• Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

Card Range To Study

through

image

Play button

image

Play button

image

Progress

1/56

Click to flip

Use LEFT and RIGHT arrow keys to navigate between flashcards;

Use UP and DOWN arrow keys to flip the card;

H to show hint;

A reads text to speech;

56 Cards in this Set

  • Front
  • Back
what does hte O2/Hb disassociation curve do to change affinity
shift left
shift right
where does gas exchange occur
Lungs: O2 from alv gas into pulm capillary. CO2 from pulm capillary into alv gas

Tissue: O2 from blood to cells, CO2 from tissues into pulm blood
Fick does what?
diffusion

V = D A P/X

*the volume of gas transferred is equal to the diffusion coef times area times pressure/thickness
so diffusion is proportional to...
inversely proportional to...
Directly: Pressure, SA, Dif coef (vaires with gas)

Inverse: membrance thickness
when does membrane thickness really affect diffusion

what about SA
not normally an issue except in fibrosis when thickness increases

** V= D A P/X

SA increased with exercise, decreased with emphysema
what does emphysema do to diffusion, how
it decreased it by decreaseing SA

V = D A P/X
what is the friving force for diffusion
PRESSURE GRADIENT

V = D A P/X FICK
what is the diffusion coeffecient of a gas. what determines it
what gas has a higher D
its the ability of it to diffuse. MW and solubility
changes with gasses

CO2 is WAY more soluble thatn O2 so CO2 has a higher diffusion coef
for a given P what diffeses faster CO2 or O2, why
CO2. it has a higher D (MW and solubility, CO2 solubility > O2 solubility)
what is lung diffusing capacity
A single term that combines these:
1. D (MW/SOlubility)
2. SA
3. THickness
4. Time required for gas & protein to combine

**measured with CO
why do we use CO to measure the lung diffusing capacity
its limited only by diffusion in the lungs

**Dl is proportional to the rate of disappearance of CO from a mixed gas while the pt breathes this gas in

Dl: SA, Dif, Thick, Time to combine with protein
how does Dl change in emphysema
decreases

Alv destruction decreases SA

Dl: SA, Thick, Dif, Time to combine
what does Dl do in fibrosis or pulm edem
decrease

**increased thickness, this makes diffusion limited transport. The membranes are SO thick there is not enough time to get all of the O2 transported

Dl: thickness, SA, diffusion, time to combine with protein
how does Dl change with anemia
decreased Dl

((decreased Hg so increased time to combine)

Dl: SA, D, thick, time to combine
how does Dl change with exercise
increases

Increased SA for gas exchange

**Dl: SA, Diffusion, Thick, time to combine
how is Dl measured
with CO, its diffusion limited

*CO moves from alv to blood, as soon as the CO enters blood it binds to Hg. we know that when the CO is bound it no longer exerts a partial pressure. In this manner the PCO is always kept low and there is a constant driving force to move CO into the blood. diffusion limited


*contrast to the process of N20, this gas is always dissolved so the partial pressures (only contributed by dissolved blood) equilibrate quickly and transport is perfusion limited
where is CO solubility low, high
low: capillary membrane
high: blood

Dl= diffusion/delta P
why is it a good idea to know the Dl
tells us about diffusion across the alv/pulm cap

1. ability of gas to move
2. Dx obstructive/restrictive disease
3. general assessment of how healthy
what is the method employed to measure Dl
single breath method

Pt breathes a mixture of gases, incldugin a small amt of CO, the Dl is proportional to the disappearance of CO


**Pt exhales and then inhales max (RV to TLC is breathed of the mixed gas)
**wait to allow diffusion to occur
**breath out first part of air (conducting), measure the second part of breath (respiratory zone)
what is the formula for Dl

what is a normal value
DL = VCO/Delta PCO

OR

Vent rate of CO/PACO

20-30
what is the diffision capacity for CO if PCO=0.1 and 0.25 ml CO was taken up
0.25 x 6 / 0.1

**multiply 0.25 by 6 to get the diffusion for a full minute (we held breath for 10 sec)
what decreases Dl
increases
1. increased thickness (fibrosis)
2. decrease SA (emphysema)
3. loss of lung tissue (pulm resection)
4. anemia, increased time for gas combining with protein (?????)

Dl is increased by exercise which increases the SA
Is Dl the same for everyone
nope:
large young men have the highest Dl

age decreased Dl
size increased Dl
males have larger Dl
where are gasses found in soln
the blood

**alv air has one gas and is expressed at a partial pressure

**blood has a muxture (dissolved, modified, bound)
how are gasses carried in the blood
blood, soln of gasses

gasses are:
1. bound: ex O2/ HG
2. Dissolved:
3. Modified: CO2 --> HCO3
what gas in the blood is never bound or modified, what is it
nitrogen, dissolved
where is CO2 converted to HCO3
RBC
what is henrys law
C= P x Solubility

For Dissolved gasses

AMt of gas in a liquid is equal to the partial pressure of the gas times its solubility
what 3 circumstances give diffusion limited transport, what gas is diffusion limited
1. exercise
2. fibrosis
3. emphysema

CO

**diffusion limited, pressure differnece is maintained
where is Henrys Law applicable
blood, with dissolved gas

**only dissolved gas contributes to partial pressure of a gas

Amt of gas= PP x Solubility

**N2 is the ONLY gas that is found ONLY in its dissolved form (used to measure respiratory Fx)
what are the levels of CO2 and O2 in:
dry inspired air
humidified air
Alv air

Blood
Mixed venous blood
systemic arterial blood
Dry Inspired: O2 160, CO2 0
Humidified Air: O2 150, CO2 0
Alv Air: O2 100, CO2 40

Venous blood: O2 40, CO2 46
Arterial Blood: O2 100, 40
what is the CO2/O2 of blood that entert the lung, what about when it leaves
Venous (enter): O2 40, CO2 46

Arterial (exit): O2 100, CO2 40

**The arterial and alveolar levels will equilibrate
the levels of CO2/O2 in what two areas equilibrate
Alv Air
Arterial Blood

CO2 40
O2 100
what happens to air as it is inhaled
dry: O2 160
humidified: O2 150
Alv: O2 100

**CO2 is 0 until the alv where it is 40
what is daltons law of partial pressures
the pp of a gas in a mixture of gasses is the pressure that gas would exert if it were the only gas present

partial Pressure = total pressure x fractional gas [conc]
Px- pp of gas
Pb- barometric pressure (constant)
F- fraction of gas (in ATM wont change)
calc the pp of O2 in dry inspired air

ATM: 760
fractional is 21%
Pp=total P x fractional gas conc


PP= 760 x 0.21
pp=160mmHg

**Daltons law
what is the pp of humidified tracheal air

37* C
PP H20= 47
PO2 = 760-47 x 0.21
PO2=150

Daltons Law
the amt of gas dissolved in blood is proportional to what
the partial pressure of the gas

Dissolved [O2] = PO2 X solubility of O2 in blood
in perfusion limited gas exchange what will increase diffusion
increased BF
what is the difference in equliibration in perfusion and diffusion gas exchange
1. Perfusion: equilibrates early along the pulm cap, pp of alv gas = pp of gas in blood

2. Diffusion: equilibration does NOT occur by the time blood passes through the pulm cap. Usually the PP in the alv = alv blood but not in diffusion limited cases
what is daltons law
PARTIAL PRESSURE

*PP of gas = barometric P x fraction of gas (O2 is 0.21)
how does daltons law change for humidified air
PP= Baromet - 47 x 0.21
what is the pp of O2, and what is the pp of humidified O2
PP= 760 x .21

PP humidified= 760-47 x .21
what is the fractional concentration of O2 in air
0.21
whats the ppO2 of dry inspired air?
humidified?
alveolar?

**what formula allows us to calc thses
dry: 160
humidified: 150
alveolar: 100

**Daltons Law
PO2 = Pbar x 0.21
PO2= Pbar - 47 x 0.21
what is the PaO2 and PaCO2 of mixed venous blood? what is the PaO2 and PaCO2 after this blood leaves the alv
O2 40
CO2 46

After Gas exchange
PaO2 100
PaCO2 40
why is the PaO2/CO2 the same as PAO2/CO2 (arteriolar, not venous)
equilibration of diffusion
what are the 2 ways gas exchange can be limited
1. diffusion: equilibration wont occur, gases always have driving force for diffusion

2. perfusion: pressures equalize, the only way to increase gas transport is by increaseing BF
what kinds of gases exert a pp
the kind that are directly disolved in the blood

**bound gases wont exert a pp
is O2 usually diffusion or diffusion limited
perfusion

*regulated bt BF
what would cause O2 transport to be diffusion limited rather than perfusion limited

What gas is diffusion limited, what gad is perfusion limited
usually perfusion

**diffusion limited w/ fibrosis
-decreased time for diffusion to take place
-Dl is low
-PAO2 is low


**CO is diffusion limited (no equilibration)
**N2O is perfusion limited (wquilibration)
what would decreased time for gas transport do to diffusion/perfusion limited gas exchange
difusion limited
if Dl is low how is diffusion/erfusion limited gas exchange affected
diffision limited rather than perfusion
if PAO2 is low will gas transport be diffsion or perfusion limited
diffusion
how do we know normally gas exchange is perfusion limited
the PaO2 and PAO2 equilibrate at the first 1/3 of the capillary and then just float down the rest of teh blood river without transort

**only an increase on BF will increase transport
in diffusion limited gas exchange what happens to pp gradient
maintained throughout the length of the vessel. anything that causes diffusion to decrease will maintain the dradient and become diffusion limited