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Respiratory Physiology > Quiz 4 Physical Principles of Gas Exchange > Flashcards

Quiz 4 Physical Principles of Gas Exchange Flashcards

1
Q

What is the mechanism and rate of molecule transfer dependent on ?

A
  • Physics of gas diffusion

- Partial pressures of gases involved

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2
Q

What is the energy source for gas diffusion?

A

Kinetic motion

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3
Q

Molecular movement is ______ and ______

A

Continual and random

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4
Q

Movement of a gas in one direction is the effect of what?

A

Concentration gradient

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5
Q

Direction of diffusion occurs for areas of ______ to _______ concentration.

A

High to low

Simple diffusion

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6
Q

Rate of diffusion is dependent on what?

A

Pressure

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7
Q

What is partial pressure?

A

The pressure a gas would exert by it’s self.

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8
Q

What is the total pressure of a mixture?

A

The summation of all the partial pressures in a gas

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9
Q

True or False: Each gas exerts its own individual pressure on the respiratory wall surface?

A

True

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10
Q

What is the mixture of air?

A

Nitrogen 79%

Oxygen 21%**

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11
Q

What is the total pressure of the air mixture?

A

760 mm Hg*

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12
Q

What does 1 atmosphere equal?

A

760 mm Hg*

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13
Q

What is the partial pressure of nitrogen in one atmosphere?

A

600 mm Hg

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14
Q

What is the partial pressure of oxygen in one atmosphere?

A

160 mm Hg

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15
Q

What does Henry’s Law say about the solubility of a gas in a liquid (what is it dependent on)?

A

Depends on the

  • temperature
  • partial pressure of the gas over the liquid
  • nature of the solvent
  • nature of the gas

For a gas, low temp and high pressure increases solubility

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16
Q

What does highly soluble mean?

A

When dissolved molecules are attracted by water, more can be accumulated without building up excess pressure in a solution.

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17
Q

What does poorly soluble mean?

A

Molecules which are repelled by water will dissolve less and have lower concentration

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18
Q

What is the rate of net diffusion determined by?

A

Difference of partial pressures (pp)*

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19
Q

If the pp of gas in the alveoli greater than blood which way will the gas move?

A

The gas will move into the blood (oxygen)

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20
Q

What is the vapor pressure when a gas mixture is fully humidified at 37 C?

A

47 mmHg*

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21
Q

What is vapor pressure of water?

A

Partial pressure of water escaping surface into gas phase

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22
Q

What factors affect gas diffusion rates in fluid?

A
  • Pressure differences
  • Gas solubility in fluid
  • Area of fluid
  • Distance which gas must diffuse
  • Molecular weight of gas
  • Temperature of fluid
23
Q

What is diffusion coefficient of the gas?

A

Characteristics of the gas which affect the ability and rate of net diffusion.
(Solubility/ square root Molecular weight)

24
Q

What is the limiting factor for gas movement into tissues?

A

Diffusion rate of gas through tissue water

Respiratory gasses are highly soluble in lipids (cell membranes)

25
Q

True or False: Alveolar air has the same gas concentration as atmospheric air?

A

False

Different because alveolar air is partially replaced by atmospheric air during each breath

26
Q

Normal alveolar ventilation removes half of the gas in ____ seconds?
What about hyper/hypoventilating?

A

17 seconds

Hyperventilating removes gas faster
Hypoventilating removes gas slower

27
Q

What is the normal alveolar PO2?

A

100 mm Hg

28
Q

What is the normal alveolar PCO2?

A

40 mm Hg

29
Q

Alveolar air is expired at ____________

A

end of exhalation

30
Q

How thick is the alveolar membrane?

A

0.6 micrometers

31
Q

What is the total surface area of the alveoli?

A

70 square meters

32
Q

How wide are the alveolar capillaries?

A

5 micrometers

33
Q

What are the factors that affect rate of gas diffusion through the respiratory membrane?
What Law?

A

Frick’s Law

  1. Thickness of the membrane
  2. Surface area of the membrane
  3. Diffusion coefficient
  4. Pressure difference across the membrane
34
Q

CO2 diffuses ___ times faster than Oxygen.

A

20

35
Q

Oxygen diffuses _______ times faster than Nitrogen.

A

2

36
Q

Can the factors which affect diffusion through the respiratory membrane affect the diffusion capacity?

A

Yes

37
Q

What is the diffusing capacity?

A

Volume of a gas that will diffuse through the respiratory membrane each minute for a pressure difference of 1 mm Hg.

38
Q

What is the diffusing capacity for O2?

A

21 mL/min/mmHg

39
Q

How do you get the total quanitity of O2 diffusing across the membrane per minute?

A

Pressure difference multiplied by the diffusing capacity.

40
Q

How much does exercising increases the diffusing capacity to?

A

65 mL/min/mmHg

41
Q

What increases the diffusion capacity during exercising?

A
  • Recruitment of capillary fields (surface area)

- Better ventilation/perfusion match with blood (All ZONE 3)

42
Q

CO2 diffusing capacity estimate is based on the ______ _______.

A

diffusion coefficient

unable to calculate, so based off of this

43
Q

Diffusing capacity of CO2 at resting is ________ and during exercise is ______?

A

400 mL/min/mmHg,

1200 mL/min/mmHg

44
Q

If the V/Q ratio is either zero or infinity there is ______ exchange of gases.

A

NO

45
Q

When V/Q = Zero this means what?

A

There is no ventilation= airway obstruction

Shunt

46
Q

When V/Q = infinity this means what?

A

There is no perfusion= PE

Dead Space

47
Q

Normal deoxygenated blood PO2 is _____..

A

40 mmHg

48
Q

Normal deoxygenated blood PCO2 is _____.

A

45 mmHg

49
Q

Inspired air PO2 is ______ mmHg

A

150 mmHg

713mmHg (ppAir)*0.21= 150mmHg

50
Q

Inspired air PCO2 is ______mmHg.

A

0 mmHg

51
Q

What happens in emphysema?

A

Dissolution of many alveolar walls to coalesce alveoli into larger chambers (surface area decreases up to 5-fold)

Can effect gas diffusion rate through respiratory membrane d/t decreasing surface area

52
Q

Normal alveolar partial pressures:
Alveolar PO2:____mmHg
Alveolar PCO2: ___mmHg

A

100 mmHg

40 mmHg

53
Q

Perfusion, but no ventilation?

V/Q is ____ normal?

A

Physiologic Shunt- total amt blood shunted/min

Below/ 0

54
Q

Ventilation, but no perfusion?

V/Q is ____ normal?

A

Dead space

Above/ Infinity

Respiratory Physiology (11 decks)

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