Blood gas - exam 3

Question 1

What is normal Hb for our class

Answer 1

15g/dL

Question 2

How much O2 can be bound per gram Hb

Answer 2

1.34mL O2/ gram Hb

Question 3

Using normal values, what is the O2 carrying capacity of Hb

Answer 3

20.1mL O2/100mL blood

Question 4

Oxygen content of blood includes O2 that is ______ and ______

Answer 4

dissolved and bound

oxygen content = 20.1 (bound) + 0.3 (dissolved) = 20.4 mL O2

Question 5

Adult Hb has which sub-units

Answer 5

2 alpha, 2 beta

Question 6

Fetal Hb has which sub-units

Answer 6

2 alpha, 2 gamma

Question 7

Fetal Hb has ______ affinity for O2 compared to adult; which allows for what?

Answer 7

higher; allows O2 to unload to fetus more easily

Question 8

Myoglobin has ______ affinity for O2 compared to Hb

Answer 8

higher affinity than Hb

allows for O2 to unload to muscles more readily

Question 9

Which hormone is secreted by the kidney to produce RBCs, and what regulates it

Answer 9

Erythropoietin (EPO);
dec hemoglobin → dec oxygen to kidneys → EPO released → more RBCs formed

Question 10

solubility of O2 =

Answer 10

0.003 mL O2/mmHg/dL of blood

per mL of solution: 0.00003 mL O2/mmHg PO2

Question 11

solubility of CO2 =

Answer 11

0.06 mL CO2/mmHg/dL of blood

Question 12

How much CO2 is dissolved vs bound in blood

Answer 12

5% dissolved, 5% carbamino bound, 90% HCO3-

Question 13

carbon monoxide causes a ______ shift of the oxy-Hb diss. curve

Answer 13

left

Question 14

carbon monoxide has a _____ affinity for hemoglobin than O2

Answer 14

higher; 200-250x

Question 15

What 2 things does carbon monoxide do to Hb

Answer 15

• CO decreases carrying capacity of O2
• CO increases affinity for O2 when just 1 CO bound, preventing O2 from unloading

Question 16

systemic venous Hb is _____ saturated; how does this compare to coronary sinus Hb

Answer 16

systemic venous Hb= 3/4 O2 saturated
coronary sinus Hb= 1/4 O2 saturated

Heart extracts much more O2:
more efficient (reduces coronary perfusion needs), but leaves little room for error (not a lot of extra oxygen to help perfuse injured areas)

Question 17

A leftward shift of the oxy-Hb dissociation curve means Hb has a _______ affinity for O2

Answer 17

higher; O2 less likely to unload

Question 18

A rightward shift of the oxy-Hb dissociation curve means Hb has a _____ affinity for O2

Answer 18

lower; O2 more likely to unload

Question 19

What results in a rightward shift of the oxy-Hb dissociation curve

Answer 19

• inc acidity (dec. pH)
• inc. PaCO2
• inc. temp (hyperthermia)
• inc 2,3 BPG

Question 20

What results in a leftward shift of the oxy-Hb dissociation curve

Answer 20

• dec acidity (inc. pH)
• dec PaCO2
• dec temp (hypothermia)
• dec 2,3 BPG

Question 21

What is the normal P50 value for Hb

Answer 21

26.5mmHg

Question 22

How do the rates of diffusion between CO2 and O2 compare?

Answer 22

CO2 diffuses about 20x greater than O2

Question 23

What is the primary role of 2,3-BPG in relation to Hb

Answer 23

2,3-BPG binds to deoxygenated hemoglobin and decreases its affinity for oxygen.

2,3-BPG promotes oxygen unloading at the tissue level

Question 24

What percentage of total CO2 in blood is typically in dissolved form

Answer 24

5%

Question 25

What is the P50 value of Hb mean

Answer 25

The partial pressure needed to saturate 50% Hb changes when affinity for O2 changes

Question 26

How does right shift affect the P50 value

Answer 26

higher P50, need higher PO2 to reach 50%

Question 27

How does left shift affect the P50 value

Answer 27

lower P50, lower PO2 needed to reach 50%

Question 28

Normal arterial CO2 content =

Answer 28

48mL CO2/dL (97.5% saturated)

Question 29

Normal venous CO2 content =

Answer 29

52.5mL CO2/dL (70% saturated)

Question 30

Which compound is reversibly binding O2 to hemoglobin

Answer 30

Iron (Fe)

Question 31

What enzyme breaks down carbonic acid (H2CO3) to CO2 and water

Answer 31

Carbonic anhydrase reaction will occur without it depending on amount of CO2, but carbonic anhydrase speeds it up.

Question 32

What proportion of CO2 is dissolved vs. HCO3- vs. carbamino bound

Answer 32

- 5% dissolved - 5% carbamino - 90% HCO3-

Question 33

Under normal conditions, what is the normal amount of O2 exchanged in the lungs

Answer 33

5mL O2/dL (20 - 15 = 5)

Question 34

Under normal conditions, what is the normal amount of CO2 exchanged in the lungs

Answer 34

4.5mL CO2/dL (52.5 - 48 = 4.5)

Question 35

What are the 3 functions of hemoglobin

Answer 35

- bind or release O2 - form carbamino compounds - buffer protons (H+)

Question 36

How does the ratio of CO2 forms change in venous blood compared to arterial blood?

Answer 36

Less bicarb form, more carbamino and dissolved forms

Question 37

The fact that deoxygenated blood has more room to transport CO2 is called the _______ effect

Answer 37

Haldane - depends on oxyhemoglobin saturation levels

Question 38

How is bicarb transported in/out of RBCs? Which direction in which tissues?

Answer 38

Bicarb-chloride exchanger - peripheral tissues: bicarb out - lung tissue: bicarb in

Question 39

The most notable buffer of protons in a RBC is ________

Answer 39

Hb - deoxygenated

Question 40

Deoxygenated Hb is a ______ acid, while oxyhemoglobin is a ______ acid

Answer 40

weak - wants to accept protons (good buffer) strong - wants to get rid of protons

Question 41

Describe which direction the bicarb buffer equation goes in the RBCs of peripheral tissue

Answer 41

H2O + CO2 → H2CO3 → bicarb + H+

Question 42

Describe which direction the bicarb buffer equation goes in the RBCs of lung tissue

Answer 42

bicarb + H+ → H2CO3 → H2O + CO2

Question 43

How long does it take for gas exchange to happen in pulmonary capillaries?

Answer 43

0.25 sec

Question 44

How long does blood stay in a healthy alveolus at rest?

Answer 44

0.75 sec

Question 45

At max CO, how long does blood stay in pulmonary capillaries?

Answer 45

0.25 sec

Question 46

Compared to oxygen, nitrous is _____ soluble, and therefore spends ____ time in the pulmonary capillaries

Answer 46

less, less

Question 47

CO can be used as a diagnostic tool to test what? Why?

Answer 47

Diffusing capacity bc it has a similar diffusability to oxygen

Question 48

A __________ gas has equilibration between blood moving through the capillary and alveolar air. What is an example?

Answer 48

perfusion-limited; PO2

Question 49

A __________ gas does not have equilibration between blood moving through the capillary and alveolar air. What is an example?

Answer 49

diffusion-limited - issue with diffusion, CO

Question 50

Fick's law

Answer 50

diffusion of gas Vgas = (A*D*ΔP)/T speed of diffusion = (surface area*diffusivity*pressure difference)/thickness

Question 51

Gas diffusivity depends on what two factors?

Answer 51

solubility and sqrt(molecular weight)

Question 52

Compare the diffusivity of CO2 and O2

Answer 52

- CO2 larger but more soluble than O2 - solubility of CO2 24x > O2 - diffusivity of CO2 20x > O2 (0.85 is MW ratio of O2/CO2; inverse is 1.17 = diffusion rate)