CO2, Blood pH and Respiratory Alkalosis: Causes and Effects
Blood pH is tightly regulated by a system of buffers that continuously maintain it in a normal range of 7.35 to 7.45 (slightly alkaline). Blood pH drop below 7 can lead to a coma and even death due to severe acidosis. This causes depression of the central nervous system. High blood pH (above 7.45) is called alkalosis. Severe alkalosis (when blood pH is more than 8) can also lead to death, as it often happens during last days or hours of life in most people who are chronically and terminally ill.
Hyperventilation is the most common cause of respiratory alkalosis. Note that overbreathing is exceptionally common in people with chronic diseases (for clinical studies, see the Homepage of this site).
The main mechanisms for blood pH maintenance and control
- Carbonic Acid-Bicarbonate Buffer System
- Protein Buffer System
- Phosphate Buffer System
- Elimination of Hydrogen Ions via Kidneys
Carbon dioxide plays one of the central roles in respiratory alkalosis. Note, however, that tissue hypoxia due to critically-low carbon dioxide level in the alveoli is usually the main life-threatening factor in the severely sick. As we discussed before, CO2 is crucial for vasodilation and the Bohr effect.
Respiratory alkalosis caused by low CO2 in the arterial blood
Many people believe that if you eat certain foods, it can cause your blood to become more alkaline or acidic. Medical research studies have clearly shown that breathing and blood carbon dioxide and bicarbonate ions levels are more significant factors in blood-pH control. Alveolar hyperventilation that is common in the sick reduces cell oxygenation, increases resting blood lactate levels, intensifies production of free radicals due to tissue hypoxia (cells are deprived of oxygen), causes diabetic ketoacidosis in the genetically predisposed patients, and suppresses the immune system and main blood-pH buffer systems of the human organism.
Changes in carbon dioxide and breathing cause immediate and long-term effects of blood pH. They are not necessary the same. The immediate effects are simple: higher-CO2 content causes blood acidification and pH decrease, while reduced carbon dioxide levels increase blood pH, often causing death in the critically ill (see a review of medical studies below). Long-term effects depend on the direction of change (moving closer to normal breathing or not), genetic factors, existing pathologies, diet, physical exercise, thermoregulation, and many other parameters.
CO2 gas, when dissolved in blood, is the second largest group of negative ions of blood plasma. Hence, breathing directly affects blood pH. In its turn, blood pH is tightly monitored within a very narrow range (from about 7.3 to 7.5) by the group of nerve cells located in the medulla oblongata in order to have normal-body biochemistry. The same nerve cells control breathing by through several independent mechanisms, including peripheral and central CO2 and O2 chemoreceptors.
Hence, arterial CO2, carbon dioxide, through several independent biochemical mechanisms, can influence blood pH and cause respiratory alkalosis in patients with chronic diseases.
CO2, hypocapnia and viscosity of blood
CO2 also influences viscosity of blood. Acute hyperventilation and arterial hypocapnia makes blood more viscous. This effect is a part of the fight-and-flight response (an immediate reaction to stress). While useful in a short run to prevent blood losses due to bleeding, increased blood viscosity produces a large strain on the heart muscle and causes other negative effects leading to, for example, thrombosis (formation of a blood clot).
Dr. KP Buteyko and over 180 of his medical colleagues also found that CO2 controls and regulates composition and properties of many all other bodily fluids, including secretions of the stomach, composition and properties of saliva and mucus, pH of the urine. For example, for most people, in conditions of hyperventilation, stomach and urinary pH become too low (too acidic), promoting development of gastritis and ulcers, or urinary stones. Apart from respiratory alkalosis, there are many other negative effects of overbreathing.
Reference pages: Breathing norms and the DIY body oxygen test:
- Breathing norms: Parameters, graph, and description of the normal breathing pattern
- Body-oxygen test (CP test) : How to measure your own breathing and body oxygenation (two in one) using a simple DIY test
References: pages about CO2 effect:
- Vasodilation: CO2 expands arteries and arterioles facilitating perfusion (or blood supply) to all vital organs
- The Bohr effect: How and why oxygen is released by red blood cells in body tissues
- Nerve stabilization: Carbon dioxide has powerful calmative and sedative effects on brain neurons and nerve cells
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