CO2: A Highly effective Device to Reverse the Ravages of Stress

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*That is an article from the Summer season 2022 problem of Contentment Journal. 

 

By Lewis Coleman, MD, FAIS

Introduction

Insanity is uncommon in people – however in teams, events, nations, and ages it’s the rule. Friedrich Nietzsche

Of all of the ignorance and superstition that bedevils human existence, the notion that carbon dioxide is poisonous and harmful is arguably essentially the most outrageous. The extensively ballyhooed notion that carbon dioxide is a “greenhouse fuel” that threatens to soften the polar ice and drown civilization appears foolish contemplating that CO2 is a “hint fuel” that exists in atmospheric concentrations of 0.03% that fluctuates slowly over geologic time. Episodes of “international warming” happen each few hundred years regardless of negligible change in atmospheric CO2 concentrations. For instance, an episode of “international warming” within the early 1400’s enabled a fleet of gigantic Chinese language junks to discover and map the world and doc an ice-free passage across the North Pole that has just lately re-appeared, in order that business transport now enjoys an alternative choice to the Panama Canal. The panic that adopted the Apollo 13 explosion gives maybe essentially the most dramatic up to date instance of the ignorant concern of CO2 that permeates science and society. The supposedly subtle astronaut help workforce assumed that exhaled CO2 may kill the astronauts inside the few days earlier than they returned to earth, and their development of a makeshift CO2 absorption contraption was hailed as a triumph of American ingenuity. However the hazard was imaginary, as a result of weeks would have been required weeks for the CO2 focus to strategy harmful ranges, and the CO2 might have been flushed from the spacecraft utilizing considerable remaining oxygen reserves.1 How did this concern of CO2 come up and grow to be so pervasive?

Each cell within the physique produces CO2 constantly as a by-product of metabolism. The grownup male physique accommodates about 1.8 L/kg—as much as 126 L of carbon dioxide.2 Most of it combines with calcium and collagen to type bone. About 20 Liters exists as free fuel within the lung or is dissolved in physique fluids and tissues, as in comparison with 1 L of oxygen and 1 L of nitrogen.3 If it had been poisonous, we’d all be useless. If it had been narcotic, we’d all be drunk. As an alternative, CO2 is benign, helpful, and important for all times. Oxygen is ineffective with out it, as a result of it allows all parts of oxygen seize from the environment and its transport and supply to cells deep inside the physique. Moreover, it supplies essentially the most potent, sensible, inexpensive, and protected medical remedies but found, and it might assist us reverse the ravages of stress. However CO2 remedies, which had been commonplace 100 years in the past, have been hidden and forgotten in our period of supposedly superior medication, and this ignorance has brought on numerous pointless deaths.4,5 How can sufferers belief docs who’re blind to such elementary information? This essay will assessment the chemistry, pathophysiology, and therapeutic properties of carbon dioxide, and clarify the mechanism of oxygen transport and supply, in hopes of counteracting ignorance.

CO2 Chemistry and Pathophysiology

Carbon dioxide differs from the opposite gases in a number of ways in which clarify the way it facilitates oxygen transport and supply, and the way it mimics basic anesthesia and toxicity:

  1. It’s odorless at regular atmospheric concentrations of 0.03% nevertheless it causes a painful sense of suffocation when it’s inhaled in concentrations above 1%. That is generally mistaken as toxicity, however CO2 is benign and inert, and can’t harm tissues.
  2. It has refrigerant properties. When compressed it releases warmth and converts from fuel to liquid. When launched from a pressurized container it absorbs warmth.
  3. It’s theoretically preferable to business refrigerants as a result of it’s low cost, chemically inert, and devoid of toxicity.
  4. It’s extra readily remoted from the environment by compression and cooling than different atmospheric gases. This explains why it was the primary fuel to be remoted from the environment.
  5. Though it mixes uniformly with different gases within the environment, it has a barely better molecular weight than the opposite gases, so that almost all atmospheric CO2 hovers close to the earth’s floor.
  6. When launched from a pressurized container it kinds a cool, invisible, colorless cloud that’s quickly affected by gravity in order that it pours like water and collects in dependent areas till it absorbs sufficient warmth to combine with surrounding gases.
  7. It inhibits the binding of oxygen to hemoglobin molecules in pink blood cells. Respiration lowers the focus of carbon dioxide within the lungs to five% to optimize the saturation of hemoglobin with oxygen. Greater partial pressures of CO2 in organs and peripheral tissues launch oxygen from blood into organs and tissues.
  8. It immediately stimulates respiratory chemoreceptors to allow respiration.
  9. It counteracts the respiratory melancholy attributable to narcotics.
  10. It accelerates narcotic metabolism and clearance.
  11. It immediately releases nitric oxide from capillaries, and thereby reduces microvascular stream resistance through the mechanism of “nitrergic neurogenic vasodilation.” This will increase cardiac output and accelerates oxygen transport to cells.
  12. Respiration fuel mixtures supplemented with CO2, or absorbing CO2 by means of the pores and skin, can enhance each tissue perfusion and tissue oxygenation, and thereby counteract the results of illness extra successfully than standard medicines.
  13. When combined with atmospheric air in concentrations as much as 10%, CO2 enhances the discharge of oxygen from hemoglobin and improves tissue oxygenation. Greater concentrations of CO2 in atmospheric air disrupt hemoglobin loading with oxygen within the lung and threaten asphyxiation. This mimics basic anesthesia as a result of it disrupts consciousness however is instantly reversed by restoration of oxygen to the mind. This was a standard trick produced by “shills” in circus aspect reveals on the flip of the earlier century.
  14. When combined with oxygen in concentrations of two% to 30%, CO2 enhances tissue and organ oxygenation by optimizing the discharge of oxygen from hemoglobin. CO2 concentrations better than 30% trigger asphyxiation no matter oxygen supplementation.

Within the spring problem of Contentment journal, I discussed the mechanism of oxygen transport and supply, which captures oxygen from the environment and delivers it to cells deep inside the physique. This vital mechanism was understood by the flip of the earlier century, however is inexplicably absent from trendy medical publications. Carbon dioxide allows all elements of this mechanism, and is due to this fact as important to vertebrate life as oxygen. It prompts respiratory chemoreceptors to stimulate respiration, reduces microvascular stream resistance to hurry the transport of oxygenated arterial blood to peripheral tissues, and releases oxygen from pink cells into organs and tissues.

Mobile metabolism constantly releases carbon dioxide. It readily dissolves in physique fluids and tissues, and slowly leaks by means of the pores and skin and equilibrates with the ambient environment. Respiratory chemoreceptors adapt to this equilibrium and search to keep up it. Nearly all oxygen within the physique is sure tightly to hemoglobin in pink cells, and hemoglobin is often 100% saturated with oxygen as blood transits the lung. The oxygen is shortly consumed by cells when it’s launched from hemoglobin into tissues. Due to this fact, there’s little “oxygen reserve” within the physique, and oxygen transport and supply should be steady to keep up mobile oxygenation. If a coronary heart assault, drowning, or airway obstruction disrupts oxygen transport and supply, the accessible oxygen in blood can be consumed inside minutes, adopted by mind cell oxygen hunger and dying.

Inhaling atmospheric air supplemented with small quantities of carbon dioxide beneficially enhances the discharge of oxygen from hemoglobin into tissues, and counteracts the mobile hypoxia attributable to of illness and incapacity. In distinction, CO2 depletion disrupts oxygen transport and supply by lowering cardiac output and tissue perfusion, and by inhibiting the discharge of oxygen from hemoglobin into tissues.

CO2 is a “hint fuel” that constitutes solely 0.03% of atmospheric air at sea degree; most CO2 hovers close to the floor of the earth and is sort of absent at excessive altitudes comparable to the highest of mountains. This explains “mountain illness” and the “dying zone” phenomenon that happens close to the height of Mt. Everest. Individuals respiration CO2 poor air at excessive altitudes undergo mind hypoxia that generally causes unpredictable and catastrophic lack of consciousness, and repeated publicity to such circumstances causes the mind harm. Respiration CO2 is the best therapy.6

In contrast to CO2, oxygen is poisonous. Respiration pure oxygen for greater than 24 hours causes deadly lung irritation, and invitations oxygen fueled fires. Moreover, it doesn’t enhance tissue oxygenation in most circumstances, as a result of hemoglobin is often 100% saturated with oxygen because it transits the lung even with out oxygen supplementation. However, sufferers are routinely flooded with 100% oxygen, and the necessity for carbon dioxide is ignored.

Oxygen Transport and Supply

 

The mechanism of oxygen transport and supply happens in a sequence of steps, as follows:

  1. Carbon dioxide stimulates respiratory chemoreceptors, which prompts respiration.
  2. Respiration replenishes oxygen within the lung, and lowers carbon dioxide concentrations within the lung to five%, which optimizes the loading of oxygen onto the hemoglobin molecules in pink blood cells transiting the lung, inflicting oxygenated arterial blood to show shiny pink.
  3. The center pumps oxygenated arterial blood from the lungs to capillary beds in organs and tissues.
  4. Carbon dioxide releases nitric oxide (NO) from capillary partitions to open the “capillary gate” through the mechanism of “nitrergic neurogenic vasodilation.” This reduces microvascular stream resistance, which will increase cardiac output, and speeds the supply of oxygenated blood to oxygen-starved tissues. For instance, exercising muscle cells enhance their CO2 manufacturing, inflicting localized CO2 elevations that scale back microvascular resistance and velocity supply of oxygenated blood to the lively muscle tissues. CO2 is thus the first regulator of blood stream and distribution.
  5. Elevated CO2 partial pressures launch oxygen from hemoglobin molecules into organs and tissues to fulfill mobile oxygen demand.
  6. Hemoglobin turns blue after releasing its oxygen into tissues.
  7. Oxygen depleted venous blood returns to the lungs to be re-oxygenated.

 

Hyperventilation versus Hypoventilation

Due to the Leake/Waters hoax (defined under), anesthesiologists are historically skilled to make use of mechanical hyperventilation to eradicate the supposedly poisonous and narcotic results of carbon dioxide. Hyperventilation is inherently dangerous and confers no advantages.7 That is counterintuitive, as a result of respiration is clearly important for all times, in order that it appears affordable that extra respiration is best, however such shouldn’t be the case. Hemoglobin is often 100% saturated with oxygen as blood transits the lung, in order that hyperventilation can’t enhance “oxygen reserve” or tissue oxygenation. As an alternative, hyperventilation dangerously depletes CO2 tissue reserves, which disrupts oxygen transport and supply, causes oxygen hunger in organs and tissues, and unpredictably undermines postoperative respiratory drive.8-10 Even temporary voluntary hyperventilation causes cerebral oxygen hunger that manifests as dizziness and disorientation. That is particularly problematic in geriatric sufferers with low metabolic charges who can’t readily replenish depleted CO2 tissue reserves.

The next examples illustrate the risks of hyperventilation:

  1. Shallow Water Blackout Syndrome: Wholesome younger swimmers lose consciousness and drown after voluntarily hyperventilating within the mistaken perception that this can enhance their oxygen reserves and allow them to swim longer below water. As an alternative, the hyperventilation depletes CO2 tissue reserves, which paralyzes respiratory chemoreceptors and dangerously abolishes the urge to breathe. The swimmer thus exhausts the provision of oxygen in blood and suffers painless mind hypoxia that undermines judgment, in order that he loses consciousness and drowns.
  2. The “dying zone” on Mt. Everest: Spontaneous hyperventilation and CO2 depletion attributable to low concentrations of oxygen and carbon dioxide at excessive altitudes causes mountain climbers to unexpectedly faint and fall to their deaths. Greater than 400 Darwin Award winners reside completely on the peak of Mt. Everest.
  3. Guides who routinely expose themselves to the intense circumstances of Mt. Everest usually undergo hypoxic mind harm.
  4. Hyperventilated sufferers unexpectedly go to sleep, cease respiration, and die whereas recovering from uneventful surgical procedure as a result of the hyperventilation depletes CO2 tissue reserves, paralyzes respiratory chemoreceptors, and renders respiratory drive unstable till metabolic exercise replenishes CO2 tissue reserves. In geriatric sufferers, this could generally require a number of hours, as within the mysterious dying of Andy Warhol.8
  5. Hyperventilation throughout surgical procedure depletes carbon dioxide physique reserves and prevents the discharge of oxygen from the hemoglobin molecule.9 This causes dangerous tissue and organ oxygen hunger that manifests as postoperative delirium and dementia, particularly in geriatric sufferers.
  6. New child respiratory arrest after Cesarean part: Hyperventilation depletes the CO2 tissue reserves of the fetus in addition to the mom, and new child infants are extra weak to CO2 depletion than their moms.
  7. Extended postoperative respiratory melancholy after cardiac bypass, as a result of bypass technicians, like anesthesiologists, consider that CO2 is “poisonous waste, like urine” that should be “rid from the physique.”
  8. Extended melancholy of respiratory drive after mechanical hyperventilation throughout surgical procedure.
  9. “Opioid hypersensitivity” for hours after surgical procedure, as a result of narcotics and CO2 depletion synergistically depress respiratory chemoreceptor perform.
  10. Elevated ECMO (extra-corporeal membrane oxygenation) morbidity and mortality.
  11. Exaggerated morbidity and mortality within the presence of Obstructive Sleep Apnea (OSA).
  12. Intra-operative infarction (coronary heart assaults and strokes) attributable to oxygen hunger in coronary heart muscle.
  13. Elevated morbidity and mortality attributable to most cancers, coronary heart illness, and power diseases within the distant aftermath of seemingly profitable surgical procedure attributable to insufficient narcotic analgesia throughout surgical procedure.11
  14. Retrolental fibroplasia attributable to hyperventilation with 100% oxygen in untimely infants, as a result of CO2 depletion prevents the discharge of oxygen into immature retinal cells.

These examples of CO2 pathophysiology are mentioned intimately in my beforehand talked about paper known as “4 Forgotten Giants of Anesthesia Historical past” that may be downloaded from its writer or from my web site, www.stressmechanism.com, together with copies of all my printed papers. They’re additionally defined in my e book “50 Years Misplaced in Medical Advance: The Discovery of Hans Selye’s Stress Mechanism” that’s printed by the AIS through Amazon.com.

The Shortcomings of Pulse Oximetry

Few nurses, docs, and even anesthesiologists admire the difficult traits and misleading shortcomings of pulse oximetry, which is the most typical means to observe oxygen in hospitals and clinics. It doesn’t measure the partial strain of oxygen in tissues, which is the vital measure of mobile oxygenation. As an alternative, it determines blood oxygen saturation utilizing an algorithm that assesses gentle frequencies mirrored from oxygen in blood. Sadly, it can’t distinguish between oxygen sure to hemoglobin and oxygen saturated in plasma, and it may be “fooled” by quite a few circumstances. For instance, it can’t detect hypoventilation when sufferers are respiration 100% oxygen, and it can’t detect mobile oxygen hunger attributable to mechanical hyperventilation that depletes carbon dioxide and disrupts the discharge of oxygen from hemoglobin into tissues. This occurs routinely when sufferers are hyperventilated throughout surgical procedure, based mostly on the false perception that carbon dioxide is a “waste fuel” that should be faraway from the physique.

The Forgotten Therapeutic Advantages of CO2

The approaching apocalypse of WWI impressed medical analysis that clarified the mechanism of oxygen transport and supply. Friedrich Miescher (1844–1895), the Swiss doctor who found DNA, demonstrated that carbon dioxide regulates respiration.12,13 Christian Bohr (1855-1911), a Danish researcher, found that carbon dioxide inhibits the affinity of hemoglobin for oxygen.14 Physicians of that period had been astonished by the therapeutic properties of carbon dioxide.15 Yandell Henderson, a well-known American researcher, demonstrated that CO2 optimizes cardiorespiratory perform and prevents sudden postoperative respiratory arrest.10,16 American nurse-anesthetists embraced carbon dioxide supplementation to discourage ether explosions, optimize cardiorespiratory perform, and stop postoperative bronchial asthma, atelectasis, pneumonia, nausea, and unpredictable respiratory arrest. Their successes impressed widespread utilization of Carbogen, a mix of oxygen and carbon dioxide in pressurized tanks, to deal with medical emergencies together with drowning, smoke inhalation, bronchial asthma, pneumonia, coronary heart assaults, strokes, alcohol inebriation, narcotic overdose, sepsis, infections, and new child infants with respiration issues. Carbogen grew to become normal gear on fireplace vehicles in main cities and saved quite a few lives.7

Carbon Dioxide Therapies

Illness is dangerous stress mechanism hyperactivity that wastes its substrates and produces extreme and faulty variations of its merchandise that harm tissues and disrupt mobile oxygenation. Tissue hypoxia induces irregular fibroblast collagen manufacturing, which causes tissue sclerosis that progressively disrupts tissue and organ perform and undermines longevity. CO2 remedy counteracts mobile hypoxia by opening the capillary gate, inducing angiogenesis (capillary proliferation), and selling oxygen launch from hemoglobin into tissues. Thus, CO2 can palliate illness, promote remedy, and enhance consequence in almost all types of illness. For instance, “facultative anaerobes” trigger most cussed and harmful bacterial infections, together with osteomyelitis, Lyme illness, fuel gangrene, MRSA (methicillin-resistant staphylococcus aureus), and stasis ulcers. These microbes are poisoned by oxygen and thrive in its absence, however can tolerate low oxygen ranges, in order that they thrive in poorly perfused and oxygenated bones, ligaments, and prostate. Carbon dioxide promotes antibiotic penetration by enhancing tissue perfusion, and it promotes antibiotic efficiency by poisoning facultative anaerobes with oxygen.

CO2 remedies could be made much more efficient utilizing trendy medical machines, screens, and medicines. For instance, hyperbaric oxygen therapy could possibly be improved by the addition of carbon dioxide to the inhaled fuel combination. With trendy capnography, sufferers with power diseases might safely sleep in tents with air enriched with carbon dioxide to counteract the signs of their diseases. Carbon dioxide can be safely absorbed by means of the pores and skin to enhance the administration of quite a few medical circumstances.13

The Hoax that Halted Medical Advance

Dr. George Washington Crile based the nurse anesthesia career after WWI, when physicians had been briefly provide.16 Crile was well-known in his personal time and ought to be remembered as the daddy of anesthesia, however his achievements have been relegated to obscurity. He invented cardiopulmonary resuscitation, carried out the primary profitable blood transfusion, proved that narcotics can remedy deadly infections, and that preoperative sedation and narcotic supplementation of basic anesthesia optimizes surgical consequence. The nurses mixed ether anesthesia with Crile’s narcotic ideas and the equally well-known CO2 analysis of Dr. Yandell Henderson.7

Their success impressed widespread use of Carbogen (a synergistic combination of 5% CO2 with 95% oxygen) to deal with bronchial asthma, atelectasis, pneumonia, alcohol inebriation, smoke inhalation, coronary heart assaults, strokes, morphine overdose, and respiration issues in new child infants. It saved numerous lives. Their rising fame brought on consternation amongst physicians, who coveted their follow.17 Drs. Chauncey Leake and Ralph Waters (who famously based the anesthesiology career) conspired to vilify the nurses’ status by concocting specious scientific experiments and fictitious medical accounts that characterised carbon dioxide as “poisonous waste, like urine, that should be rid from the physique” utilizing mechanical hyperventilation throughout surgical procedure.

Seldom have so few civilians brought on a lot hurt to so many. They perpetrated a devastating hoax that has continued to the current and killed numerous sufferers, although it flies within the very face of science.7 The hoax was so efficient that Carbogen and carbon dioxide, that are maybe essentially the most potent and sensible medical remedies but found, had been frightened from medical information and follow. The hoax discourages remedies with helpful narcotics as a result of they’re incompatible with mechanical hyperventilation.18 It has escaped the bounds of anesthesia. It has even been embraced by animal researchers, who illogically use carbon dioxide for each anesthesia and euthanasia with out contemplating its inhumane penalties.19-22 It persists regardless of current analysis that has re-discovered the therapeutic advantages of narcotics and hypercarbia. Its persistence can solely be defined by covert company affect that earnings on the worth of public well being. The proof is reviewed in my e book, “The Nice Medical Hoax of the 20th Century.”17

My query is: why have these scientific and medical triumphs been deserted and forgotten, and the way has this hoax continued within the presence of science? Might it’s that highly effective chemical companies are threatened by the prospect of low cost, non-toxic CO2 changing their worthwhile refrigerants? Might it’s that highly effective medical companies promote hyperventilation that’s incompatible with protected narcotic use so as to promote their poisonous NSAID analgesics and in any other case undermine public well being for the sake of earnings?

Conclusion

Too many sufferers have died on account of the harmful CO2 hoax. What’s thrilling is that carbon dioxide remedy represents however certainly one of a set of straightforward, protected, highly effective, and predictable remedies guided by stress idea that may optimize cardiorespiratory perform, decrease stress mechanism hyperactivity, restore organ perform, remedy illness, and save lives. Moreover, stress idea paves the trail to worthwhile pharmaceutical growth that guarantees to eradicate illness altogether. I’ll discover these prospects in future problems with Contentment Journal.

For these , the next sources illustrate the in depth therapeutic makes use of of carbon dioxide that had been employed within the forgotten previous:

https://site visitors.libsyn.com/safe/stressmechanism2/Foregger-O2-CO2-pages-hz.pdf

https://www.consciousbreathing.com/science/carbon-dioxide-in-medicine-part-i/

References

1              Eisele, J. H., Eger, E. I., 2nd & Muallem, M. Narcotic properties of carbon dioxide within the canine. Anesthesiology 28, 856-865 (1967).

2              Cherniack, N. S. & Longobardo, G. S. Oxygen and carbon dioxide fuel shops of the physique. Physiological critiques 50, 196-243, doi:10.1152/physrev.1970.50.2.196 (1970).

3              Campbell, A. & Poulton, E. P. Oxygen and carbon dioxide remedy.  (Oxford College Press, H. Milford, 1934).

4              Overdyk, F. J. postoperative Opioids Want System-Extensive Overhaul. Anesthesia Affected person Security Basis Publication (2010).

5              Overdyk, F. J. Postoperative opioids stay a severe affected person security risk. Anesthesiology 113, 259-260; creator reply 260-251, doi:10.1097/ALN.0b013e3181e2c1d9

00000542-201007000-00041 [pii] (2010).

6              Harvey, T. C. et al. Impact of carbon dioxide in acute mountain illness: a rediscovery. Lancet 2, 639-641, doi:10.1016/s0140-6736(88)90465-5 (1988).

7              Coleman, L. S. 4 Forgotten Giants of Anesthesia Historical past. Journal of Anesthesia and Surgical procedure 3, 1-17, doi:10.15436/2377-1364.16.468 (2015).

8              Coleman, L. S. in apsf Publication Vol. Winter 2009-2020   (Anesthesia Affected person Security Basis, Administrator, Deanna Walker Anesthesia Affected person Security Basis Constructing One, Suite Two 8007 South Meridian Avenue Indianapolis, IN 46217-2922 e-mail deal with: [email protected] FAX: (317) 888-1482, 2010).

9              Coleman, L. S. A name for requirements on perioperative CO(2) regulation. Can J Anaesth, doi:10.1007/s12630-011-9469-7 (2011).

10            Henderson, Y. Resuscitation with Carbon Dioxide. Science 83, 399-402, doi:10.1126/science.83.2157.399 (1936).

11            Monk, T. G., Saini, V., Weldon, B. C. & Sigl, J. C. Anesthetic administration and one-year mortality after noncardiac surgical procedure. Anesth Analg 100, 4-10 (2005).

12            Dahm, R. Friedrich Miescher and the invention of DNA. Dev Biol 278, 274-288, doi:10.1016/j.ydbio.2004.11.028 (2005).

13            Buess, H. Joh. Friedrich Miescher and the contribution of Basle physicians to the biology of the nineteenth century. Yale J Biol Med 25, 250-261 (1953).

14            Chr. Bohr, Ok. H., and August Krogh. Regarding a Biologically Necessary Relationship -The Affect of the Carbon Dioxide Content material of Blood on its Oxygen Binding. Skand. Arch. Physiol. 16, 401-412 (1904).

15            Rose, A. Carbonic Acid In Drugs/Carbon Dioxide in Drugs.  (Funk & Wagnalls Firm, 1905).

16            Henderson, Y. in Cyclopedia of Drugs    (1940).

17            Coleman, L. S.     170 (American Institute of Stress/Amazon.com, California, 2022).

18            Ainslie, S. G., Eisele, J. H., Jr. & Corkill, G. Fentanyl concentrations in mind and serum throughout respiratory acid–base adjustments within the canine. Anesthesiology 51, 293-297 (1979).

19            Conlee, Ok. M., Stephens, M. L., Rowan, A. N. & King, L. A. Carbon dioxide for euthanasia: considerations concerning ache and misery, with particular reference to mice and rats. Lab Anim 39, 137-161, doi:10.1258/0023677053739747 (2005).

20            Danneman, P. J., Stein, S. & Walshaw, S. O. Humane and sensible implications of utilizing carbon dioxide combined with oxygen for anesthesia or euthanasia of rats. Lab Anim Sci 47, 376-385 (1997).

21            Hawkins, P. et al. A Good Loss of life? Report of the Second Newcastle Assembly on Laboratory Animal Euthanasia. Animals (Basel) 6, doi:10.3390/ani6090050 (2016).

22            Makowska, J., Golledge, H., Marquardt, N. & Weary, D. M. Sedation or inhalant anesthesia earlier than euthanasia with CO2 doesn’t scale back behavioral or physiologic indicators of ache and stress in mice. J Am Assoc Lab Anim Sci 51, 396-397; creator reply 397-399 (2012).