Blood Gas Transport Flashcards
1
Q
common measure of oxygenation
A
Alveolar to arterial oxygen gradient (A-a)
2
Q
How do you measure PaO2?
A
arterial blood gas
3
Q
How do you calculate PAO2?
A
alveolar gas equation
4
Q
FiO2
A
fraction of inspired O2
5
Q
what is FiO2 in room air?
A
0.21
6
Q
what is atm P at sea level
A
760 mmHg
7
Q
what is the partial P of water
A
47 mmHg
8
Q
what is PaCO2?
A
arterial CO2 tension
9
Q
the A-a gradient calculated may deviate from the true gradient by up to –
A
10 mmHg
10
Q
the normal A-a gradient varies with –
A
age
11
Q
A-a gradient increases with –
A
higher FiO2
12
Q
How does A-a gradient increase with high FiO2?
A
both PAO2 and PaO2 increases but PAO2 increases disproportionately
13
Q
The use of a 100 percent non-rebreathing mask reasonably approximates actual – and can be used to measure shunt.
A
delivery of 100 percent oxygen
14
Q
normal PaCO2
A
40
15
Q
normal PaO2
A
100
16
Q
Henry’s lawstates that at a constant temperature, the amount of a gas that is dissolved in a liquid is directly proportional to –
A
the partial pressure of that gas
17
Q
This law provides the explanation for decompression sickness and nitrogen narcosis.
A
Henry’s law
18
Q
Henry’s law directly – the amount of gas that can be dissolved in plasma.
A
limits
19
Q
Hemoglobin is an –
A
iron-porphyrin compound
20
Q
each globin chain has a –
A
heme moeity
21
Q
amount of hemoglobin in an adult male
A
[Hb] = 15 g/dL
22
Q
how much oxygen can Hb carry
A
200 ml/L
23
Q
Different types of heme have different – and disorders of hemoglobin affect the ability to carry oxygen
A
oxygen affinity
24
Q
which type of iron doesn’t bind oxygen that well
A
ferric (Fe3+)
25
Hemoglobin undergoes a conformational change when --
oxygenated
26
Hb conformational change leads to -- in pulse oximetry
color change
27
hemoglobin/oxygen binding curve, we see a steep slope up to a --, then starts to flatten
PO2 of about 50
28
Note that beyond a --, the hemoglobin binding of oxygen barely increases at all
PO2 of 100
29
Oxygen saturation is determined by the percentage of --
available Heme binding sites that have bound oxygen
30
In normal conditions, a PO2 of 100 gives SpO2 (oxygen saturation) of about --.
97.5%
31
A shift to the right in the hemoglobin-oxygen association/dissociation curve indicates that a -- partial pressure of oxygen is required to saturate hemoglobin at the level of the lungs
larger
32
a right shift in the hemoglobin-oxygen association/dissociation curve, corresponds to -- affinity
reduced oxygen
33
potent modulator of the affinity of hemoglobin for oxygen
2,3 bisphosphoglycerate
34
2,3-BPG is a polyanion that binds strongly to --
deoxyhemoglobin
35
2,3-BPG is a polyanion that binds weakly to
oxyhemoglobin
36
Binding takes place in the -- where the negative charges of 2,3-BPG are neutralized by the beta NH2 terminus histidine, beta82 lysine, and beta143 histidine.
central cavity between the two beta chains
37
Binding to -- helps to stabilize the tense (T) structure of hemoglobin and decrease oxygen affinity.
deoxyhemoglobin
38
In oxyhemoglobin, the -- are insufficiently spread apart to permit firm binding of 2,3-BPG.
H helices of the beta chains
39
Increasing levels of 2,3-BPG -- oxygen affinity
decrease
40
Increasing levels of 2,3-BPG shift the hemoglobin oxygen dissociation curve to the --
right
41
Increasing levels of 2,3-BPG -- the delivery of oxygen to tissues
increase
42
Decreased levels of 2,3-BPG due to a BPGM mutation lead to a -- shift in the hemoglobin oxygen dissociation curve
left
43
Decreased levels of 2,3-BPG leads to a -- delivery of oxygen to tissues.
decreased
44
Decreased delivery of oxygen to tissue leads to increased production of --
erythropoietin
45
Oxygen affinity varies -- with temperature
inversely
46
CO2 can react with free amino groups at the N termini of the alpha and beta chains to form --
carbamino complexes
47
carbamino complexes is formed more readily by --
deoxyhemoglobin
48
at any given pH, CO2 -- oxygen affinity
lowers
49
Normally, approximately 10 percent of CO2 is -- in the form of carbamino hemoglobin
transported to the lungs
50
The oxygen affinity of hemoglobin increases as a function of pH over a range of --, a phenomenon known as the Bohr effect.
6.0 to 8.5
51
Under physiologic conditions, a molecule of hemoglobin releases approximately -- upon oxygenation.
2.8 protons
52
A substantial portion of the Bohr effect is due to an -- between the positively charged imidazole of beta146 histidine and the negatively charged carboxyl of beta94 aspartate
intrasubunit salt bond
53
Molecular changes when Hb is oxygenated?
salt bond breaks and protons are released
54
two main physiological consequences of Bohr Effect
more oxygen is delivered to tissues and oxygen is more easily taken up in pulmonary circulation
55
how is CO2 carried in blood?
dissolved gas, bicarbonate ions, carbamino compounds
56
solubility CO2 in plasma
0.67 ml/L/mmHg
57
solubility O2 in plasma
0.03 ml/L/mmHg
58
what makes up the bulk of CO2 transport
bicarbonate ions
59
CO2 dissociates in water to --
carbonic acid
60
the dissociation of CO2 into water and carbonic acid is -- in plasma
slow
61
the dissociation of CO2 into water and carbonic acid is accelerated in the cell by --
carbonic anhydrase
62
dissociation of carbonic acid into -- happens quickly
bicarbonate and hydrogen ions
63
-- shifts into the cell from the plasma to maintain electrical neutrality
Chloride
64
-- shifts easily out of the cell
bicarbonate
65
hydrogen ions diffuse more slowly due to the -- of the cell membrane to cations
relative impermability
66
since deoxy Hb is -- it can readily bind the protons of the dissociated hydrogen ions
reduced (proton acceptor)
67
higher dissolved CO2 proportion in --
venous
68
higher bicarbonate proportion in --
arterial
69
higher carboamino proportion in --
venous
70
CO2 dissociation curve is much more -- than oxygen curve
linear and steeper
71
the difference between the arterial and venous CO2 dissociation curves is explained --
Haldane effect
72
Haldane effect
oxygen unloading increases CO2 affinity
73
T/F: CO forms stable bonds with heme moiety
true
74
compared to oxygen, CO has a -- affinity to Hb
higher (200x)
75
In general, a -- difference in arterial and venous oxygen content per 100 mL blood is expected at rest.
5 mL
76
the effect of a 50% decrease in Hb (anemia) decreases -- but does not change the partial pressure at which Hb is 50% saturated (same P50)
A' (arterial) and venous oxygen content
77
bind more CO2 on -- side (deoxygenated) than arterial
venous
78
CO2 dissociation curve is -- than the O2 dissociation curve
steeper
79
CO will shift O2 dissociation curve to the --
left
80
anemia = lower Hb decreases O2 content but not --
oxygen saturation
81
effect of carboxyhemoglobinema (COHb)
decreases oxygen carrying capacity and impairs peripheral unloading of O2 at low oxygen tension
82
methemoglobinemia occurs when Fe2+ in heme are -- to ferric fe3+
oxidized
83
methemoglobinemia unable to --
reversibly bind oxygen
84
methemoglobinemia -- shift oxygen dissociation curve
left
85
methemoglobinemia has higher incidence in -- due to medication toxic effects
G6-PD deficiency
86
methemoglobinemia creates less functional Hb and impairs --
delivery of oxygen to tissues
87
clinical clues of methemoglobinemia
sudden cyanosis with hypoxia, hypoxia doesn't improve with O2, dark red muddy brown blood
88
does methemoglobinemia blood change color like deoxyHb when exposed to oxygen?
no
89
T/F: methemoglobinemia has a normal arterial PO2 (PaO2)?
true
90
methemoglobinemia can be caused by --
topical local anesthetics
91
can cyanide poisoning resolve with time?
no
92
what causes a left shift in the Hb-O2 dissociation curve?
decreased temp, decreased 2,3-BPG, decreased [H+], increased pH, CO
