Carbon Dioxide And Breathing

When we take a breath of fresh air into our lungs, oxygen passes from the lungs to the blood where it is picked up and carried through the blood vessels by a molecule called haemoglobin. This oxygen-rich blood is then pumped by the heart throughout the body so that oxygen can be offloaded to cells for conversion to energy. In order to release oxygen from the blood, however, haemoglobin requires a catalyst which involves an increase in body temperature, along with the presence of carbon dioxide. Physical exercise is a good example of these conditions: when we move our muscles the body requires more oxygen to give us energy and perform at a higher intensity. During exercise, our body temperature increases and our cells produce carbon dioxide, allowing extra oxygen to be released by the blood to the muscles and organs. However, when carbon dioxide levels are less than adequate, the transfer of oxygen from the blood to the muscles and organs is limited, leading to poor body oxygenation.

This necessary presence of carbon dioxide was discovered in 1904 by the physiologist and Nobel laureate Christian Bohr, who recognised that CO2 affects the release of oxygen from the blood to tissues and organs. According to the Bohr Effect, when there is sufficient pressure of carbon dioxide in the blood and lungs, pH drops and oxygen is released more readily. Conversely, when carbon dioxide levels are low, haemoglobin molecules are less able to release oxygen from the blood. The way we breathe determines the amount of carbon dioxide present in our blood, and therefore how well our bodies are oxygenated.

Another function of carbon dioxide is that it relaxes the smooth muscle embedded in airways, arteries and capillaries, enabling smooth breathing and healthy blood flow. For those genetically predisposed to asthma, the loss of CO2 caused by over-breathing leads to constriction of the airways. By breathing calmly and quietly, you will retain healthy levels of carbon dioxide and your blood vessels and airways will remain open and clear.

Constriction of the airways and blood vessels in response to hyperventilation can reduce the amount oxygen available to the brain by one half. It is no coincidence that symptoms like fatigue, anxiety and poor concentration are so common nowadays – chronic over-breathing/chronic hyperventilation contributes to all these issues, as well as more serious conditions such as high blood pressure and heart disease.

So how do we ensure that we take in enough carbon dioxide? The solution is clearly not to breathe more: We cannot inhale carbon dioxide from the atmosphere; it is a by-product of metabolic chemical reactions which are required to supply the body with energy. While it is true that carbon dioxide can be classed as a waste gas, we only exhale CO2 to get rid of the excess and it is vital that a certain amount of carbon dioxide is retained in the blood for healthy body function.

To understand how the Buteyko method works and why some people develop chronic hyperventilation, you first need to know how our body reacts to levels of carbon dioxide (CO2) in the blood. Central chemoreceptors located in the brain (0.2 mm below the ventrolateral surface of the medulla in the retro trapezoid nucleus (RTN) inside the blood-brain barrier) monitor levels of CO2. They respond to increases in the partial pressure of CO2 by increasing the respiratory rate and depth of our breathing. Thus, CO2 serves as the stimulus for our breathing. Put simply, when CO2 levels rise, we feel a need to breathe more. What is shown, however, is that central chemoreceptors can become hypersensitive to CO2, which results in feeling a need to breathe (air hunger) more often than necessary, thus causing chronic hyperventilation and poor oxygen delivery. It is worth noting there are many studies which show a correlation between stress disorders like anxiety and depression and a hypersensitivity to CO2 (see below).

Carbon dioxide is produced through the body’s metabolism – when oxygen meets with the food we eat to create energy, carbon dioxide is generated. There are only two ways to increase the amount of carbon dioxide in the body:

  1. By practising breathing exercises to gently reduce the amount of air we breathe;
  2. By increasing metabolic activity through physical exercise.

While exercise is beneficial, it is vitally important not to breathe too much during physical activity, otherwise your efforts will be counterproductive. A much more controlled method of increasing the body’s tolerance to carbon dioxide is to simply practise breathing lightly.

By taking less air into the lungs during rest, carbon dioxide is able to accumulate in the blood. After just ten minutes, the part of the brain that regulates breathing volume can be reset to tolerate a greater amount of carbon dioxide. By reducing breathing volume towards normal, blood vessels and airways dilate, and oxygen is more readily released from the red blood cells. Each time you practise reduced breathing exercises and reset your breathing volume, you are one step closer to a permanent change in optimal breathing patterns.





Hyperventilation and Stress Disorder Studies

Role of chemoreceptors in mediating dyspnea:Gordon F. Buchanan , George B. Richerson

 Carbon Dioxide Sensitivity in Panic Anxiety: S W Woods, D S Charney, J Loke,W K Goodman, D E Redmond Jr, G R Heninger

Journal of Anxiety Disorders: Unexpected arousal, anxiety sensitivity, and their interaction on CO2-induced panic

Hypersensitivity to inhalation of carbon dioxide and panic attacks: Giampaolo Perna, Angela Gabriele, Daniela Caldirola, LauraBellodi

 Hyperventilation Challenge Test in Panic Disorder and Depression With Panic Attacks: A E Nardi, A M Valença, I Nascimento, W A Zin