Oxygen Extraction Rate in Lungs | Lung Efficency at Capturing Oxygen
How efficient are our lungs in oxygen extraction?
What is the percentage of oxygen that is extracted from the outer air? The lungs oxygen absorption rate in sick people and most modern people is much less than normal because they breathe much more than the medical norm (see links with dozens of studies below). Indeed, if they extract about the same total volume of oxygen as healthy people, their rate (percentage or efficiency) of extraction is much less. Let us consider these effects in detail. We can start with the normal values for breathing at rest.
Normal gas exchange parameters
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).
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 is extracted or captured as oxygen. This oxygen remains in the lungs and 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 oxygen per min that is captured by the human body.
How efficient are our lungs at capturing oxygen from the air?
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). The result is about 27%. Hence, people with normal breathing parameters retain about a quarter of the oxygen, the remaining three quarters are exhaled back.
Why might some people be more efficient at capturing oxygen than others?
Since most people breathe much more than the medical norm, they capture much less of inhaled oxygen. Note that overbreathing also reduces O2 content in body cells and promotes chronic diseases.
Oxygen extraction rate in 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 being exhaled back. In the severely sick it can be only 5% or less.
Oxygen capturing rate in very healthy people
Very healthy people, who breathe very little (down to about 1.5-2 L/min or only 3-4 breaths per min), can extract over 50% or more of the oxygen they inhale. The maximum value of the lungs oxygen extraction coefficient (or ideal oxygen extraction rate in humans) is probably close to 70%.
Chart: Efficiency of lungs at capturing oxygen from the air
|Health state of people||Oxygen extraction in the lungs|
|People with chronic diseases||Less than 10%|
|Most modern people||About 10-20%|
|People with normal breathing||27%|
|Very healthy people||Over 50%|
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