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EXCI 357 Pulmonary Physiology > 4. Factors Affecting Diffusion of Gases Through Respiratory Membrane > Flashcards

4. Factors Affecting Diffusion of Gases Through Respiratory Membrane Flashcards

1
Q

Respiratory unit or lobule Includes

A

respiratory bronchioles, alveolar ducts, atria, and alveoli

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2
Q

Alveoli have very ____walls + are separated from each other by ___ ___ ___

A

thin

extensive capillary network

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3
Q

True or false. Alveoli have very thick walls + are separated from each other by extensive capillary network. Explain.

A

False. They have very thin walls b/c –>alveolar gases are in very close proximity to blood stream. Thick walls would hinder diffusion

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4
Q

Which portion of the lungs does gas exchange between alveolar air and pulmonary blood occur?

A

through membranes of all terminal portion of lung (not only in alveoli themselves)

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5
Q

What are the layers of the respitory memebrane?

A

Fluid and surfactant layer (in alveolar lining)
Alveolar epithelium composed of epithelial cells
Alveolar epithelial basement membrane
Thin interstitial space between alveolar epithelium and capillary membrane
Capillary basement membrane
Capillary endothelial membrane

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6
Q

The difference between the gas in alveoli and the gas in pulmonary blood. Is the measure of the ______ for gas molecules to move _____ _____. (Hint: Partial pressure difference )

A

Net tendency

through the membrane

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7
Q

What would cause CSA of the respiratory membrane to decrease?

A

Removal of lung tissue (if entire lung, A by half)

Loss of alveolar walls in emphysema (5-fold in A)

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8
Q

True or false. When total surface area is reduced to 1/3-1/4 of normal, gas exchange through membrane is only minutely impeded under resting conditions

A

False. it would be significantly impeded!

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9
Q

In ______ exercise, the _______ decrease in surface area of the lung can be a serious detriment to gas exchange

A

strenuous

slighest

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10
Q

Distance of diffusion (d) is related too?

A

membrane thickness

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11
Q

Membrane thickness increases in the following conditions (2)

A

Edema in interstitial space of membrane and in alveoli

Fibrosis of lung caused by pulmonary diseases

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12
Q

Increase thickness to > ___times normal can affect significantly exchange of gases

A

2-3 times

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13
Q

Diffusion coefficient of each gas through membrane depends on what two factors?

A

Gas’ solubility in the membrane (S)

It’s molecular weight (MW)

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14
Q

Diffusion of O2 and CO2 across respiratory membrane occurs very quickly because?

A

Alveoli and blood capillary membrane are very close to each other (usually touch each other)

Respiratory membrane is very thin with average thickness

Total surface area of respiratory membrane (A) is considerably large ( More opportunity)

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15
Q

What is the measure of ability of respiratory membrane to exchange a gas between alveoli and pulmonary blood

A

Diffusing Capacity of Respiratory Membrane

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16
Q

What is defined as volume of a gas that will diffuse through membrane each minute for pressure difference of 1 mmHg

A

Diffusing Capacity of Respiratory Membrane

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17
Q

True or False. Factors that affect diffusion can affect also affect Diffusing Capacity of Respiratory Membrane?

A

True.

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18
Q

define “Diffusing capacity of lung for O2 (DLO2)”

A

Membranes capacity to diffuse O2 @ 1mmHg

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19
Q 
How would you calculate the Net Diffusion Rate for O2 given that;
-> DLO2  =  21 ml O2/min/mmHg
 and;
-> ΔPO2  =  11 mmHg
(At rest
A 
Simply by multiplying them DLO2 and ΔPO2 
-> giving you an answer ml of O2/min 
so...
DLO2  x ΔPO2  
21 x 11 = 230  ml O2 /min.
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20
Q

DLO2 x ΔPO2 give you?

A

Net Diffusion Rate of O2

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21
Q

What is the relationship between METs and Net Diffusion rate of O2?

A

Net diffusion rate / Weight = ( DLO2 x ΔPO2 ) / Weight (in kg)
-> = 230 ml O2 /min / 66kg = 3.5 ml (O2)/ kg/min
= 1 MET which is resting O2 consumption

22
Q

How does the diffusion rate of O2 go up by in strenuous exercise

A

3 x resting values!

23
Q

A. Increased diffusion capacity DLO2 due to:
______of capillaries and ______ of “______” capillaries.
B. This changes which variable in the Difusion formula (increase or decrease)?
C. This results in?

A 
A.
Dilation 
Perfusion
"dormant" 
B. increase in Area 
C. Better match between ventilation of alveoli and perfusion of capillaries
24
Q

What is a ventilation-perfusion ratio

A

match between ventilation of alveoli and perfusion of capillaries

25
Q

Decreased match between ventilation of alveoli and perfusion of capillaries causes?

A

a decrease in Ventilation-Perfusion ration

- Resulting in Decreased O2 difusion rate

26
Q

During exercise, blood oxygenation is _____ by an/a (increased/decreased) ____ in _____ and an/a (increased/decreased) _____ in ______

A

INcrease
increase VA ;
Increased DLO2

27
Q

Is DLCO2 difficult to asses? If so how can it be obtained?

A

Yes it is.

It can be obtained by comparing Diffusion COeff

28
Q

How is PAO2 measure?

A

Last 1/3rd of Expired air

29
Q

How is PaO2 measured

A

CO method (DLCO)

30
Q

Principle of DLCO method:

  1. ______ amount of CO is inhaled into alveoli, _____ in lungs for ______, and exhaled
  2. ______ is measured from appropriate air sample
  3. PaCO ~ 0 (b/c Hb binds to CO so quickly that partial pressure does not have time to _____). So _____
  4. Measure CO uptake (CO ____ - CO ______)
  5. Solve for DLCO (How?)
  6. Multiply by _____ to obtain DLO2
A
  1. small; held ~10s
  2. PACO
  3. Increase; So ΔPCO ~= PACO
  4. CO exipired - CO inspired
  5. DLCO = CO uptake / ΔPCO
    6 1.23
31
Q

When using the CO method do can we take the raw value for DLCO or should we convert it DLCO to get the diffusion COeff for O2?

A

CO is good enough since it’s proportional O2 diff coeff. Thereby a problem with DLCO would be indicitive of a problem with O2 diffusion Coeff

32
Q

Ventilation-perfusion?

A

VA/Q
( Q= rate of Pulmonary blood flow) .
(VA = Alveolar Ventilation Rate)

33
Q

At which VA/Q ratios do no exchange happen?

A

0 or infinity

34
Q

Normal VA/Q Ratio?

A

0.84

35
Q

VA / Q ratio = 0
No ___, so alveolar air _________ (come to equilibrium with/ Surpasses/ falls bellow) alveolar blood.
Why do this happen?

A

VA
Comes to equilibrium with

Partial pressures of O2 and CO2 are equal to those in normal systemic venous blood (pulmonary arterial).

36
Q

Partial pressures of O2 and CO2 in the aveolus are equal to those in normal systemic venous blood (pulmonary arterial). When would this happen? Give an example of diseases condition

A

When VA= 0
No alveolar Ventilation
-> COPD’s

37
Q

Which value being 0 would cause VA / Q = ∞

A

Q = 0

38
Q

Physiologically, what would cause VA / Q = ∞

A

No capillary blood flow to carry O2 away from or to bring CO2 to alveolus

39
Q

When VA/Q = ∞ Alveolar air comes to equilibrium with humidified inspired air or Alveolar Blood?

A

Humidified Inspired air

40
Q

VA/Q = ∞

What disease conditions would cause this?

A

. Pulmonary Embolism

41
Q

VA = decreased ventilation rate, Q = normal level of blood flow. This would happen in which class of Disease conditions

A

COPD

42
Q

Which disease conditions: VA / Q = below normal level

A

COPD

43
Q

Which disease Conditions: VA is normal, Q is decreased

A

Pulmonary embolism

44
Q

Which disease Conditions: VA / Q = above normal levels

A

Pulmonary embolism

45
Q

______ caused by plaque dislodgement from periphery

A

Pulmonary embolism

46
Q

When VA/Q is below normal (i.e. inadequate VA), certain fraction of venous blood passes through pulmonary capillaries without getting oxygenated. This fraction of blood is known as?

A

Shunted blood

47
Q

What is a physiologic shunt?

A

Total quantitative amount of shunted blood per minute

48
Q

Finish this sentence. The greater the physiologic shunt, the greater…

A

The amount of blood that fails to be oxygenated as passes through lungs

49
Q

When is ventilation is said to be “wasted”?

A

When VA is adequate, but Q is low (i.e. high ratio), far more O2 in blood than can be transported away from alveoli

50
Q

What does wasted ventilation contribute to?

A

physiologic dead space

51
Q

When the physiologic dead space is great, much of the work of breathing is said to be?

A

Wasted

EXCI 357 Pulmonary Physiology (7 decks)

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