Chapter 17 (Pt. 2)

Question 1

what does PaO2 stand for?

Answer 1

partial pressure of arterial oxygen

Question 2

what does PaO2 measure?

Answer 2

the amount of O2 dissolved in plasma

Question 3

why does PaO2 measure the amount of O2 dissolved in plasma?

Answer 3

indicates how well lungs are ventilating

Question 4

why does the amount of O2 dissolved in plasma indicate how well the lungs are ventilating?

in other words, what is the significance of more dissolved O2?

what happens once O2 molecules bind to hemoglobin?

Answer 4

more dissolved O2 = increased O2 available to enter RBCs and bind to hemoglobin

once bound to hemoglobin, O2 molecules don’t exert pressure, not detected

Question 5

what are three things that hypoxia can result from?

Answer 5

1. insufficient O2 transfer
2. low RBC count
3. low Hb levels

Question 6

what effect would anemia and malaria have on PaO2? why?

Answer 6

no effect. PaO2 looks at the amount of O2 in plasma.

Question 7

what effect would anemia and malaria have on SaO2? why?

Answer 7

no change. SaO2 looks at the percentage of heme groups that are bound to O2, not the amount.

Question 8

what effect would anemia and malaria have on CaO2? why?

Answer 8

decrease. low oxygen.

Question 9

what is SaO2? and what does that mean it measures?

Answer 9

arterial oxygen saturation.

% of hemoglobin in the blood that is bound to oxygen.

Question 10

what is CaO2?

Answer 10

arterial oxygen content.

total amount of oxygen in the blood; bound to Hb and dissolved in the plasma.

Question 11

why is the O2 saturation curve for hemoglobin sigmoidal (bending) rather than linear?

Answer 11

as partial pressure changes, Hb affinity for O2 changes

less O2 in atmosphere = greater release of O2 in body

O2 is released to oxygen-depleted tissue, which is good!

Question 12

what does sigmoidal mean?

Answer 12

bending, not linear

Question 13

what does the sigmoidal O2 saturation curve for hemoglobin represent?

Answer 13

as the concentration of O2 changes, the affinity of Hb for oxygen changes too. in other words, as there’s less O2 in the atmosphere, hemoglobin affinity for O2 decreases too.

Question 14

why is the change in Hb’s affinity for O2 as partial pressure of O2 decreases a good thing?

Answer 14

decreased affinity @ decreased partial pressure of oxygen means that O2 is released to hypoxic tissues

Question 15

how does the change in PO2 affect hemoglobin’s affinity for O2? (saturation)

Answer 15

increased PO2 = increased Hb affinity for O2 = increased % saturation

Question 16

where in the body would you find the values indicated by the three red arrows on the chart of percent oxygen saturation of hemoglobin vs. partial pressure of oxygen

Answer 16

1. blood leaving tissues
2. blood entering tissues @ rest
3. blood exiting the lungs

Question 17

at rest, the Hb in deoxygenated blood sent to the lungs is still 75% saturated at rest. what does this tell you bout the O2 holding capacity of hemoglobin?

Answer 17

hemoglobin is very efficient at holding oxygen!