About: Room air alveolar-arterial gradient (A-a gradient)
Calculating the A-a gradient can help the clinician determine the severity of pulmonary shunting. This can be useful in following the progression of a disease, and also may be a more subtle assessment of pulmonary disease than the oxygen saturation or the partial pressure of oxygen. This value is used in other tools, such as the Apache II score. A simplified formula can be used for patients on room air.
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