Module 5 Gas Transport Flashcards
1
Q
Oxygen transport:
Blood carries O2 in 2 forms, what are they?
A
Dissolved (physical) and (chemically) bound to hemoglobin
2
Q
How is O2 dissolved into hemoglobin (Hb)?
In other words, what are 2 routes for O2 to get transported?
A
Physically dissolved in plasma (2%) O2 enters the blood and dissolves (98%)
3
Q
Which law calculates how blood is dissolved?
A
Henry’s law.
Dissolves O2 (ml/dl) = PaO2 (mmhg) x 0.003 (ml/dl/mmhg)
4
Q
How many grams of hemoglobin bind to oxygen?
A
each gram of Hb can bind 1.34 ml of O2
5
Q
What does mL/dL refer to?
A
Volumes percent milliliters per 100 millilitres
6
Q
How do you calculate O2 capacity?
A
[Hbg] x 1.34 ml O2
7
Q
True or false:
There is more O2 transported bound than dissolved.
A
True.
70 times more O2 transported bound than dissolved
8
Q
How do you calculate Hemoglobin saturation?
A
[HbO2 / Total Hb] x 100
Normal SaO2 is 95% to 100%
9
Q
What is hemoglobin saturation?
A
The percentage of Hb saturated with O2 compared to total Hb.
10
Q
Why does no one get 100% O2 saturation?
A
If every hemoglobin were saturated with O2, it would mean nothing was being offloaded to tissue.
(ask Harjot)
11
Q
What is the HbO2 dissociation curve?
A
A S-shaped curve that describes the relationship between PaO2 and SaO2.
TLDR: how ready hemoglobin acquires/releases O2 into fluid around it.
12
Q
HbO2 dissociation curve question: What does SaO2 > 90% indicate?
(think plateu)
A
Facilitation of loading O2 at pulmonary capillaries
-even with low PaO2?
13
Q
HbO2 dissociation curve question:
What does SaO2 < 90% indicate?
A
The steep portion reflects the unloading of O2 at tissues.
14
Q
True or False:
The more Oxygen is bound, the easier it is for the next O2 molecule to bind.
A
True.
They speed up rapidly and eventually slow when there are no more binding sites.
15
Q
What is Ischemia?
A
condition in which the blood flow (and thus oxygen) is restricted or reduced in a part of the body
16
Q
What factors support O2 binding to Hb?
A
More O2 binding to each molecule
The presence of Iron (to be specific ferrous iron)
17
Q
What is PvO2 and what is a normal saturation?
A
Mixed venous oxygen pressure
Norm = 40 mmhg
18
Q
What does the steep and flat part of the HbO2 curve reflect?
A
Conditions in the tissue and lungs.
19
Q
Oxygen dissociation curve: if O2 binds, does SaO2 and PaO2 increase?
A
Yes. this exchange occurs at the lungs when it is leaving.
20
Q
When it O2 leaves the blood + Hb at tissue (entering the cell), O2 dissociates. Does SaO2 and PaO2 go up or down?
A
They both decrease.
21
Q
Oxygen dissociation curve: what happens during a right shift?
A
When the curve shifts right, SaO2 decreases.
22
Q
Oxygen dissociation curve: what does the x and y axis represent?
A
Y reps SaO2
X reps PaO2
23
Q
Oxygen dissociation curve: what does a right shift mean?
A
O2 Dissociation.
There is less O2 on the Hb, meaning it SHOULD be in the tissue.
24
Q
Oxygen dissociation curve: what does a right shift mean?
hint Bohr effect
A
There is less O2 on the Hb, meaning it SHOULD be in the tissue.
AKA increase in O2 from Hb to tissue.
25
Oxygen dissociation curve: What happens during a left shift?
SaO2 increases
Hb affinity increases so there is a decrease in O2 dissociation.
26
What is the Bohr effect
The rate of O2 unloading is increased in metabolically active tissues due to increased acidity.
27
How do you calculate the amount of O2 unloaded to tissue?
You subtract arterial blood (blood before gas exchange) and venous blood (blood after gas exchange)?
28
Bohr vs Haldane effect?
The Bohr effect helps the metabolizing tissues release oxygen from oxyhemoglobin, while the Haldane effect helps the lungs release carbon dioxide from carboxyhemoglobin.
Bohr reps high affinity for O2 while Haldane is the opposite.
29
Haldane effect?
The ability of deoxygenated hemoglobin to carry more CO2 than in the oxygenated state.
30
Oxygen dissociation curve: what does a left shift indicate?
O2 must be away from tissue.
There is a decreased release of O2 from Hb to tissue
31
Oxygen dissociation curve: which shift is a acidosis and alkalosis
Right: Acidosis
(H+, Ph down) 2-3 dpg up
Left: Alkalosis
(H+ down, Ph up) 2-3 dpg down
32
What is DPG?
Diastolic Pulmonary GRadient
33
What is P50
measure of Hb's affinity for O2
34
P50 Normal?
27 mmhg
35
If 1g Hb carries a max of 1.34 ml of O2, what is a normal Hb level ?
12-15 g/dL
36
What is CaO2?
The total oxygen content of arterial blood.
37
What does CaO2 (arterial oxygen content) depend on?
hemoglobin content (bound and unbound)
SaO2
amount of dissolved O2
38
What is a normal range for CaO2?
16 - 20 ml/dl (Volume %)
39
What does this equation represent?
(Hb x 1.34 x SaO2) + (0.003 x PaO2)
How to calculate CaO2
40
What is CvO2?
Mixed venous oxygen saturation
41
What does this equation represent?
=(Hb x 1.34 x SvO2) + (0.003 x PvO2)
CvO2
42
What is the Arterio-venous difference?
a-vO2 is the difference in the oxygen content of the blood between the arterial blood and the venous blood.
43
What does the Arterio-venous difference indicate?
It indicates how much oxygen is removed from the blood in capillaries as the blood circulates in the body.
44
What is normal Arterio-venous difference?
5ml/dl
45
What is a normal cardiac output (Q) value?
5 l/min
46
What is the equation for cardiac output
Q = Stroke volume (ml/beat) x Heart rate (beats/min)
47
What is cardiac output?
The amount of blood ejected by the heart (to be specific, each ventricle) in one minute
48
What is DO2?
O2 delivered to all body tissue
Norm = 1000ml O2/min
49
What is VO2?
O2 consumed by tissues
Norm = 250ml/min
50
O2 delivery requires 4x the bodies resting requirement, what does this mean?
tissues use 25% of the O2 delivered to them
(ask Harjot)
51
What is the Oxygen-extraction ratio?
(O2ER)
A ratio of the body's oxygen consumption (VO2) compared to the systemic oxygen delivery (DO2)
52
What is a normal O2ER ratio value?
25%
53
If oxygen delivery decreases, what happens to O2ER?
It increases because tissues extract more of the delivered oxygen.
54
What is the equation for O2ER?
[O2ER]= C(a-v)O2 / CaO2
55
What two factors effect cardiac output?
Heart rate and stroke volume
56
What is stroke volume?
The volume of blood pumped by each ventricle with each heart beat (mL/beat)
57
Cardiac output is a good reflection of what?
The amount of blood passing through the heart each min
58
What are positive and negative chronotropes?
Factors that increase or decrease or heart rate.
59
What are factors of positive chronotropes?
Sympathetic stimulation
->Adrenaline (epinephrine/norepinephrine)
-> Drugs - Atropine
60
What are factors of negative chronotropes?
Parasympathetic stimulation
-> Acetylcholine
Drugs -> adenosine
61
What is preload?
The amount of blood entering the ventricles during diastole.
Also known as, end diastolic volume.
62
What 3 factors influence preload?
Venous return
Fluid volume
Atrial contraction
63
What is afterload ?
When the ventricles are contracting, ejecting blood out of the aorta and into the pulmonary trunk.
This occurs during systole.
64
What is after load indicate about circulation?
The resistance ventricles must overcome to circulate blood.
65
What factors affect afterload?
hypertension
vasoconstriction
These factors increase resistance, and inturn afterload.
66
What is contractbility?
How hard the myocardium contracts for a given preload
67
what is myocardium
muscles in the heart.
68
What factors influence contracbility?
Positive and negative Iontropic factors?
69
What are positive and negative iontropic factors?
Positive inotropic drugs help your heart beat with more force.
->dobutmaine + sympathetic stim
Negative inotropic drugs tell your heart muscles to contract with less force
-> parasympathetic stim.
->beta blockers and calcium channel blockers.
70
What are 4 determinants of cardiac output
Heart rate
Preload
Afterload
Contractability
71
What are 4 factors that affect O2 delivery (O2DEL or DO2)?
Hb concentration
SaO2
PaO2
Cardiac output
72
Why is the conversion done?
CaO2 x 10dL/L
To convert the dL -> mL O2/L blood
73
what does DO2 depend on?
CaO2 and Q (multiply them)
74
If O2 consumption is constant, what affect does a increase in O2 extraction have on cardiac output?
it decreases.
75
What is DO2crit?
A threshold value when DO2 fails to satisfy tissue demands
76
What happens when DO2crit is below its threshold?
Hypoxia
Lactic acid formation
decrease in plasma bicarbonate (a major blood buffer)
77
DO2crit is difficult to measure, what is a expected min in the ICU?
8-10ml/kg/min
(ask harjot)
78
What are 2 types of cyanosis?
Peripheral and Central cyanosis?
79
What causes Cyanosis?
when DeoxyHb > 5 g/dL
CO inhalation could be a cause as well.
Anemia OR polycythemia
80
What is peripheral cyanosis?
When tissue extracts a higher percentage of O2 from the blood than normal (low SvO2)
81
What is SvO2
Measure of the oxygen content of the blood returning to the right side of the heart after perfusing the entire body
82
Where would you see Peripheral cyanosis
Skin and nail beds (extremities)
83
Central cyanosis causes?
Low SaO2 < 83%
More profound hypoxemia than peripheral?
(ask harjot)
84
Where would you see central cyanosis?
Mucous membranes; so the eyes, mouth
85
what is anemia?
lack enough health RBC to carry adequate O2 to tissues.
low Hb
86
What is polycythemia?
a type of blood cancer that causes the bone to make too many RBC.
87
Why is polycythemia bad in relation to cyanosis?
Excess thickens blood, slowing its flow (circulation) and in turn creates the risk of blood clots
AKA SHUNTS
88
Shunt vs Deadspace
tip: ventilation = air entering.
Dead space = you're ventilating an area that isn't perfused. This means you're wasting ventilation, as no gas exchange occurs in the area of dead space.
Shunting = you're perfusing an area without ventilation, meaning that blood doesn't participate in gas exchange.
89
why are shunts bad?
If the blood doesn't participate in gas exchange, it won't blow off CO2 or load up new oxygen.
When that blood mixes with the other blood, it lowers the overall oxygen content of the arterial blood and increases the CO2 amount.
90
Why is someone who is anemic hypoxemic long before they are cyanotic?
Cyanosis is not reached initially due to less Hb available.
91
why is someone who is polycythemic cyanotic before they're hypoxemic?
Increased Hb means more Hb will be found in the reduced state.
(ask Harjot)
92
What hemoglobin abnormality has a greater affinity for CO than O2?
Carboxyhemoglobin (HbCO)
Hb has 210x greater affinity for CO
93
which direction does HbCO2 shift the oxyhemoglobin equilibrium curve?
Left
94
Why does HbCO2 shift the curve left? what does this indicate?
That Tissue PO2 must be very low to cause Hb to release O2
95
How do you reduce CO poisning or high levels of HbCO?
Hyperbaric O2 thearpy.
96
What are 3 hemoglobin varients?
Sickle cell (HbS)
Methemoglobin (metHb)
Fetal Hb (HbF)
97
What are 2 traits of HbF?
High affinity for O2
P50 = 22mmHg
98
Methemoglobin (metHb) what are its main traits?
It cannot bind O2
It is caused by nitrate poisoning or related toxic reactions to oxidant drugs.
99
what is Methemoglobin?
Methemoglobin is a form of hemoglobin that has been oxidized, changing its heme iron configuration from the ferrous (Fe2+) to the ferric (Fe3+) state.
Unlike normal hemoglobin, methemoglobin does not bind oxygen and as a result cannot deliver oxygen to the tissues.
100
What is normal MetHb levels?
Normal <1% of total Hb
101
What are sickle cell Hb?
c shaped hemoglobin that cause deoxygenation and blood clots in veins (Thromboemboli)
They also carry blood poorly
102
3 ways/mechanisms CO2 is transported?
Dissolve in plasma (10%)
Carbaminohemoglobin (20%) (CO2 + Hb)
Bicarbonate plasma (70%)
-performing HCO3 can be done in
RBC (fast) or plasma (slower)
103
How does CO2 dissolve in blood?
[H2O + CO2] -> HCO3 + [H+]
104
What is a by product aerobic metabolism?
CO2 and lactate.
105
What is average tissue PCO2?
46mmhg
106
What is VCO2? and what is its normal?
Carbon Dioxide Output (VCO2): refers to the amount of carbon dioxide exhaled from the body per unit time.
Its increases progressively overtime.
107
What is a normal range of CO2 produced by the body at rest?
200 mL/min at rest. (VCO2)
108
what is average PaCO2?
40mmhg
109
What is average tissue PCO2
46mmHg
110
What is dissolved CO2 expressed in?
mmol/L
111
When CO2 is hydrolyzed, what does it form?
H2CO3, it is a right shift equation and is treated like a acid.
112
At equilbrium, the concentration of HCO3 (bicarbonate) is much greater than the concentration of H2CO3 (carbonic acid), what is the ratio?
20:1
113
what does H2CO3 dissociate into?
HCO3 + [H+]
114
How much dissolved CO2 is found in venous blood (normal)
3mL/dL
115
what is carbonic anhydrase?
an enzyme catalyst that assists rapid inter-conversion of CO2 and H2O into carbonic acid.
116
Chloride shift: what happens within the RBC when HCO3 and [H+] forms?
*hint* think balance and gradients.
Hb Removes [H+]
HCO3 diffuses into plasma
Cl in plasma diffuses into RBC
keeps electrolytic equilbrium.
117
In a chloride shift, why does HCO3 and Cl shift sides?
HCO3 in RBC > in plasma
Cl in plasma > than in RBC
This is all kicked off when Hb removes [H+] from solution.
118
Hypoventilation: which way will hydrolysis shift and what factors are affected?
Right shift
CO2 Increase = PaCO2 increase
119
Hypoventilation: what does CO2 and PaCO2 increase indicate? what does the right shift indicate?
CO2 production momentarily exceeds CO2 elimination
120
Hypoventilation: when alveolar gas and blood eventually reach equilibrium what happens to PaCO2? what are the implications on ventilation?
When equilibrium is finally reached, CO2 elimination = CO2 production match each other at a higher PaCO2
This implies Ventilatory reserve decreases.
121
what does lower ventilatory reserve imply?
Higher blood acid levels (low ph)
Less ventilatory work to eliminate CO2
122
which way does Hyperventilation affect the hydrolysis reaction?
Left shift reaction
Notes - H2CO3 decreases as a result because of the left shift.
123
what happens to CO2 and PaCo2 during hyperventilation?
CO2 elimination momentarily exceeds CO2 production
124
what are the implications of hyperventilation?
More ventilatory work to eliminate CO2
so, blood acid levels will be lower (higher pH)
125
What binds with heme?
O2
126
What does CO2 combine with?
amino groups of proteins
127
What does the Haldane effect imply about Hb and binding sites for O2/CO2?
Hb affinity for CO2 is greater when not combined with O2
128
what does the Bohr effect have to do with Hb and binding sites for O2/CO2?
Hb has decreased affinity for O2
129
How do you calculate how much CO2 is taken up by blood at the tissues.
CvCO2 – CaCO2 = CO2 taken up at tissue level.
130
What are the normal values for CO2 picked up from blood at the tissue for the following?
DCO2
HCO3
Carbamino compounds
DCO2 = 8%
HCO3 = 80&
Carbamino compounds = 12%
131
True or false:
Bohr and Haldane effects mutually enhancing?
True.
132
why is the Bohr effect advantageous
The Bohr effect is important because it improves oxygen supply to muscles and tissues where metabolism and carbon dioxide production occur.
This aids in the delivery of oxygen to the areas where it is most needed.
133
why is the Haldane effect advantageous
Haldane effect are to promote unloading of CO2 in the lungs when blood is oxygenated, and CO2 loading in the blood when O2 is released to tissues.
134
How do you improve SpO2
Increase FiO2
135
If Henry's Law identifies how much O2 is dissolved in Hb, how do you calculate the total oxygen content of arterial blood?
Its a combo of dissolved and bound to Hb via formula
CaO2 = ([Hb] x 1.34 x SaO2) + (0.003 x PaO2)
136
Normal CaO2 Range?
(normal = 16-20 ml/dl)
137
Normal CvO2 range?
(normal = 12-15 ml/dl)
