Medical MCQ-Aerial blood gas of a 5-year-old child done at sees level gives the following results: pH 7.41, PaO2 100 mgHg, and PaCO2 40 mm Hg. The child is being ventilated with 80% oxygen. What is the (A-a) PO2?

Aerial blood gas of a 5-year-old child done at sees level gives the following results: pH 7.41, PaO2 100 mgHg, and PaCO2 40 mm Hg. The child is being ventilated with 80% oxygen. What is the (A-a) PO2?

570.4 mm Hg

520.4 mm Hg

470.4 mm Hg

420 mm Hg

Question Category:

Physiology

Correct Answer:

420 mm Hg

Description:

The alveolar gas equation is a formula used to approximate the paial pressure of oxygen in the alveolus (PAO2):PAO2=(PB-PH2O)FiO2-(PaCO2/R)where PB is the barometric pressure, PH2O is the water vapor pressure (usually 47mmHg), FiO2 is the fractional concentration of inspired oxygen, and R is the gas exchange ratio. Ref: guyton and hall textbook of medical physiology 12 edition page number:331,332,333

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