Transport of Gases (CO2, O2, dissociation curves)

Question 1

________ is d\t or a function of oxygen tension (partial pressure).

Answer 1

Hgb saturation

Question 2

What is P50 and what is the normal value for it?

Answer 2

The partial pressure of oxygen at which Hgb is 50% saturated with oxygen.
normal is 26-28mmhg

Question 3

What SO2 corresponds to PO2’s of 40 and 60mmHg?

Answer 3

remember 40, 50, 60= 70, 80, 90
70%=40mmHg
90%=60mmHg

Question 4

What is the significance of the flat portion of the oxyHgb dissociation curve?

Answer 4

facilitates the unloading of oxygen by blood…. b\c in the flat portion of the curve, large changes in partial pressure of oxygen in arterial blood (PaO2) produce only small changes in oxygen saturation

Question 5

What is the significance of the steep portion of the oxyHgb dissociation curve?

Answer 5

facilitates unloading of oxygen at tissues b\c large amounts of oxygen are unloaded from Hgb (large decrease in oxygen saturation) in response to small changes in the partial pressure of oxygen

Question 6

Name the factors that cause a rightward shift in the oxyHgb dissociation curve. (using “RIGHTS”)

Answer 6

"R"ightward shift
"I"ncreased PCO2
Increased 2, 3, DP"G"
"H"ydrogen ions increased (decreased pH)
"T"emperature increases
"S"ickle cell (HbS)

Question 7

P50 ______ when there is a rightward shift.

Answer 7

increases

Question 8

P50 ______ when there is a leftward shift.

Answer 8

decreases

Question 9

The ______ refers to the shift in oxyHgb dossociation curve in response to an increase or decreased PCO2.

Answer 9

Bohr effect

*studied factors that shift the curve right or left. Bohr assessed how a change in CO2 shifts the curve.

Question 10

Administration of opioids shifts the oxyHgb dissociation curve right or left?

Answer 10

Right–> produces resp depression, so CO2 accumulates and the curve shifts rightward

Question 11

Name the comprehensive list of factors that cause a rightward shift in the oxyHgb dissociation curve.

Answer 11

• increased temp
• decreased pH (increased H+ concentration)
• increased PCO2
• increased 2, 3 DPG
• maternal Hgb
• sickle cell (HbS)

Question 12

Name the comprehensive list of factors that cause a leftward shift in the oxyHgb dissociation curve.

Answer 12

• decreased temperature
• increased pH (decreased H+ concentration)
• decreased PCO2
• decreased 2, 3, DPG
• fetal Hgb (HbF)
• carboxyhemoglobin
• methemoglobin

Question 13

A rightward shift facilitates _____.

Answer 13

unloading

Question 14

A leftward shift facilitates ______.

Answer 14

loading

Question 15

Explain the normal process of the utility of the Bohr effect involved with the transport of gases (CO2 and O2).

Answer 15

blood travels through the capillaries in the systemic circuit, CO2 and acids diffuse into the blood from the tissue cells—> tissue metabolism causes an increase in temperature–> rightward shift–> O2 unloading is facilitated (for a given PO2, the blood holds less O2)

blood then diffuses through capillaries in the pulmonary circuit, CO2 then diffuses out of the blood to the alveoli–> curve shifts leftward, facilitating the loading of O2 (a given PO2, the blood holds more O2 when the oxyHgb curve shifts left)

Question 16

Is oxygen release from hemoglobin to the tissues increased or decreased by acidosis?

Answer 16

increased; acidosis causes a rightward shift facilitating the unloading of O2 to the tissues–> increasing O2 delivery to the tissues

Question 17

Total O2 carrying capacity of the blood is the sum of what two values?

Answer 17

hgb bound to O2 and dissolved Hgb

Question 18

Who’s law explains O2 dissolved in the blood?

Answer 18

Henry’s

dissolved oxygen= 0.003 x PO2

Question 19

Most of the contribution to the O2 carrying capacity of the blood is from _______.

Answer 19

Hb bound O2

dissolved O2 only makes up a small portion

Question 20

dissolved oxygen = ________ x ________

Answer 20

0.003 x PO2

Question 21

How much oxygen is dissolved in arterial blood if PaO2 is 90mmHg?

Answer 21

dissolved O2: 0.003 x 90= 0.27

Question 22

What is the difference in PO2 and PaO2?

Answer 22

nothing–> for the exam purpose

Question 23

Calculate the increase in dissolved oxygen in the arterial blood if PaO2 increases from 50mmHg to 300mmHg.

Answer 23

50 x 0.003= 0.15
300 x 0.003= 0.9
0.15-0.9= 0.75
the increase in dissolved O2 is 0.75mL O2/100mL blood

Question 24

_______ liquids to dissolve gas, _______ liquids to dissolve solids.

Answer 24

cool; heat

Question 25

What is 0.003 in the dissolved O2 equation?

Answer 25

solubility coefficient

Question 26

O2 is carried in blood in two forms: ________ and _______

Answer 26

Hgb bound and dissolved

Question 27

In a young, healthy individual, normal arterial blood (PaO2-100mmHg) has ______ mL O2/100mL blood dissolved and ______ mL O2/100mL blood bound to hemoglobin (98.5% SaO2; 15g Hg/100mL blood).

Answer 27

0.3mL dissolved; 19.8mL bound

Question 28

What is the maximum oxygen carrying capacity of arterial blood in a young, healthy person breathing room air?

Answer 28

20.4mL; 20.1mL bound (100% saturation) and 0.3mL dissolved

Question 29

Therapy with 100% O2 will produce much greater increases in oxygen content of blood if ________.

Answer 29

if the Hgb was poorly saturated prior to the admin of O2

• pulmonary disease (pulm edema, deadspacing)
• poor perfusion in relation to ventilation respond well
• pt with shunt (poor ventilation in relation to perfusion) are less responsive

Question 30

Oxygen hemoglobin dissociation curve is a _______ shaped curve. The steep portion occurs when PO2 is ______.

Answer 30

S shaped; <60

Question 31

It is important to remember that most of the O2 carried in the blood is combined with hemoglobin. Only a small portion of the total amount of oxygen in blood is dissolved. This is an application of ______ law.

Answer 31

Henry’s

Question 32

To calculate the amount of O2 bound to hemoglobin, you need to know:
the amount of oxygen carried by each gram of fully saturated hemoglobin = _________

the normal concentration of Hemoglobin = ________

and the % saturation (ex: 90%)

Answer 32

1.34mL O2 per g Hgb

15g Hb per 100mL blood

Question 33

What is the equation to calculate bound hemoglobin?

Answer 33

bound Hgb= 1.34 x 15 x % sat

so for 90% saturation= 1.34 x 15 x 0.9= 18.1 mL O2/dl

Question 34

Since you know the equation for dissolved Hgb is PO2 x 0.003…. what is the total amount of O2 carried by blood when it is 90% saturated?

Answer 34

1.34 x 15 x 0.9= 18.1 (bound)
90% is ~ 60mmHg PO2, so:
60 x 0.003= 0.18
then just add:
0.18 + 18.1= 18.28 mL O2/100mL blood

Question 35

If SvO2 is 70%, how much oxygen is dissolved in venous blood?

Answer 35

so if SvO2 is 70%, PvO2 is 40mmHg;

so, 0.003 x 40= 0.12 mL O2/100mL

Question 36

The CO2 dissociation curve shifts _____ and to the _____ when PO2 decreases, and shifts _____ and to the _____ when PO2 increases.

Answer 36

The CO2 dissociation curve shifts UP and to the LEFT when PO2 decreases, and shifts DOWN and to the RIGHT when PO2 increases.

Question 37

What effect does opioid administration have on the blood CO2 dissociation curve?

Answer 37

opioids shift the CO2 dissociation curve up and to the left b\c of the decrease in PaO2 secondary to opioid induced respiratory depression

Question 38

The _______ describes how a change in partial pressure of oxygen (PO2) in the blood influences the blood CO2 dissociation curve.

Answer 38

Haldane effect

Question 39

A shift in the CO2 dissociation curve leftward facilitates _______.

Answer 39

loading of CO2 into the blood (at the tissues)

Question 40

A shift in the CO2 dissociation curve rightward facilitates _______.

Answer 40

unloading of CO2 (blood to alveoli)

Question 41

_____ % of CO2 in the plasma is in the form of ______. Total amount of CO2 that is _______ is _______%

Answer 41

70% of CO2 in plasma is HCO3-

total amount of CO2 that is HCO3= is 90%

Question 42

CO2 is carried in the blood:

1) in _____ form
2) as ______
3) chemically bound to ______

Answer 42

CO2 is carried in the blood:

1) in dissolved form
2) as bicarbonate
3) chemically bound to proteins (to plasma proteins and Hgb)

Question 43

What are the two main byproducts of ATP?

Answer 43

CO2 and H2O (mitochondria)

Question 44

Dissolving gases= ______ law

Diffusing gases= ______ law

Answer 44

dissolving = Henry (dissolved O2)
diffusing = Fick's

Question 45

Explain the general process of conversion of CO2 to bicarbonate in red blood cells.

Answer 45

CO2 diffuses from the metabolizing cell into plasma down a gradient—> gets hydrated (CO2 + H2O)—> forms carbonic acid (H2CO3–> weak acids like to give up a H+—> Le Chatliers principle “if you are not in equilibrium, Le Chatlier is here”–> dissociates to HCO3 and H+–> HCO3 diffuses out of the RBC down a concentration gradient (70% of CO2 is in plasma)–> Cl- diffuses into the RBC as HCO3- diffuses out (Hamburger shift)

Question 46

The exchange of Cl- for HCO3- is the chloride shift, which is also referred to as the ______.

Answer 46

Hamburger shift

Question 47

How do you calculate the amount of CO2 dissolved in blood?

Answer 47

multiply PCO2 x 0.067 (Henry’s law applies)