00:00 / 00:00
Alveolar gas equation
0 / 5 complete
0 / 2 complete
alveolar gas equation p. 690
Normally, during an inhale - the diaphragm and chest muscles contract to pull open the chest and that sucks in air like a vacuum cleaner, and then during an exhale - the muscles relax, allowing the lungs to spring back to their normal size pushing that air out.
When we breathe in, oxygen-filled air from the environment enters through the nostrils, goes through the airways, and finally reaches the alveoli, the tiny air-filled sacs in the lungs where oxygen finally moves into the blood.
The total pressure of the air in the alveoli is equal to the atmospheric pressure outside, Patm.
But unlike atmospheric air, the air inside the alveoli gets saturated with water vapor after travelling through the moist airways.
The partial pressure of water vapor is Pvapor.
Now, let's take this mixture of gas particles, red being oxygen and blue being CO2, the partial pressure of one of the gases is proportional to the fractional concentration of the gas in that mixture, which is a fancy way of saying the fraction of that gas molecule to all the gas molecules, so in this case CO2 would have a fractional concentration of 0.3, since it accounts for 30% of the gas molecules, and O2 would be .7, since it accounts for the remaining 70%.
Alveolar gas equations are a set of mathematical equations used to calculate the alveolar oxygen partial pressure. It is used extensively in medicine and physiology and is considered to be one of the most important tools in understanding how the alveolar gas exchange works.
PAO2 = (Patm - PH2O) FiO2 - PaCO2/RQ
PAO2: oxygen partial pressure inside the alveoli; Patm: atmospheric pressure (at sea level 760 mm Hg); PH2O: partial pressure of water (approximately 45 mm Hg); FiO2: fraction of inspired oxygen; PaCO2: partial pressure of carbon dioxide in alveoli (in normal physiological conditions around 40 to 45 mmHg). RQ is the respiratory quotient (average value is around 0.82)
Copyright © 2023 Elsevier, its licensors, and contributors. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
Cookies are used by this site.
USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the National Board of Medical Examiners (NBME). COMLEX-USA® is a registered trademark of The National Board of Osteopathic Medical Examiners, Inc. NCLEX-RN® is a registered trademark of the National Council of State Boards of Nursing, Inc. Test names and other trademarks are the property of the respective trademark holders. None of the trademark holders are endorsed by nor affiliated with Osmosis or this website.