Usefulness of the Arterial/Alveolar Oxygen Tension Ratio in the Care of Infants with Respiratory Distress Syndrome

We compared the validity of the arterial/alveolar oxygen tension ratio (Pao₂/PAO₂), the alveolar-arterial oxygen tension difference P(A-a)o₂, and the calculated shunt fraction (Qs/Qt) as indices of the severity of respiratory distress syndrome (RDS) in 6 infants up to 3 hours old, in 1 infant to the age of 72 hours, and in I infant to the age of 108 hours. We found that, in infants with acute RDS in whom hypoxemia is related to shunt, the Pao₂/PAO₂ was more useful than the P(A-a)o₂ in following the course of the severity of RDS and in comparing the disease state among infants. In addition, the Pao₂/PAO₂ may be useful in predicting the Pao₂ that would result from a given decrease in the fraction of inspired oxygen (Fro₂) in such infants. (Cohen A, Taeusch HW Jr, Stanton C. Usefulness of the Arterial/Alveolar Oxygen Tension Ratio in the Care of Infants with Respiratory Distress Syndrome . Respir Care 1983:28:169-173