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The atmospheric pressure is roughly equal to the sum of partial pressures of constituent gases – oxygen, nitrogen, argon, water vapor, carbon dioxide, etc.. In a mixture of gases, each constituent gas has a partial pressure which is the notional pressure of that constituent gas as if it alone occupied the entire volume of the original mixture at the same temperature. [1]
The alveolar gas equation is the method for calculating partial pressure of alveolar oxygen (p A O 2). The equation is used in assessing if the lungs are properly transferring oxygen into the blood. The alveolar air equation is not widely used in clinical medicine, probably because of the complicated appearance of its classic forms.
Dalton's law (also called Dalton's law of partial pressures) states that in a mixture of non-reacting gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases. [1] This empirical law was observed by John Dalton in 1801 and published in 1802. [2] Dalton's law is related to the ideal gas laws.
where P is the pressure, V is the volume, N is the number of gas molecules, k B is the Boltzmann constant (1.381×10 −23 J·K −1 in SI units) and T is the absolute temperature. These equations are exact only for an ideal gas, which neglects various intermolecular effects (see real gas). However, the ideal gas law is a good approximation for ...
The analysis here shows the simple unattributed formula and the Antoine equation are reasonably accurate at 100 °C, but quite poor for lower temperatures above freezing. Tetens is much more accurate over the range from 0 to 50 °C and very competitive at 75 °C, but Antoine's is superior at 75 °C and above.
P a O 2 – Partial pressure of oxygen at sea level (160 mmHg in the atmosphere, 21% of standard atmospheric pressure of 760 mmHg) in arterial blood is between 75 mmHg and 100 mmHg. [4] [5] [6] Venous blood oxygen tension (normal) P v O 2 – Oxygen tension in venous blood at sea level is between 30 mmHg and 40 mmHg. [6] [7]
Atmospheric pressure, also known as air pressure or barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as 101,325 Pa (1,013.25 hPa ), which is equivalent to 1,013.25 millibars , [ 1 ] 760 mm Hg , 29.9212 inches Hg , or 14.696 psi . [ 2 ]
The partial pressures obey Dalton's law: =, where P is the total pressure and y i is the mole fraction of the component (so the partial pressures add up to the total pressure). The fugacities commonly obey a similar law called the Lewis and Randall rule: f i = y i f i ∗ , {\displaystyle f_{i}=y_{i}f_{i}^{*},} where f *