2. Alveolar Gas Exchange Flashcards

1
Q

when air flows thru a tube, the air resistance makes —

A

airflow more difficult

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2
Q

if airway resistance is high, what is needed from Ms

A

more effort to produce air flow

(overall airflow is slower)

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3
Q

what is the equation for resistance

& what changes resistance the most

A

radius change = greatest impact on resistance

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4
Q

what controls the bronchiole diameter

A

Sm. M

  • change airway resistance
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5
Q

why do you need to change airway resistance

A

send air to right places & away from areas w/o oxygenations

(right places = alveoli that have good supply & good oxygenation)

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6
Q

what is alveolar ventilation

A

volume of air reaching the alveoli

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7
Q

what is VA(dot) & what is the average value

A

ventilation per min –> VA * F

4 L/min

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8
Q

What is perfusion

A

similar to cardiac output

normal vol = 5 L/min

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9
Q

what is the equation that helps you determine rate of diffusion

A
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10
Q

what are the normal J-values for O2 & CO2?

A

O2 = 250 mL exchanged every min

CO2 = 200 mL exchanged every min

(Rmr each are evaluated differently)

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11
Q

which factors influence diffusion rate and depend directly on the structure of the alveolus

A

SA = # of alveoli in lung (specifically # of caps available

& distance: diffusion distance

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12
Q

how does SA vary

& what happens if it increases

A

at rest = 70 mL in pul cap

during exercise = up to 200 mL of blood in caps

  • ALL DEPENDS ON NUMBER OF OPEN PUL CAPS

–> if SA increases - J increases

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13
Q

what happens to alveoli in COPD and emphysema

A

lost alveoli –> decreased SA –> decrease ability to get O2 in (decreased diffusion rate)

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14
Q

what affects the distance btn alveoli and caps?

what is the avg

A

fluid layer, alveolar epithelium, interstitial space, blood vessel wall

avg = 0.6 micron

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15
Q

what happens when you have deposition of collagen w/i interstitial spaces

A

increase diffusion distance –> decreases diffusion rate

-happens in interstitial lung disease-

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16
Q

What does the diffusion coefficient depend on

A
  1. solubility of the gas in h2o (CO2 more soluble = advantage)
  2. molecular weight of gas (O2 = lighter = advantage)
17
Q

what is the difference of diffusion constant for CO2 and O2

A

DCO2 (20x) DO2

  • which means CO2 will cross even if O2 has difficulty crossing
18
Q

where is the P gradient for O2 the highest

A

at start of cap

PcapO2 = 40 mmHg & PalvO2 = 104 mmHg

gradient = 60 mmHg & O2 flows into caps

19
Q

when is the pressure gradient for CO2 the highest

A

PcapCO2 = 45 mmHg & PalvCO2 = 40 mmHg

gradient = -5 mmHg; so CO2 flows out of cap

20
Q

how long does it take O2 to equilibrate as the RBC flows thru pul caps?

What does it depend on

A

0.25 sec ==> perfusion limited

depends on perfusion

21
Q

what happens to RBC movement thru pul cap during exercise

how can this be a prob

A

RBC spends just enough time to get to O2 equilibrium

if you have lung disease - you notice problems with exertion bc dont spend enough time to equilibrate –> becomes diffusion limited bc sending more blood doesn’t help

*1st sign of lung disease - difficulty w/ exercise*

22
Q

what is DLO2

A

diffusion capacity of lung for O2

= 21 mL O2/min/mmHg at rest

23
Q

how do you measure DLO2

A

use Carbon monoxide (CO)

-it binds to only Hb (none in plasma) so you can administer very small amount of CO and measure how much is exhaled –> then multiple by 1.23 (correction factor)

*cant measure O2 directly bc som bind to Hb and some dissolve in plasma*

24
Q

what is the average amount of time a RBC spends in a pul cap

25
how fast does CO2 equilibrate as RBC flows thru cap how is this affected in lung disease
almost immediately (bc its so soluble) - thats why.. have to have very SEVERE case of lung disease for CO2 for be affected (have problems w/ O2 first)
26
what is LaPlace's Law
Pressure = 2T/r P is dependent on r bc T is the constant surface tension
27
what happens if you dont have surfactant
large alveoli have low P & small alveoli have high P so you build a P gradient and air from the small alv flow into large ==\> poor lung inflation & collapsed alveoli!
28
what does surfactant do
it reduces the surface tension (T) in small alveoli so the Ps of small and large alveoli match and small ones dont have collapse \*help maintain different sized alveoli
29
what are components of surfactant and where is it stored
phospholipid: DPPC & proteins (SPA, SPB SPC, SPD) --\> SPB imp in fxn stored in intracelluar lamellar bodies (granules w/ high [DPPC] & [SPB])