Pulmonary Gas Exchange Flashcards Preview

A. White- Human Physiology > Pulmonary Gas Exchange > Flashcards

Flashcards in Pulmonary Gas Exchange Deck (27)
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1
Q

What is Dalton’s Law?

A

Ptotal of non-reactive gases = sum of partial pressures of individual gases.

2
Q

What is Boyle’s Law?

A

P = 1/V

For a fixed amount of an ideal gas kept at a fixed temperature.

3
Q

What is Henry’s Law?

A

At a constant temperature, the amount of a gas that dissovles in a type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.

4
Q

What is the ideal gas law?

A

P = nRT/V

5
Q

What is the partial pressure of oxygen at the alveolar membrane?

A

150 mm Hg

6
Q

What is the partial pressure of gas determined by?

A

concentration and solubility coefficient of the gas.

Partial pressure = [dissolved gas]/solubility coefficient

7
Q

What are the major components of the air?

A

Nitrogen (78%)

Oxygen (21%)

Argon (0.93%)

Carbon dioxide (0.03%)

8
Q

Pressure is ___ proportional to the concentration of gas molecules.

A

directly

9
Q

What is the vapor pressure of water?

A

The partial pressure exerted to escape from the liquid to the gase phase.

At normal body temperature, vapor pressure = 47 mm Hg

10
Q

What is vapor pressure dependent upon?

A

temperature of the water

11
Q

What factors affect rate of gas diffusion in a fluid?

A

solubility of gas in the fluid

cross-sectional area of the fluid

distance through which the gas must diffuse

molecular weight of the gas

temperature of fluid

12
Q

HOw do the solubility coefficients of oxygen and carbon dioxide compare?

A

Solubility of oygen = 0.024

Solubility of carbon dioxide = 0.57

Because carbon dioxide is more soluble in water than oxygen, it will exert a partial pressure that is less than 1/20th that of oxygen.

13
Q

What are the factors that control oxygen concentration in the alveoli?

A

Rate of absorption of oxygen into the blood

Rate of new oxygen entry into the lungs.

14
Q

Why can alveolar ventilation not increase pO2 above 149 mm Hg under normal conditions?

A

Too high of a level of alveolar ventilation is needed.

15
Q

What are the facotrs that control carbon dioxide concentration in the alveoli?

A

Rate of carbon dioxide excretion (pressure increases in direct proportion to excretion)

alveolar ventilation (alveolar PCO2 decreases in inverse proportion to alveolar ventilation).

16
Q

What are the components of the alveolar respiratory membrane?

A

capillary endothelium

capillary basement membrane

interstitial space

epithelial basement membrane

alveolar epithelium

17
Q

The respiratory membrane allows for the diffusion of what gases?

A

oxygen and carbon dioxide

18
Q

What factors determine how rapidly a gas will pass through the respiratory membrane?

A

membrane thickness

membrane surface area

Diffusion coefficient of gas

partial pressure difference of gas between two sides of the membrane.

19
Q

What does the Va/Q ratio refer to?

A

It is a ratio of ventilation-perfusion

20
Q

When is the Va/Q ratio normal?

A

When both factors are normal for a given alveolus.

21
Q

What is the normal Va/Q ratio?

A

0.8

This indicates gas exchange is complete in initial third of capillary.

22
Q

What occurs when Va/Q = 0?

A

There is still perfusion, but there is an airway opstruction.

Blood gas composition remains unchanged.

23
Q

What occurs when Va/Q = infinity?

A

There is still ventilation, but no gas exchange.

This is due to a vascular obstruction (i.e. pulmonary embolism).

Alveolar gas composition remains unchanged because there is no blood contact. This creates a physiologic shunt.

24
Q

What is shunted blood?

A

venous blood passing through pulmonary capillaries that does not become oxygenated.

It ocurs whenever Va/Q is below normal.

25
Q

The greater the physiologic shunt, the ___ the amount of blood that fails to be oxygenated.

A

Greater

26
Q

What occurs when ventilation of some of the alveoli is great but alveolar blood flow is low?

A

There is far more available oxygen in the alveoli than can be transported away from the alveoli by the flowing blood. The ventilation of these alveoli is wasted.

27
Q

What is the physiologic dead space?

A

The sum of oxygen transported (When there is an exess of oxygen) + anatomic dead space