Is Carbon Dioxide (CO2) Really a Waste Gas? – How Does Breathing Affect pH Levels?
CO2 from cellular respiration is not just a waste product for at least 5 reasons:
1: Only about 15% of the CO2 generated from cellular respiration is expelled when one is at rest and breathing normally. CO2 plays a critical role throughout the body. When not in adequate supply, internal chemistry goes awry and “lights start to flicker” in the body. The variety of symptoms that can show up (see figure 1) are a function of genes and other epigenetic variables going on in one’s life. Unfortunately, very few clinicians or practitioners realize that these symptoms are triggered, exacerbated or caused by internal chemical imbalances associated with dysfunctional breathing.
CO2 plays a critical role in keeping pH levels balanced in the body. Nearly all the biochemical reactions in the body are affected by the pH level of the fluids around them. This is not the pH of the GI tract which varies immensely to break down and digest foods. It is also the pH of the cerebral spinal fluid, blood plasma, interstitial fluids, and the lymph system. These fluids must stay within a range of 7.34 to 7.45 for one to survive. The body has several safeguards, called buffer systems, to ensure that pH remains in this range. Our biggest buffer for pH is bicarbonates [HCO3‾] which is regulated by the kidneys. To understand why there is a need to get a little technical and into the science:
A key to understanding pH in the body and internal respiration is the Henderson-Hasselbalch (H-H) equation. It describes pH regulation in extracellular fluids as pH = [HCO3‾] ÷ PCO2 (in its simplified conceptual format where PCO2 represents the partial pressure of CO2 in the fluid), wherein PCO2 is regulated by breathing, and bicarbonate concentration [HCO3‾] is regulated by the kidneys. Changes in the numerator of the equation, which is bicarbonate concentration, are generally slow (8 hours to 5 days), whereas changes in the denominator, which is partial pressure carbon dioxide (PCO2), are immediate since it is a function of breathing. This places CO2 and breathing centre stage in the moment to moment acid-base regulation (Litchfield 2011) in the body. pH balance is thus a function of both physiology, ([HCO3‾]) in the numerator, and breathing behaviour (CO2 is a direct function of breathing) in the denominator.
Side note: Upon eating a high caloric or acidifying meal or upon vigorous exercise, the pH of the blood becomes more acidic. Metabolic acid and lactic acid levels increase respectively. Breathing picks up a notch to compensate for the extra acidity – Additional breathing decreases PaCO2 and since it is in the denominator of the HH equation there is an increase in alkalinity — meaning pH goes up. So, the additional breathing which affects pH minute by minute compensates for the acidic change by driving the pH back up to the norm – or “survival levels”.
So, what happens if our breathing is dysfunctional? What if we over-breathe on a regular basis and the pH levels of our interstitial fluids are pushed closer to “out of range” more regularly?
Let’s just say that things can get pretty ugly; see figure 1.1 below summarizes conditions within the body that dysfunctional breathing can cause, trigger or exacerbate. Breathing’s effect on health and performance is profound.
2nd Reason CO2 is not just a waste gas: In the healthy breather, it is not the lack of oxygen (O2) that causes the reflex to breathe, but rather it is the build-up of CO2 that sends signals to the brain that it’s time to inhale. Hyperventilating before holding the breath does allow for longer breath-holds since CO2 is blown off and takes longer to build up to alarm levels. Given this fact, do not hyperventilate before breath-holding underwater as it increases the chance of passing out before the “I need to breathe NOW!” trigger gets activated. Many deaths have occurred because of this little-known fact. Wim Hoff’s fire-breathing exercise is not intended to be done before his cold-water swims or at least not before a cold-water dive.
3rd Reason CO2 is not just a waste gas: CO2 helps Nitric Oxide (NO) do its job as a vasodilator. As CO2 builds, more NO is released into the blood which serves to dilate blood vessels and capillaries. This enhances blood flow to muscles, organs and tissues in need, especially the heart, muscles, brains and sex organs too when the time is right! CO2 itself is a dilator and hence its build-up relaxes smooth muscles in the airways and bronchial tract. This is especially helpful for asthmatics.
4th Reason CO2 is not just a waste gas: This one is crucially important. Haemoglobin won’t release O2 molecules to the tissues, organs and muscles that need it when CO2 levels are too low (a condition known as hypocapnia). This is called the Bohr effect. Turns out a 1mm drop in the partial pressure of CO2 (PaCO2) in the airways corresponds to a 2% drop in blood flow to the brain. In my practice, we consistently come across individuals (over 40%) who have CO2 levels 10mmHG below that required for adequate internal chemistry. This means that their brain is only getting 80% of its normal blood flow. The fallout is likely a prefrontal cortex and executive functioning that is not fully online.
5th Reason CO2 is not just a waste gas: Without enough CO2 the kidneys don’t generate enough new bicarbonates to replace those lost in the urine caused by buffering acids (e.g., phosphoric acid) generated by protein breakdown. The resulting bicarbonate and sodium deficiencies may include some of the same effects as those identified with chronic stress, e.g., fatigue. Other effects include elevated platelet levels and the propensity of blood to clump. Antioxidant depletion also can occur as a result of excitotoxin production (e.g. glutamate) and systemic inflammation.
Click for next FAQ: What is Hypocapnia?