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FS Exam 3 > Gas Exchange > Flashcards

Gas Exchange Flashcards

1
Q

Partial Pressure of Gases

A

Each gas in the mixture of air exerts a portion of the total pressure of gas

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2
Q

PO2

A

Air is 20.93% oxygen

PO2 = 0.2093 * 760 = 159mmHg

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3
Q

Inspired air is

A

100% humidified and warmed

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4
Q

Lung partial pressure is calculated as a ___ value

A

dry values, so you have to subtract the effect of water vapor
PH2O = 47mmHg
Trachea = 760 - 47 * 0.21 = 150mmHg

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5
Q

When oxygen moves to a fluid medium (blood) PO2 is defined by…

A

O2 dissolved in solution

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6
Q

Gas Exchange depends on…

A

Diffusion

Gas diffuses from high to low partial pressures

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7
Q

Fick’s Law of Diffusion

A

A/T * D * (P1-P2)
Primary driving force is the pressure gradient
D - coef of gas is proportional to its solubility in the membrane
CO2 is more soluble in membrane

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8
Q

Rate of diffusion of gas is proportional to ____ and inversely related to ____

A 
tissue area (A)
and inversely related to tissue thickness (T)
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9
Q

Diffusion path for lung

A
  1. Layer of fluid lining the alveolus containing surfactant
  2. Alveolar epithelium
  3. Epithelial basement membrane
  4. Interstitial space
  5. A capillary basement membrane
  6. Capillary endothelial membrane
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10
Q

Lung Interstitum

A

Very small under normal conditions

Can become enlarged with inflammatory cells and fluid (edema) and this would interfere with gas exchange

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11
Q

Diffusion depends on…
O2
CO2

A

Pressure gradient
O2 = 100 to 40
CO2 = 40 to 46
CO2 = more soluble in membrane, better diffusion coef.

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12
Q

Hemoglobin

A

Pigment in RBCs gives blood red color

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13
Q

Oxygen ____ when binding heme

A

Ox reversibly binds heme

Consists of porphyrin ring and central iron atom

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14
Q

Hemoglobin # of Ox molecules can bind

A

Hemoglobin cooperatively binds 4 oxygen molecules -
Oxygen of 1st heme inc the affinity for 2nd molecule of O2 - when 1st binds, there is more attraction for second and so on until 4 are bound

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15
Q

O2 uptake depends on

A
  1. diffusion characteristics (Ficks Law)

2. Pulmonary capillary blood flow

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16
Q

Oxygen diffusion along pulmonary capillary - how long to saturate hemoglobin under norm conditions

A

Only 1/4 of a sec to saturate hemoglobin under normal conditions

17
Q

Oxygen diffusion along pulmonary capillary - how long to saturate hemoglobin with exercise

A

Changing time blood cells take to fly across the capillary, generally saturation stays the same
Pathology –> can have problem with saturation and may never get fulls aturation

18
Q

Oxygen carrying capacity of blood

A

Hemoglobin = 15Hb/dL
1 g Hb binds 1.34 mL of O2
20.1 mL O2/dL blood = oxygen content of arteriole blood

19
Q

O2 saturation is ratio of…

A

)2 content (amount actually bound) over O2 capacity (usually 98%)
Ratio of how much is bound to what the capacity is

20
Q

Bohr Effect

A

Inc H+ combines with Hb changing its shape so oxygen cant bind

21
Q

Increase in PCO2 causes…what with pH

A

Decrease in pH

Carbonic anahydrase causes CO2 and water to combine reversibly and form H2CO3 that then ionizes H+ and HCO3-

22
Q

Increasing temperature…

A

Decreases tendency for oxygen to remain bound to hemoglobin

23
Q

BPG released by…

A

RBCs as they break down glucose for energy
Lowers affinity for O2
Binds to hemoglobin and increases release of O2
Increased with anemia, chronic hypoxia, and acclimatization to altitude

24
Q

Oxygen content is critical factor affecting…

A

metabolism

25
Q

Anemia

A

Dec. in RBCs
Can have normal PO2 and SO2 but a dec oxygen content
O2 content and O2 capacity are both decreased, so the ratio stays the same

26
Q

Carbon Monoxide

A

Affinity of Hb for CO is 210X that of O2
No feedback mechanism when O2 is low
CO shifts curve to the left - dec in O2 unloading at the tissues

27
Q

CO2 transport in blood

A

Dissolved = 7%
Bound to Hb = 23%
Bicarbonate = 70%

28
Q

CO2 diffusion along pulmonary capillary

A

46 mmHg to 40 mmHg as you go across pulmonary capillary
Takes 1/3 of a sec for CO2 to get to 40
With pathology might not get this, would get to 41 or 42

29
Q

Primary driver for inspiration

A

CO2

Just a little change will impact inspiration

30
Q

CO2 Equilibrium - Dissociation Curve

A

Describes relationship btw PCO2 and CO2 content of the blood

Oxygen helps CO2 diffusion

31
Q

Haldane Effect

A

Increased PO2 drives the curve down (facilitates unloading of CO2 at the lungs)
Decreased PO2 drives curve up (facilitates CO2 loading at the tissues)

32
Q

Integration of Dissociation Curves - blood can carry more….

A

Blood can carry more CO2 than O2

33
Q

Integration of Dissociation Curves

A

Shape of CO2 equilibrium curve allows lungs to unload lots of CO2 with small change in PCO2
Change in CO2, large change in content
O2 change, not much impact on content

FS Exam 3 (10 decks)

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