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The partial pressure of oxygen (pO 2) in the pulmonary alveoli is required to calculate both the alveolar-arterial gradient of oxygen and the amount of right-to-left cardiac shunt, which are both clinically useful quantities. However, it is not practical to take a sample of gas from the alveoli in order to directly measure the partial pressure ...
Because A–a gradient is approximated as: (150 − 5/4(PCO 2)) – PaO 2 at sea level and on room air (0.21x(760-47) = 149.7 mmHg for the alveolar oxygen partial pressure, after accounting for the water vapor), the direct mathematical cause of a large value is that the blood has a low PaO 2, a low PaCO 2, or both.
The partial pressure gradient, also known as the concentration gradient, can be used as a model for the driving mechanism of diffusion. The partial pressure gradient is the rate of variation of partial pressure (or more accurately, the concentration) of the solute (dissolved gas) from one point to another in the solvent.
The alveolar oxygen partial pressure is lower than the atmospheric O 2 partial pressure for two reasons. Firstly, as the air enters the lungs, it is humidified by the upper airway and thus the partial pressure of water vapour (47 mmHg) reduces the oxygen partial pressure to about 150 mmHg.
is the partial pressure of oxygen in the systemic veins (where it can actually be measured). Thus, the higher the diffusing capacity , the more gas will be transferred into the lung per unit time for a given gradient in partial pressure (or concentration) of the gas. Since it can be possible to know the alveolar oxygen concentration and the ...
Low partial pressure of oxygen in the lungs when switching from inhaled anesthesia to atmospheric air, due to the Fink effect, or diffusion hypoxia. Air depleted of oxygen has also proven fatal. In the past, anesthesia machines have malfunctioned, delivering low-oxygen gas mixtures to patients.
For F I O 2 values equal to or greater than 0.5, the alveolar–arterial gradient value should be used in the APACHE II score calculation. Otherwise, the PaO 2 will suffice. [4] The ratio between partial pressure of oxygen in arterial blood and F I O 2 is used as an indicator of hypoxemia per the American-European Consensus Conference on lung ...
If the solvent outside the bubble is saturated or unsaturated, the partial pressure will be less than in the bubble, and the surface tension will be increasing the internal pressure in direct proportion to surface curvature, providing a pressure gradient to increase diffusion out of the bubble, effectively "squeezing the gas out of the bubble ...