NDE, cardiac massage and oximetry

#1
Hallo,
this is my first posting here in this forum.
I would like to discuss the results of two studies in relation to the
hypothesis that NDEs are caused by cardiac massage.
In a study from 2014 Parnia et. al measured the regional cerebral oxygen saturation (rSO2)
while performing CPR.
The mean rSO2 of people with return of spontaneous circulation was 43.8 (95% CI 40.1 to 47.6).
While people who could not be resuscitated had a much lower rSO2.
Interestingly there is a study of Borchardt who measured the rSO2 in gravity induced loss of
consciousness. He found that (in trained pilots) the mean rSO2 where G-LOC was induced was
mainly above 50%.
Relevant is the mean baseline reduction.
In G-LOC the mean baseline reduction was 14.91 %.
If we take an older study of Parnia we can say, the baseline value was around 65 %.
I would say that is a good estimation. Then we would have a mean baseline reduction of
appr. 33 %.
This shows clearly that we are far away from a clear conscious state while cardiac massage.

Sources:
Parnia et. al, 2014
Cerebral oximetry levels during CPR are associated with return of spontaneous
circulation following cardiac arrest: an observational study
Borchardt 2003,
Cerebral oxygen saturattion as a predictor of imending gravity induced loss of consciousness (GLOC)
 
#3
This is an argument against Woerlees hypothesis.
Maybe some EEG activity is present while CPR but this activity is -due to the low amount of oxygen in the cortical tissue- not compatible with some form of consciousness, neither dreamlets nor scotomas (experienced while acceleration).
 
#5
Hallo,
this is my first posting here in this forum.
I would like to discuss the results of two studies in relation to the
hypothesis that NDEs are caused by cardiac massage.
In a study from 2014 Parnia et. al measured the regional cerebral oxygen saturation (rSO2)
while performing CPR.
The mean rSO2 of people with return of spontaneous circulation was 43.8 (95% CI 40.1 to 47.6).
While people who could not be resuscitated had a much lower rSO2.
Interestingly there is a study of Borchardt who measured the rSO2 in gravity induced loss of
consciousness. He found that (in trained pilots) the mean rSO2 where G-LOC was induced was
mainly above 50%.
Relevant is the mean baseline reduction.
In G-LOC the mean baseline reduction was 14.91 %.
If we take an older study of Parnia we can say, the baseline value was around 65 %.
I would say that is a good estimation. Then we would have a mean baseline reduction of
appr. 33 %.
This shows clearly that we are far away from a clear conscious state while cardiac massage.

Sources:
Parnia et. al, 2014
Cerebral oximetry levels during CPR are associated with return of spontaneous
circulation following cardiac arrest: an observational study
Borchardt 2003,
Cerebral oxygen saturattion as a predictor of imending gravity induced loss of consciousness (GLOC)
I don't understand why you are comparing blood oxygen levels of two completely different physiological conditions, and trying to draw some incorrect conclusions from them.

G-LOC is caused by blood draining away from the brain under acceleration interactions, and pooling lower in the body... crucially the heart has not stopped pumping... hence we should expect blood oxygen levels to be much higher when unconsciousness occurs due to G-LOC, than when unconsciousness occurs due to cardiac arrest.
 
#6
I don't understand why you are comparing blood oxygen levels of two completely different physiological conditions, and trying to draw some incorrect conclusions from them.

G-LOC is caused by blood draining away from the brain under acceleration interactions, and pooling lower in the body... crucially the heart has not stopped pumping... hence we should expect blood oxygen levels to be much higher when unconsciousness occurs due to G-LOC, than when unconsciousness occurs due to cardiac arrest.
We don't talk about the oxygen levels measured normally with a clamp on the fingers.
We just look at the oxygen levels in the cortical areas of the brain. Unindependent of the cause of the low oxygen supply to the brain, we can expect that the values have to be the same under different conditions.
In G-LOC you have a low oxygen supply to the brain and you loose consciousness, in CPR you receive (often) cardiac massage which leads also to a low oxygen supply to the brain.
When we say that the baseline level is 65 and by a lowering of 15 or 20 percent you are unconscious, because the presynaptic communication fails, than you can not argue that you have lucid conscious activity by a lowering of 33 percent, which normally occurs while CPR.
 
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#8
We don't talk about the oxygen levels measured normally with a clamp on the fingers.
We just look at the oxygen levels in the cortical areas of the brain. Unindependent of the cause of the low oxygen supply to the brain, we can expect that the values have to be the same under different conditions.
In G-LOC you have a low oxygen supply to the brain and you loose consciousness, in CPR you receive (often) cardiac massage which leads also to a low oxygen supply to the brain.
When we say that the baseline level is 65 and by a lowering of 15 or 20 percent you are unconscious, because the presynaptic communication fails, than you can not argue that you have lucid conscious activity by a lowering of 33 percent, which normally occurs while CPR.
Such studies using this equipment produce qualitative, rather than quantitative results. Both studies are looking at completely different physiological situations. You can't compare meaningfully, sorry.
 
#9
Of course they use quantitave results.
If the oxygen saturation is this low in the cortical areas while resuscitation, you can not expect conscious activity.

The oxygen saturation is a quantitave value and tissue always needs enough saturation for working properly .

Especially presynaptic communication does not really work under this conditions, so even some EEg activity while cardiac arrest and even while resuscitation will just result from the firing of a lot of neurons at the same time, which are not synaptically connected.

I think even if Dr. Woerlee does good work here, he fails to consider that even if there is some EEG activity, this activity does not correspond to clear thoughts or perceptions.
 
#10
Of course they use quantitave results.
If the oxygen saturation is this low in the cortical areas while resuscitation, you can not expect conscious activity.

The oxygen saturation is a quantitave value and tissue always needs enough saturation for working properly .

Especially presynaptic communication does not really work under this conditions, so even some EEg activity while cardiac arrest and even while resuscitation will just result from the firing of a lot of neurons at the same time, which are not synaptically connected.

I think even if Dr. Woerlee does good work here, he fails to consider that even if there is some EEG activity, this activity does not correspond to clear thoughts or perceptions.
Nope, they only use qualitative type measurements.

They are useful because if qualitative oxygen levels increase during cardiac massage, you know your doing something right, and if they fall you know you need to do something else.

Similarly with the pilots, if the plane can recognise sudden qualitative falls in oxygen it can be programmed to do something.

Interpreting these studies as producing quantitative measurements which can be meaningfully compared is simply incorrect.
 
#11
I can't really see what you mean.

A normal rSO2 is appr. between 63 and 73 %
This is the baseline value.
If this value falls to a limit value, consciousness is lost. This limit and also the baseline value is a parameter which varies from person to person.
The values measured by Parnia et. al are very low.
Also from other studies we can say, that consciousness should not be possible.
 
#12
I can't really see what you mean.

A normal rSO2 is appr. between 63 and 73 %
This is the baseline value.
If this value falls to a limit value, consciousness is lost. This limit and also the baseline value is a parameter which varies from person to person.
The values measured by Parnia et. al are very low.
Also from other studies we can say, that consciousness should not be possible.
Additionally...
http://www.skeptiko-forum.com/threads/possible-hits-on-target-during-aware.653/#post-14913
http://www.skeptiko-forum.com/threads/possible-hits-on-target-during-aware.653/#post-14913
 
#13
I think Peter's point here is being completely misinterpreted.
The lack of oxygen to the brain was or is one of the loop holes for skeptics. Things like the other studies mentioned have been implicated in the reasoning, However as Peter points out it does not stand up because consciousness should not be possible during cardiac massage by those same standards.

This is an argument against that skeptic loop hole. Correct me if I am wrong.
 
#14
I think Peter's point here is being completely misinterpreted.
The lack of oxygen to the brain was or is one of the loop holes for skeptics. Things like the other studies mentioned have been implicated in the reasoning, However as Peter points out it does not stand up because consciousness should not be possible during cardiac massage by those same standards.

This is an argument against that skeptic loop hole. Correct me if I am wrong.
I don't know what skeptic arguments your referring to.

I'm merely pointing out that you can't use comparisons of the results of these two completely different physiological conditions, which themselves use non invasive qualitative type measurements, that have also been shown to be extremely inaccurate at lower oxygen levels.
 
#15
I don't know what skeptic arguments your referring to.

I'm merely pointing out that you can't use comparisons of the results of these two completely different physiological conditions, which themselves use non invasive qualitative type measurements, that have also been shown to be extremely inaccurate at lower oxygen levels.
But the skeptics do. So by those standards it is refuted according to Peters reasoning. It is not entirely qualitative, a measurement by definition is quantative. Acurracy is another thing, but the range is certainly large enough to make some conclusions.
 
#16
But the skeptics do. So by those standards it is refuted according to Peters reasoning. It is not entirely qualitative, a measurement by definition is quantative. Acurracy is another thing, but the range is certainly large enough to make some conclusions.
You can't use these measurements in the way Peter wants to... period. It's meaningless. If anybody else wants to use them in the same way, it's also meaningless. That's the last I have to say on the matter. It's pointless discussing it further as it's so clear cut.
 
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#17
You can't use these measurements in the way Peter wants to... period. It's meaningless. If anybody else wants to use them in the same way, it's also meaningless. That's the last I have to say on the matter. It's pointless discussing it further as it's so clear cut.
Well I don't think that is clear at all. Meaningless. Since you are not aware of the skeptic argument related to oxygen depletion I think you have missed the point.

There is a direct correlation to the rSO2 levels and loss of consciousness. Period. Which is hardly meaningless. Repeatable and testable. Why should we expect cardiac patients at much lower levels to be consciouss?

It is kind of absurd to me.
 
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#18
Interesting...I didn't know this study.

But I have some remarks on this:

1. In this study they say:
"However, as few values <50% were available for comparison, the assumption that accuracy deteriorates with progressive hypoxia may be inaccurate".

2. This study is quite old. Parnia uses a much modern device. Maybe the results are more accurate.

3. In the study of Borchardt the values when G-LOC sets in were higher than 50%. Sometimes even 60%.
In this range the values should be quite accurate.

So I think, even if the device is not this accurate, we can say that the blood flow while CPR is very low. Too low for conscious activity.

But you are right.
I just didn't know that, so we should wait for further results.
 
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