Here is a sample of the answers for Chapter 12 of the Egan’s Workbook. For rest of the answers, check out our Workbook Helper. We have both the 10th and 11th Edition available.

1. Formula: PAO2 = (PB – PH2O) FiO2 – (PaCO2 ÷ 0.8) Solution: PAO2 = 713 × 0.21) 40 ÷ 0.8 or 149.73 – 50, Answer: PAO2 = 99.73 mm Hg (~100)

2. Formula: A-a gradient = PAO2 PaO2 Solution: A-a gradient = 100 – 90

Answer: A-a gradient = 10 mm Hg

3. Formula: PAo2 = (PB – PH2O) FiO2 – PaCO2; (FiO2 is ≥0.6)

Solution: PAO2 = 713 × 0.6 – 40 or 428 – 40 = 377.8 mm Hg

Answer: ~388 mm Hg

4. Formula: A-a gradient = PAO2 – PaO2

Solution: A-a gradient = 388 – 90

Answer: A-a gradient = 298 mm Hg

5. Patient A is perfusing well because he has a PAO2 of 99.7 mmhg while breathing room air and a

PO2 of 90 mmhg. This makes the A-a gradient approximately 10 mmhg, which is in the normal range, and shows that the oxygen is perfusing properly from the alveoli to the arteries. Patient B, on the other hand, is not perfusing well; likely has a shunt, due to the fact that his A-a gradient is so high.

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