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Gas Diffusion Flashcards

Week 4

1
Q

What is Boyels Law

A

gas pressure is inversely proportional to volume at a constant temperature

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2
Q
  • what is Henry’s law?
A

the amount of gas in solution is proportional to the partial pressure of the gas

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3
Q

W- hat is Dalton’s law?

A

gases exert a pressure proportional to their abundance

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4
Q

What is Ficks Law?

A

Vgas= AD(P1-P2) / T

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5
Q

What layers do gases pass through in the diffusion pathway?

A
  1. gas space with alveolus
    1. alveolar fluid lining
    2. tissue barrier
    3. plasma layer
    4. diffusion into RBC
    5. O2 uptake by Hb
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6
Q

What factors would make the perfect lung?

A
  • increased SA, coefficient of diffusion, and partial pressure gradient
  • decreased thickness
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7
Q

why is alveolar PO2 so much lower than atmospheric atm PCO2?

A

RV and VD volume = high CO2 = dilutes O2

Increased VD vs VT compromises alveloar pressure

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8
Q

How does Po2 of blood Change in pulmonary circulation?

A
  • loading of arterial blood equilibrates PaO2 with PAO2

-lowered by V/Q mismatch

  • diluted by venous blood from bronchial veins
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9
Q

what is oxyhaemoglobin?

A

deoxyhaemoglobin with 4 O2 molecules

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10
Q

What is Hb saturation?

A

% heme units containing bound O

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11
Q

how does Hb promote O2 movement from the alevoli to venous blood?

A

O2 binding lowers PO2 = Boyle’s Law sees increased pressure differential between blood and alveoli = gradient = movement

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12
Q

Where does O2 and CO2 bind to Hb?

A
  1. Heme part
  2. globin part
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13
Q

What is meant to positive cooperativity?

A

reaction rates increase as more 2 binds to Hb

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14
Q

Arterial PO2 and saturation

A

= 100mmHG at ARTERIAL end

= 97.5% sat (Hb loaded w O2)

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15
Q

Venous PO2 and saturation

A

= 40mmHG at VENOUS enf

= 75% sat (O2 unloaded from Hb)

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16
Q

What is the advantage of the plateau region of Oxygen-HB dissociation curve ?

A

safety margin for maintain O2 saturation

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17
Q

What is the adv of the steep region of Oxygen-HB dissociation curve ?

A

small changes in Po2 = rapid desaturation

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18
Q

What is the significance of R shift of Oxygen-HB dissociation curve?

A

decreased Hb sat = decreased PO2 = favours O2 unloading in TISSUES

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19
Q

What is the significance of L shift of Oxygen-HB dissociation curve

A

increased Hb sat = increased PO2 = favours loading in LUNGS

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19
Q

What factor favour R shift?

A

increased PCO2
decreased pH
Increased Temp

20
Q

What are the 3 ways by which CO2 is transported?

A
  1. dissolved in plasma
    1. bound to Hb
    2. in HCO3
21
Q

What is the overall function of Chloride shift?

A

maintains RBC electroneutrality

22
Q

What is the function of Chloride shift in lungs?

A

increases HCO3 = CA reaction moves BACKWARDS

Maintains pressure gradient for moving CO2 out of RBCs

23
Q

What is the function of Chloride shift in Tissues?

A

influx Cl in RBC echange CO2

decreases HCO3 to keep CA moving FORWARDS

mainatins pressure grandet for moving CO2 INTO RBCs

24
How is Left Shift created and where does it occur?
decreased H+ and CO2 to HbO2 = favours O2 unloading - L shift in Lungs (Bohrs effect)
25
How is right shift created and where does it occur?
Increased binding of H+ and CO2 = favours UNLOADING of O2 in tissues (bohrs efffect)
26
what is the function of the Haldane effect in the lungs ?
OcyHb binds O2 more readily loading of O2 favours releae of CO2 and H+
27
what is the function of the Haldane effect in the tissues
deoxyHb binds CO2 and H= more readily UNLOADNG of O2 favours binding of CO2 and H+
28
What are the PO2 partial pressure values in: a) PiO2 b) Alveolar c) Tissues?
a) 150mmHg b) 100mmHg c) 40mmHg
29
What are the PO2 partial pressure values in: a) Arterial Blood b) venous blood
a) 100mmHg b) 40mmHg
30
What are the PCO2 partial pressure values in: a) PiO2 b) Alveolar c) Tissues?
a) 150mmHg b) 40mmHg c) 46mmHg
31
What are the PCO2 partial pressure values in: a) Arterial Blood b) venous blood
a) 40mmHg b) 46mmHg
32
What is pressure due to?
Collision of gas molecules
33
What is Dalton's Law?
Gases exert P proportional to their abundance
34
What is Henry's law?
Amount of gas in solution is proportional to partial pressure of the gas Increased P = Increased gas dissolved in fluid
35
What do membranes need for diffusion to occur in
maintain a partial pressure gradient across all membranes and fluid layers
36
What three things will increase diffusion according to Fick's Law?
1. increased SA 2. Decreased thickness of resp membrane 3. increased partial pressure
37
Describe Coopertivity
Hb shape changes when O2 binds increases reaction rate: - as O2 binds it gets easier for subsequent ones to bind - as O2 is released, it strats of easier but then gets harder
38
PaO2 =
O2 dissolved in plasma
39
SaO2 =
% O2 bound to Hb
40
CaO2 =
= total O2 in blood
41
What occurs to the Hb dissociation curve at increased Temperature?
Right shift decreased SaO2 favours unloading O2
42
Summarise Bohr Effect
Relationship between PO2 and HBO2 how CO2 affects affinity of Hb for O2 Decrease in 1 = increase in another
43
Summarise Haldene's Effect
HbO2 + CO2 How O2 affects affinity of Hb for CO2 increase in Hb)2 = decreased Hb affinity for CO2
44
What is the effect of humidifying inhaled air? normally.
moist environment creates a more favourable environment for O2 to move from lungs to blood
45
Humidifed air impact at sea level vs high altitude
HA= Fixed partial pressure of humidified air in resp tract (47) displaces other gases, reducing available pressure available for O2. puts strain as already less PO2. SL: O2 is in abundance to humidification is not as essential.
46
what are the advantages of of the slow rate at which alveolar air is renewed?
stable gas exchange (composition of air is constant) prevents sudden changes in blood gas levels
47
Why is the partial dif between arterial and venous saturation levels much lower for CO2 than O2?
Tissues use O2 faster than the rate that CO2 is produced
48
Is CO2 or O2 more soluble?
CO2

RM (8 decks)

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