Question

Subject 5 is a 21 year old Boise State student who has the following values at baseline: PaO2 54 mm Hg, PaCO2 = 60 mm Hg while breathing FIO2 = 0.21 @ PB = 690 mm Hg. A Respiratory Therapist administers additional oxygen with an FIO2 = 0.4. Identify whether each of the following are correct or incorrect.

a. At baseline, the PaCO2 is within normal limits

b. At baseline, the PaO2 is within normal limits

c. At baseline, the value for PaO2 explained by hypoventilation alone

d. The a/A ratio is consistent with low V/Q or shunting

e. Administration of oxygen will result in a decrease in PaCO2 proportional to the increase in PaO2

f. Administration of 40% oxygen would be expected to result in a PAO2 = 257 mm Hg

6. Subject 6 has the following values: FIO2 = 0.7, PaO2 250 mm Hg, Hb 6 g/dl, SVO2 = 50%, CO = 6 lpm, PaCO2 = 35 mm Hg. Estimate the SaO2 and PVO2 using the normal oxyhemoglogin dissociation curve, and identify whether each of the following is correct or incorrect.

a. The subject has low V/Q

b. The SaO2 = 100%

c. The PVO2 = 26 mm Hg

d. The oxygen consumption is about 280 ml/minute

e. The subject must be exercising

f. Dissolved CO2 = 0.105 meQ/L

Please explain in detail why it is right or wrong.

Answer 1

1) subject 5

a) Wrong

While breathing  FIO2 - 0.21 the PaCo2( partial pressure of carbon dioxide) should be 38 - 42 mm Hg. This condition patient's PaCo2 is 60mm Hg that means respiratory acidosis.

b) Wrong

The patient's PaO2( Partial pressure of oxygen) level is 54mm Hg, the normal level must be 75 - 100mm Hg. That means patient not getting enough oxygen.

c) Correct

Patient's PaO2 level is low and PaCO2 level is high so patient is under hypoventilation.

d)Correct

Due to high PaCO2 level V/Q ( ventilation) level become low. So it will affect the a/A ratio.

e) Correct

Administration of oxygen will deliver oxygen to the lungs and high PaCO2 level will decrease.

f) Wrong

PAO2 level will increase with FIO2. Here FIO2 is 40% so we need to multiply FIO2 by 5, that is 40 ✖ 5 = PaO2 is 200mm Hg .