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Flashcards in Alveolar Gas Exchange Deck (46)
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1
Q

Alveolar Ventilation

A

The volume of air reaching the alveoli per minute

2
Q

How do you calculate Alveolar Ventilation?

A

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

3
Q

Tidal volume - volume of dead space gives you?

A

Volume of alveoli

4
Q

Perfusion

A

Cardiac output from right ventricle

5
Q

Average value of perfusion?

A

5 L/min

6
Q

Average value of Alveolar Ventilation?

A

4 L/min

7
Q

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

A

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

8
Q

J =

A

Diffusion rate per minute

– how much gas is exchanged per minute

9
Q

Diffusion of each gas is _____ from one another

A

INDEPENDENT

10
Q

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

A

Alveolus

11
Q

What does the Surface Area correspond to?

A

The NUMBER of alveoli in the lungs

12
Q

Distance =

A

Thickness of the Alveolar Membrane

13
Q

What 4 things does the Alveolar membrane include?

A

Fluid layer
Alveolar epithelium
Interstitial space
Blood vessel wall

14
Q

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

A

DECREASE

15
Q

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

A

INCREASE

16
Q

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

A

INCREASE

17
Q

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

A

DECREASE

18
Q

With Interstitial lung disease, what gets deposited where?

A

Collagen is deposited in the interstitial space of the alveolar membrane

19
Q

How does Interstitial lung disease decrease diffusion rate of gases?

A

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

20
Q

D =

A

Diffusion coefficient for each gas

21
Q

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

A
  1. Solubility of gas in water

2. Molecular weight of gas

22
Q

Which is more soluble, O2 or CO2?

A

CO2

23
Q

Is the Diffusion coefficient greater for CO2 or O2?

A

20 times greater for CO2!!

24
Q

P1 - P2 =

A

Pressure gradient across alveolar membrane

25
Q

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

A

0.75 seconds

26
Q

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

A

0.25 seconds

27
Q

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

A

0.25 seconds

28
Q

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

A

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

29
Q

DLo2

A

Diffusion capacity of the lung for oxygen

30
Q

Diffusion capacity of the lung for oxygen

A

DLo2

31
Q

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

A

USE CARBON MONOXIDE

32
Q

What is the PaCO?

A

0 - binds to Hb very well

33
Q

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

A

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

34
Q

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

A

Almost IMMEDIATE

35
Q

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

A

CO2

36
Q

What creates surface tension in the lungs?

A

Air in the alveolus and

Water in the tissues

37
Q

What is the equation that correlates with surface tension?

A

Pressure = 2(tension)/radius

38
Q

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

A

LOW

39
Q

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

A

HIGH

40
Q

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

A

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

41
Q

Surfactant ____ tension in the small alveoli

A

DECREASES!

42
Q

Which form of surfactant is the most important?

A

SP - B

43
Q

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

A
Pressure = 2 (LOW tension)/radius
== pressure will DECREASE and small alveoli will not collapse
44
Q

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

A

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

45
Q

Equation for DLo2 =

A

1.23 X DLcarbon monoxide

46
Q

What is a resting DLo2?

A

21 mL/min/mmHg