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Physiology Part 2 > Lec 36 Ox Transport and Delivery > Flashcards

Lec 36 Ox Transport and Delivery Flashcards

1
Q

What percent of O2 in blood is dissolved free in solution?

A

2% of total O2

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2
Q

What is henry’s law?

A

Cx = Px * Solubility

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3
Q

What is solubility of O2?

A

0.0003 mL O2/100 mL blood / mmHg

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4
Q

What is conc of dissolved O2 when arterial PO2 is 100 mmHg?

A

0.3 mL O2/ 100 mL blood

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5
Q

What is O2 consumption of a person at rest?

A

250 mL O2/min

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6
Q

True or false: O2 deliver base on dissolved O2 alone is sufficient to meet tissue demands

A

false: dissolved O2 alone is too low/insufficient

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7
Q

What are the forms of O2 in blood?

A

2% free dissolved

98% bound to HbA

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8
Q

How much of O2 in blood is bound to HbA?

A

98%

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9
Q

How many O2 bind each HbA?

A
  • each molec HbA has 4 subunits [2 a and 2 B]
  • each subunit binds one molec O2
  • each Hb binds 4 molec O2
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10
Q

How many mL O2 can 1 gm of HbA bind when 100% saturated?

A

1.34 mL O2

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11
Q

What is normal Hb concentration of blood?

A

15 gm/dL

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12
Q

What is normal O2 binding capacity of blood?

A

15 gm/dL * 1.34 mL = 20.1 mL O2/100 mL blood

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13
Q

What is O2 content of blood?

A

O2 content = actual amt O2 in mL/100 mL bood

= O2 bound to HbA + dissolved O2

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14
Q

What is equation for O2 bound to HbA?

A

O2 bound to HbA = O2 binding capacity * percent saturation

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15
Q

What is equation for O2 binding capacity?

A

O2 binding capacity = Hb conc * 1.34 mL O2/gm Hb at 100% saturation

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16
Q

What is the equation for O2 delivery to tissues?

A

O2 delivery = blood flow * O2 content of blood

in more detail:
O2 delivery = CO [Q] * (Oxygenated Hb + dissolved O2)

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17
Q

Is O2 binding Hb reversible or irreversible?

A

reversible

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18
Q

Is relationship of % saturation Hb and PO2 in arteries linear?

A

no - its nonlinear

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19
Q

What is P50?

A

PO2 at which Hb is 50% saturated

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20
Q

What is positive cooperativity?

A

change in affinity of heme groups for O2 as each successive O2 molecule binds = steep part of Hb-O2 dissociation curve

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21
Q

Where is Hb loading of O2?

A

into pulmonary capillaries from alveolar gas

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22
Q

Where is Hb unloading of O2?

A

from systemic capillaries into tissues

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23
Q

How saturated is Hb in systemic venous capillaries?

A

75% saturated

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24
Q

How saturated is Hb in alveolar arterial capillaries?

A

97.5% saturated = basically 100%

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25
Q

What is PO2/PCO2 right before and right after alveoli?

A 
before
PO2  = 40 
PCO2 = 45
after
PO2 = 100
PCO2 = 40
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26
Q

What is PO2/PCO2 right before and right after peripheral tissue?

A 
before
PO2  = 100
PCO2 = 40
after
PO2 = 40
PCO2 = 45
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27
Q

What 3 things cause shift to right in O2-Hb dissociation curve?

A
  • increased temp
  • increased 2-3 DPG
  • increased H+ or PCO2
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28
Q

What does decreased affinity of Hb for O2 do to dissociation curve?

A

shift to the right

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29
Q

What does decreased affinity of Hb for O2 do to P50?

A

increase in P50

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30
Q

What does shift right in Hb curve mean for O2 unloading?

A

easier to unload O2

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31
Q

What is effect of acidic pH on Hb dissociation curve?

A

shift right, decreased affinity

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32
Q

What is effect of high CO2 on Hb dissociation curve?

A

shift right, decreased affinity via BOHR effect

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33
Q

What is effect of 2,3 DPG on Hb dissociation curve?

A

shift right

binds B chain and reduces affinity for O2

34
Q

What 5 things cause shift to left on O2-Hb dissociation curve?

A
  • decreased temp
  • decreased 2-3 DPG
  • decreased H+
  • fetal HbF
  • CO
35
Q

What does increased affinity of Hb for O2 do to Hb dissociation curve?

A

shift left

36
Q

What does increased affinity of Hb for O2 do to P50?

A

decrease in P50

37
Q

What does shift to left in Hb dissociation curve do to unloading of O2 in tissues?

A

decrease in unloading of O2 to tissues

38
Q

What is HbF? What does it do to Hb dissociation curve?

A
  • fetal hemoglobin, contains gamma chain instead of B chain
  • 2,3 DPG doesn’t bind to gamma chain
  • has higher affinity for O2
  • shift left dissociation curve
39
Q

What is affinity of CO for Hb compared to O2?

A

CO has 250x higher affinity than O2

40
Q

What forms in blood due to presence of CO?

A

carboxyhemoglobin

41
Q

What is shape of curve of CO-Hb binding?

A

asymptotic [rather than sigmoid like the O2 one]

42
Q

What are 3 forms CO2 transported in blood?

A
  • free in solution [7% dissolved]
  • bound to proteins [3% bound to Hb]
  • chemically modified [90% to HCO3-]
43
Q

What is solubility of CO2?

A

0.07 mL CO2/100 mL blood / mmHg

44
Q

What is conc of CO2 following Henry’s law?

A

conc = PCO2 * solubility = 40 mmHg * 0.07 = 2.8 mL CO2/100 mL blood

45
Q

Does CO2 bind to same or different site than O2 on Hb?

A

CO2 binds to different site than O2

46
Q

What is haldane effect?

A
  • less O2 bound to Hb [less saturation ] –> higher Hb affinity for CO2
  • get left shift on CO2 dissociation curve when you have less O2 bound
47
Q

Path of CO2 transport in blood starting with tissue

A

at tissue site:
- tissue produces CO2 from metabolism
- CO2 diffuses across cell membranes into RBC
- carbonic anhydrase in RBC catalyzes hydration of CO2 into H2CO3
- H2CO3 dissociates into H+ and HCO3
- H+ buffered by deoxyHb within RBC
- HCO3 diffuses out to plasma and exchanged with Cl-
in lung:
- H+ released from buffering site on deoxyHb
- HCO3 enters RBC in exchange for Cl-
- H and HCO3 form H2CO3
- H2CO3 dissociates to CO2 and H2O
- CO2 expired from lungs

48
Q

What is normal blood pH?

A

7.38-7.42

49
Q

What is normal arterial PCO2/PO2?

A

PCO2: 40 mmHg
PO2: 100 mmHg

50
Q

What is equation for minute ventilation [MV]?

A

MV = Vt [tidal vol] * RR [resp rate]

51
Q

What are two equations for alveolar ventilation [V[A]]?

A

V[A] = (Vt [tidal vol] - Vd [dead space vol])*RR

V[A] = VCO2 * K / PACO2

52
Q

What is equation for Vd?

A

Vd = Vt * [PaCO2 [arterial] - PECO2 [expired]] / PaCO2

53
Q

What is equation for alveolar PO2?

A

alveolar PO2 = PIO2 [inspired] - (PACO2 [alveolar] / R [respiratory exchange ratio])

54
Q

What is equation for PIO2?

A

PIO2 = (Pb [barometric] - Ph2o) * FIO2 [fraction inspired O2]

55
Q

What is definition of hypoxemia?

A

decrease in arterial PaO2

56
Q

What is the A - a gradient?

A

alveolar PAO2 - arterial PaO2 = (PIO2 - PACO2/R) - PaCO2

a = arterial, A = alveolar, I = inspired

57
Q

What is normal Aa gradient?

A

< 12 mmHg

58
Q

What can causes normal Aa gradientt? big gradient?

A

normal: small amount of blood goes through physiologic shunt
big: age [due to loss elastic recoil of lungs], alveolar disease [abnormal gas exchange], shunt [such as R-L]

59
Q

Can you derive the Aa gradient from oximetry or %SaO2?

A

No

60
Q

Can you derive the Aa gradient from ABG info?

A

yes

61
Q

What is the respiratory exchange ratio?

A

rate of CO2 production compared to rate of O2 production

62
Q

What is value of R in steady state?

A

0.8

63
Q

What are 5 causes of hypoxemia?

A
  • high altitude
  • hypoventilation
  • diffusion defect
  • V/Q defect
  • R–>L shunt
64
Q

In high altitude what happens to PaO2, A-a gradient, effect of supplemental O2?

A
  • decreased PaO2
  • normal A-a gradient
  • supplemental O2 improves
65
Q

In hypoventilation what happens to PaO2, A-a gradient, effect of supplemental O2?

A
  • decreased PaO2
  • normal A-a gradient
  • supplemental O2 improves
66
Q

In diffusion defect what happens to PaO2, A-a gradient, effect of supplemental O2?

A
  • decreased PaO2
  • increased A-a gradient
  • supplemental O2 improves
67
Q

In V/Q defect what happens to PaO2, A-a gradient, effect of supplemental O2?

A
  • decreased PaO2
  • increased A-a gradient
  • supplemental O2 improves
68
Q

In R–>L shunt what happens to PaO2, A-a gradient, effect of supplemental O2?

A
  • decreased PaO2
  • increased A-a gradient
  • supplemental O2 does not help
69
Q

What is mech of high altitude changing PaO2?

A
  • low Pb [barometric] causes low PIO2 and thus PAO2 [alveolar[
  • normal diffusion across capillaries to PaO2 is same as PAO2 [both low]
  • normal A-a gradient [since diffusion works]
  • supplemental helps by increasing inspired PIO2 and thus PAO2/PaO2
70
Q

What is mech of hypoventilation changing PaO2?

A
  • decreased alveolar PAO2 in hypoventilation
  • normal diffusion so normal A-a gradient
  • since low PAO2 get low PaO2 [arterial]
  • supplemental O2 helps by increasing PAO2 alveolar
71
Q

What is mech of diffusion defects changing PaO2?

A
  • pulm fibrosis or edema or other causes increased diffusion distance or decreased surface area
  • get increased A-a gradient
  • thus PaO2 [arterial ] < PAO2
  • supplemental O2 helps by increasing alveolar PAO2 and increasing driving force for diffusion
72
Q

What is mech of V/Q defects changing PaO2?

A
  • have increased dead space
  • high V/Q –> pulm clot
  • low V/Q –> area of alveolar flooding with pus [pneumonia or obstruction]
  • get increased A-a gradient
  • have low PaO2 since not as much diffusion
  • supplemental O2 helps
73
Q

What is mech of right to left shunt changing PaO2?

A
  • blood is completely bypassing the alveoli
  • deox blood mixed with normal ox non-shunted blood and dilutes it
  • A-a gradient is increased
  • supplemental O2 does not help because shunted blood just keeps diluting the oxygenated blood
74
Q

What is hypoxia?

A
  • decreased O2 delivery to tissue
75
Q

true or false: hypoxemia leads to hypoxia?

A

true: if you aren’t getting any air in it certainly can’t go to the tissues

76
Q

What is eq. for O2 delivery?

A

O2 delivery = CO * O2 content of blood

77
Q

What is biggest contributor to O2 content of blood?

A

Oxy-Hb

78
Q

What 4 things can cause hypoxia [other than causes of hypoxemia]?

A
  1. low CO: due to low blood flow
  2. anemia
  3. CO poisoning
  4. CN poisoning
79
Q

What are two mech that anemia does?

A
  • lowers Hb conc

- low O2 content of blood

80
Q

What are two mech that CO does?

A
  • lowers O2 content of b lood

- shifts left the Oxy-Hb curve

81
Q

What does CN poisoning do?

A

decreases O2 utilization by tissues

Physiology Part 2 (19 decks)

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