Gas Exchange

Question 1

How big is the gas exchange area?

Answer 1

70 m^2

Question 2

what is the alveolar capillary diffusion distance?

Answer 2

0.4 micrometers

Question 3

Where does respiration occur?

Answer 3

mitochondria

Question 4

What are the 3 different kinds of dead space VD?

Answer 4

1. anatomic dead space
2. alveolar dead space
3. physiological dead space

Question 5

alveolar dead space

Answer 5

the volume of inspired air that is delivered to alveoli in which there is no gas exchange or gas exchange is incomplete

Question 6

anatomic dead space

Answer 6

volume of all non-gas exchange airways from the nose (or mouth, during mouth breathing) down to the respiratory bronchioles

Question 7

physiologic dead space

Answer 7

the sum of anatomic dead space and alveolar dead space

*defines the portion of each inspiration that does not participate in gas exchange

Question 8

why is alveolar ventilation less than pulmonary ventilation?

Answer 8

less because of anatomical dead space

Question 9

What is convection?

Answer 9

convection is the bulk movement of gas due to pressure gradients and requires mechanical power input

Question 10

What two transport processes occur by means of convection?

Answer 10

1. transport from the environment to terminal bronchioles

2. transport of erythrocytes between pulmonary capillaries and peripheral capillaries

Question 11

what is diffusion?

Answer 11

transport based on random motion of thermally energetic particles situated in a concentration gradient

Question 12

What transport processes occur by means of convection?

Answer 12

1. transport between terminal bronchioles to erythrocytes

2. transport between erythrocytes and peripheral mitochondria

Question 13

Whats the difference between convection and diffusion?

Answer 13

in convection, gas moves from high pressure to low pressure. In diffusion, there is no pressure or mechanical movement

Question 14

the movement of particles by convection is driven by what?

Answer 14

the pressure gradient between the atmosphere and terminal bronchioles

Question 15

The mechanical work required for convection is a function of what 3 factors?

Answer 15

1. resistance of the transport path to air flow (diameter and cross-sectional area of airways)
2. the viscosity and density of air being moved
3. the compliance of the lung and chest wall

Question 16

The movement of particles by diffusion is driven by what two factors?

Answer 16

1. concentration gradient

2. diffusivity

Question 17

What is diffusivity?

Answer 17

a measure of the tendency of a molecule to avoid getting hung up in the surrounding media, specific for solute, solvent, temperature.

Question 18

dalton’s law

Answer 18

the total pressure of a gas mixture is the sum of the partial pressures of its constituents

Question 19

henry’s law

Answer 19

the partial pressure of a gas in equilibrium with a volume of liquid is proportional to the amount of gas dissolved in the liquid

P=kc

k = constant 
c = [ ] of the gas

Question 20

partial pressure

Answer 20

the pressure exerted by each type of gas in a mixture

Question 21

What determines the concentration of a gas in a liquid

Answer 21

1. partial pressure

2. diffusivity (solubility coefficient)

Question 22

How do gases dissolve in fluids?

Answer 22

by moving down a partial pressure gradient rather than a concentration gradient

Question 23

what is the partial pressure of oxygen and carbon dioxide in the pulmonary artery?

Answer 23

oxygen: 40 mmHg

carbon dioxide: 46 mmHg

Question 24

what is the partial pressure of oxygen and carbon dioxide in the lungs?

Answer 24

oxygen: 105 mmHg

carbon dioxide: 40 mmHg

Question 25

what is the partial pressure of oxygen and carbon dioxide in the pulmonary vein?

Answer 25

oxygen: 100 mmHg

carbon dioxide: 40 mmHg

Question 26

what is the A-a gradient?

Answer 26

alveoli - artery gradient

It is the difference between oxygen content in alveolus gas (measured during exhalation) and the oxygen content in arterial blood (equivalent to that leaving the lungs)

Question 27

what is abnormal A-a?

Answer 27

~10 mmHg

Question 28

What are the factors contributing to the A - a gradient?

Answer 28

1. blood shunts
2. blood mixing
3. matching

Question 29

what 3 things does gas diffusion in the lung depend on?

Answer 29

1. area of the respiratory membrane
2. distance of the diffusion
3. V/Q (ventilation and perfusion)

Question 30

what is pulmonary diffusion capacity?

Answer 30

the ability of the respiratory membrane to exchange a gas between the alveoli and the pulmonary blood.

defined as the volume of gas that diffuses through the membrane each minute for a pressure of 1 mmHg.

DL = V/Pa-Pc

Question 31

oxygen has low solubility in blood. What does the blood have that helps increase oxygen solubility?

Answer 31

hemoglobin

Question 32

what happens when the oxygen saturation of hemoglobin curve is shifted to the left?

Answer 32

more loading of oxygen and less unloading (increased affinity) –> might occur in the lungs

Question 33

what happens when the oxygen saturation of hemoglobin curve is shifted to the right

Answer 33

less loading of oxygen more unloading (tissues)

Question 34

what are the 3 main forms in which carbon dioxide is carried in the blood?

Answer 34

1. in simple solution (dissolved CO2)
2. as bicarbonate
3. combined with protein of hemoglobin as carbamino compound

Question 35

Does the affinity of Hb change in diff places?

Answer 35

Yes Hb affinity changes in diff places to make loading and unloading of oxygen easier

Question 36

what is DLCO?

Answer 36

carbon monoxide diffusing capacity; thickened alveolar capillary membrane

Question 37

What are the factors that are related to DLCO?

Answer 37

1. membrane barrier thickness
2. perfused alveolar surface area (COPD, lung resection)
3. cardiac output
4. hemoglobin concentration