Oxygen Absorption in the Body - Extraction of Oxygen from Air
How efficient are our lungs in oxygen extraction?
Oxygen absorption in the body depends on minute ventilation and metabolic rate (oxygen demands). Normal minute ventilation at rest for a 70-kg healthy man, as we discussed above, is 6 L/min. Dr. Buteyko's norm is 4 L/min.
Normal gas exchange parameters
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Composition of outer or inhaled air: |
Composition of the expired air: |
From Summary of values useful in pulmonary physiology: man. Section: Respiration and Circulation, ed. by P.L. Altman & D.S. Dittmer, 1971, Bethesda, Maryland (Federation of American Societies for Experimental Biology).
Oxygen absorption rate in sick people and most modern people is much less than normal, because they breathe much more than the medical norm. Indeed, if they require and extract about the same amount of oxygen as healthy people, modern and sick people extract much less oxygen from air. Extraction of oxygen from air (as well as cell and body oxygenation) is higher in those people, who have lighter and easier breathing pattern and greater body oxygen stores. Let us consider these effects in detail.
During normal breathing, oxygen content in the inhaled air is 20.9%, while in the expired air is 15.3% (see above). Hence, 5.6% of air remains in the lungs or is used by the human body. If we multiply this result by 6 L/min (normal minute ventilation), it is equal to 336 ml of air per min that remains in the human body.
Normal oxygen absorption in the body (in %)
Oxygen absorption in the body (in %) or the efficiency of extraction of oxygen from air is 5.6% (left in the lungs) divided by 20.9% (total oxygen in outer air), or about 27%. Hence, people with normal breathing parameters retain about a quarter of the oxygen, the remaining three quarters are exhaled back.
Most modern people
As we previously learned, normal subjects or ordinary modern people breathe about 12 L/min at rest: see this Table with 17 research papers and medical science articles related to 1990s and more recent years. Since oxygen demands of modern people at rest are about the same as for people with normal breathing, modern people have reduced coefficient of extraction of oxygen from air. In average, it is about 13-14%.
People with chronic diseases
People with chronic diseases breathe about 12-18 L/min (as we learned from the Minute Ventilation Table for the Sick) or about 2.5 times more than the norm. Since they have about the same metabolic rate or oxygen demands, chronic hyperventilators extract only 10% of oxygen, 90% of oxygen in exhaled back. In the severely sick it can be only 5% or less.
Very healthy people
Those very healthy people, who breathe very slowly or little (down to about 1.5-2 L/min or only 3-4 breathe per min), can extract over 50% or more of the oxygen they inhale. Maximum value of oxygen extraction coefficient (or ideal oxygen extraction rate in humans) is probably close to 70%.
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For more details about respiratory parameters and various health zones, visit the web page with the Buteyko Table of Health Zones. Breathing less also means much fewer toxic fumes, dust particles, pollens, and other dangerous substances from air. This is another reason to learn how to breathe less. |
Check your rate of oxygen extraction using the stress-free breath holding time test done after usual exhalation. The normal CP test result is 40 s, which corresponds to 27% for oxygen absorption in the body. The formula is simple: divide your CP in seconds by 40 seconds and multiply by 27%. |
These ideas about oxygen extraction efficiency help us to understand why it is much easier to exercise when we get higher CP. With higher CPs, we start to extract more oxygen at rest. During exercise, changes in the CO2 level in the arterial blood are relatively small and, therefore, if we breathe lighter just before the exercise, we continue to have lighter breathing during exercise as well. Vice versa, sick people breathe heavier before exercise in the state of rest. Hence, their arterial blood CO2 remains low during exercise too due to heavy panting. Moreover, due to cellular hypoxia and anaerobic energy production mechanism in mitochondria, they generate too much lactic acid during intensive exercise causing severe respiratory distress due to dis-proportionally heavy breathing.
Summary for efficiency of extraction of oxygen from air
| Health state of people | Oxygen absorption in the body |
| People with chronic diseases | Less than 10% |
| Most modern people | About 10-20% |
| People with normal breathing | 27% |
| Very healthy people | Over 50% |