Blood Gas Transport

Question 1

What is the mutation of sickle cell disease?

Answer 1

it is caused by a single-base mutation in the beta chain of hemoglobin. the sixth amino acid in the chain is converted from glutamic acid to valine

Question 2

What is the alveolar gas equation?

Answer 2

PAO2 = PIO2 - PACO2/RQ

Question 3

How do you solve for PIO2?

Answer 3

(Pb-Ph2o) * FO2
Ph2o should be 47
FO2 is usually 0.21 unless stated otherwise

Question 4

How do you solve for RQ?

Answer 4

VCO2/VO2 = CO2 produced / O2 consumed
should be about 0.8

Question 5

How to solve for oxygen concentration?

Answer 5

Pressure (PAO2) * Solubility of O2

Question 6

What is dissolved oxygen delivery?

Answer 6

15mL O2/min

Question 7

What is hemoglobin

Answer 7

protein complex consisting of four polypeptide chains (2 alpha and 2 beta chains) each containing a heme group that reversibly binds with O2
Hb + O2 <–> HbO2
deoxyhemoglobin <–> oxyhemoglobin

Question 8

without hemoglobin… alveolar O2 diffuses down its pressure gradient and PAO2

Answer 8

increases to equilibration

Question 9

with hemoglobin… O2 is quickly bound in the blood and is no longer exerting pressure. this maintains a

Answer 9

low blood PO2 that maintains a pressure gradient for additional diffusion

Question 10

CO2 exchange at alveoli
PCO2 is at a steady state
alveolar PCO2 is maintained
bc of a greater CO2 solubility…

Answer 10

a similar volume of gas is exchanged with a smaller pressure gradient

Question 11

Oxygen Dissociation Curve:
PaO2 =
PvO2 =
only ___ of the O2 delivered to the tissues is extracted
at a lower PvO2, ___ of the O2 can be extracted

Answer 11

PaO2 = 100mmHg and 95% saturation
PvO2 = 40mmHg and 75% saturation
~20-25%
~70%

Question 12

Oxygen Dissociation Curve:
the plateau assures what?
the steep curve enables what?

Answer 12

the plateau assures saturation of Hb
the steep curve enables greater unloading

Question 13

Hemoglobin’s affinity for O2 is measured by the pressure required to saturate Hb to

Answer 13

50%

Question 14

Will a decrease in Hb-O2 affinity shift the ODC to the left or right?

Answer 14

right

Question 15

Will a decrease in Hb-O2 affinity be beneficial at the tissues or lungs?

Answer 15

tissues

Question 16

What is the Bohr effect?

Answer 16

the rightward shift of the ODC due to a fall in pH (decreased affinity = increased P50)

Question 17

All of the following will promotes the release of oxygen from oxyhemoglobin (shift to right) except…
a) increased carbon dioxide conc
b) increased blood temp
c) increased pH
d) increased 2,3 DPG

Answer 17

c) increased pH

Question 18

left shift on ODC

Answer 18

decrease P50
increased affinity
decrease temp
decrease PCO2
increase pH
decrease 2,3 DPG

Question 19

right shift on ODC

Answer 19

increase P50
decrease affinity
increase temp
increase PCO2
decrease pH
increase 2,3 DPG

Question 20

Blood oxygen content =
it is dependent on…

Answer 20

dissolved O2 + bound HbO2
1. PO2 and gas solubility
2. Hb conc.
3. Hb-O2 saturation

Question 21

What is hypoxic hypoxia?

Answer 21

the blood contains an abnormally low PO2. this can occur during hypoventilation and when PIO2 is low such as at high altitude

Question 22

What is anemic hypoxia?

Answer 22

PO2 is normal but Hb conc is low. oxygen content is reduced. occurs with carbon monoxide poisoning

Question 23

What is hypoperfusion hypoxia?

Answer 23

aka circulatory, ischemia or stagnant hypoxia. may occur if there is a reduction in tissue blood flow

Question 24

What is histotoxic hypoxia?

Answer 24

occurs when exposed to cyanide. O2 conc. ov venous blood is high

Question 25

Carbon Dioxide transport:
1) carbamino compound

Answer 25

carbamino compound: CO2 binds Hb and Proteins
Deoxyhemoglobin has a greater affinity for CO2 than oxyhemoglobin (haldane effect)
accounts for ~5% of transport

Question 26

Carbon dioxide transport
3) dissolved

Answer 26

CO2 is 20x more soluble than O2
account for ~5% of transport

Question 27

Carbon dioxide transport
2) bicarbonate

Answer 27

CO2 is converted to bicarbonate by carbonic anhydrase
accounts for 90% of CO2 transport.
occurs in RBCs

Question 28

Tissue: Mechanism for Carbon Dioxide Exchange

Answer 28

big CO2 + H2O –> H2CO3 –> H + HCO3 (rxn favors right side of eq)
1. CO2 diffuses into blood and RBCs
2. CO2 binds Hb: high affinity for Hb v HbO2 (haldane effect)
3. CO2 will combine with H2O via carbonic anhydrase to form H+ and HCO3

Question 29

Tissues: Carbon Dioxide Exchange

Answer 29

H+ and HCO3 accumulate in RBCs (rxn favors right side of eq)
1. H binds Hb
2. HCO3 exchanged for Cl to maintain electrical neutrality
3. chemcial rxn continues
4. HCO3 more solubel than CO2

Question 30

Lung: Carbon Dioxide Exchange

Answer 30

small CO2 + H2O <– H2CO3 <– H + HCO3 (rxn favors left side of eq)
low CO2 pressure in lung creates pressure gradient required to drive rxns
1. CO2 and H released from Hb
Co2 diffuse to lung
Hb is free to bind O2
H is free to bind HCO3
2. Cl is exchanged for HCO3
3. CO2 is free to diffuse to lung

Question 31

Key point for At TISSUES:
tissues have lower PO2 –>
lower HbO2 saturation facilitates…

Answer 31

lowers HbO2 saturation
CO2 binding and transport of CO2 as HbCO2

Question 32

At the tissues:
Bohr effect

Answer 32

low pH –> decreases HbO2 affinity with promotes oxygen unloading

Question 33

At the tissues:
Haldane effect

Answer 33

low HbO2 saturation –> facilitates HbCO2 binding and CO2 transport

Question 34

At the tissues, both the Bohr and Haldane effects work together to…

Answer 34

increase O2 delivery and CO2 uptake from the tissues

Question 35

At the lung:
CO2 is exhaled and pH increases

Answer 35

this increases HbO2 affinity, which increases HbO2 saturation, which facilitates CO2 unloading from Hb
both effects maximize O2 uptake and CO2 delivery at lungs