Abstract
The mechanism by which oxygen (O2) administration improves systemic arterial saturation (SA sat) in patients (pts) with Tetralogy of Fallot (ToF) has not been previously elucidated. In order to explain this phenomenon, hemodynamic measurements were made before and after 90-100% 02 administration to 16 pts, age 4 mos. - 8 yrs. (M= 3.4 yrs.).
During O2 administration, mean SA sat increased from 76.5±1.7%(M±SEM) to 90.9±1.9%(p<.001), mean SA pressure increased from 68.3±3.1 mmHg to 76.5±4. lmmHg(p<.02), mean systemic flow index decreased from 4.6±0.4L/min/m2 to 3.3±0.2L/min/m2 (p <.01), and mean systemic vascular resistance (SVR) increased from 15.6±1.2 Units/m2 to 24.4±1.3 Units/m2 (p <.001). Mean pulmonary flow index increased from 2.4±0.4L/min/m2 to 2.7±0.6L/min/m2 (p>.05). The mean % right to left (R→L)shunt decreased from 51.4±3.6% in room air to 35.5±4.6% in O2(p<.001). In room air, 4 pts had bidirectional shunts. However, with O2, an additional 7 pts developed bidirectional shunts. In all pts, the increment in oxygen saturation was significantly greater than could be due to dissolved O2 alone.
It is concluded that O2 administration in pts with ToF increases SA sat by inducing systemic vasoconstriction. The resultant increased SVR causes a decrease in the R→L shunt and improved oxygenation. Thus, in ToF, the beneficial effect of O2 results primarily from its effect on the systemic vascular bed.
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Boxer, R., Krongrad, E., Hordof, A. et al. 88 EFFECT OF OXYGEN ON THE SYSTEMIC VASCULAR BED IN PATIENTS WITH TETRALOGY OF FALLOT. Pediatr Res 12 (Suppl 4), 378 (1978). https://doi.org/10.1203/00006450-197804001-00093
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DOI: https://doi.org/10.1203/00006450-197804001-00093