Ch. 6 West

Question 1

Oxygen is carried in the blood in what two forms

Answer 1

Dissolved
Combined with hemoglobin

Question 2

Henry’s law states that the amount of dissolved oxygen in the blood is proportional to the partial pressure. For each mmHg of PO2, there is _____ mL O2 per 100 mL blood.

Answer 2

0.003

Thus, normal arterial blood with a PO2 pf 100 mmHg contains 0.3 mL O2 as dissolved O2 per 100 mL.

Question 3

Oxygen forms an easily reversible combination with hemoglobin to give oxyhemoglobin via the following reaction:

Answer 3

O2 + Hgb ⇌ HbO2

Question 4

The oxygen-hemoglobin dissociation curve shows that the amount of O2 carried by Hgb rapidly increases up till a PO2 of ___ mmHg then the curve becomes much flatter.

Answer 4

60 mmHg

Question 5

T/F: The amount of oxygen bound by Hgb at any time is a function of the PO2

Answer 5

True

Question 6

Oxygen saturation of Hgb formula

Answer 6

= [O2 combined with Hgb/O2 capacity] x 100%

Question 7

How much oxygen (mL) can 1 gram of Hgb combine with?

Answer 7

1.39 mL

Question 8

The oxygenated form of hemoglobin (the relaxed state) undergoes conformational change to its deoxygenated form, also called the _____ state

Answer 8

Tense state

Question 9

Equation for oxygen concentration of blood (in mL O2 per 100 mL blood)

Answer 9

= [1.39 x Hgb x (% sat/100)] + 0.003(PO2)

Hgb in grams/100 mL
PO2 is in mmHg

Question 10

T/F: Anemia will decrease O2 carrying capacity and O2 concentration but will not decrease the % saturation.

Answer 10

True

Question 11

T/F: The steep lower part of the oxygen hemoglobin dissociation curve means that the peripheral tissues can withdraw large amounts of oxygen for only a small drop in PO2.

Answer 11

True

Question 12

Why do polycythemic patients often appear cyanotic?

Answer 12

Because deoxyhemoglobin is purple in color; and cyanosis is determined by the proportion of deoxygenated hemoglobin

Question 13

When the curve shifts to the right, O2’s affinity for hemoglobin is __________

Answer 13

Decreased

Question 14

Factors which shift the O2/Hgb dissociation curve to the right:

Answer 14

Acidosis
Increased PCO2
Increased temperature
Increased 2,3-DPG in RBC’s

Question 15

Explain the Bohr effect

Answer 15

Most of the effect of PCO2 on the oxygen-hemoglobin dissociation curve, can be attributed to its action on H+ concentration.

Question 16

PO2 of 100 mmHg corresponds to a saturation of ____ %

Answer 16

97.5%

Question 17

PO2 of 40 mmHg corresponds to a saturation of ___ %

Answer 17

75%

Question 18

PO2 of 60 mmHg corresponds to a saturation of ____ %

Answer 18

90%

Question 19

PO2 of 27 mmHg corresponds to a saturation of ____ %

Answer 19

50%
This is also called the P50

Question 20

Carbon monoxide has ____ times the affinity of oxygen for hemoglobin

Answer 20

240 times

This means that CO will combine with the same amount of Hgb as O2 when the CO partial pressure is 240 times lower!

Question 21

Why is the measured saturation potentially normal in CO poisoning patients?

Answer 21

Because technically the RBCs combined with O2 are saturated. Pulse ox measures oxyhemoglobin, not carboxyhemoglobin.
Small CO addition shifts the curve to the left, impairing oxygen offloading.

Question 22

CO2 is carried in the blood in three forms:

Answer 22

Dissolved CO2
Bicarb
Combination with proteins such as carbaminos

Question 23

Carbonic anyhydrase equation

Answer 23

CO2 + H2O ⇌(CA)⇌ H2CO3 ⇌ H+ + HCO3-

Question 24

When the above reaction occurs in cells, HCO3- moves out of the cell, but the cell membrane is relatively impermeable to cations so H+ cannot move out. To maintain electroneutrality, which ion has to move into the cell from the plasma and by what exchanger does this occur?

Answer 24

Chloride
Chloride-bicarbonate exchanger
Also called the chloride shift

Question 25

Some of the liberated hydrogen ions combine with reduced hemoglobin in the following manner:

Answer 25

H+ + HbO2 ⇌ H+ *Hb + O2

Reduced hemoglobin is less acidic than the oxygenated form and accepts protons better.

Question 26

What is the Haldane effect?

Answer 26

Reduced hemoglobin in the peripheral blood accepts acids better and therefore helps with CO2 unloading.
Deoxygenation of the blood increases its ability to carry CO2.

Question 27

The bulk of CO2 in the blood is as ______ and the dissolved form is small, and that which is protein bound is as the form of ______

Answer 27

The bulk of the CO2 in the blood is bicarb
A small amount is dissolved
The protein bound form is called carbaminohemoglobin

Question 28

T/F: Bicarbonate reactions are the major source of expired CO2

Answer 28

True

Question 29

T/F: Bicarb levels depend on the carbonic anhydrase in the cell

Answer 29

True

Question 30

T/F: Transport of CO2 in solution (i.e. the dissolved portion) accounts for about 10% of the CO2 evolved by the lung.

Answer 30

True

Question 31

T/F: Carbamino compounds are formed mainly with hemoglobin and account for about 30% of the CO2 evolved by the lung.

Answer 31

True

Question 32

T/F: CO2 carriage in the form of carbaminohemoglobin is enhanced by deoxygenation of the blood.

Answer 32

True

Question 33

Why is the PO2 difference between arterial and venous samples huge, but the difference between CO2 between arterial and venous samples is small?

Answer 33

The CO2 curve is steeper and shorter

Question 34

The typical arterial and mixed venous blood difference in PO2 is typically close to ___ mmHg.

Answer 34

60 mmHg

Question 35

The CO2 curve is shifted to the right by ______ (Haldane effect)

Answer 35

Increases in SO2

Oxygenation of blood in the lungs displaces carbon dioxide from hemoglobin, increasing the removal of carbon dioxide.

Carbon dioxide carriage in the blood in the form of carbaminohemoglobin is enhanced by deoxygenation of the blood.

Question 36

As long as the ratio of bicarb concentration to (PCO2 x 0.03) remains equal to _____ , the pH will remain at 7.4.

Answer 36

20

Question 37

Respiratory acidosis is caused by a ____ in PCO2, which reduces the HCO3/PCO2 ratio and therefore depresses the pH.

Answer 37

Increase in PCO2

Question 38

Four causes of tissue hypoxia

Answer 38

1) Low PO2 in arterial blood caused by pulmonary disease (“hypoxic hypoxia”)
2) A reduced ability of blood to carry O2, as in anemia or CO poisoning (“anemic hypoxia”)
3) A reduction in tissue blood flow, either generalized as with shock, or because of local obstruction (“circulatory hypoxia”)
4) Toxic substance interfering with the ability of the tissues to use oxygen (“histotoxic hypoxia”), an example of which would be cyanide poisoning which prevents use of O2 by cytochrome oxidase

Question 39

The acid-base status of the blood is determined by the ______ equation, especially the ratio of ____ to ____.

Answer 39

Henderson-Hasselbalch equation
Ratio of HCO3 to CO2

Question 40

The PO2 in some tissues is less than ___ mmHg, and is much higher in the blood so that the gradient for diffusion is adequate.

Answer 40

5 mmHg