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PPoS > Lung Mechanics 2 #1 > Flashcards

Lung Mechanics 2 #1 Flashcards

1
Q

What is movement of air through the airways driven by?

A

P gradient between mouth + alveoli

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2
Q

What is the formula for flow?

A

change in P/R

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3
Q

What is needed for air to flow out quickly?

A

low R

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4
Q

What is the formula for airway R?

A

alveolar P - mouth P / airflow at mouth

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5
Q

What is elastic R (stiffness) usually measured as?

A

compliance (stretchiness)

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6
Q

What is needed to stretch the lung + why?

A

work needed as lung nat has elastic coil inwards

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7
Q

What is the formula for lung compliance?

A

change in lung vol/change in transmural P gradient

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8
Q

How does change in lung vol differ between compliant + stiff lung?

A
  • compliant: not much P for change in lung vol

- stiff: need more distending P harder work needed to change lung vol

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9
Q

What happens to compliance of stiff lung?

A
  • change v/change P ratio dec due to inc P

- compliance dec if need higher P change to get change in vol

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10
Q

What is formula for transmural P gradient?

A

alveolar P - intrapleural P

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11
Q

What does alveolar P equal if there is no airflow?

A

0 - equal to atmospheric

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12
Q

How can intrapleural P be measured?

A

with an oesophageal balloon as its same as oesphageal P

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13
Q

How is tidal vol measured?

A
  • spirometer
  • breathe in from RV to TLC in steps
  • at each step as hold breath, measurements of vol inspired + Ppl recorded + used to construct static P-V loop
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14
Q

What can a static P-V loop show?

A

compliance as measuring changes in lung vol/changes in P

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15
Q

When does lung have low compliance?

A

high + low lung vol

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16
Q

What is transmural P?

A
  • distending P of lung

- +ve when you breathe in

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17
Q

Describe P + V from RV to FRC

A
  • v. low vol + compliance

- need to gen lots of TMP to get small vol change

18
Q

Describe P + V from FRC to TV

A
  • small inc in TMP cause large inc in TV therefore lung v. compliant which is in normal breathing circumstances
19
Q

When is compliance at its max + sig?

A
  • normal TV

- usually breathing at most compliant part of lung

20
Q

Describe P + V at TLC

A
  • high vol

- v. hard to breathe as compliance low at this point despite inc TMP, gen little vol + flow

21
Q

Why are the P-V curves for exp + insp diff?

A
  • at any given TMP, lung has higher vol at exp than insp

- why exp curve slightly higher

22
Q

What is shape of P-V curves?

A

sigmoid

23
Q

What is typical value of lung compliance in adult male?

A

1.5l.kPa-1 (varies acc to size of indiv)

24
Q

What is consequence of having stiff lungs?

A
  • low compliance
  • high elastic R
  • diff to lungs to expand + always want to spring back to small voll all of the time
25
Q

What are characteristics of lung fibrosis + what causes it?

A
  • stiff/scarred lung
  • low compliance
  • caused by asbestos exposure, tumors, aspergilus etc
26
Q

What are characteristics of emphysema?

A
  • elastic tissue destruction
  • floppy lung
  • high compliance
27
Q

What is gross pathology shown by lung fibrosis?

A
  • honeycomb appearance

- fibrous tissue + inflammatory cells

28
Q

What is centrilobar emphysema?

A
  • rel normal alveoli around outside

- destruction of lobules in centre

29
Q

What is COPD?

A
  • chronic bronchitis = inflamm + excess mucus of airways

- emphysema = alveolar mem break down

30
Q

What is consequence of COPD?

A
  • inc R to exp air flow + cause airflow obstruction
31
Q

Where does elastic R come from?

A
  • lung tissues - elastin + collagen fibres

- air-fluid interface in alveoli

32
Q

How can you stretch air-fluid interface?

A

need to overcome surface tension

33
Q

What is La Place equation?

A

P = 2 x surface tension (T)/r

34
Q

How does bubble compare to small alveoli?

A
  • if P high, T high + R low - bubble wants to collapse in
35
Q

Describe surface tension between bubble + fluid

A
  • T at interface between bubble (air) + fluid
  • H2O mol attracted to each other more than to air
  • H2O mol get v.close together to dec SA so as close together as poss at air-H2O interface
  • as H2O tries to get v.close - shrinks down + gen inward P + bubble shrinks
36
Q

Explain what T between H2O + bubble shows about small alveoli?

A
  • bubble in water wants to occupy smallest vol poss so it can be as close as poss to other bubbles and therefore gen inward P inside it
  • P inc if T high + R low - bubble wants to collapse in
  • small alveoli with high T more likely to have high collapsing P
37
Q

How does small alveolus differ to large one + sig?

A
  • small r so greater collapsing in P than big one
  • big alveoli has big r so P small
  • small will want to collapse into big as a result which don’t want
38
Q

What happens if small alveoli collapses into big one?

A
  • radii change so P1 progessively inc + P2 dec so process speeds up
39
Q

Which cells prod surfactant?

A

type II alveolar

40
Q

What is surfactant?

A
  • mix of phospholipids e.g. phosphatidyl choline + surfactant proteins (SP-A to D)
  • lowers T of alveolar lining fluid

PPoS (11 decks)

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