Exam Ii - Adv Pathophys - Diffusion Of O2 And Co2 Through A Respiratory Membrane

Front 1

What is diffusion

Back 1

simple molecules moving freely and randomly among each other

Front 2

What type of energy is associate with diffusion

Back 2

kinetic

Front 3

When does kinetic motion theoretically stop

Back 3

0 K

Front 4

Oxygen and CO2 move via

Back 4

diffusion

Front 5

Net diffusion is from

Back 5

an area of high concentration to an area of low concentration

Front 6

What is partial pressure

Back 6

the pressure of a gas acting on respiratory passages and alveoli is proportional to the sum of all forces of all the molecules

Front 7

Sum of all partial pressures equals

Back 7

the atmospheric pressure

Front 8

The pressure of a gas is ______ to the concentration

Back 8

directly proportional

Front 9

Does gas in a liquid exert a pressure

Back 9

yes

Front 10

Partial pressure of a gas is determined by what two things

Back 10

concentration and solubility coefficient

Front 11

Explain Henry's Law

Back 11

if gas molecules are physically or chemically attracted to H2O far more of them can be dissolved without building up an excess partial pressure within the solution

Front 12

Henry's law formula

Back 12

partial pressure = % dissolved gas/solubility coefficient

Front 13

Per Henry's law and given solubility coefficients: CO2 = 0.57, oxygen = 0.024 - explain the solubility and partial pressure differences between oxygen, CO2

Back 13

If oxygen solubility coefficient = 0.024 and CO2 solubility coefficient = 0.57
...then CO2 is about 20x more soluble than oxygen and
...the partial pressure of CO2 is about 1/20th of that of oxygen

Front 14

If the partial pressure of a gas is high in the alveoli, it tends to

Back 14

push it into solution (interstitial fluid)

Front 15

If the partial pressure of a gas is high in solution (interstitial fluid) it tends to

Back 15

push it into the alveoli

Front 16

Net movement depends on

Back 16

difference in partial pressures

Front 17

The partial pressure of H2O is dependent on

Back 17

body temperature

Front 18

Normal vapor of water at 37 deg C is

Back 18

47torr
at 0 deg C vapor pressure is 5 torr
at 100 deg C vapor pressure is 760 torr

Front 19

Factors other than partial pressure differences and solubility coefficients that determine diffusion

Back 19

1. distance a gas must diffuse (thickness of membrane)
2. molecular weight of gas
3. temp of fluid
4. cross sectional area

Front 20

All gases in the respiratory system are lipid soluble so the major limitation of gas in tissues is

Back 20

through H2O

Front 21

Why is composition of alveolar air and atmospheric air different

Back 21

O2 leaving alveoli
CO2 entering alveoli
H20 vapor is higher
atmospheric air is mixed with deadspace air

Front 22

Partial pressure of atmospheric air

Back 22

159torr

Front 23

Partial pressure of alveolar air

Back 23

149 torr - water vapor has diluted out

Front 24

If TV is 500ml - how much is dead space

Back 24

150ml

Front 25

How quickly does alveolar air turn over

Back 25

16 breaths?

Front 26

Alveolar concentration of alveoli is controlled by two things

Back 26

rate of absorption of oxygen into the blood
rate of entry of new oxygen into the lungs

Front 27

Without perfusion, the normal partial pressure gradients would be

Back 27

slowed - thus oxygen from alveoli to interstitial fluid would be slowed

Front 28

Rate of entry of new oxygen into lungs is dependent on

Back 28

ventilation - rate, depth, deadspace

Front 29

Normal oxygen consumption rate

Back 29

250 ml/min

Front 30

250 ml/min must be absorbed to maintain a PO2 of

Back 30

104torr

Front 31

With optimal ventilation at 250ml/min consumptive rate - PO2 can never exceed

Back 31

149torr

Front 32

With optimal ventilation at 250ml/min consumptive rate - the only way to exceed a PO2 of 149 is to

Back 32

increase the FiO2

Front 33

If consumptive rate falls below 100ml/min will have

Back 33

anaerobic metabolism

Front 34

Normal CO2 rate of excretion is

Back 34

200ml/min

Front 35

at normal ventilation, PCO2 is

Back 35

40torr

Front 36

The alveolar PCO2 increases directly in proportion to the rate of

Back 36

CO2 production

Front 37

The alveolar PCO2 decreases directly in proportion to the rate of

Back 37

alveolar ventilation rate

Front 38

With higher metabolic rate (temp) CO2 production

Back 38

increases

Front 39

How many alveoli are there in two lungs of an adult

Back 39

300million

Front 40

Diameter of each alveoli

Back 40

0.2mm

Front 41

Air exchange occurs between alveoli and

Back 41

the respiratory zone

Front 42

Layers of respiratory zone (thickness of 0.2mm)

Back 42

1. surfactant and fluid layer
2. alveolar epithelium
3. epithelial basement membrane
4. interstitial space
5. capillary basement membrane
6. capillary epithelium

Front 43

Four factors that affect rate of diffusion

Back 43

1. thickness of membrane
2. surface area
3. diffusion coefficient
4. partial pressure difference

Front 44

What would increase the thickness

Back 44

pulmonary fibrosis or pulmonary edema

Front 45

What would cause reduced surface area of lung

Back 45

lobectomy, emphysema,

Front 46

CO2 diffuses____ faster than oxygen

Back 46

20x

Front 47

oxygen diffuses___ faster than nitrogen

Back 47

much

Front 48

What is V:Q ratio

Back 48

compares ventilation of lung area to perfusion - set up as ratio

Front 49

Normal V:Q ratio

Back 49

0.8-1

Front 50

West zone I - describe Pa:PA:Pv and V:Q ratio

Back 50

PA > Pa > Pv (no flow)
V:Q >1

Front 51

West zone II - describe Pa:PA:Pv and V:Q ratio

Back 51

Pa > PA >> Pv
V:Q ratio = waterfall effect
resistance set by Pa and PA

Front 52

West zone III - describe Pa:PA:Pv and V:Q ratio

Back 52

Pa > Pv > PA
V:Q 0.8-1 - ideal for perfusion/placement of swan ganz or PA catheter

Front 53

West zone IV - describe Pa:PA:Pv and V:Q ratio

Back 53

Pa >> Pv >>> PA
V:Q = shunt

Front 54

No ventilation but alveoli perfused - what are the alveolar gas pressures

Back 54

shunt - PO2 = 40torr, PCO2 = 45torr

Front 55

ventilation but no perfusion - what are the alveolar gas pressures

Back 55

dead apace - PO2 = 149torr, PCO2 = 0torr

Front 56

V:Q normal - what are the alveolar gas pressures

Back 56

PO2 = 104torr (mixing 149torr with inspired air), PCO2 = 40torr (mixing venous 45torr with 0torr inspired)

Front 57

What is considered shunt blood

Back 57

when venous blood passing through the pulmonary capillaries is not oxygenated

Front 58

Why is physiological dead space bad

Back 58

wasted energy due to the body's response to increase ventilation or wob

Front 59

How can shunt trauma occur

Back 59

ETCO2 = 12 drop vent rate send ABG (CO2 72) this is because of poor or no perfusion

Front 60

Does physiological shunt normally occur

Back 60

yes

Front 61

When does normal physiological shunting occur

Back 61

zone I - V and Q are both low but Q < V
zone IV - V and Q are both low but Q > V - still have physiologic shunt

Front 62

COPD causes air trapping/overstretching of alveoli - what 2 V:Q problems exist

Back 62

1. obstructed alveoli are not ventilated V:Q = 0 or dead space
2. intact alveoli may ventilate but perfusion through destroyed walls is inhibited = physiologic shunt