Alveolar Gas Exchange

Question 1

Alveolar Ventilation

Answer 1

The volume of air reaching the alveoli per minute

Question 2

How do you calculate Alveolar Ventilation?

Answer 2

= (Tidal volume - volume of dead space) X frequency

Question 3

Tidal volume - volume of dead space gives you?

Answer 3

Volume of alveoli

Question 4

Perfusion

Answer 4

Cardiac output from right ventricle

Question 5

Average value of perfusion?

Answer 5

5 L/min

Question 6

Average value of Alveolar Ventilation?

Answer 6

4 L/min

Question 7

What is the equation (thus the factors) that determine how much CO2 and O2 will cross alveolar barrier?

Answer 7

J = Surface Area X D X (P1-P2)/ Distance

Question 8

J =

Answer 8

Diffusion rate per minute

– how much gas is exchanged per minute

Question 9

Diffusion of each gas is _____ from one another

Answer 9

INDEPENDENT

Question 10

Surface Area and Distance both depend on the structure of the?

Answer 10

Alveolus

Question 11

What does the Surface Area correspond to?

Answer 11

The NUMBER of alveoli in the lungs

Question 12

Distance =

Answer 12

Thickness of the Alveolar Membrane

Question 13

What 4 things does the Alveolar membrane include?

Answer 13

Fluid layer
Alveolar epithelium
Interstitial space
Blood vessel wall

Question 14

As the Distance increases, what will happen to the Diffusion rate?

Answer 14

DECREASE

Question 15

As the Distance decreases, what will happen to the Diffusion rate?

Answer 15

INCREASE

Question 16

As the surface area (number of alveoli) increases, what will happen to the diffusion rate?

Answer 16

INCREASE

Question 17

As the surface area decreases, what will happen to the diffusion rate?

Answer 17

DECREASE

Question 18

With Interstitial lung disease, what gets deposited where?

Answer 18

Collagen is deposited in the interstitial space of the alveolar membrane

Question 19

How does Interstitial lung disease decrease diffusion rate of gases?

Answer 19

It deposits collagen into the interstitial space and thus increases the distance (thickness of alveolar membrane)

Question 20

D =

Answer 20

Diffusion coefficient for each gas

Question 21

What 2 things does the Diffusion coefficient for each gas depend on?

Answer 21

1. Solubility of gas in water

2. Molecular weight of gas

Question 22

Which is more soluble, O2 or CO2?

Answer 22

CO2

Question 23

Is the Diffusion coefficient greater for CO2 or O2?

Answer 23

20 times greater for CO2!!

Question 24

P1 - P2 =

Answer 24

Pressure gradient across alveolar membrane

Question 25

At rest, how long does a RBC spend in a pulmonary capillary?

Answer 25

0.75 seconds

Question 26

How long does oxygen require in a pulmonary capillary to reach equilibrium?

Answer 26

0.25 seconds

Question 27

At exercise, how long does a RBC spend in a pulmonary capillary?

Answer 27

0.25 seconds

Question 28

Why will someone with lung disease first notice problems with exertion/exercise?

Answer 28

Oxygen cannot diffuse fast (reach equilibrium) enough to reach equilibrium before the RBC's leave the pulmonary capillary - Both for around 0.25 seconds

Question 29

DLo2

Answer 29

Diffusion capacity of the lung for oxygen

Question 30

Diffusion capacity of the lung for oxygen

Answer 30

DLo2

Question 31

What do you use to measure the diffusion capacity of the lung for oxygen (DLo2)?

Answer 31

USE CARBON MONOXIDE

Question 32

What is the PaCO?

Answer 32

0 - binds to Hb very well

Question 33

Describe how to measure the diffusion capacity of the lung for oxygen (DLo2)

Answer 33

Have patient inhale one breath with a small amount of carbon monoxide in it - Take the diffusion capacity of the lung for CO and multiply it by 1.23!! = diffusion capacity of the lung for O2

Question 34

How long does CO2 require in a pulmonary capillary to reach equilibrium?

Answer 34

Almost IMMEDIATE

Question 35

Between CO2 and O2, which has a greater diffusion capacity in the lung?

Answer 35

CO2

Question 36

What creates surface tension in the lungs?

Answer 36

Air in the alveolus and | Water in the tissues

Question 37

What is the equation that correlates with surface tension?

Answer 37

Pressure = 2(tension)/radius

Question 38

In a large alveolus the radius is large, describe the pressure

Answer 38

LOW

Question 39

In a small alveolus the radius is small, describe the pressure

Answer 39

HIGH

Question 40

Without surfactant, the HIGH pressure in the small alveolus causes?

Answer 40

Air to be pushed into the larger alveolus and then the small alveolus collapses

Question 41

Surfactant ____ tension in the small alveoli

Answer 41

DECREASES!

Question 42

Which form of surfactant is the most important?

Answer 42

SP - B

Question 43

Describe the equation that correlates with surface tension in the presence of surfactant

Answer 43

``` Pressure = 2 (LOW tension)/radius == pressure will DECREASE and small alveoli will not collapse ```

Question 44

Surfactant decreases the tension in small alveoli. What does this do for the pressure there and the flow of air?

Answer 44

LOWERS the pressure and there is no gradient of flow! (does not get pushed into larger alveoli)

Question 45

Equation for DLo2 =

Answer 45

1.23 X DLcarbon monoxide

Question 46

What is a resting DLo2?

Answer 46

21 mL/min/mmHg