CO2 Deficiency: the Main Physiological Effect of Hyperventilation

- Updated on December 9, 2021

CO2 Deficiency: the Main Physiological Effect of Hyperventilation 1By Dr. Artour Rakhimov, Alternative Health Educator and Author

Let us look at some of the known carbon dioxide effects, which are confirmed by professional Western studies. Note that these effects can be found, in varying degrees, in any normal human organism.

Stabilizer of transmission of signals between nervous cells

Hyperventilation in people

The normal work of our senses, conscious thinking, decision making, and all other mental activities require the stable transmission of electrical signals between nerve cells. Such transmission is possible when CO2 content in nerve tissues is normal. Logic, sense, reason, wisdom, focus, memory, concentration, and many other qualities are based on this stability of the signal transmission.

The signal is passed from one nerve cell to another only when the strength or voltage of the signal is higher than a certain threshold value so that accidental signals will not be amplified causing disruption in the work of the CNS. This threshold value is very sensitive to the local CO2 content.

When we hyperventilate and CO2 content is suboptimal, accidental weak signals can be amplified and transmitted further interfering with the real signals based on senses, memory, logic, and other objective factors. Hence, CO2 has a calming effect on the excessive excitability of brain areas responsible for conscious thinking (e.g., Krnjevic, 1965). Other researchers (Balestrino & Somjen, 1988; Huttunen et al, 1999) also concluded that increased CO2 pressure generally reduces cortical excitability, while hyperventilation “leads to spontaneous and asynchronous firing of cortical neurons” (Huttunen et. al., 1999).

Hence, breathing too much makes the human brain abnormally excited due to reduced CO2 concentrations. As a result, the brain gets literally out of control due to the appearance of spontaneous and asynchronous (“self-generated”) thoughts. Balestrino and Somjen (1988) in their summary directly claimed that “The brain, by regulating breathing, controls its own excitability“.

These effects of CO2 on brain cells are of special importance in understanding anxiety, insomnia, panic attacks, epilepsy and other psychological and neurological problems and disorders to be discussed later. Besides, this effect is important to understand the mechanism of the mind-body connection.

Bohr effect (or supply of oxygen to all body cells)

CO2 is a catalyst for the chemical release of O2 from hemoglobin cells. This phenomenon is called the Bohr effect and it can be found in many medical textbooks (e.g., Ganong, 1995, Starling & Evans, 1968). Bohr and his colleagues (1904) first described this effect. How does it work?

In normal conditions (when we breathe about 6 l/min), arterial blood is 96-98% saturated with O2 due to a fresh air supply to the lungs. When the arterial blood arrives at the tissues, some O2 is released by its carriers, the hemoglobin cells (red blood cells). What is the reason for this chemical release? The cells of the organism also breathe, and the more they breathe the more CO2 is produced. These elevated values of CO2 in tissues increase the CO2 level in the blood due to CO2 diffusion from the tissues. As a result, the greater the amount of CO2 in the blood, the more O2 is going to be released from the hemoglobin cells for the tissues to use, since CO2 is a catalyst causing this chemical reaction.

This mechanism is especially effective during physical exercise. Indeed, depending on the type of exercise, some of our muscles work harder than others. Those muscles that produce more CO2, are going to get more O2 in exchange (due to the Bohr effect), so they can continue to work at high rates. Were this mechanism to be absent, a human organism would quickly tire at the slightest physical exertion due to lack of oxygen.

Therefore, carbon dioxide is a necessary factor for the oxygenation of tissues. No carbon dioxide means no oxygen in the tissues, while no oxygen means no energy for various processes and no life. Let us look at the events when people over-breathe. On the one hand, breathing more can raise blood saturation from normal 96-98% to 97-99% (by about 1%). However, it follows from the Bohr effect that those who chronically breathe too much (in comparison with physiological norms) suffer from hypoxia (low oxygen concentrations) in tissues due to the low carbon dioxide level in the blood and tissues. (Low tissue oxygenation is normally found in malignant cells, diseased nervous cells, and inflamed tissues of various organs). Meanwhile, normal breathing (about 6 l/min) provides more O2 for the tissues of the organism.

CO2 Deficiency: the Main Physiological Effect of Hyperventilation 2Hence, the paradox of breathing is in the fact that acute over-breathing, while bringing more oxygen during the first seconds, creates the opposite effect: in a few minutes (or even earlier). The cells start to suffer from the lack of oxygen. Therefore, chronic deep breathing causes chronic tissue hypoxia.

Prolonged forceful over-breathing can have disastrous consequences, as Yale Professor Yandell Henderson and his colleagues demonstrated in their work with dogs almost a century ago (Henderson et al, 1908). In these experiments, forceful respiration was created using a suction and exhaust pump. The dogs after many minutes were disconnected from the machine and died without attempting to draw a single breath due to failure of the cardiovascular system. This result was completely unexpected by the researchers. Later, it became clear that hypoxia was one of the factors contributing to these deaths. However, there was also another factor: constriction of small blood vessels due to low carbon dioxide level.

Local vasodilation

CO2 locally dilates arteries and arterioles making the work of the heart easier, creating conditions for delivering more oxygen to tissues and removing more waste products.

Vice versa: low carbon dioxide stores have a local vasoconstrictive effect leading to spasms, hypoxia (this time due to poor blood supply), and accumulation of metabolic wastes in different vital organs and tissues. One may argue that there are many other blood vessels that also contribute to total resistance to blood flow. Why should we concentrate on CO2 effects on arteries and small blood vessels? Basic physiology of the human organism explains, that the total relative resistance to blood flow in arteries and arterioles is about 3-8 times greater than in any other type of blood vessel (Ganong, 1995).

The effect of vasoconstriction due to hyperventilation is so powerful, that Soley and Shock (1938) reported their difficulty in obtaining blood samples from fingers of their patients following voluntary hyperventilation. It is more difficult for the heart to pump blood through the body when small blood vessels, due to low carbon dioxide, are constricted. Moreover, the heart muscle itself receives less blood if the person is over-breathing.

Therefore, low CO2 level in the organism produces a profound adverse impact on the cardiovascular system and blood supply to the heart and other organs.

What about the human brain? Does it suffer from heavy breathing? The following results were obtained by measuring blood flow through the main artery (the carotid artery) leading to the brain. Voluntary hyperventilation led to a 35% reduction in the blood flow to the brain in comparison with the conditions at rest. This result is quoted in the medical textbook written by Starling & Evans (1968), while the effect is well documented and has been confirmed by dozens of professional experiments.

By the way, do you notice that when people passionately argue with each other or are angry, or violent, they usually breathe heavily? Would it be reasonable, in the light of these physiological studies, to conclude that it is useless to argue or try to reason with the person whose brain is not normally oxygenated due to excessive breathing?

There are numerous studies that indeed do reveal the negative effects of over-breathing on different skills (motor, memory, logic) and general performance, which require combinations of various human abilities. Hence, a low carbon dioxide level not only reduces the oxygenation of tissues but also impairs blood supply to vital organs of physiological functioning.

Relaxation of smooth muscles

CO2, when applied locally, is a relaxant of smooth muscles (e.g., Hudlicka, 1973). Dr. Brown in his article “Physiological effects of hyperventilation” analyzed almost 300 professional studies and stated, “Studies designed to determine the effects produced by hyperventilation on nerve and muscle have been consistent in their finding on increased irritability” (Brown, 1953).

This fact, together with the properties of CO2 mentioned previously, will help us to understand the mechanism by which normal carbon dioxide concentrations can restore the harmonious work of different muscular groups (such as the heart, respiratory muscles, muscles of the digestive tract, etc.) to eliminate muscular spasms (e.g., heart attacks, asthma attacks, constipation, etc.). Moreover, since muscles get irritated it is normal to expect that when people breathe too much, they are more likely to be tense, anxious, stressed, aggressive, and violent. Vice versa, normal carbon dioxide concentrations would result in muscular relaxation, composure, and sensible actions.


Normal level aCO2 eliminates possible constriction of bronchi and bronchioles which can appear due to low aCO2. The article “The mechanism of bronchoconstriction due to hypocapnia [low CO2 concentrations] in man” (Sterling, 1968) described the following effect of CO2 on air passages. Bronchoconstriction (narrowing of air passages), which is the main problem of asthmatics, is mainly mediated by special nerve cells. Low aCO2 makes them, among many other nervous tissues, more excited, causing narrowing of bronchi and bronchioles.

Therefore, over-breathing can cause bronchoconstriction (as it is observed in asthma) leading to the feeling of suffocation.

Blood pH balance

CO2 is the most important factor in controlling blood pH, the balance of electrolytes, and the pH of other body fluids (urine, saliva, stomach secretions, etc). Indeed, bicarbonate is the largest CO2 component of the blood, as well as intracellular and extra-cellular fluids, while a typical medical or physiological textbook will indicate its leading role in the control of pH of the blood and other body fluids (e.g., medical textbooks by Starling & Evans, 1968; Guyton, 1984; and Ganong, 1995). Hence, changes in bicarbonate concentration must influence the ionic composition of every human cell.

As one of the numerous effects in this area, Carryer (1947) found that “While no significant change in total calcium of the blood takes place, the readily available, or ionized portion is affected markedly [due to hyperventilation]… The decrease in available calcium increases excitability of the neuromuscular mechanism, inducing tetany”.

These medical conclusions point out the cause of problems (low carbon dioxide due to hyperventilation) with calcium metabolism, which is found in osteoporosis, arthritis, and other health conditions.

Participation and catalisation of chemical reactions

CO2 is a participant of numerous other biochemical reactions involving virtually all vitamins, minerals, amino acids, hormones, carbohydrates, and other vital substances. Some of the chemical reactions, all requiring CO2 as a catalyst or as one of the reagents, were described by Kazarinov (1990).

Apart from these known effects, there are probably many other processes of the human organism that require normal CO2 levels and normal breathing for optimal physiological functioning.

The first respiratory physiologists were called “cardio-respiratory physiologists” since the link between the cardiovascular and respiratory systems, as they found it, was very intimate. Professor Yandell Henderson was one of the most prominent scientists in this area. His article “Carbon dioxide” was published in 1940 in Cyclopedia of Medicine. In the section with the title “Relations of Carbon Dioxide and Oxygen in the Body” he wrote, “Carbon dioxide is, in fact, a more fundamental component of living matter than is oxygen. Life probably existed on earth for millions of years prior to the carboniferous era, in an atmosphere containing a much larger amount of carbon dioxide than at present. There may even have been a time when there was no free oxygen available in the air…

Another natural, but very obstructive misconception is that oxygen and carbon dioxide are so far antagonistic that in blood a gain of one necessarily involves a corresponding loss of the other. On the contrary, although each tends to raise the pressure and thus promote the diffusion of the other, the 2 gases are held and transported in the blood by different means…

A sample of blood may be high in both gases, or low in both gases. Moreover, under clinical conditions low oxygen and low carbon dioxide—anoxemia and acapnia—generally occur together. Each of these abnormal states tends to induce and intensify the other. Therapeutic increase of carbon dioxide, by inhalation of this gas diluted in air, is often the effective means of improving the oxygenation of the blood and tissues.

In the section “As a factor in the Acid-base Balance of the Blood”, he continued,

Modern physiology has shown that, in addition to the control and regulation exerted by the nervous system, there are many chemical substances produced in the body that influence function and form. To these active principles, Starling gave the name of “hormones.” Among the hormones are epinephrine (often called adrenaline), pituitrin, thyroxin, insulin and many other products of the glands of internal secretion and other organs. Carbon dioxide is the chief hormone of the entire body; it is the only one that is produced by every tissue and that probably acts on every organ. In the regulation of the functions of the body, carbon dioxide exerts at least 3 well-defined influences: (1) It is one of the prime factors in the acid-base balance of the blood. (2) It is the principal control of respiration. (3) It exerts an essential tonic influence upon the heart and peripheral circulation.

Finally, he stated in the section “In the Control of Respiration and the Circulation”, “Carbon dioxide is the chief immediate respiratory hormone.”

Extract from Dr. Artour Rakhimov's Amazon book "Normal Breathing: The Key to Vital Health", also available in PDF.