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I & M > Oximetry and Pulse Ox > Flashcards

Oximetry and Pulse Ox Flashcards

1
Q

What is the respiratory quotient?

A

Amount of CO2 produced / % of O2 consumed

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2
Q

Why is oximetry measured?

A

Der b/c we need O2 to live

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3
Q

What is the normal O2 consumption of a 70 kg patient?

A

3.3 mL / kg

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4
Q

On room air (21% FiO2) what is the normal FeO2 and that means we consume approximately how much O2?

A

Normal FeO2 = 18%

so that means we consume about 3% of minute ventilation

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5
Q

According to the normal O2 consumption of a 70 kg patient, how much O2 is that per min?

A

3.3 mL / kg and 70 kg

= 250 mL of O2 / min

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6
Q

Hypoxemia and hypoxia both give a determination of what?

A

Amount of O2 in the blood and tissues

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7
Q

What is an easy deadspace calculation?

A

The pt’s weight in lbs

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8
Q

What is the minimum tidal volume to maintain oxygenation and to reduce amount of atelectysis?

A

3-4 x deadspace

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9
Q

What is the minimum oxygen percent you can give to your patient that has 0 V/Q mismatch and no circuit leaks of any kind?

A

5%

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10
Q

What is carboxyhemoglobin?

Who does this occur in?

A

Carbon monoxide bound hemoglobin

Smokers

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11
Q

What is methemoglobin?

A

Where the heme molecule losses an electron of iron (Fe) and causes hemoglobin molecule to lose its shape

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12
Q

What is sulfhemoglobin? Who does this occur in?

A

Sulfar bound Hb

Diabetics

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13
Q

What is sickle cell hemoglobin?

A

Sickled Hb which decreases the O2 carrying capacity

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14
Q

What is fetal Hemoglobin?

A

haha according to Biggs, the fetal people Hb

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15
Q

What is the oxygen content equation?

A

CO2 = 0.0031 x PO2 + 1.31 x O2 Hb x SO2

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16
Q

What does your minute ventilation approximately need to be equal to?

A

Cardiac output

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17
Q

What is oxyhemoglobin?

A

O2 bound hemoglobin

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18
Q

What is deoxyhemoglobin?

A

Reduced O2 bound hemoglobin

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19
Q

What is the standard for measuring oximetry? (we don’t use in OR)

A

Laboratory Bench Co-oximeters

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20
Q

What do we use in the OR for measuring oxygen saturation?

A

Pulse Oximeter

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21
Q

What is the fractional SaO2 formula used in the Co-oximeters?

A

O2 Hb /

O2 Hb + Deoxy Hb + CO Hb + Met Hb + HbF

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22
Q

What is the functional SaO2 formula used in pulse ox?

A

O2 Hb / O2 Hb + deoxy Hb

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23
Q

What are the 2 wavelenths used in pulse ox readings?

A

Red @ 660 nm

Infrared @ 940 nm

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24
Q

KNOW THE GRAPH ON PAGE 6 which is of the Hemoglobin extinction curves. If someone knows how to put pics in please do on the answer part of this question.

A

INSERT YOUR THINGY HERE

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25
Q

What does someone who has carboxyhemoglobin read on the pulse ox?

A

90%

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26
Q

What does someone who has methemoglobin read on the pulse ox?

A

85%

27
Q

What kind of pulse ox is used in adults?

A

Transmission

LED and photodetectors on opposite sides

28
Q

What kind of pulse ox is used in fetal monitoring?

A

Reflectance

LED and photodetectors on same side and reflects off bone

29
Q

Where can you put the pulse ox we use in the OR?

A 
Any protuberance
\:fingers
\:ears
\:tongue
\:nose
\:toes
\:lip
\:penis
30
Q

Which light wavelength is shown on the screen when using a pulse ox and why?

A

Infrared (940 nm) because it shows the greatest amplitude and is stronger at 100% O2 sat

31
Q

What is the assumed difference between what the screen shows and what the actually saturation may be?

A

+/- 2%

32
Q

What is the isobestic point?

A

Point at which frequency the two wavelengths absorb exactly the same amount of two hemoglobins

33
Q

What is the isobestic point of oxyhemoglobin and deoxyhemoglobin?

A

800 nm

34
Q

What causes right shifts in the oxygen-hemoglobin dissociation curve?

A 
R  (rightward)
I   (increase of CO2)
G  (2,3 DPG increase)
H  (H+ increase)
T   (Temp increase)
35
Q

What does a rightward shift indicate on the curve?

A

A decreased affinity for O2 binding or increased oxygen uploading

36
Q

What causes left shifts in the oxygen-hemoglobin curve?

A 
Exact opposite of right
\:Decreased CO2
\: decreased 2,3 DPG)
\: decreased H+
\: decrease in temp
But also:
\:Fetal hemoglobin
\:CO poisoning
37
Q

What does a leftward shift indicate on the curve?

A

Increased affinity for O2 binding and therefore decreased oxygen unloading

38
Q

In white patients, SpO2 of >92% predicted PaO2 of 60 mmHg. However in black patients SpO2 of _______ predicted PaO2 of 60 mmHg

A

> 95%

39
Q

What are some causes of low perfusion?

A

Vasoconstriction
Severe PVD
Hypothermia
Hypovolemia

40
Q

What kind of lights obscure pulse ox readings?

A

Fluorescent

41
Q

What causes blood to become a very bright red color?

A

Carbon monoxide

42
Q

Will anemia have any affect on pulse ox readings?

A

No because just because there are fewer Hb molecules available does not change the saturation of the ones that are present

43
Q

In the masimo SET instrument, what does the SET stand for and what does it do?

A

Signal extraction technology

Separates the signal from noise

44
Q

Of the dyes that effect Pulse ox, which has the greatest effect?

A

Methylene blue

45
Q

What are the dyes that have effects on pulse ox in order from greatest distortion to least?

A 
Methylene blue
Lympharzurine blue
Indocyanine green
Indigo carmine
Fluorescein (no effect)
46
Q

What colors of nail polish may effect absorbance of pulse ox?

A

Blues and blacks

47
Q

How much lower of a SO2 will wearing nail polish produce because of low signal strength?
What can be done to alleviate this problem?

A

6% lower

Rotate probe 90* from normal so it is looking across the finger

48
Q

What is the only real hazard of pulse ox today?

A

Pressure necrosis

49
Q

What is PI?

A

Perfusion Index

is a relative assessment of the pulse strength at the monitoring site

50
Q

CO binds hemoglobin how many more times than 02 binds?

A

240 x

51
Q

On page 26 and 27, read the Clinical moments part , biggs said there would be 1 or 2 questions from these.

A

Again if someone wants can copy and paste them into here

52
Q

What is NIRS?

A

Near infrared spectroscopy

53
Q

What does NIRS give you?

A

Will give you absorption of the brain tissue but not the blood, so is referred to rSO2

54
Q

What is difference of rSO2 and tSO2?

A

regional SO2 and tissue SO2

rSO2 is for brain
tSO2 is for other tissues in the body

55
Q

How many probes come with Cerebral oximetry and why?

A

2 probes so you can measure oxygenation of both hemispheres at same time

56
Q

Most anesthetics increase or decrease cerebral blood flow ?

A

Increase

57
Q

What are the average values for cerebral oximetry?

A

55 - 75 %

58
Q

What are the main problems with cerebral oximetry ?

A

Depends on partition of arterial and venous blood which depend on:
PaCO2
Hypoxia
pH

59
Q

What is SvO2?

A

Mixed venous oxygen saturation

60
Q

Where do you usually obtain SvO2?

A

PA catheter advanced near a capillary

61
Q

What are some variables that affect SvO2?

A

Q (blood flow)
Hb concentration
SaO2 (arterial oxygenation)
VO2 (oxygen uptake - metabolic rate - perfusion)

62
Q

What does SjvO2 measure?

A

Jugular venous saturation

63
Q

Which way do you place the catheter that reads SjvO2?

A

Towards the brain

I & M (37 decks)

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