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The equation relies on the following assumptions: The alveolar gas equation allows the calculation of the alveolar partial pressure of oxygen from data that is practically measurable.

However, it is not practical to take a sample of gas from the alveoli in order to directly measure the partial pressure of oxygen. 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. The alveolar air equation is not widely used in clinical medicine, probably because of the complicated appearance of its classic forms. The equation is used in assessing if the lungs are properly transferring oxygen into the blood. Positive pressure ventilation (i.e.The alveolar gas equation is the method for calculating partial pressure of alveolar oxygen (P AO 2).Neck extension and jaw protrusion (can increase it twofold).General anesthesia – multifactorial, including loss of skeletal muscle tone and bronchoconstrictor tone.The ratio of physiologic dead space to tidal volume is usually about 1/3. Alveolar dead space is the volume of gas within unperfused alveoli (and thus not participating in gas exchange either) it is usually negligible in the healthy, awake patient. Anatomic dead space is the volume of gas within the conducting zone (as opposed to the transitional and respiratory zones) and includes the trachea, bronchus, bronchioles, and terminal bronchioles it is approximately 2 mL/kg in the upright position. Physiologic or total dead space is the sum of anatomic dead space and alveolar dead space. Dead space is the volume of a breath that does not participate in gas exchange.