Given the following values collected at the end of a symptom limited stress test

Question

Given the following values collected at the end of a symptom limited stress test, which of the following are true for this 60 kg female? VE = 20 lpm, respiratory rate = 50, FIO2 = 0.35, FEO2 = 0.29, FECO2 = 0.06, PaCO2 = 70 mm Hg, mixed expired PCO2 = 39 mmHg. Label each of the following as correct or incorrect.

A. VO2 = 1.2 L/min

B. RER = 1.0

C. This subject was hyperventilating at the end of the test

D. The VD/VT is within normal limits.

E. VT = 2.5L/breath

F. This subject must have stopped the text due to shortness of breath rather than tachycardia

Explanation / Answer

** Note: I am answering this question, because I have already skipped this question twice. Now, it would be a third time. Please post different parts of the question separately.

A. VO2 is volume of oxygen the body utilizes per minute. It is given by the formula: - VO2 (mL/min) = (HR x SV) x a-vO2; where HR= heart rate, SV= stroke volume and a-vo2= amount of oxygen which goes in the muscle - amount of oxygen which goes out; Here a-vo2 = 0.35-0.29 = 0.06. Now we need to know the HR and SV to calculate it.

Generally HR = 75 beats per min and SV= 74.6 ml/beat; Then, VO2 = (75*74.6) * 0.06 = 336 ml/min~ 0.3litre/min

So, for a normal person, the statement is wrong.

If HR and SV vary, then the statement may be correct.

** Also please note. The two terms given, PaCO2 and PCO2 are same. Both stand for partial pressure of Carbon-di-oxide.

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