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BMS 615 Cardiovascular > Test 3: Wk11: 7.2 Gas Transport and Diffusion - Dasgupta > Flashcards

Test 3: Wk11: 7.2 Gas Transport and Diffusion - Dasgupta Flashcards

1
Q

alveolus PO2

A

100mmHg

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2
Q

Steps of O2 diffusion

A
  1. O2 dissolves in water layer of alveolus
  2. Diffuses through thin layer of surfactant
  3. alveolar epithelium
  4. interstitial space
  5. capillary endothelium
  6. diffuse through plasma and bind Hb
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3
Q

PO2 in deoxygenated blood

A

40mmHg

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4
Q

what drives O2 diffusion

A

Partial pressure gradient

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5
Q

Diffusion is governed by

A

Fick’s Law

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6
Q

Fick’s Law

A

V*Gas = (A x D x deltaP) / T

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7
Q

gas exchange factors

A
  1. Partial Pressure Gradient
  2. Thickness and Properties of Membrane
  3. Surface Area of Alveoli
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8
Q

what limits O2 uptake in pulmonary capillaries

A

perfusion limitation

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9
Q

perfusion limitation

A

situation where gas diffuses through the membrane well and equilibrates quickly

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10
Q

The amount of perfusion limited gas that gets taken up is determined by

A

how much blood you pump through the capillary

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11
Q

on the average, blood is fully saturated with O2 by the time it is about — of the way down a pulmonary capillary.

A

1/3

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12
Q

The uptake of O2 in a pulmonary capillary is said to be perfusion limited
because

A

blood is saturated with O2 at the end of the pulmonary capillary.
Thus, the more blood you pump through, the more O2 is taken up

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13
Q

the amount of O2 is taken up into the blood is determined the

A

rate of

perfusion of pulmonary capillaries

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14
Q

Other gases which

are perfusion-limited are

A

N2O and CO2

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15
Q

The classic example of the diffusion limited gas is

A

CO

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16
Q

The partial

pressure of CO on the blood side of the capillary is always — because

A

0

because of the
high affinity of Hb for it

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17
Q

what limits CO uptake?

A

The ability of

the membrane to transfer CO by diffusion

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18
Q

The mean pulmonary capillary partial pressure of CO is zero

because the gas does not

A

get time to equilibrate in the blood

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19
Q

DLCO

A

Diffusing Capacity of Lung

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20
Q

Diffusing Lung Capacity Test is used

A

to measure gas exchange

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21
Q

DLCO Overview

A

pt breaths a known amount of a gas

determine how much gas gets taken up by pt

compare to normal values

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22
Q

To measure DLCO — and — are needed

A

CO measuring device and a spirometer

23
Q

“Diffusing capacity” is not a capacity… it is a measure of

A

CONDUCTANCE

24
Q

conductance will reflect anything that alters the ability of a lung to exchange gases

A

area available for exchange, and barrier thickness

25
Q

Obstructive disease DLCO will be

A

reduced because of alveolar simplification

and loss of pulmonary capillary structures.

26
Q

Restrictive disease DLCO will be

A

reduced because of thickening of the alveolar

capillary membrane, which impairs diffusion

27
Q

Fibrosis will — DLCO because

A

decrease because of increased thickness

28
Q

Emphysema will — DLCO because

A

decrease because it destroys areas of gas exchange

29
Q

Pulmonary Edema due to ARDS will — DLCO because

A

decrease because of thickening of capillary membrane from inflammation and edema

30
Q

Alveolar Hemorrhage will — DLCO because

A

increase from red blood cells in alveolar membrane

31
Q

Normal DLCO

A

20-30ml/min per mmHg

32
Q

Emphysema decrease DLCO By

A

changes effective area because alveolar simplification lowers effective
area, and poorly ventilated units don’t contribute much to gas exchange

33
Q

Embolus decrease DLCO By

A

blocks perfusion to alveolar capillaries

34
Q

Alveolar Fibrosis or lung Fibrosis decrease DLCO By

A

decreases effective area

35
Q

Interstitial or Alveolar Edema decrease DLCO By

A

fluid accumulation increases thickness of diffusion barrier

36
Q

Tumors/lung reseaction decrease DLCO By

A

decreased surface area

37
Q

Sarcoidosis, Asbestosis decrease DLCO By

A

Lesions thicken alveolar walls

38
Q

Collagen vascular disease decrease DLCO By

A

Conditions like scleroderma, systemic lupus erythematous

alter or obilterate capillary walls which block diffusion

39
Q

Anemia decrease DLCO By

A

reducing pulmonary capillary hemoglobin, the rate of uptake of CO is reduced,
so DLCO is decreased

40
Q

Pregnancy decrease DLCO By

A

cause is not known

41
Q

Alveolar Proteinosis decrease DLCO By

A

Alveoli are filled with protein and phospho-lipid-rich material so
DLCO goes down

42
Q

Smokers decrease DLCO By

A

High levels of carboxyhemoglobin due to smoking reduce the rate of uptake of DLCO

43
Q

Pulmonary Hypertension decrease DLCO By

A

Reduction of pulmonary capillary volume due to thickening of arteries

44
Q

Disease that dont change DLCO

A

Bronchitis
Neuromuscular Dz
Chest wall deformities
Asthma

45
Q

Bronchitis doesn’t decrease DLCO because

A

chronic bronchitis only affects upper airways

46
Q

Neuromuscular Junction/chest wall deformities doesn’t decrease DLCO because

A

do not affect the alveolar

capillary membrane

47
Q

Asthma DLCO

A

The status of DLCO in asthma is variable. Sometimes it is normal and
sometimes increased.

48
Q

Causes of increased DLCO (7)

A 
supine position
Exercise 
Polycythemia
Asthma 
Interalveolar hemorrhage 
L-R Cardiac Shunts 
Extreme Obesity
49
Q

Intracardiac Shunts or left-right cardiac shunts increase DLCO by

A

Increased pulmonary

capillary volume

50
Q

Intra-alveolar hemorrhage increase DLCO by

A

refers to hemorrhage when blood comes
into the alveoli. The hemoglobin in the alveoli combines with CO to raise the
DLCO.

51
Q

Polycythemia increase DLCO by

A

increase in hemoglobin and therefore the uptake of

carbon monoxide is higher

52
Q

Extreme Obesity increase DLCO by

A

have higher pulmonary

blood volumes and therefore have higher DLCO

53
Q

— observed in Goodpasture’s syndrome

A

Intra-alveolar hemorrhage

hemoglobin in the alveoli combines with CO to raise the
DLCO

54
Q

How does DLCO help in dx lung dz

A

diffusion is governed by changes of partial pressure and characteristics of alveolar capillary membrane which are changed in restrictive or obstructive dz

BMS 615 Cardiovascular (49 decks)

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