Search results
Results from the WOW.Com Content Network
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.
Natural air includes 21% oxygen, which is equivalent to F I O 2 of 0.21. Oxygen-enriched air has a higher F I O 2 than 0.21; up to 1.00 which means 100% oxygen. F I O 2 is typically maintained below 0.5 even with mechanical ventilation, to avoid oxygen toxicity , [ 2 ] but there are applications when up to 100% is routinely used.
The Alveolar–arterial gradient (A-aO 2, [1] or A–a gradient), is a measure of the difference between the alveolar concentration (A) of oxygen and the arterial (a) concentration of oxygen. It is a useful parameter for narrowing the differential diagnosis of hypoxemia. [2] The A–a gradient helps to assess the integrity of the alveolar ...
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.
Just as dead space wastes a fraction of the inhaled breath, dead space dilutes alveolar air during exhalation. By quantifying this dilution, it is possible to measure physiological dead space, employing the concept of mass balance, as expressed by the Bohr equation. [8] [9]
Fig. 11 A highly diagrammatic illustration of the process of gas exchange in the mammalian lungs, emphasizing the differences between the gas compositions of the ambient air, the alveolar air (light blue) with which the pulmonary capillary blood equilibrates, and the blood gas tensions in the pulmonary arterial (blue blood entering the lung on ...
The only source of CO 2 is the alveolar space where gas exchange with blood takes place. Thus the alveolar fractional component of CO 2, F A, will always be higher than the average CO 2 content of the expired air because of a non-zero dead space volume V d, thus the above equation will always yield a positive number.
The anatomy of the airways means inspired air must pass through the mouth, trachea, bronchi and bronchioles (anatomical dead space) before it gets to the alveoli where gas exchange will occur; on exhalation, alveolar gas must return along the same path, and so the exhaled sample will be purely alveolar only after a 500 to 1,000 ml of gas has ...