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Respiratory Exam 1 > Alveolar Gas Exchange > Flashcards

Alveolar Gas Exchange Flashcards

1
Q

blood entering the pulmonary capillary is (what type of blood)

A
  • mixed venous
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2
Q

blood leaving the pulmonary capillary is

A
  • arterial
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3
Q

rate of movement of gas through tissue over time directly proportional to

A
  • permeability
  • partial pressure gradient
  • tissue surface area
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4
Q

rate of movement of gas through tissue over time inversely proportional to

A
  • tissue thickness
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5
Q

gas permeability is directly proportional to

A
  • solubility of gas in barrier tissue and blood
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6
Q

gas permeability is inversely proportional to

A
  • molecular weight
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7
Q

which gas is more permeable in the lung (O2 or CO2)

A
  • CO2
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8
Q

alveolar type I epithelial cell and pulmonary microvascular endothelial cell share

A
  • opposite sides of a common basement membrane
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9
Q

which gradient is higher for O2 and CO2

A
  • O2 but CO2 is more soluble
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10
Q

alveoli are richly supplied with

A
  • capillaries
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11
Q

the diffusing distance from oxygen extends from

A
  • alveolus to hemoglobins molecules within erythrocytes
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12
Q

what does the diffusion barrier consist of?

A
  • alveolar air
  • surfactant and fluid layer
  • alveolar type I cell
  • lung interstitial
  • endothelial cell
  • blood plasma
  • RBC hemoglobin
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13
Q

what is the thickness of the blood-gas barrier?

A
  • miniscule
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14
Q

what drives diffusion across the blood gas barrier

A
  • differences in partial pressures
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15
Q

which gas molecules can exert a partial pressure

A
  • free, unbound gas molecules
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16
Q

how long does it take for an erythrocyte to traverse the capillary across the width of an alveolus

A
  • about .75 seconds
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17
Q

how long does it take O2 and CO2 to equilibrate across the blood gas barrier

what does this mean?

A
  • about .25 seconds

- there is reserve time for additional gas exchange

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18
Q

does O2 bound to Hb exert a partial pressure?

A
  • no
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19
Q

in what forms can oxygen exist in the blood

what form has greater existence

A
  • dissolved O2
  • O2 bound to hemoglobin
  • O2 bound to hemoglobin
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20
Q

N2O permeability

does it bind to hemoglobin?

considered in partial pressure determination

A
  • highly permeable
  • it does not.

considered in partial pressure determination

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21
Q

CO permeability

does it bind to hemoglobin

considered in partial pressure determination?

A
  • low permeability
  • it does. almost irreversibly.
  • takes it out of partial pressure determination
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22
Q

the greater the perfusion

A
  • the greater the uptake of gas by the lung
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23
Q

what is a perfusion limitation

A
  • blood leaves pulmonary capillary fully equilibrated with a gas
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24
Q

what is diffusion limitation

A
  • when blood leaves pulmonary capillary before it is equilibrated with a gas
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25
Q

which gasses are perfusion limited under normal conditions?

A
  • N2O
  • O2
  • CO2
26
Q

which gasses are diffusion limited under normal conditions

A
  • CO
27
Q

when can O2 or CO2 become diffusion limited

A
  • heavy exercise in elite athletes
  • high altitudes
  • severe pulmonary disease
28
Q

approximately half of the overall resistance to O2 loading of the alveolar capillary blood due to

A
  • kinetics of Hb-O2 binding reaction
29
Q

result of pulmonary fibrosis

effect on O2 equilibrium

A
  • thickened interstitium due to collagen deposition

- increases time for O2 equilibration

30
Q

result of pulmonary edema

effect on O2 equilibrium

A
  • interstitiium thickened by excess fluid

- increase O2 equilibration time

31
Q

conditions that impair diffusion at rest

what about exertion

A
  • may allow O2 equilibration

- will probably cause disequilibration

32
Q

high hydrostatic pressure favors

A
  • fluid out of capillary into intersitium

- does not push out protein

33
Q

as you go down the capillary, what will happen with the colloid osmotic pressure

A
  • as fluid leaves the vessel, colloid oncotic pressure increases down vessel length
  • will draw water back into the capillary at the pulmonary vein
34
Q

pulmonary edema on capillary permeability

A
  • increases capillary permeability
35
Q

pulmonary edema on capillary hydrostatic pressure

A
  • increases capillary hydrostatic pressure
36
Q

pulmonary edema on plasma oncotic pressure

A
  • decreases plasma oncotic pressure
37
Q

how can we measure how well diffusion is happening?

A
  • diffusion capacity of the lung for CO
38
Q

factors affecting diffusion of CO across the lung

A
  • surface area
  • permeability of blood-gas barrier
  • Hb status
  • body position
  • exercise
39
Q

what parts of Hb status would affect CO diffusion across the lung?

A
  • anything that reduces Hb
  • anemia
  • carboxy-Hb (smoking)
  • oxyhemoglobin (O2 therapy)
40
Q

2/3 of O2 consumed goes to

A
  • skeletal muscle
  • brain
  • liver
41
Q

slope of Hb-O2 dissociation curve

A
  • sigmoid
42
Q

hemoglobin is nearly saturated with O2 at partial pressures as low as

A
  • 70 mmHg
43
Q

large amount of O2 are ________ in response to small decrements in PO2 in the ___________

A
  • unloaded

- metabolizing tissues

44
Q

affinity of Hb for O2 is modified by

A
  • pH
  • pCO2
  • temperature
  • 2,3 DPG (glycolytic product)
45
Q

what is the Bohr effect

A
  • low pH and CO2 shifting Hb-O2 curve to the right
46
Q

rightward shift means Hb affinity for O2 is _______ at a given PO2

A
  • lower
47
Q

CO2 is carried in what forms

which one mainly

A
  • dissolved gas
  • bound to Hb as carbamino Hb
  • bicarbonate (HCO3-) (mainly)
48
Q

bicarbonate reaction

A
  • CO2 + H2O -> H2CO3 -> HCO3 + H+
49
Q

what is the chloride shift

A
  • exchange of HCO3- for Cl- that occurs in red blood cells

- how bicarb gets into the plasma

50
Q

protons generated in the bicarbonate reaction help to

A
  • dissociate O2 from Hb so it can be delivered to the tissues
51
Q

high PO2 in the lungs helps to

what is this known as

A
  • remove CO2 to deliver to alveolus

- Haldane effect

52
Q

CO2 dissociation curve

A
  • much more linear over a wide range
53
Q

what happens to deoxygenated hemoglobin

A
  • it picks up CO2
54
Q

CO2 is directly proportion to ______ ventilation

A
  • lung ventilation
55
Q

result of hypoventilation on alveolar PCO2

A
  • alveolar PCO2 will increase
56
Q

result of hyperventilation of alveolar PCO2

A
  • alveolar PCO2 will decrease
57
Q

what does pulse oximetry provide us

A
  • pulse

- Hb saturation

58
Q

oxygenated hemoglobin absorbs which light

which light passes

A
  • infrared light

- red light passes

59
Q

deoxygenated hemoglobin absorbs which light

which light passes

A
  • absorbs red light

- infrared light passes

60
Q

what does pulse oximetry measure

A
  • ratios of red and infrared light
61
Q

when would hemoglobin not bind to oxygen normally

A
  • CO poisoning

- heme iron in ferric instead of ferrous state

Respiratory Exam 1 (27 decks)

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