Which of the following statements are true of the PaO₂/FIO₂?
I.A normal range is approximately 380 to 475.
II.Its usefulness as a shunt indicator is limited.
III.A major problem with PaO₂/FIO₂ is that changes in PaCO₂ affect it.
IV.PaO₂/FIO₂ is the least accurate indicator of shunt.

Question

Quizplus · Accepted Answer

The PaO₂/FIO₂, called the oxygenation ratio, is another measure of oxygenation efficiency. A normal range is approximately 380 to 475 (i.e., when PaO₂ is 80 to 100 mm Hg on an FIO₂ of 0.21). The PaO₂/FIO₂ is easy to calculate because it does not require calculation of the PAO₂. However, its usefulness as a shunt indicator is limited. A major problem with PaO₂/FIO₂ is that changes in PaCO₂ affect it. For example, if PaCO₂ increases from 40 to 80 mm Hg during general hypoventilation, the PaO₂ decreases by approximately the same amount (i.e., from 90 to 50 mm Hg). If the patient is breathing room air, the PaO₂/FIO₂ is 50/0.21 = 238. This low value implies that oxygen trAnswerfer efficiency is impaired when in fact it is not; the P(A-a)O₂ does not change in this situation. For this reason, PaO₂/FIO₂ is the least accurate indicator of shunt, especially at low FIO₂ where the effect of PaCO₂ is greatest.

Which of the Following Statements Are True of the PaO2/FIO2

Which of the Following Statements Are True of the PaO₂/FIO₂