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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.
The waterfall represents the alveolar and capillary walls, and the second part of the river represents the arterial system. The river empties into a lake, which can represent end-organ perfusion. The A-a gradient helps to determine where there is flow obstruction. [2] For example, consider hypoventilation.
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]
Dry air: 159: Air is ~21% oxygen [2] Moist air: 150: Air is humidified in the respiratory tract [2] Alveolar air: 110-100: Alveolar air includes exhaust gases such as CO 2 [2] [3] Arterial blood (PaO 2) 98-95: Oxygen must cross the alveoli, leading to a drop in PO 2 called the alveolar-to-arterial gradient (typically a drop of 1-5 mmHg, but ...
Therefore, under these conditions, the ideal ventilation perfusion ratio would be about 0.95. If one were to consider humidified air (with less oxygen), then the ideal v/q ratio would be in the vicinity of 1.0, thus leading to concept of ventilation-perfusion equality or ventilation-perfusion matching. This matching may be assessed in the lung ...
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.
Alveolar gas volume: V L: Actual volume of the lung including the volume of the conducting airway. FVC: Forced vital capacity: the determination of the vital capacity from a maximally forced expiratory effort: FEV t: Forced expiratory volume (time): a generic term indicating the volume of air exhaled under forced conditions in the first t ...
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 ...