Question

Please explain in detail why it is right or wrong?

1. 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

2. 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

Answer 1

1.
a. Wrong, normal paco2 level is between 35- 45 mm of Hg.

b. Wrong , normal pao2 range is 80 - 100 mm of Hg.

c. Wrong, Hypoventilation is defined by an abnormally elevated arterial carbon dioxide tension (Paco2) and high serum bicarbonate levels with an associated reduction of arterial oxygen tension (Pao2).

e. Wrong, During hyperventilation, which lowered arterial PCO2 and increased pH of the blood, the average PO2 decreased in proportion to the decrease in arterial PCO2.

f. a patient on 40% oxygen has a pulse oximetry SpO2 of 95%. Referring to the Table above, SpO2 of 95% is equal to a pO2 of 80mmHg. The P/F ratio = 80 divided by 0.40 = 200.

2.
b. Normal readings in a healthy adult, however, range from 94% to 100%.

c. Normal mixed venous oxygen tension (PvO2) is approximately 40 mmHg, representing the balance between oxygen consumption and oxygen delivery.

e. No exercise can reduce oxygen consumption that is deficit.

f. Dissolved CO2 (S x pCO2) contributes approximately 1.2 mmol/L to the total CO2 in the plasma of arterial blood (see above), so that ctCO2 is around 1.2 mmol higher than plasma bicarbonate.