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CPR Exam 2 > 3. Pulmonary Blood Flow & V/Q > Flashcards

3. Pulmonary Blood Flow & V/Q Flashcards

1
Q

where do alveolar caps recieve blood & what are its contents

A

from RV

low O2 & high CO2

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2
Q

what are extra-alveolar caps

A

recieve blood from LV

high O2 & low CO2

-deliver O2 and CO2 to tissues of lung

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3
Q

what is venous admixture

A

the blood that goes thru extra-alv caps exit into pul V

-reduce PaO2 of arterial blood and increase PaCO2 (slightly)

mixes with blood from alveolar caps (came from alveoli)

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4
Q

what is PBP

A

pul BP = CO * PVR

(PVR = resistance of blood thru lungs)

= 25/15 mm Hg

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5
Q

how does the R in pul vasculature and systemic vasculature differ

& what is PVR determined by

A

PVR = much lower R compared to systemic side

PVR determine by high number caps, how many caps are open at given time (not all open at rest!) & lung vol

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6
Q

what happens to PVR with exercise

A

drops as more pul caps open up to accomodate the increased CO

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7
Q

how does lung vol affect PVR

A

at low (compress vessls) and high (stretch) lung vols –> resistance increases

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8
Q

why do you pass out if you lock knees while standing for a long time

A

gravity pulls blood into legs - less blood returns to heart bc locked knees

w/o locked knees you can use Sk M to increase flow from legs back to thorax

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9
Q

what is the BP, blood flow and size of alveoli at the apex of the lung

A

reduced bc gravity pulls blood down to base

Palv > Pa > Pv

less blood flow & alveoli kinda expanded

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10
Q

what is the BP, blood flow and size of alveoli in the middle of the lung

A

BP little higher than at apex –> Pa > Palv > Pv

normal blood flow

average sized alveoli

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11
Q

what is the BP, blood flow and size of alveoli at the base of the lung

A

higher BP (bc gravity pull blood down to base) –> Pa > Pv > Palv

smaller alveoli

greater blood flow

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12
Q

how is blood flow determined

A

how gravity acts on blood

how much air is in that region

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13
Q

what modulates blood flow & what is the result

A

nitric oxide (made by endothelium)

-cause Sm M relaxation and vasodilation

–> slow down and get more blood

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14
Q

what chemical modulators are often present with pathologic conditions

A

endothelin 1

thromboxane A2

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15
Q

why do you have to keep alveoli “dry”

A

if alveoli have water –> impair the ability of O2 to cross bc its not very h2o soluble

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16
Q

what forces favor filtration of fluid from cap to alveoli

A

Pc

πtissue

** PT (diff from rest of body bc its neg)

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17
Q

What are the forces that favor movement of fluid out of the alveolus to the capillary?

A

interstitial oncotic pressure

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18
Q

what forces move h2o from alv to cap

A

πc

related to proteins in plasma

19
Q

what is the greatest force driving fluid flow back and forth caps/alveoli

A

Pc

* always favor filtration - Pc + πt + PT = larger component in starling equation!

20
Q

Why doesn’t fluid build up in the alveolus if there is a net pressure moving fluid from the capillary to the alveolus?

A

The lymphatics

–> rapidly remove the fluid

21
Q

What extra-pulmonary disease would contribute to pulmonary edema?

A

CHF

22
Q

how do lungs play into metabolic fxn

A

contain ACE –> convert angiotensin 1 to angiotensin 2 & inactivate bradykinin

metabolism of arachidonic acid - breakdown leukotrienes, prostaglandins E2 & F2alpha

23
Q

what is the equation to solve PalvO2

A
24
Q

How do you calculate PIO2

A

(barometric P - water vapor P) * fraction of inspired aire

(760-47) * FiO2

(FiO2 normally = 21%)

25
Q

How do you solve for the respiratory quotient (R)?

A

R = consumption of CO2/Consumption of oxygen.

Normally = 200/250 = 0.8

change under certain circumstances (administration of glucose or exercise)

26
Q

what is the A-a O2 gradient

what is normal range

A

PAO2 - PaO2

normally < 20 mm Hg

27
Q

How do you solve for PAO2 (partial alveolar pressure of O2)?

A

PAO2 = PIO2 - (PaCO2/R)

28
Q

What would an increase in the AA gradient indicate?

A

diffusion impairment. Something is wrong at the alveoli

29
Q

what does it mean if A-a gradient is normal BUT PaO2 and PAO2 are low

A

problem is other than the alveoli

-pt maybe hypoventilating

30
Q

Due to gravity pulling intrapleural fluid lower in the intrapleural space, what is the effect on intrapleural pressure?

A

Intrapleural pressure at the apex = -10 cm H2O (less than normal)

& at the base = -2 cm H2O (more than normal)

normal = -5

31
Q

why are the alveoli at the apex of the lung large at rest

A

PIP is more neg

32
Q

why are the alveoli at the base small at rest

A

not as expanded bc less neg PIP

33
Q

how are the alveoli in the apex and base affected during inspiration

A

apex - only get a little larger bc almost fully inflated

base - get much larger and have more complliance bc already slightly inflated

34
Q

What is the average V/Q ratio?

A

0.8

usually described as either high or low

35
Q

What will occur in extreme cases of a low V/Q ratio?

A

Alveolar and capillary O2 and CO2 pressures equilibrate

and there will be a V/Q of 0

  • cause by an obstruction
36
Q

What is a V/Q ratio of 0 (aka very low)?

A

right to left shunt

37
Q

In a low V/Q ratio, what will be the values of PaO2, PaCO2, pHa, and volume of blood?

A

PaO2: Low

PaCO2: High

pHa: Low

volumbe - high* relative to ventilation

38
Q

If you have a very high V/Q ratio, what is happening?

A

no blood is coming to the alveolus

–> becomes alveolar dead space

39
Q

What happens to PAO2 and PACO2 in a high V/Q ratio?

A

equilibrate with the atmosphere

so in alveoli O2 gets very high & CO2 gets very low (not much blood benefits from this bc little blood flowing thru)

40
Q

If you have a high V/Q due to lack of blood flow, what happens in other alveoli?

A

other alveoli –> low V/Q ratio

bc increased blood flow to the area

41
Q

In a high V/Q ratio, what are the values of PaO2, PaCO2, pHa, and volume of blood?

A

PaO2- High

PaCO2- Low

pHa- High

Volume of blood: Low

42
Q

What is the V/Q ratio at the apex of the lung?

A

high

(high PaO2 and low PaCO2)

43
Q

What is the the V/Q ratio at the vase base of the lung?

A

low

(low PaO2 and high PaCO2)

44
Q

What is the V/Q ratio in the middle of the lung?

A

normal, about 0.8

CPR Exam 2 (20 decks)

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