Question

You have a subject with the following values: Pbar = 690 mm Hg, FIO2 = 0.21, PaO2 = 55 , PaCO2 = 60 mm Hg, VT = 400 ml, f = 6/min. Select either correct or incorrect for each of the following statements.

*Please show all formulas, work to support your answers of either Correct or Incorrect

PaO2/FIO2 = 262   A. Correct B. Incorrect

This subject must have an elevated VD/VT   A. Correct B. Incorrect

This subject is hyperventilating A. Correct B. Incorrect

The a/A ratio indicates that hypoventilation alone is responsible for the hypoxemia A. Correct B. Incorrect

Answer 1

1. A. CORRECT

ANSWER: FORMULA TO CALCULATE PaO2 AND FIO2 simply divide the given PaO2 (55) by the FIO2 ( 0.21). Then, it will be like this: 55 divided by 0.21 = 261.9 which is equal to 262.

2. A. CORRECT

VD/VT is a routine measurement used to express the ratio of dead space ventilation to tidal volume in case of patients with respiratory diseases. The normal range of dead space ventilation (VD) is considered approximately as 150ml. The normal ratio of VD/VT ranges from approximately 0.28 to 0.33. Then, VD/VT = 150/400 = 0.37

3. B. INCORRECT

ANSWER: Normal PaO2 level is 75 to 100 mmHg and normal PaCO2 level is 35 to 45 mmHg. In this case, the oxygen level is low and the carbondi oxide level is high rsulting in hypoventilation not hyperventillation.

4. A. CORRECT

ANSWER: The Alveolar- arterial gradient (A/a ratio) is a measure of the difference between the alveolar concentration( A) of oxygen and the arterial (a) concentration of oxygen to diagnose the source of hypoxemia.