ICU Primary PrepCast #Epi 90 - ICU Primary Snippet 33 - Venous Admixture and effect of Supplemental Oxygen
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May 16, 2024 Exploring venous admixture and the effects of supplemental oxygen on arterial hypoxemia in adult patients. Understanding the impact of supplemental oxygen on arterial oxygen levels in VQ mismatch, diffusion limitation, and true shunt. Identifying the cause of hypoxia for optimal oxygen therapy.
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Venous Admixture
- Venous admixture is the volume of mixed venous blood added to ideal pulmonary capillary blood to obtain the pulmonary capillary arterial PO2 difference.
- It represents deoxygenated blood bypassing the lungs without gas exchange.
Shunt Fractions
- Normal shunt fraction is up to 5%, with sources including physiological (bronchial, Thebesian veins) and pathological shunts.
- Pathological shunts can be intracardiac (VSDs) or intrapulmonary (AVMs, V/Q mismatch).
Oxygen's Effect on Hypoxemia
- Supplemental oxygen's effect on hypoxemia varies depending on the cause.
- It helps in hyperventilation or low inspired oxygen, but less so in V/Q mismatch or shunt.