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

Question 1

alveolus PO2

Answer 1

100mmHg

Question 2

Steps of O2 diffusion

Answer 2

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

Question 3

PO2 in deoxygenated blood

Answer 3

40mmHg

Question 4

what drives O2 diffusion

Answer 4

Partial pressure gradient

Question 5

Diffusion is governed by

Answer 5

Fick’s Law

Question 6

Fick’s Law

Answer 6

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

Question 7

gas exchange factors

Answer 7

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

Question 8

what limits O2 uptake in pulmonary capillaries

Answer 8

perfusion limitation

Question 9

perfusion limitation

Answer 9

situation where gas diffuses through the membrane well and equilibrates quickly

Question 10

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

Answer 10

how much blood you pump through the capillary

Question 11

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

Answer 11

1/3

Question 12

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

Answer 12

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

Question 13

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

Answer 13

rate of

perfusion of pulmonary capillaries

Question 14

Other gases which

are perfusion-limited are

Answer 14

N2O and CO2

Question 15

The classic example of the diffusion limited gas is

Answer 15

CO

Question 16

The partial

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

Answer 16

0

because of the
high affinity of Hb for it

Question 17

what limits CO uptake?

Answer 17

The ability of

the membrane to transfer CO by diffusion

Question 18

The mean pulmonary capillary partial pressure of CO is zero

because the gas does not

Answer 18

get time to equilibrate in the blood

Question 19

DLCO

Answer 19

Diffusing Capacity of Lung

Question 20

Diffusing Lung Capacity Test is used

Answer 20

to measure gas exchange

Question 21

DLCO Overview

Answer 21

pt breaths a known amount of a gas

determine how much gas gets taken up by pt

compare to normal values

Question 22

To measure DLCO — and — are needed

Answer 22

CO measuring device and a spirometer

Question 23

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

Answer 23

CONDUCTANCE

Question 24

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

Answer 24

area available for exchange, and barrier thickness

Question 25

Obstructive disease DLCO will be

Answer 25

reduced because of alveolar simplification | and loss of pulmonary capillary structures.

Question 26

Restrictive disease DLCO will be

Answer 26

reduced because of thickening of the alveolar | capillary membrane, which impairs diffusion

Question 27

Fibrosis will --- DLCO because

Answer 27

decrease because of increased thickness

Question 28

Emphysema will --- DLCO because

Answer 28

decrease because it destroys areas of gas exchange

Question 29

Pulmonary Edema due to ARDS will --- DLCO because

Answer 29

decrease because of thickening of capillary membrane from inflammation and edema

Question 30

Alveolar Hemorrhage will --- DLCO because

Answer 30

increase from red blood cells in alveolar membrane

Question 31

Normal DLCO

Answer 31

20-30ml/min per mmHg

Question 32

Emphysema decrease DLCO By

Answer 32

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

Question 33

Embolus decrease DLCO By

Answer 33

blocks perfusion to alveolar capillaries

Question 34

Alveolar Fibrosis or lung Fibrosis decrease DLCO By

Answer 34

decreases effective area

Question 35

Interstitial or Alveolar Edema decrease DLCO By

Answer 35

fluid accumulation increases thickness of diffusion barrier

Question 36

Tumors/lung reseaction decrease DLCO By

Answer 36

decreased surface area

Question 37

Sarcoidosis, Asbestosis decrease DLCO By

Answer 37

Lesions thicken alveolar walls

Question 38

Collagen vascular disease decrease DLCO By

Answer 38

Conditions like scleroderma, systemic lupus erythematous | alter or obilterate capillary walls which block diffusion

Question 39

Anemia decrease DLCO By

Answer 39

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

Question 40

Pregnancy decrease DLCO By

Answer 40

cause is not known

Question 41

Alveolar Proteinosis decrease DLCO By

Answer 41

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

Question 42

Smokers decrease DLCO By

Answer 42

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

Question 43

Pulmonary Hypertension decrease DLCO By

Answer 43

Reduction of pulmonary capillary volume due to thickening of arteries

Question 44

Disease that dont change DLCO

Answer 44

Bronchitis Neuromuscular Dz Chest wall deformities Asthma

Question 45

Bronchitis doesn't decrease DLCO because

Answer 45

chronic bronchitis only affects upper airways

Question 46

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

Answer 46

do not affect the alveolar | capillary membrane

Question 47

Asthma DLCO

Answer 47

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

Question 48

Causes of increased DLCO (7)

Answer 48

``` supine position Exercise Polycythemia Asthma Interalveolar hemorrhage L-R Cardiac Shunts Extreme Obesity ```

Question 49

Intracardiac Shunts or left-right cardiac shunts increase DLCO by

Answer 49

Increased pulmonary | capillary volume

Question 50

Intra-alveolar hemorrhage increase DLCO by

Answer 50

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

Question 51

Polycythemia increase DLCO by

Answer 51

increase in hemoglobin and therefore the uptake of | carbon monoxide is higher

Question 52

Extreme Obesity increase DLCO by

Answer 52

have higher pulmonary | blood volumes and therefore have higher DLCO

Question 53

--- observed in Goodpasture’s syndrome

Answer 53

Intra-alveolar hemorrhage hemoglobin in the alveoli combines with CO to raise the DLCO

Question 54

How does DLCO help in dx lung dz

Answer 54

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