Maybe there were exceptions to the rule.” *
(*all quotes from The Lazarus Effect / Erasing Death by Dr Sam Parnia. Ch10)