Lecture 5: Transport Of Oxygen And Carbon Dioxide Flashcards
1
Q
What is tissue oxygenation?
A
Process of moving O2 and CO2 in and out of body tissues
2
Q
Diffusion is too slow for distances > than ___
A
100 micrometers
3
Q
What are four types of hypoxia?
A
- Hypoxic hypoxia
- Stagnant (ischemic) hypoxia
- Anemic hypoxic
- Histotoxic hypoxia
4
Q
Hypoxic hypoxia
A
- Inadequate O2 uptake into blood in lungs
- COPD
5
Q
Stagnant (ischemic) hypoxia
A
- Inadequate blood flow to an organ
- Arteriosclerosis, PVD
6
Q
Anemic hypoxia
A
- Inadequate blood oxygen carrying capacity
- Inactivated hemoglobin
7
Q
Histotoxic hypoxia
A
- Interference with mitochondrial respiration
- Cyanide poisoning
8
Q
Hypoxic hypoxia =
A
Low PO2 (because blood can’t take it up in the lungs)
9
Q
Anemic hypoxia =
A
Low hemoglobin
10
Q
Ischemic hypoxia =
A
Low perfusion (to an organ)
11
Q
Cytotoxic hypoxia =
A
Cells can’t utilize O2
12
Q
What is O2 carried by?
A
Red blood cells (erythrocytes)—hemoglobin (Hb)
13
Q
What is normal hemoglobin concentration?
A
150 g/L or 15 g/dL
14
Q
Hemoglobin carries ___ times more O2 than plasma
A
65 times more
15
Q
Plasma has a ___ capacity to carry or transport O2
A
Low
16
Q
___ amount of O2 dissolved in solution (plasma)
A
Small
17
Q
Hemoglobin is a ___
A
Oxygen carrier protein
18
Q
Subunits in hemoglobin
A
- 2 alpha
- 2 beta
19
Q
How many heme groups in hemoglobin?
A
4
20
Q
Only ___ can bind O2
A
Fe2+
21
Q
Molecular weight of hemoglobin is ___
A
64,000
22
Q
Each gram of hemoglobin can carry up to ___ ml of O2
A
1.31 ml of O2, theoretically up to 1.39 ml/gm
23
Q
Hemoglobin is the ___ form
A
Unoxygenated
24
Q
Oxyhemoglobin is when ___ is combined
A
O2
25
Very ___ coordination bonds between Fe2+ and O2
Loose—easily reversible
26
Oxygen is carried in its ___ state, not ___
Molecular (O2) state, not ionic O2-
27
The oxyhemoglobin curve is ___ shaped
Sigmoid
28
How many oxygen molecules can bind to one hemoglobin (Hb)?
Up to 4 oxygen molecules
29
What is oxygen saturation?
The ratio of oxygen bound to hemoglobin compared to the total amount that can be bound
30
What is oxygen capacity?
Maximal amount of O2 bound to hemoglobin
31
Sat 100 = PaO2 ___
100+
32
Sat 95 = PaO2 ___
75
33
Sat 90 = PaO2 ___
60
34
Sat 75 = PaO2 ___
40 (mixed venous blood in pulmonary artery)
35
Sat 60 = PaO2 ___
30
36
Sat 50 = PaO2 ___
27 (Hb P50 point)
37
Very rough rule—PaO2 40,50,60 for Sat ___
70, 80, 90
38
P50 of Hb =
PaO2 27
39
What are ligands of hemoglobin?
Form covalent bonds to the ferrous iron in hemoglobin
40
The covalent bonds of ligands have ___ affinity to iron than oxygen
More affinity
41
Oxygen binds ___ to hemoglobin
Weakly
42
Two types of ligands of hemoglobin:
- Carbon monoxide
| - Nitric oxide
43
Carbon monoxide has ___ times the affinity of oxygen for hemoglobin
250 times
- Does not dissociate readily
- Requires hours to rid body of CO
44
Nitric oxide binds to Hb ___ times more strongly than oxygen
200,000 times
45
Hemoglobin binds ___ to NO
Irreversibly
46
Nitric oxide is used to treat ___
Pulmonary hypertension
47
The hemoglobin-oxygen equilibrium curve shows the relationship between ___ and ___
Hemoglobin oxygen concentration and oxygen partial pressure
48
What is the shape of the hemoglobin-oxygen equilibrium curve?
Sigmoid also shape
49
P50 is the PO2 when hemoglobin is ___ saturated
50%
50
P50 of Hb = PO2 of ___
27 mm Hg
51
How is the hemoglobin-oxygen equilibrium curve affected? (2 ways)
- Shift in position
| - Change in shape
52
What indicates a greater interference with O2 transport—change in shape or curve shift?
Change in shape
53
Increased O2 affinity = shift to the ___
Left
54
Examples of increased affinity (7)
- Acute alkalosis
- Decreased PCO2
- Decreased temperature
- Low levels of 2,3 DPG
- Carboxyhemoglobin
- Methemoglobin
- Abnormal hemoglobin
55
Decreased O2 affinity = shift to the ___
Right
56
Examples of decreased affinity (5)
- Acute acidosis
- High CO2
- Increased temperature
- High levels of 2,3 DPG
- Abnormal hemoglobin
57
Shift to the right reduces the affinity for O2 below PO2 ___ mm Hg
70 mm Hg
58
Shift to the right occurs because of ___ PCO2 and ___ ions
Rising PCO2 and rising H+ ions
59
What is the Bohr effect?
An increase in H+ decreases Hb’s affinity for O2
60
A shift to the right enhances the quantity of...
O2 released in systemic capillaries
61
A shift to the right increases ___ of O2 to ___
Delivery of O2 to tissues
62
Right shift = Hb has ___ affinity for O2, ___ O2, saturation will be ___ for a given PO2
Hb has less affinity for O2, releases O2, saturation will be less for a given PO2
63
Left shift = Hb has ___ affinity for O2, ___ O2, saturation will be ___ for a given PO2
Hb has higher affinity for O2, binds O2, saturation will be higher for a given PO2
64
Increased CO2 = shift to the ___
Right
65
Increased temperature = shift to the ___
Right
66
Increased metabolism = shift to the ___
Right
67
Increase H+ = shift to the ___
Right (Bohr Effect)
68
Acidosis/lactic acid production = shift to the ___
Right
69
Increased 2,3 DPG = shift to the ___
Right
| -2,3 DPG binds to Hb over O2, thus decreases Hb’s affinity for O2
70
PRBCs are stored ___
Cold
71
PRBCs have significantly ___ levels of 2,3 DPG
Diminished
72
Hb in stored blood would initially show a ___ shift in the Hb-O2 dissociation curve
Left shift
73
What is myoglobin?
Single chained heme pigment found in skeletal muscle
74
Myoglobin has an ___ affinity for O2
Increased—binds O2 at a lower PO2
75
Myoglobin stores O2 temporarily in ___
Muscle
76
What does CaO2 stand for?
O2 content in blood
77
What does CaO2 measure?
The sum of O2 carried on Hb AND dissolved in plasma
78
How to calculate CaO2:
CaO2 = (SO2 x [Hb] x 1.31) + (PO2 x 0.003)
79
CaO2 =
O2 content in blood (ml/dL)
80
SO2 =
Hb saturation (can use SPO2–pulse ox. Or SaO2–saturation from blood gas (ABG), as a %)
81
[Hb] =
Hb concentration in gm/dL
82
1.31 =
O2 binding to Hb (ml/gm)
83
PO2 =
Arterial blood’s partial pressure of O2
84
What does DO2 stand for?
Oxygen delivery
85
How do you calculate DO2?
DO2 = CaO2 x CO (cardiac output)
86
What can alter the equilibrium curve?
Any factors that reduce Hb’s ability to transport O2
87
What are two things that can reduce Hb’s ability to transport O2?
- CO
| - Anemia
88
CO ___ the available Hb able to transport O2
Reduces
89
Anemia
- Decrease in hemoglobin
| - Decreases O2 content in blood
90
Tissue PCO2 is ___ mm Hg
50 mm Hg
91
Carbonic acid is converted to ___ to be exhaled in the lungs
CO2
92
CO2 production averages ___ ml/min in resting adult
200 ml/min
93
During exercise, CO2 production may increase ___
Six-fold
94
___ amount of CO2 remains in blood and is required in maintenance of the ___
High amount, maintenance in hydrogen ion concentration
95
Carbon dioxide is transported by blood in three forms:
- Dissolved directly in blood
- Bicarbonate ion (HCO3-) and carbonic acid (H2CO3)
- Bound to hemoglobin and plasma proteins
96
Most CO2 is ___ for transport
Dissolved directly in the blood
97
How is the HbCO2 curve different than the HbO2 curve? (2)
- Relationship is linear
| - Venous blood transports more CO2 than arterial blood
98
CO2 equilibrium is affected by ___
O2 saturation of Hb
99
Ability to bind with CO2 is increased in ___ Hb
Deoxygenated Hb
100
Deoxygenated Hb is a ___ than oxygenated Hb
Weaker acid
101
Haldane effect = upon binding O2, Hb releases ___ and ___, which in turn is converted into ___
Releases CO2 and H+, converted into CO2
102
A-a PCO2 levels are not as affected by ___
V/Q mismatch
103
Why are A-a PCO2 levels not as affected by V/Q mismatch?
Because the diffusing capacity of CO2 is 20x’s greater than that of O2
