More than a decade ago, Lees1 provided a rational and systematic approach for differentiating pulmonary from cardiac causes of neonatal cyanosis. One of the modalities discussed was the response of arterial oxygen partial pressure (Pao2) to 100% oxygen inhalation. Despite the caution that the response to 100% oxygen inhalation may be deceptive, some authors have since implied (erroneously) that a Pao2 greater than 100 to 200 mm Hg2,3 in response to 100% oxygen breathing rules out cyanotic congenital heart disease. This article was written to clarify persistent misconceptions regarding the response to hyperoxia and to explain the mechanisms of response to 100% oxygen breathing by infants with cyanotic heart disease.
BASIC CONCEPTS AND DEFINITIONS
What follows is a brief discussion of the concepts of oxygen transport and the relationships between the various laboratory tests for measuring and expressing the oxygen concentration in blood.4Arterial oxygen
Yabek SM. Neonatal Cyanosis: Reappraisal of Response to 100% Oxygen Breathing. Am J Dis Child. 1984;138(9):880–884. doi:https://doi.org/10.1001/archpedi.1984.02140470078027
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