RS Lec 4 Flashcards

1
Q

lung compliance (def.) - (3)

A
  • measure of the elastic properties of lungs
  • measure of how easily the lungs can expand
  • magnitude of change in lung volume produced by change in transpulmonary pressure (slope in P-V curve)
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2
Q

two types of lung compliance

A
  • static compliance

- dynamic compliance

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3
Q

static compliance (def.)

A

-lung compliance during periods of no gas flow (during inspiratory/expiratory pause)

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4
Q

static compliance determined by

A

-P/V slope measured at FRC (end of expiratory effort)

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5
Q

dynamic compliance (def.)

A

-lung compliance during periods of gas flow (inspiration, when Ptp changes)

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6
Q

dynamic compliance reflects

A

-lung stiffness, airway resistance

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7
Q

dynamic compliance decreases when (2)

A

lung stiffness/airway resistance increase

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8
Q

dynamic compliance & static compliance relationship

A

-dynamic compliance is less than/equal to static lung compliance

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9
Q

pressure-volume relationship (1. Stable VL)

A

-at low lung volumes, difficult to pop open airways, rising Ptp little effect on lung volume

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10
Q

pressure-volume relationship (2. Opening of airways)

A

-first increases in lung volume open proximal airways, recruitment of other airways

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11
Q

pressure-volume relationship (3. expansion of airways)

A

-all airways are open, Pip is more negative by chest wall expansions, increases V (linear)

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12
Q

pressure-volume relationship (4. limit airway inflation)

A

-at high lung volumes, lung compliance decreases

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13
Q

hysteresis

A

-difference between inflation + deflation compliance paths

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14
Q

greater pressure difference (lung compliance)

A

-needed to open airway than keep from closing

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15
Q

lung compliance determined by (2)

A
  • elastic components of lungs + airway tissue (elastin + collagen)
  • surface tension at air-water interface in alveoli
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16
Q

location of elastic components of airways

A

-alveolar walls, around vessels, bronchi

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17
Q

elastic behaviour determined by

A

-geometrical arrangements, not typically elongation of fibers

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18
Q

collagen (twine) characteristics (3)

A
  • high tensile strength
  • inextensible
  • stiff (low compliance)
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19
Q

elastin (weak spring) characteristics (3)

A
  • low tensile strength
  • extensible
  • spring- high compliance
20
Q

emphysema (def.)

A

-floppy lungs due to elastin destruction + alveolar wall destruction

21
Q

emphysema effects (3)

A
  • increased compliance, less elastic recoil
  • little Ptp changes, large changes in lung volume
  • time to fill increased
22
Q

pulmonary fibrosis (def.)

A

-collagen deposition in alveolar walls in response to injury, silica dust, asbestosis

23
Q

pulmonary fibrosis effects (2)

A
  • reduction in lung compliance (stiff lungs)

- large Ptp needed for little changes in Lung volume

24
Q

Surface tension (amount for elastic recoil)

A

-2/3 of elastic recoil of lungs, decreases lung compliance

25
surface tension (def.)
- water molecules at surface attracted to each other | - measure of attracting forces pulling surface molecules together
26
surface tension is seen at
-air-fluid boundaries (hydrogen bonding of water molecules)
27
effect of surface tension
-cause the surface to maintain as small an area as possible
28
saline-filled lung
-surface tension eliminates= small Ptp changes large increase lung volume
29
alveolar collapse due
-ST created inward recoil
30
increased pressure needed to balance
-surface tension, reduces tendency to collapse
31
laplace's equation
P=2T/r T- surface tension (c0nstant) r - radius P - pressure
32
smaller alveolar radius --->
-greater pressure needed to keep the bubble inflated
33
smaller alveoli collapse
into the large ones, T is constant, pressure greater in the smaller bubbles
34
surfactant produced by
-type II alveolar cells
35
surfactant action (3)
- lowers the surface tension of the lining - stabilize alveoli collapse - increase lung compliance, easier to expand lungs
36
surfactant made of (molecules) (5)
- phospholipids: - dipalmitoyl-phosphatidylcholine (DPPC), - phosphatidyl-choline - surfactant apoproteins, Ca2+ ions
37
surfactant properties
-hydrophobic & hydrophilic properties: | enable air-water interface,decreases the density of water molecules, reduces attraction between H20
38
thickness of surfactant relationship with surface area
- thickness decreases with increasing SA, | - cause increase ST as radius increases
39
surface tension remains (regardless of radius/size in lungs)
constant, equalize pressures in alveoli of different sizes (no differences in pressure gradient between small/larger alveoli)
40
surfactant produced during
-last week of gestation
41
IRDS
- infant respiratory distress syndrome | - lack of surfactant
42
ventilation (upright lung)
-largest at bottom lung
43
ventilation (upside down)
-largest at top lung
44
ventilation (back)
-largest at back of lungs
45
weight of lungs increase P at bottom effect on Pip
makes Pip less negative, Ptp decrease- able to expand more
46
Alveoli at bottom
- starting more deflated, can expand more | - bottom regions of lung receive a larger portion of air