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Pulse Oximeter Flashcards

1
Q

how many hemoglobin are in each RBC?

A

~300 million

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2
Q

how many subunits does a hemoglobin molecule have?

A

4 subunits

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3
Q

what is heme composed of?

A

porphyrin ring

iron

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4
Q

what is the oxygen binding site?

A

iron

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5
Q

How many oxygen molecules can one RBC hold?

A

over 1 billion

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6
Q

hematocrit

A

percentage of blood that is RBC

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7
Q

what are the three components of blood?

A

plasma
WBC/thrombocytes
RBC

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8
Q

what is a normal male hematocrit?

A

45%

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9
Q

what is a normal female hematocrit?

A

39%

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10
Q

for lab results is hematocrit a percentage or concentration?

A

percentage

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11
Q

for lab results is hemoglobin a percentage or concentration?

A

concentration

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12
Q

T/F hematocrit is usually ~3x the Hb

A

True

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13
Q

anemia

A

decrease in hemoglobin and/or a decrease in hematocrit

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14
Q

what are the causes of anemia?

A

blood loss
fluid administration
lysed RBC
decreased production of RBCs

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15
Q

what is common in people with renal failure?

A

decreased production of RBCs b/c of decreased EPO production

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16
Q

PAO2

A

partial pressure of oxygen in the alveoli

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17
Q

can PAO2 be measured?

A

no

but it can be calculated

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18
Q

PaO2

A

partial pressure of oxygen in the arteries

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19
Q

can PaO2 be measured?

A

yes with blood sample

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20
Q

SaO2

A

% of hemoglobin saturated with oxygen

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21
Q

what is the indirect way to measure SaO2?

A

pulse ox

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22
Q

what is the direct way to measure SaO2?

A

blood sample

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23
Q

what are the two primary determinants of PAO2?

A

FiO2

barometric pressure

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24
Q

if you have a low barometric pressure is your PAO2 lower or higher?

A

lower

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25
what is the PAO2 minimally determined by?
minute ventilation
26
What is a normal PAO2?
70-100mmHg | 5x FiO2
27
T/F a patients PAO2 increases with age?
false, the PAO2 decreases with age
28
What is the PaO2 mainly determined by?
PAO2
29
A-a gradient
the difference in PAO2 and PaO2
30
what is a normal A-a gradient?
5-15mmHg room air | 10-110mmHg on 100% FiO2
31
What widens the A-a gradient?
lung disease (PAO2 will stay the same but PaO2 will decrease)
32
What is SaO2 primarily determined by?
PaO2
33
when the PaO2 is 60mmHg what is SaO2?
90%
34
when the PaO2 is 27mmHg what is SaO2?
50%
35
what are the 7 other things that can affect SaO2?
``` ph CO2 temp anemia 2,3 DPG carboxyhemoglobin levels methemoglobin levels ```
36
right shift of HbO2 curve
better oxygen delivery to tissues | hemoglobin doesnt hold oxygen as well
37
what causes a right shift in the HbO2 curve?
acidosis increased 2,3-DPG anemia hyperthermia
38
acidosis
increased CO2 (hypoventilation) or decreased pH
39
left shift of the HbO2 curve
worse oxygen supply to the tissues | Hb has a higher affinity for oxygen
40
what causes a left shift of HbO2 curve?
``` alkalosis decreased 2,3-DPG hypothermia methemoglobinemia (MetHb) carboxygemoglobinemia (COHb) ```
41
alkalosis
decreased CO2 (hyperventilation) or increased pH
42
P50
a PaO2 that will cause an SaO2 of 50%
43
P50 of sickle cell anemia patient
31mmHg
44
P50 of pregnant mother
30mmHg
45
P50 of a normal adult
27mmHg
46
P50 of fetus
19mmHg
47
P50 of packed RBC after ~35 days (end of storage)
18mmHg
48
ABG
arterial blood gas | how to directly measure SaO2
49
What are the two things that the SaO2 measures for us?
oxygen saturation | HR
50
plethysmography
light shines through blood on each pulse
51
beer lambert law
oxygenated and deoxygenated blood absorb light differently
52
what nm is red?
660nm
53
what nm is infrared?
940nm
54
which light does oxygenated Hb absorb more of?
infrared | red light passes through
55
which light does deoxygenated Hb absorb more of?
red light | more infrared passes through
56
Is the SpO2 accurate if the waveform is bad?
no
57
accuracy of SpO2 monitor
saturation above 70%= 95% accurate saturation below 70% = +/- 4% error sat below 50% = +/- 15% error
58
when can/should you trust the SpO2 monitor
if it has a good waveform
59
other places to monitor SpO2
ear | nose
60
causes of low SpO2, despite normal SaO2
1- inaccurate waveform 2. motion or shivering 3. diagnostic dye 4. dark nail polish 5. manual BP cuff inflation (on same arm) 6. CO poisoning 7. CN- toxicity
61
what can inaccurate waveform be caused by?
decrease Q/ hypotension/ low perfusion state vasoconstriction (compensatory mechanism or cold pt) misplaced probe
62
Carbon monoxide (CO) poisoning
CO binds Hb and displaces O2 | skin appears pink red
63
how much more affinity does CO have for Hb compared to O2?
230x
64
what are the clinical implications of CO poisoning?
1. SpO2 is normal or elevated 2. SaO2 is decreased 3. patients PaO2 doesn't change
65
when is it possible to have hypoxia with a normal PaO2?
CO poisoning | CN toxicity
66
how do we diagnose CO poisoning?
draw blood | special pulse ox called co-oximeter
67
What are the causes of COHb?
1. smoking/smoke inhalation (fire) | 2. dried out CO2 absorbent
68
why does dried out CO2 absorbent cause COHb?
degredation of volatile agents will produce CO
69
how to treat CO poisoning?
administer oxygen
70
what are the causes of CN- poisoning?
1. high doses of nitroprusside (Nipride) 2. smoke inhalation 3. inhaling chemicals
71
what are the two treatments for cyanide poisoning
sodium nitrate | sodium thiosulfate
72
how to diagnose CN- poisoning
ABG | co oximeter
73
Methemoglobinemia (methemoglobin formation)
changes the Fe 2+ to a Fe3+ (loses electron)
74
what are the causes of MetHb?
1. high doses of nitroprusside (nipride) 2. high doses of nitroglycerin (NTG) 3. local anesthetic spray 4. factory/mine/pesticide/chemical workers
75
nipride
potent vasodilator | light sensitive
76
when do we use benzocaine or cetacaine?
fiberoptic intubation
77
clinical implications of MetHb
1. SaO2 decreases 2. SpO2 reads 85% 3. PaO2 doesn't change 4. cyanosis
78
what is the treatment for MetHb?
methylene blue
79
diagnosis for MetHb?
ABG | co oximeter
80
SpO2 of 85%
MetHb

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