Author Question: If the total hemoglobin content (Hb + HbO2) of a sample of blood is 20 g/dl and the oxyhemo-globin ... (Read 59 times)

michelleunicorn · **on:** Jul 16, 2018

If the total hemoglobin content (Hb + HbO2) of a sample of blood is 20 g/dl and the oxyhemo-globin (HbO2) content is 15 g/dl, what is the HbO2 saturation?

a. 17
b. 50
c. 75
d. 83

Question 2

Why is it necessary to keep the patient's PaO2 greater than 60 mm Hg?

a. A level of 60 mm Hg marks the beginning of the steep part of O2Hb dissociation curve.
b. Below the 60 mm Hg level, tissue hypoxia is ensured.
c. Oxygen deprivation will cause severe cer-ebral vasoconstriction below 60 mm Hg.
d. The PaCO2 will start to rise precipitously if the PaO2 falls further.

tsternbergh47 · **Reply #1 on:** Jul 16, 2018

Answer to Question 1

ANS: C
If there were a total of 20 g/dl Hb in the blood, of which 15 g was HbO2, the SaO2 would be calculated as follows:
SaO2 () = 15 20 100 = 75

Answer to Question 2

ANS: A
With a PO2 lower than 60 mm Hg, the curve steepens dramatically. Here, in the normal operating range of the tissues, even a small drop in PO2 causes a large drop in SaO2, indicating a decreasing affinity for O2. This normal decrease in the affinity of hemoglobin for O2 helps release large amounts of O2 to the tissue, where the PO2 is low. This also explains why it is necessary to keep the PaO2 higher than 60 mm Hg in clinical practice.