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22 spring: Physiology > exam 2 lecture 17 and 18 > Flashcards

exam 2 lecture 17 and 18 Flashcards

1
Q

blue membranes

A

cyanosis

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2
Q

PaO2

A

pressure of oxygen gas ***dissolved*** in the arterial blood; in mmHg

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3
Q

PaCO2

A

–pressure of carbon dioxide gas ***dissolved*** in the arterial blood; in mmHg

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4
Q

SpO2

A

percentage ***saturation of hemoglobin (Hb) *** in the arterial blood; in %

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5
Q

PiO2

A

partial pressure of oxygen in inspired gas; mmHg

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6
Q

FiO2

A

–fraction of oxygen in inspired gas; in %

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7
Q

low PaO2 means

A

hypoxemia

PaO2 is pressure of oxygen dissolved in arterial blood.

Units: mmHg

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8
Q

PaO2 vs PAO2

A

a= arterial

A = alveolar

pressure of dissolved oxygen

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9
Q

dalton’s law

A

•In a gas mixture, the pressure exerted by each gas is independent of the pressure of the others, so all pressures will sum to the total measured pressure

Pair = PN2 + PO2 + P(other gases)

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10
Q

Pair = PN2 + PO2 + P(other gases)

A

daltons law

•In a gas mixture, the pressure exerted by each gas is independent of the pressure of the others, so all pressures will sum to the total measured pressure

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11
Q

•For dalton’s law. In a gas mixture, the pressure exerted by each gas is independent of the pressure of the others, so ___

A

all pressures will sum to the total measured pressure

Pair = PN2 + PO2 + P(other gases)

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12
Q

FIO2

A

fraction of inspired oxygen

=21% or 0.21

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13
Q

what happens to atmospheric pressure as you climb a mountain?

A

decreases

at sea level 760 mmHg

on everest: 235 mmHg

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14
Q

how to calculate PiO2

A

PiO2 pressure of oxygen in airways

PiO2= (Patm - 47 mmHg) x FiO2

Patm depends on elevation 760 mmHg at sea level

47 is water vapor evaporating in the body

FiO2= % inspired oxygen =0.21 at room air, 1.0 on 100% O2

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15
Q

PiO2 is the the oxygen pressure in the ___, NOT in the ___

A

airways

alveolus

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16
Q

what is the FiO2 at room air and on oxygen?

A

room air= 21% or 0.21

oxygen= 100% or 1

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17
Q

-Atmospheric pressure at 9000m (Everest summit) is 253 mmHg. What is the partial pressure of oxygen in the air?

A

253 x FiO2

253x 0.21

53.13

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18
Q

what is the PiO2 in Amsterdam (760mmHg)?

Philly (749 mmHg)?

Everest (220 mmHg)?

A

PiO2= (PATM - 47 mmHg) x FiO2

(760-47) x 0.21 = 149.73 mmHg

(749-47) x 0.21= 147.42 mmHg

(220-47) x 0.21= 36.33 mmHg

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19
Q

what is the PiO2(1 atm) on

100% oxygen

Amsterdam (760mmHg)?

Philly (749 mmHg)?

Everest (220 mmHg)?

A

PiO2= (PATM - 47 mmHg) x FiO2

(760 -47) x 1= 713 mmHg

(749-47)x 1= 702 mmHg

(220-47) x 1= 173 mmHg

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20
Q

what is the FiO2 needed to get a PiO2 of 200 mmHg at sea level?

A

PiO2= (PATM - 47 mmHg) x FiO2

200= (760-47) x F

FiO2= 0.28

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21
Q

What FiO2 would you need to supply to get a PiO2 of 50 mmHg at seas level

A

PiO2= (PATM - 47 mmHg) x FiO2

50= (760-47) x F

FiO2= 0.07

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22
Q

PaO2 in arterial vs venous blood

A

150 in airways

100 in alveoli

100 in arterial

40 in venous

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23
Q

Gas exchange across blood-gas barrier in the lung is by ___

A

passive diffusion

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24
Q

Passive movement of gas down a partial pressure gradient (difference in PO2, PCO2) are influenced by:

A

Gas diffusivity (D; solubility)

  • Surface area (A)
  • B-G barrier thickness (T)
  • Driving pressure gradient between alveolar-capillary blood (PA – Pcap)
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25
Q

Fick’s law

A

The amount of gas that moves across a sheet is:

  • Proportional to the area of the sheet
  • Inversely proportional to its thickness

the bigger the sheet the more things can diffuse, the thicker the sheet the less things can diffuse

Flow of gas= Area/thickness x diffusion constant (P1-P2)

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26
Q

why is PaCO2=PACO2

A

CO2 is 20 times more soluble than O2

will diffuse willingly across membrane and balance itself out

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27
Q

what is more soluble CO2 or O2

A

CO2 is 20x more soluble then O2

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28
Q

what happens to pleural pressure when you breathe very hard

A

more negative!!

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29
Q

Oxygen diffuses into ___ and CO2 diffuses into ___

A

tissues

blood

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30
Q

anatomic dead space

A

volume of conducting airways- O2 here will never get to the blood

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31
Q

alveolar dead space

A

gas in alveoli not participating in gas exchange

if an blood clot blocks blood flow to some alveoli

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32
Q

physiologic dead space

A

alveolar + anatomic dead space(conducting airway deadspace)

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33
Q

•We measure hemoglobin-associated oxygen using __

A

SaO2

pulse ox → % of oxygen on hemoglobin

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34
Q

how is O2 carried in the blood

A

98% is carried on hemoglobin

1-2% is dissolved in plasma

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35
Q

normal SaO2

A

95-100%

% saturation of O2 = pulse ox= % of oxygen on hemoglobin

36
Q

how to measure amount of oxygen dissolved in plasma?

A

arterial blood gas PaO2

37
Q

•A very small quantity of O2 is carried dissolved in plasm. The amount dissolved is based on the ___of the air in the alveolus. Oxygen molecules are pushed down a gradient

A

PiO2

38
Q

units of PaO2

A

mmHg

(partial pressure of O2 in arterial blood)

39
Q

normal PaO2

A

85-95 mmHg

partial pressure of O2 in arterial blood= measured by blood gas machine

40
Q

how to calculate CaO2

  • Oxygen carrying capacity of hemoglobin is 1.34 ml/g
  • Oxygen carrying capacity of plasma 0.003 ml O2/dl plasma per mmHg PaO2
A

CaO2 = (SaO2 x Hb x 1.34) + .003(PaO2)

= (98% x 19 g/dL x 1.34) + 0.003(92)

=(24.95) + 0.276

=25.226 ml/dL O2

CaO2= total oxygen content in the blood

41
Q

what does CaO2 measure

A

total Oxygen in the blood

=(amount of O2 on hemoglobin) + (amount of O2 dissolved in plasma)

CaO2 = (SaO2 x Hb x 1.34) + .003(PaO2)

normal = 16-20 ml/dl O2

42
Q

on admission on room air:

–What is the FiO2?

–PaO2: 39 mmHg

–SaO2: 71%

–Hb: 12 g/dL

CaO2? ________________________________

A

FiO2= 0.21 on room air

CaO2 = (SaO2 x Hb x 1.34) + .003(PaO2)

=(0.71 x 12 x 1.34) + 0.003 (39)

=11.42+0.117

=11.537 ml/dL O2

normal = 16-20 ml/dl O2

43
Q

•On nasal oxygen at 4L/min

–PaO2: 58 mmHg

–SaO2: 85%

–Hb: 12 g/dL

CaO2? ______________

CaO2 = (SaO2 x Hb x 1.34) + .003(PaO2)

A

CaO2 = (SaO2 x Hb x 1.34) + .003(PaO2)

= (0.85 x 12 x 1.34) + 0.003 (58)

=13.842 ml/dl O2

normal = 16-20 ml/dl O2

44
Q

CaO2 = (SaO2 x Hb x 1.34) + .003(PaO2)

•On the ventilator, on pure O2

–What is the FiO2?

–PaO2: 124 mmHg

–SaO2: 99%

–Hb: 12 g/dL

CaO2? ___________________________

A

CaO2 = (SaO2 x Hb x 1.34) + .003(PaO2)

FiO2 on pure O2= 100%

(0.99 x 12 x 1.34) + 0.003 (124)

=16.29 ml/dl O2

normal = 16-20 ml/dl O2

45
Q

•On admission, on room air

–What is the FiO2?

–PaO2: 96 mmHg

–SaO2: 98%

–Hb: 3.5 g/dL

CaO2? ____________________

CaO2 = (SaO2 x Hb x 1.34) + .003(PaO2)

A

FiO2= 0.21

(.98 x 3.5 x 1.34) + (0.003 x 96)

=4.88 ml/dl O2

normal = 16-20 ml/dl O2

46
Q

•In surgery to ligate the artery, on pure O2

–What is the FiO2?

–PaO2: 496 mmHg–SaO2: 99%–Hb: 3.5 g/dL

CaO2? __________

CaO2 = (SaO2 x Hb x 1.34) + .003(PaO2)

A

FiO2 on oxygen = 1

CaO2 = (SaO2 x Hb x 1.34) + .003(PaO2)

= (.99 x 3.5 x 1.34) + (0.003 x 496)

=6.13 ml/dl O2

normal 16-20 - need hemoglobin to fix the horse

47
Q

Gas exchange influenced by

A
  1. ventilation (delivery of atmospheric O2 to alveoli);
  2. perfusion (transport of O2 from lungs in the blood);
  3. gas exchange at level of alveoli (influenced by amount of gas, properties of gas, tissue properties). Amount of gas available for transport (partial pressure) changes as move from atmosphere to alveolus
48
Q

Driving pressure (ΔP) = PAO2 – PVO2

A

100-40

60 mmHg

arterial blood - venous blood

this will pull O2 into the blood from the alveolus until PAO2 and PaO2 are equal

49
Q

how long does it take for a RBC to get fully loaded with O2?

A

0.25 seconds

50
Q

at rest how fast does RBC go across alveoli?

A

0.75 seconds

51
Q

what does this graph show?

A

how long is takes for RBC to get fully loaded with O2

in normal takes 0.25 seconds to reach full load. partial pressure of O2 in the arterial blood (PaO2) goes from 40→100 mmHg

in abnormal= takes 0.75 seconds, if exercising this is not enough cause blood is moving faster then it can pick up O2

in grossly abnormal= RBC never reaches normal even at rest and it barely gets any O2 with exercise

52
Q

•Normal transit time for an RBC across the capillary:___

A

0.75 seconds

53
Q
A

PAO2 a high altitude or hypoventilation

amount of O2 in your lungs can not be greater then the amount of O2 in the air, therefore max O2 is 50 at high altitude

that means any pulmonary disease or exercise would lead to even smaller amount of O2 in the blood

54
Q

what is a pulmonary disease that can increase barrier thickness?

A

edema and fibrosis

55
Q

what kind of pulmonary disease can lead to decrease in surface area?

A

capillary destruction and tumor

56
Q

explain hemoglobin cooperativity

A

deoxygenated O2= tense

oxygenated = relaxed

(shy person drinking at a party)

Hb has different affinities for oxygen based on how much oxygen it’s already carrying. The first oxygen molecule is hard to bind, but when one oxygen attaches, the second binds more easily, and the third and fourth easier yet.

The same process works in reverse: once fully loaded hemoglobin lets go of one oxygen, it lets go of the next more easily, and so forth.

This is known as cooperativity

57
Q
A

oxygen hemoglobin dissociation curve

x axis= Pa O2=partial pressure of O2 dissolved in the plasma= measured by total blood gas

y axis= SpO2= pulse ox

illustrates the % of hemoglobin that is chemically bound to O2 at each oxygen pressure

steep part of curve loose or gain O2 quickly

end of curve- max out at 100% no matter how much extra O2 you add

start of curve- hard to get started

58
Q

why a sigmoid curve?

A

hemoglobin cooperativity

hard to get started, then very fast, then maxed out

steep slope between 10 and 60 mmHg

flat portion between 70 and 100 mmHg.

59
Q

There are different oxygen levels in venous blood versus arterial. Why?

A

In venous blood, the PvO2 is about 40mmHg, which corresponds to an SaO2 of about 75%

tissues have used up O2 and it has dropped to 75%

60
Q

The amount of oxygen in the arterial blood can be lower in patients with lung disease, or on the top of Everest. Why?

A

there is less O2 to begin with at the top of Everest= PiO2 is low

or lung disease: can’t get O2 into lungs or into blood so they drop even lower

61
Q

arterial vs venous

SaO2

PAO2

PACO2

A

99%→75%

100 → 40

40→ 46

62
Q

What happens if the oxygen-hemoglobin dissociation curve shifts to the RIGHT?

A

more O2 will be unloaded if shifted to the right instead of tissues using 25% they will use 50%

63
Q

how to move oxygen hemoglobin dissociation curve to the right and left?

A

right- exercise= decrease pH (lactic acid- more acid), increase temp and DPG

left= increase pH, decrease temp and DPG

64
Q

how does pH effect oxygen hemoglobin dissociation curve?

A

•↓pH–When you exercise, or in some forms of shock, blood pH goes down (acidemia)–This moves the curve to the RIGHT, so at a given PaO2, the SaO2 is LOWER so more O2 was delivered to the tissues–This is called the Bohr effect

65
Q

Bohr effect

A

during exercise

pH decreases (more acid)

this shifts the curve to the right, this means more O2 is delivered to tissues so they can exercise more

66
Q

What increases 2,3 DPG?

A

–High altitude, anemia, chronic hypoxia, hyperthyroidism, chronic alkalosis (high pH)

67
Q
A
68
Q

•Myoglobin is an oxygen-carrying protein in the muscles. Why is its curve so far to the left of Hb?

A

At any given PaO2, it more saturated than Hb – this means it can “grab” the O2 off the Hb as the arterial blood passes by in capillaries to feed the tissues

myoglobin grabs really fast and really well to O2, only need very small amount of O2 to reach full capacity of myoglobin

69
Q

P50

A

a way to measure how far the curve moves

at normal 27

left= 10

right =40

70
Q

•When the O2/saturation curve shifts RIGHT, the oxygen affinity of hemoglobin ___ causing the hemoglobin to be ___saturated at a given PaO2

A

DECREASES,

LESS

right = 40 where normal = 27

71
Q

•When the curve shifts LEFT the oxygen affinity of hemoglobin ___, causing the hemoglobin to be ___ saturated at a given PaO2

A

INCREASES,

MORE

left = 10 where normal =27

72
Q
  • On room air (FiO2 0.21), Hb is almost 100% saturated, and PaO2 is usually in the high 90s
  • What happens to the amount oxygen carried in the blood when a patient receives 100% oxygen (FiO2 1.0) and their PaO2 goes up to ~500 mmHg?
A

will increase the amount of oxygen dissolved in the plasma which is 1-2% of all oxygen

will not make a big difference

73
Q

how is CO2 transported in the blood?

A

10% dissolved in blood

22% carbamino compounds in hemoglobin

68% bicarbonate ion formation

74
Q

explain how CO2 is transported on hemoglobin

A

22% of CO2 carried by Carbamino compounds in Hb

–CO2 joins reversibly with non-ionized terminal amino groups (-NH2) of Hb in RBC–Hb.NH2 + CO2 ↔ Hb.NH.COOH

75
Q

explain bicarbonate ion formation for carrying CO2

A

68% of CO2

–most CO2 in the blood is transported in the bicarbonate ion form

–bicarbonate ion is from reversible reaction accelerated by enzyme, carbonic anhydrase, in RBC:

CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3-

–the first reaction is slow in plasma but fast in red cells due to carbonic anhydrase

–the second reaction (carbonic acid ionic dissociation) is fast even without an enzyme

76
Q

how is most of CO2 transported in the blood?

A

as bicarbonate ion

carbonic anhydrase helps

CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3-

77
Q

CO2 transport at the tissues

A

most into RBC: bicarbonate quickly with help of carbonic anhydrase

some into hemoglobin

Plasma: some dissolved

small amount into bicarbonate slowly cause no carbonic anhydrase in plasma

78
Q

CO2 transport at the lung

A

reverse process

most out of RBC: bicarbonate quickly with help of carbonic anhydrase back into CO2

some from hemoglobin into CO2

Plasma: some dissolved

small amount from bicarbonate back into CO2 slowly cause no carbonic anhydrase in plasma

79
Q

haldane effect

A
  • Deoxygenation of blood increases its ability to carry carbon dioxide. Conversely, oxygenated blood has a reduced capacity for carbon dioxide
  • This means it is easier for Hb to pick up CO2 at the tissues (where Hb is least O2 saturated), and release it in the lungs, where O2 is the most saturated. That’s really convenient, right?
80
Q

1.What is the FiO2 of room air at sea level? What is the FiO2 in Denver, CO? What is the FiO2 of pure oxygen at sea level? In Denver?

A
  1. 21
  2. 0

????

81
Q

1.If you were in a small room of 1000 L capacity and someone accidentally opened a helium canister that released 100L of helium into the room, what would be the FiO2 in that room? What principle of physics did you use to make this answer?

A

FiO2 would still be 21%, always 21%???

82
Q

1.What is PiO2? What is the difference between FiO2 and PiO2, conceptually? Numerically? Give an example.

A

PiO2= partial pressure of inhaled O2= affected by elevation

PiO2= (PATM - 47 mmHg) x FiO2

FiO2= fraction of inhaled air that is O2= at room air always 0.21

83
Q

1.What is normal PaO2 on room air at sea level? What is normal SaO2 on room air at sea level? Include the units.

A

PaO2 on room air at seas level: measure of dissolved O2 in arterial blood= measured by a blood gas machine

PiO2= (Patm - 47 mmHg) x FiO2

PO2 of inspired air = 150, PAO2= 100 PaO2= 100 mmHg ???

SaO2=95-100%

84
Q

If you treating an animal with pneumonia, if the PaO2 is less than 60mmHg, that animal probably needs to be on oxygen. What will be the SaO2 at a PaO2 of 60mmHg?

A

use o2- saturation curve

90%

85
Q

When the PaO2 is <40mmHg, the animal develops cyanosis (what’s that?). What SaO2 does that correspond to?

A

cyanosis- blue gums

SaO2 less then 75

86
Q

If normal PaO2 and SpO2 are both the same approximate numerical value in the normal animal on room air, how come they are so different from each other in Q4 and 5? Draw a picture to illustrate.

A

ox sat curve is sigmoid

87
Q

What is expected SaO2 on 100% oxygen at sea level? Include the units.

A

100%

22 spring: Physiology (34 decks)

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