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RC Test 2 > B4.036 - Gas Exchange and Transport > Flashcards

B4.036 - Gas Exchange and Transport Flashcards

1
Q

what is the equation for pressure of a gas

A

P = nTR/V

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2
Q

what do you need to calculated partial pressure

A

Total pressure and concentration of a gas species

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3
Q

what is FO2

A

fraction of O2

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4
Q

how do you calculate PIO2

A

PIO2 = (760-47) * .21

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5
Q

in kansas city what should the sum of partial pressures of all gases add up to

A

PB aka 747

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6
Q

how do you change partial pressure of a gas

A

changing the concentration or the total pressure

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7
Q

what is the physical solution of gas in the liquid

A

the fraction of gas molecules that enters the liquid and does not undergo any chemical combination

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8
Q

does O2 combined with Hb contribute to PO2?

A

No, any gas molecule that combines with a substance in the liquid does not contribute to the partial pressure of the gas

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9
Q

in order for partial pressures of gas not to fall what must occur

A

the gas molecules must be replaced by additional molecules entering the liquid from the gas phase

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10
Q

what does hyperventilation do

A

high PAO2, low PACO2

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11
Q

what does hypoventilation do

A

low PAO2, high PACO2

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12
Q

what is the alveolar gas

A

the result of a balance between the rate of delivery and the rate of removal of each individual gas

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13
Q

describe air in the conduction system and respiration system at the end of expiration

A

the alveoli and airways are filled with alveolar air, volume of air in the lungs at that time is FRC

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14
Q

how much air remains in dead space during inspiration

A

1/3

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15
Q

what does this graph represent

A

gas composition pattern during breathing

during expiration PCO2 initially is low because of O2 left in the dead space, then once the air from the alveoli is exhaled you see a rise in PCO2. The opposite is true for PO2 for the same reason

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16
Q

how do you calculate VD/VE

A

VD/VE = (FACO2 - FECO2)/FACO2

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17
Q

what key differences does this graph demonstrate

A
  1. in the physiologic range, the blood CO2 content is about 2x the blood O2 content
  2. the curve for CO2 is fairly linear (changes in CO2 yeild proportionate changes in blood CO2 over a wide range of PCO2)
  3. teh non linearity of the ODC means the changes in O2 content produced by a given change in PO2 will depend on the initial PO2 level
  4. the CO2 curve is much steeper, note the v-a difference and its implications on PCO2 and PO2
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18
Q

what is the alveolar gas equation

A

PAO2 = PIO2 - (PaCO2 x 1.2)

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19
Q

what is the alveolar gas equation used for

A

PAO2 = PIO2 - (PaCO2 x 1.2)

to compare the measured arterial blood PO2 and the calculated one. In the normal lung PaO2 should be only 5-10 mmHg lower than calculated PAO2

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20
Q

what is normal inspired PIO2?

A

147 (PB in kansas city)

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21
Q

what is inspired PCO2?

A

always 0

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22
Q

why is alveolar PO2 lower than PIO2?

A

because the second it hits the alveoli gas exchange happens

goes from 147-100

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23
Q

what is normal aveolar PCO2?

A

40

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24
Q

how do you get the PIO2

A

(760-47) * .21

760 - atmospheric P

47 - subract H20 Pressure

.21 - fraction of inhaled air that is PO2

= 147

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25
Q

what is the difference between arterial and venous PCO2 and PO2

A

PO2 - 100 in art, 40 in veins

PCO2 - 40 in art, 46 in veins

26
Q

what is anatomical dead space

A

any air that doesnt make it to the alveoli, doest undergo gas exchange

27
Q

what is physiological dead space

A

areas of alveoli that have a pathology preventing gas exchange

28
Q

how do you calculate VD/VE

A

VD/VE = (FACO2-FECO2)/FACO2

Alveolar CO2 should be 40, so if you exhale and the Fraction of that is 30 (it will always be less because of the dilution with dead space air that has no CO2) subtract those and put it over the 40 that gives you the fraction of dead space

29
Q

give an example with numbers of how the VD could increase (use VD/VE equation)

A

FACO2 - 40

FECO2 - 20 (theres more dead space aka more dilution)

VD/VE = (40-20)/40 = .5

30
Q

what does this graph represent

A

effect of hyperventilation and hypoventilation on VA and PACO2

31
Q

how do you calculate PAO2

A

PAO2 = PIO2 - PACO2

32
Q

what is the alveolar gas equation and how do you use it

A

PAO2 = PIO2 - (PaCO2 * 1.2)

PIO2 - usually 147, comes from (atmospheric - H20) *FO2

PaCO2 - usually 40

1.2 - used to correct for the fact that O2 : CO2 isnt an exactly 1:1 ratio

its used to look at ventilation in the airways

33
Q

what is PAO2 if PIO2 is 147

and theres a 25% increase in ventilation

A

111

34
Q

what does it mean if calculated PAO2 is off from PaO2 by more than 5-10 mmHg?

A

Something is wrong with ventilation

35
Q

what is the equation for diffusion across a membrane

A

M = (C1-C2) * A * D/ X

36
Q

what is the main driver of diffusion across a membrane

A

concentration gradient

37
Q

what is the equation for diffusion of gases in the lung

A

DLx = Vx / (PA - Pa) x

DLx - diffusion capacity

38
Q

what gas is perfusion limited and what does that mean

A

N2O

It does not combine readily with anything in the blood, this means its limited unless theres a constant supply of new blood with no N2O

39
Q

what are the characteristics of CO as far as diffusion capacity

A

has a much higher diffusion capacity because its able to combine readily with Hb, this means that when its bound to a protien it does not contribute to the partial pressure so more can diffuse across

40
Q

what relationship is being demonstrated here

A

N2O is perfusion limited, concentration goes up really quickly because it does not readily combine with anything in the blood

CO - is diffusion limited because it does combine readily with Hb

41
Q

how long does it take for PO2 to go from 40 -100 when it reaches the alveoli

A

.25 seconds

42
Q

how long does it take for CO2 to diffuse out of blood into alveoli

A

.25 s

43
Q

why is it that the diffusion time of CO2 and O2 are roughly the same even though the gradient for O2 is so much higher than CO2?

A

the diffusion capacity of CO2 is a lot higher than O2

44
Q

what lung properties can change the surface area available for diffusion

A

pulmonary edema

Fibrosis

inflammation

45
Q

what effect does inflammation have on diffusion

A

increased thickness of membrane leading to lower diffusion capacity of O2

46
Q

what does the red B line represent in these graphs

A

mild/moderate reduction in DLO2

47
Q

what does the blue line C represent in these graphs

A

severe reduction in DLO2, low PaO2 beacuse of this

Compensatory hyperventilation may lower PaCO2

48
Q

desribe the use of CO for finding the diffusion capacity for lung O2

A

CO diffuses accross so readily that if theres any diffusion limitation it will be easy to tell

DLCO = VCO/PACO

49
Q

how do you calculated O2 saturation of Hb (%)

A

O2 sat of Hb = (HbO2/Hb*1.34) X 100

50
Q

how do you calculate blood O2 content

A

Blood O2 content = (dissolved portion) + (amount bound to Hb)

Blood O2 content = (.003 x PO2) + ([Hb] x 1.34 x %O2 sat)

51
Q

what does this curve domonstrate

A

Its the O2 dissociation curve of Hb (ODC)

Arterial PO2 at 100% saturation is about 100

the venous PO2 (40) still has a Hb% saturation of about 75%

52
Q

what kinds of things can cause a right shift of the ODC

A

High PCO2

Low pH

High Temperature

High 2,3, DPG

excersizing muscle

53
Q

what kinds of conditions can cause a left shift in the ODC

A

Low PCO2

High pH

Low temperature

low 2,3, DPG

54
Q

what does this graph demonstrate

what is a

what is the blue line

what is v

A

this is a graph demostrting blood O2 content (dissolved + bound)

a - arterial

v - veins

blue line - low Hb

55
Q

what kind of pathologies can account for the blue line

A

anemia

56
Q

what does this graph demonstrate

how does it change during exercise?

A

the metabolism of O2 in the body

the difference between a and v is how much oxygen is used by the body

the a-v ration can change so that the body is extracting more oxygen making the veinous O2 lower than normal

57
Q

where is bicarb produced more in the RBC or the plasma? Why?

A

RBC

the enzyme Carbonic anhydrase (CA) catalyzes the reaction

58
Q

where does the bicarb made by the RBC go and why

A

goes to the plasma because of the Cl- exchange, bicarb diffuses out easily but H+ does not so Cl - goes in in exchange

59
Q

what is the haldane effect

A

Deoxygenated Hb is a better carrier for CO2

When Hb is not bound to O2 its more likely to pick up Hydrogen ions, this drives the equation to the right producing more HCO3-

60
Q

what does this graph demonstrate

why are there 2 lines and why are they straight

A

haldane effect

Increase in O2 means a decrease in blood CO2 concentration

CO2 and Hb has a linear relationship

61
Q

what does this graph demonstrate

A

You can see the differences in a-v between CO2 and O2

PO2 drops much from arterial to veinous than PCO2

RC Test 2 (19 decks)

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