How the Fick Equation explains
Consciousness during Cardiac Arrest

©G.M. Woerlee, 2005–2023

Some of the books published by physicians denying the possibility of consciousness returning during cardiac massage applied during cardiac arrest, as well as the role of brain oxygen starvation in de genesis of NDEs during cardiac arrest are:

During 2010, Pim van Lommel (cardiologist) in the book “Consciousness Beyond Life”, on pages 114-116, and Chapter 8	In 2008, Pim van Lommel (cardioloog) in het boek “Eindeloos Bewustzijn”, op paginas 109-111, en in Hoofdstuk 8
During 1976, Raymond Moody (psychiatrist) in the book “Life after Life”, pages 162-163	In 2009, Bruce Greyson (psychiatrist) in Chapter 10 in the book “Handbook of Near Death Experiences”
During 1982, Michael Sabom (cardiologist) in the book “Recollections of Death”, on pages 240-244	During 1996, Peter Fenwick (neurologist) in the book “The Truth in the Light”, on pages 306-311
During 2010, Jeffrey Long (radiation oncologist) in the book “Evidence of the Afterlife”, on pages 56-57, 65-66	In 2013, Sam Parnia (internist) in the book “Erasing Death”, on pages 66-72, and Chapter 7

What is cardiac massage?

A person who develops a cardiac arrest will die unless cardiopulmonary resuscitation is commenced. Cardiopulmonary resuscitation is not a passive affair where physicians and nurses stand back, arms crossed, while calmly observing a person with a cardiac arrest gradually fade away, calmly waiting for that person to spontaneously revive without any activity on their part, except perhaps for interested observation on the part of the observing physicians and nurses. In clinical practice there are three different methods of applying cardiac massage.

External cardiac compression / massage. This is the most commonly applied technique. A person forcefully compresses the sternum 60-80 times per minute.
Mechanical external cardiac compression / massage. Here a machine performs the work of compressing the sternum. This is a more effective form of cardiac massage, generating a greater flow of blood and blood pressure than external manual cardiac massage.
Internal cardiac massage. The chest is opened, and the operator regularly squeezes the heart, so generating a flow of blood around the body. This is the most dramatic, but also the most effective form of cardiac massage, generating the greatest flow of blood and blood pressure.

The most commonly applied method is manual external cardiac massage. Indeed, physicians and nurses in modern Western European hospitals have a very standard reaction pattern when confronted with a person with a manifest cardiac arrest. They sound an alarm summoning a special resuscitation team, while at the same time hurling themselves upon the dying person like a pack of wild dogs. They lie the person flat on their back, place a hard plank under the chest, perform artificial respiration, insert an intravenous line through which medicines necessary to treat the cause of the cardiac arrest can be administered, and perform external cardiac massage.

External cardiac massage consists of vigorous and forceful compression and release of the chest 60-120 times per minute. The heart is a bag made of muscle tissue in which there are four one-way valves. Compression of the chest forces blood out of the heart and the chest, and because of the one-way valves in the heart, this emerges out of the heart into the arteries conducting it into the various organs and tissues of the body. Releasing the chest causes the chest to rebound to its original form, creating a negative pressure within the chest and heart, sucking blood into the chest and the heart. This cycle is repeated 60-120 times per minute, generating a pumping action, circulating blood around the body when the heart no longer does this during cardiac arrest. Circulation of blood generated by cardiac massage provides a flow of blood to the brain and other vital organs, keeping these organs alive until a normal heart rhythm is restored, and the heart pumps blood normally again. Cardiac massage is always applied during cardiac arrest. Failure to do so means no blood is pumped around the body of the person with a cardiac arrest, and that person will die. This means that people undergoing cardiac massage for cardiac arrest do have a flow of blood flowing through their brains.

So how much pumping action does cardiac massage generate? In other words, how many liters per minutes does the heart pump as a result of cardiac massage, and how much blood pressure is generated by cardiac massage? (see extensive list of references to human reasearch data in Chapter 12 of Illusory Souls).

cardiac output during cardiac arrest and near death experiences

Studies of the effects of external cardiac massage applied to people with cardiac arrest reveal that external cardiac massage not only generates a flow of blood through the body, but also generates mean arterial blood pressures greater than 40 mmHg in 15% of people undergoing cardiac massage (see extensive list of references to human reasearch data in Chapter 12 of Illusory Souls).

blood pressure during cardiac arrest and near death experiences

Chance of consciousness during cardiac massage

Studies of the distributions of blood pressure and cardiac output during cardiac massage provide essential information about whether people may, or may not be conscious during cardiac massage. These data do not tell us whether people may be conscious, instead it is first necessary to know the lowest blood pressure and lowest cardiac output capable of sustaining consciousness. The first step is to know the minimum blood flow through the brain required to sustain some form of consciousness. This can be answered with a few known facts derived from measurements of blood pressure and cardiac outputs measured during external cardiac massage.

Extensive human research reveals that adult humans can be conscious at cardiac index levels above 1.5 l/min/m², meaning cardiac output levels above 2 liters/minute, and at mean arterial blood pressure levels above 40 mmHg (see extensive list of references to human research data in Chapter 12 of Illusory Souls).
About 15% of humans undergoing external cardiac massage have a blood pressure above 40 mmHg.
Somewhat more than 45% of humans undergoing external cardiac massage have a cardiac index greater than 2 liters/minute.
This means that about 0.45 x 0.15 = 0.0675 = 6.75% of people undergoing cardiac massage for cardiac arrest have a flow of blood and blood pressure in their bodies sufficient to sustain consciousness, but does not mean that 6.75% will be conscious.

Indeed, while this explains how significant numbers of people may be conscious during external cardiac massage, it tells us nothing of the exact percentage of people experiencing consciousness during cardiac massage. After all, many people suffer severe brain damage and die, despite efficient heart massage. Nonetheless, these data do reveal that significant people may be conscious during cardiac massage, as was conclusively demonstrated in the Pim van Lommel study (2001), and the recent AWARE study of Sam Parnia (2014) (see extensive discussion, references, and data by clicking HERE).

Fick Equation and consciousness during cardiac massage

Pim van Lommel, and Sam Parnia, along with many others reject the the possibility of consciousness, or the return of consciousness during cardiac massage, as well as the mental effects of brain oxygen starvation (brain hyoxia) as an explanation for the mental experiences reported by survivors of cardiac arrest. In support of this, many people cite a patient reported by the Atlanta cardiologist, Michael Sabom during 1982. He reported the account of a patient who observed his doctors drawing blood from an artery during an out-of-body experience he underwent while undergoing resuscitation for cardiac arrest.

In this regard, I found one man in my study who actually had his blood oxygen and carbon dioxide levels measured at the time of his NDE and cardiac arrest (see page 145). While physically unconscious during this autoscopic NDE, he clearly &lasquo;observed’ a doctor inserting a needle into his groin to obtain blood from his femoral artery for a blood gas analysis. The results from the laboratory later indicated that his arterial oxygen level was well above normal (this is frequently the case when high concentrations of oxygen are administered to a patient during cardiopulmonary resuscitation) and his arterial carbon dioxide level was actually lower than normal (actual values were: p0₂ = 138, pCO₂ = 28, pH = 7.46). The fact that he had ‘visually’ observed this blood gas procedure indicates that the blood was obtained at the time his experience was occurring. Thus, in this one documented case, neither a low oxygen level (hypoxia) nor a high carbon dioxide level (hypercarbia) was present to explain the NDE! (Page 244, in Chapter 10, of Recollections of Death by M.Sabom 1982)

It is quite evident that Dr Sabom forgot some basic physiology when making this statement. The explanation for the possibility of consciousness during cardiac arrest was provided by the German physiologist, Adolf Eugen Fick (1829-1901) more than 140 years ago during 1870, in the well-known and standard “Fick Equation”. This equation is still a “golden standard” for calculating cardiac output, and goes as follows.

CO = VO₂ ÷ (0.134 × [Hb] × (S_aO₂ − S_vO₂))

Sabom did not measure the venous oxygen content at the same time as he measured the arterial blood gas concentrations. This was not normal practice during 1982, nor is it standard practice even now during 2014. Even so the Fick equation, and the measurements of Sabom when combined with known facts, reveal that the physiology of cardiac massage and blood flow, as well as the effects of brain oxygen starvation, explain how this man was able to be conscious. Indeed the effects of hypoxia were likely to hav been the cause of his near-death experience. This is demonstrated by the following calculations. But first, what do we know, and what can we reasonably assume from the data provided by Sabom during 1982?

Sabom cites a blood pH = 7.46, and a pO2 = 138 mmHg. This is from an arterial blood sample. At a pH = 7.46 and a pO₂ = 138 mmHg, the arterial saturation of blood with oxygen (S_aO₂) is maximal for a sea-level atmospheric pressure = 98%
The man was conscious. This means the the blood in his brain capillaries contained sufficient oxygen to support brain nervous activity and consciousness. Measurements of venous blood exiting the capillaries of the brain in HUMANS reveal that people develop brain oxygen starvation when the oxygen saturation of blood in the veins draining the brain capillaries drops below 20 mmHg (Meyer 1965, Schell 2000), which is a (S_vO₂) = 35-40% (see references to HUMAN research data in Chapter 12 of Illusory Souls).
Average hemoglobin level [Hb] of a healthy adult male = 14.5 gm/100 ml
Basal oxygen consumption (VO₂) of a conscious healthy adult male = 200 to 250 ml/min

Substituting these values into the Fick Equation to calculate the Cardiac Output for a basal oxygen consumption (VO₂) = 250 ml/min yields the following calculation and result:

For a VO₂ = 250 ml/min, the required Cardiac Output = CO = 250 ÷ (0.134 x 14.5 x (98 - 40)) = 2.22 liters/minute. This is a cardiac output well within the range of what is generated by efficient cardiac massage. Accordingly, this equation shows that efficient cardiac massage is well able to provide sufficient flow of blood and oxygen to the brain to support consciousness.

But this is a calculation for a healthy person with a low cardiac output, but a normal oxygen consumption. A person undergoing cardiac massage for cardiac arrest generally does not look well. Theiur skin is cold, with a pale and greyish hue, because very little oxygen is transported to the skin. This is also true of many other organs, because the body generally reduces circulation to non-essential organs during cardiac arrest. At the same time, reduction of blood flow to non-essential organs means that these organs consume less than normal amounts of oxygen, so reducing the total oxygen consumption of the body. So it is worth repeating the above calculation for oxygen an oxygen consumption (VO₂) = 100 ml/minute.

Substituting a VO₂ = 100 ml/min, into the Fick Equation, we get the required Cardiac Output = CO = 100 ÷ (0.134 x 14.5 x (98 - 40)) = 0.89 liters/minute. Once again, a cardiac output easily within the range of what is possible during cardiac massage.

These are all cardiac output levels achieved during external cardiac massage in significant numbers of persons undergoing cardiac massage, as well as blood pressure levels achieved in more than 15% of persons (see data and graphs above)—facts explaining why significant numbers of cardiac arrest patients may experience return of some degree of consciousness while undergoing cardiac massage! The residual effects of the brain hypoxia the man cited by Michael Sabom undoubtedly suffered, reveal that brain hypoxia, together with efficient cardiac massage, explains this man’s near-death experience very well. In other words, the standard Fick Equation explains restoration of consciousness during cardiac massage as reported by Michael Sabom during 1982, and the NDE he reported as being due to the well-known effects of hypoxia. Sabom evidently had forgotten all about the Fick Equation when making his statement, as did Pim van Lommel in 2001, Sam Parnia in 2014, and all other writers claiming that brain hypoxia cannot explain near-death experiences undergone during cardiac massage.

Conclusions

I find it difficult to understand how physicians such as Sam Parnia (2014), Pim van Lommel (2001), Bruce Greyson (2003,2006), and others writing popular books on NDE's, totally ignore the truly fundamental physiology explained by the venerable 140 year-old "Fick equation", as well as a considerable body of research data from extensive human research on the subject of cardiac outputs and blood pressures generated by cardiac massage published since the 1960's. The fact they ignore, or are unaware of this research is clearly evident in the scientific studies they cite as proof that cardiac massage cannot provide sufficient flow of blood to the brain to support consciousness (for example in the references provided by Pim van Lommel 2011, and references 22 to 25 in Parnia 2014). It almost seems that many persons prefer a paranormal explanation to a perfectly adequate physiological explanation, by stating that the phenomenon of consciousness during cardiac massage cannot be explained. But the fact that some people cannot explain something, does not mean that the explanation is paranormal. This latter concept was once expressed in a pithy statement written by a journalist, Gard Simons, in a national Dutch newspaper called “De Volkskrant”.