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PPoS > Lung Mechanics 2 #2 > Flashcards

Lung Mechanics 2 #2 Flashcards

1
Q

How does surfactant lower T of alveolar lining fluid?

A
  • phospholipids have insol FA end + hydrophil end
  • therefore float on surface of alveolar lining fluid - gets inbetween H2O mol trying to get close together
  • red T of alveoli in prop to surface conc of surfactant on alveoli
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2
Q

What happens to surfactant as alveolus shrinks + result?

A
  • conc inc as mol closer together so T falls
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3
Q

What happens to P in small alveolus as surfactant inc?

A
  • even though r dec, T now lower so P falls + doesn’t rise as alveolus shrinks
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4
Q

What is effect of surfactant on compliance + why?

A

inc it as now easier to expand lung as stiffness + amount it wants to collapse in dec by dec T

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5
Q

What other effects does surfactant have?

A
  • red tendency for alveoli to collapse - esp effective in small alveoli where surface conc of surfactant v. high
  • red tendency to suck fluid into alveoli (transudation) caused by collapsing P
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6
Q

What is neonatal respiratory distress syndrome?

A
  • occurs in premature babies due to inadequate surfactant prod - get stiff lung due to dec compliance + high T
  • problems: inc work of breathing due to red compliance + alveolar collapse + transudation due to high T
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7
Q

What is alveoli dependency?

A

joining of alveoli to each other to resist collapse + keep them open

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8
Q

When do abnormalities of lung compliance occur?

A
  • when either lung parenchyma e.g. scarred in fibritic lung disease/alveolar lining fluid abnormal
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9
Q

List causes of low lung compliance

A
  • lung fibrosis (scarred)

- neonatal resp distress syndrome

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10
Q

List causes of high lung compliance

A

emphysema (red quantity of lung tissue)

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11
Q

List obstructive lung diseases

A
  • asthma
  • chronic bronchitis
  • COPD
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12
Q

List restrictive lung diseases

A
  • lung fibrosis
  • resp muscle weakness
  • phrenic nerve damage
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13
Q

Describe normal resp system

A
  • airways: normal - little to no R so air can flow in + out easily
  • alveoli: normal gas exchange
  • resp muscles: normal
  • normal lung vol
  • normal airflow rates
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14
Q

Describe how resp system affected in asthma

A
  • airways: narrowed due to bronchoconstriction bc sm constricts in response to allergen
  • mucosal oedema caused by inflamm
  • alveoli: normal
  • inc R to F due to dec V
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15
Q

Are effects of asthma rev or irrev?

A

rev as if take away trigger for bronchoconstriction - airway returns to normal

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16
Q

Describe how resp system affected in chronic bronchitis

A

airways: wall damaged by cig smoke
- hypertrophied glands + mucus prod
- alveoli normal

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17
Q

Describe how resp system affected in emphysema

A
  • airways: poorly supported due to destruction of ISF + elastin
  • inc compliance + flabby lung mean likely to collapse which leads to dynamic compression
  • muscles: normal
18
Q

What is overall effect of COPD?

A

narrow airways impede air flow

19
Q

Describe how resp system affected in lung fibrosis

A
  • airways: normal
  • alveoli stiff due to fibrosis (scar tissue)
  • resp muscles normal
  • lung poorly compliant + need work to expand them
20
Q

Describe how resp system affected in resp muscle weakness

A
  • airways: normal
  • alveoli: normal
  • resp muscles: weak - can’t expand chest wall + therefore lung
21
Q

How is airway + high airway R measured?

A
  • airway R measured using body plethysmograph

- high airway R measured using forced exp manoeuvres

22
Q

What are the forced exp manoeuvres + purpose?

A
  • peak flow l.min-1
  • forced exp vol vs time (FEV1, FVC)
  • indirect assessment of airway R
23
Q

What does peak flow measure?

A

measures peak exp flow rate (how quick blow into it)

24
Q

How does airway obstruction affect peak flow?

A

causes low peak flow rate as have inc R to F in airways

25
Q

What is FEV1 + FVC?

A

FEV1: - forced exp vol over 1 sec
- measures total amount of air in 1 breath
FVC: forced vital capacity - measures vol breathed in + out over time

26
Q

How is FEV1 affected in restrictive lung disease?

A

small as can’t breathe out if you can’t breathe in

27
Q

What must indiv due in both lung tests?

A

breathe in to TLC + breathe out as hard + fast as poss

28
Q

Why are forced exp spirograms (vol vs time) esp useful?

A

pattern of changes of FEV1 + FVC help distinguish between obstructive + restrictive lung disease

29
Q

What should normal forced exp ratio be?

A
  • FEV1: 4l after 1 sec
  • FVC: 5l after 6 secs
  • FEV1/FVC = 4/5 = 80%
  • breathe out 75-80% of VC in 1 sec of forced exp so ratio should be >75% in healthy people
30
Q

What is forced exp ratio in obstructive disease?

A
  • FEV1: 1l (v.low) - breathing out more slowly due to narrow tubes
  • FVC: 4l (dec) or 5l (normal)
  • FEV1/FVC = 1/4 = 25% - vol of air breathed out in 1 sec much less than 75%
31
Q

How + why does forced exp ratio change in obstructive disease?

A
  • dec

- air moving through airways more slowly + can;t breathe it out due to inc R

32
Q

How + why does forced exp ratio change in restrictive disease?

A

FEV1: 2l (low) - dec as total vol dec
FVC: 2.5l (dec)
FEV1/FVC = 2/2.5 = 80% = normal ratio
- higher than 75% as can’t breathe in v. much + therefore can’t breathe v. much

33
Q

What is appearance of max F-V loop in obstructive disease of smaller airways?

A

concave appearance of forced exp curve

34
Q

How do forced insp + exp flow differ in obstructive disease of smaller airways?

A
  • forced insp flow affected less than forced exp flow

- as narrowing of airways + small airways dec F during exp

35
Q

What are low peak flow rates related to in restrictive lung disease?

A

low vol not F in limitation of airway

36
Q

Does asthma affect compliance?

A

No as airways affected + not alveoli/tissue

37
Q

What does stiffness of lung affect?

A
  • ease with which lungs can be inflated
  • vol in lungs when muscles are relaxed i.e. FRC which occurs when inward recoil of lungs exactly balances out outward recoil of chest wall
38
Q

How is recoil of lungs + chest wall diff in disease?

A
  • inward recoil of lungs high in fibrosis

- outward recoil of chest high at low lung vol

39
Q

How does lung fibrosis affect FRC?

A
  • stiff lung - inc lung recoil - red FRC as it springs in too quickly
  • chest wall also at low vol + that’s when its got max outward recoil as well
40
Q

How does lung fibrosis affect FRC?

A
  • tissue loss - floppy lungs - red lung recoil - inc FRC (barrel chest) - inc chest diameter
  • point at lung chest settles at resting vol is point at which there’s not much outward recoil of chest either which is at high vol
41
Q

How does resp muscle weakness affect FRC?

A
  • 2 recoils of lung + chest wall normal so FRC normal

PPoS (11 decks)

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