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CVR > elasticity and compliance > Flashcards

elasticity and compliance Flashcards

1
Q

define elasticity

A

resistance to deformation/stretch by an external force (stiffness)
-ability to recoil

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2
Q

define compliance

A

ability to stretch
-inverse of elasticity

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3
Q

what does high elasticity mean for compliance

A

low compliance

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4
Q

explain high elasticity with low compliance - resistance band

A

resistance band has high recoil
snaps back to original shape
difficult to stretch

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5
Q

low elasticity = high …….

A

compliance

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6
Q

describe low elasticity with high compliance - resistance band

A

resistance band had low recoil
returns to original shape but not as rapidly
easier to stretch

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7
Q

chest wall pulls …..

A

outwards

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8
Q

lungs pull …..

A

inwards

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9
Q

at rest what is created in the lungs

A

negative pressure in the pleural cavity

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10
Q

how do you calculate lung distending pressure

A

pressure inside - pressure outside

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11
Q

what does lung distending pressure counteract

A

elastic recoil of lungs

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11
Q

what does lung distending pressure prevent

A

lungs collapsing

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11
Q

elastic recoil of lungs - describe

A
  • elastic recoil

-lungs pull inwards

-chest wall pulls outwards

  • at rest this creates negative pressure in the pleural cavity

-lung volume under these conditions is called functional residual capacity (~2.5L)

  • ~0.5kPa relative to atmospheric (P lower B) pressure and alveolar (P lower A) pressure
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11
Q

describe the pressure changes in the lungs during inspiration

A
  1. decrease in intrapleural pressure
  2. increase in lung volume
  3. decrease in alveolar pressure
  4. inflow of air
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12
Q

symbol for compliance

A

C

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13
Q

lung distending pressure …… during inspiration

A

increases

14
Q

lung distending pressure during inspiration - describe

A
  • chest wall expands
    -small decrease in pressure in lungs
    -bigger decrease in pressure in pleural cavity - 0.5kPa
  • -0.1kPa - -1kPa = +1kPa
    -distending pressure increases
15
Q

lung compliance curves - explain

A

compliance - change in volume are a result of change in lung distending pressure
-requires more than 1 data point
-slope of line = lung compliance

-compliance INCREASES = small increase in lung distending pressure results in big increase in lung vol

-compliance DECREASES = small increase in lung distending pressure results in small increase in lung vol

16
Q

why are lung compliance curves s-shaped

A

at high vols - lung compliance is low

at normal vols - high

low vols - low

17
Q

what are the determinants of lung compliance

A

elastic properties of the tissue
surface tension

18
Q

what is surfactant used for

A

alleviating surface tension

19
Q

surfactant lines ……

A

air-water interfaces

19
Q

what are mothers given to produce surfactant in premature babies

A

a steroid shot

19
Q

c

A
  • surfactant lines air-water interfaces

-water molecules become separated by surfactant molecules

-attractive forces between water molecules decrease

-surface tension DECREASES (10% of the theoretical value:

  • secreted by type 2 alveolar cells
  • more effective in smaller alveoli

-smaller radius

-surfactant density INCREASES

-all alveoli during expiration

20
Q

what effect does surfactant have on lung compliance

A

decreases it

21
Q

describe the elastic recoil of the lungs + chest wall

A

lungs pull inwards
chest wall pulls outwards

22
Q

chest wall distending pressure at functional residual pressure

A

counteracts elastic recoil of chest wall
prevents chest wall from springing outwards

22
Q

what 2 sources restrict the chest wall

A

extrinsic
intrinsic

23
Q

examples of intrinsic sources that restrict chest wall compliance

A

scoliosis
kyphosis
ankylosing spondylitis
pectus excavatum

24
Q

why are the chest wall + lungs not isolated

A

due to the pleural fluid linkage

25
Q

chest wall and lungs are equally compliant - explain

A
  • at FRC chest wall distending pressure is negative (-0.5kPa)
  • slopes are the same
  • but chest wall and lungs are not isolated
  • pleural fluid linkage

CVR (3 decks)

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