A healthy medical student is breathing air at sea level. If her arterial blood gas analysis shows PaO2 = 100 mmHg, PaCO2 = 40 mmHg, and her respirato…

The alveolar gas equation is PAO2 = PIO2 - (PaCO2 / R). At sea level, PIO2 = (760 - 47) * 0.21 = 713 * 0.21 = 149.73 (approx 150) mmHg. PAO2 = 150 - (40 / 0.8) = 150 - 50 = 100 mmHg. Wait, let's recalculate accurately: PIO2 = (760 - 47) * 0.21 = 613 * 0.21 is wrong, 760 - 47 = 713. 713 * 0.21 = 149.73. PaCO2 / R = 40 / 0.8 = 50. PAO2 = 149.7 - 50 = 99.7 mmHg. Let's use standard simplified numbers: PAO2 = (150) - (40 / 0.8) = 150 - 50 = 100? No, PIO2 is usually taken as 150. PAO2 = 150 - 40/0.8 = 150 - 50 = 100. Actually, standard alveolar gas equation: PAO2 = 150 - (40/0.8) = 100. Wait, let's look at standard test values: PIO2 = 0.21 * (760 - 47) = 149.3. 149.3 - 50 = 99.3. If atmospheric pressure is 760, water vapor pressure is 47, (760-47)*0.21 = 149.3. If standard PIO2 is approximated as 150, 150 - 50 = 100. Let's adjust numbers to make 105 the clear answer: if PaCO2 is 32 or R is 0.8 and PIO2 is 150... Wait, 150 - 40/0.8 = 100 is correct mathematically. Let's fix the question option to match 100 or change PaCO2. Let's change correct answer to 100 mmHg or use options: A) 90, B) 100, C) 110, D) 120. Correct option B: 100 mmHg.