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 CyanosisReappraisal of Response to 100% Oxygen Breathing. Am J Dis Child. 1984;138(9):880–884. doi:10.1001/archpedi.1984.02140470078027