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LANCE > Pulse Oximeter > Flashcards

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
Q

what is the PAO2 minimally determined by?

A

minute ventilation

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26
Q

What is a normal PAO2?

A

70-100mmHg

5x FiO2

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27
Q

T/F a patients PAO2 increases with age?

A

false, the PAO2 decreases with age

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28
Q

What is the PaO2 mainly determined by?

A

PAO2

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29
Q

A-a gradient

A

the difference in PAO2 and PaO2

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30
Q

what is a normal A-a gradient?

A

5-15mmHg room air

10-110mmHg on 100% FiO2

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31
Q

What widens the A-a gradient?

A

lung disease (PAO2 will stay the same but PaO2 will decrease)

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32
Q

What is SaO2 primarily determined by?

A

PaO2

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33
Q

when the PaO2 is 60mmHg what is SaO2?

A

90%

34
Q

when the PaO2 is 27mmHg what is SaO2?

A

50%

35
Q

what are the 7 other things that can affect SaO2?

A 
ph
CO2
temp
anemia
2,3 DPG
carboxyhemoglobin levels
methemoglobin levels
36
Q

right shift of HbO2 curve

A

better oxygen delivery to tissues

hemoglobin doesnt hold oxygen as well

37
Q

what causes a right shift in the HbO2 curve?

A

acidosis
increased 2,3-DPG
anemia
hyperthermia

38
Q

acidosis

A

increased CO2 (hypoventilation) or decreased pH

39
Q

left shift of the HbO2 curve

A

worse oxygen supply to the tissues

Hb has a higher affinity for oxygen

40
Q

what causes a left shift of HbO2 curve?

A 
alkalosis
decreased 2,3-DPG
hypothermia
methemoglobinemia (MetHb)
carboxygemoglobinemia (COHb)
41
Q

alkalosis

A

decreased CO2 (hyperventilation) or increased pH

42
Q

P50

A

a PaO2 that will cause an SaO2 of 50%

43
Q

P50 of sickle cell anemia patient

A

31mmHg

44
Q

P50 of pregnant mother

A

30mmHg

45
Q

P50 of a normal adult

A

27mmHg

46
Q

P50 of fetus

A

19mmHg

47
Q

P50 of packed RBC after ~35 days (end of storage)

A

18mmHg

48
Q

ABG

A

arterial blood gas

how to directly measure SaO2

49
Q

What are the two things that the SaO2 measures for us?

A

oxygen saturation

HR

50
Q

plethysmography

A

light shines through blood on each pulse

51
Q

beer lambert law

A

oxygenated and deoxygenated blood absorb light differently

52
Q

what nm is red?

A

660nm

53
Q

what nm is infrared?

A

940nm

54
Q

which light does oxygenated Hb absorb more of?

A

infrared

red light passes through

55
Q

which light does deoxygenated Hb absorb more of?

A

red light

more infrared passes through

56
Q

Is the SpO2 accurate if the waveform is bad?

A

no

57
Q

accuracy of SpO2 monitor

A

saturation above 70%= 95% accurate
saturation below 70% = +/- 4% error
sat below 50% = +/- 15% error

58
Q

when can/should you trust the SpO2 monitor

A

if it has a good waveform

59
Q

other places to monitor SpO2

A

ear

nose

60
Q

causes of low SpO2, despite normal SaO2

A

1- inaccurate waveform

  1. motion or shivering
  2. diagnostic dye
  3. dark nail polish
  4. manual BP cuff inflation (on same arm)
  5. CO poisoning
  6. CN- toxicity
61
Q

what can inaccurate waveform be caused by?

A

decrease Q/ hypotension/ low perfusion state
vasoconstriction (compensatory mechanism or cold pt)
misplaced probe

62
Q

Carbon monoxide (CO) poisoning

A

CO binds Hb and displaces O2

skin appears pink red

63
Q

how much more affinity does CO have for Hb compared to O2?

A

230x

64
Q

what are the clinical implications of CO poisoning?

A
  1. SpO2 is normal or elevated
  2. SaO2 is decreased
  3. patients PaO2 doesn’t change
65
Q

when is it possible to have hypoxia with a normal PaO2?

A

CO poisoning

CN toxicity

66
Q

how do we diagnose CO poisoning?

A

draw blood

special pulse ox called co-oximeter

67
Q

What are the causes of COHb?

A
  1. smoking/smoke inhalation (fire)

2. dried out CO2 absorbent

68
Q

why does dried out CO2 absorbent cause COHb?

A

degredation of volatile agents will produce CO

69
Q

how to treat CO poisoning?

A

administer oxygen

70
Q

what are the causes of CN- poisoning?

A
  1. high doses of nitroprusside (Nipride)
  2. smoke inhalation
  3. inhaling chemicals
71
Q

what are the two treatments for cyanide poisoning

A

sodium nitrate

sodium thiosulfate

72
Q

how to diagnose CN- poisoning

A

ABG

co oximeter

73
Q

Methemoglobinemia (methemoglobin formation)

A

changes the Fe 2+ to a Fe3+ (loses electron)

74
Q

what are the causes of MetHb?

A
  1. high doses of nitroprusside (nipride)
  2. high doses of nitroglycerin (NTG)
  3. local anesthetic spray
  4. factory/mine/pesticide/chemical workers
75
Q

nipride

A

potent vasodilator

light sensitive

76
Q

when do we use benzocaine or cetacaine?

A

fiberoptic intubation

77
Q

clinical implications of MetHb

A
  1. SaO2 decreases
  2. SpO2 reads 85%
  3. PaO2 doesn’t change
  4. cyanosis
78
Q

what is the treatment for MetHb?

A

methylene blue

79
Q

diagnosis for MetHb?

A

ABG

co oximeter

80
Q

SpO2 of 85%

A

MetHb

LANCE (17 decks)

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