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respiratory system year 1 > pathology of restrictive lung disease > Flashcards

pathology of restrictive lung disease Flashcards

1
Q

what are restrictive lung diseases also known as

A

diffuse or interstitial lung disease

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2
Q

what area of the lung is most commonly involved in restricitve lung disease

A

the interstitium

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3
Q

what is the interstitium of the lung

A

he connective tissue space around the airways and vessels and the space between the basement membranes of the alveolar walls

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4
Q

describe the interstitium in healthy lungs

A

the normal alveolar wall, most of the alveolar epithelial and interstitial capillary endothelial cell beasement membranes are in direct contact

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5
Q

describe the changes to the alveolar wall in interstitial lung disease

A

alveolar wall thickened by interstitial infiltrate

inflammatory change –> fibrosis (production of tissue between the layers of the basement membrance, interferes with gas exchange)

introduction of collagen and fibrous tissue means the lungs become stiff and cannot stretch as easily

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6
Q

what is meant by reduced compliance

A

lungs are stiff and don’t expand as easliy

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7
Q

features of FEV1, FVC, gas transfer and V/Q ration in restrictive lung disease

A

low FEV1, low FVC
normal FEV1/FVC ratio
reduced gas transfer (diffusion abnormality)
V/Q imbalance when small airways are affected by pathology (not all conditions)

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8
Q

presentation of diffuse lung disease

A

discovery of abnormal CXR/CT

DYSPNOEA - on evertion or at rest

type 1 resp failure

heart failure - as a result of hypoxaemia and pulmonary vasoconstriction

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9
Q

what is the most common presentation of diffuse lung disease

A

dyspnoea

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10
Q

what is the difference between emphysema and interstitial lung disease on a CXR

A

emphysema - hyperinflated lungs

interstitial lung disease - reduced lung volumes, increased lung markings

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11
Q

pattern of development for interstitial lung disease

A 
parenchymal (interstitial injury) 
acute response --> chronic response
chronic response leads to one of 3 options: 
usual interstitial pnuemonitis
granulomatous response
other patterns

end result for all is fibrosis or end-stage honeycomb lung

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12
Q

what type of sensitivity is a granulomatous response

A

mix of type III and IV sensitivity

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13
Q

inflammatory conditions

A

inflammation is mostly chronic in the interstitium of the lung

can be acute which converts into chronic

there is relatively limited way in which the lung can respond to injury

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14
Q

what is diffuse alveolar damage

A

an altered form of acute inflammation

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15
Q

do all conditions lead to pulmonary fibrosis

A

NO

not all conditions result in scarring and fibrosis

pulmonary fibrosis is irreversible and may be fatal

some conditions are very rarely at risk of progressing this way

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16
Q

what is the mortality rate for DADS

A

> 50%

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17
Q

what does DADS stand for

A

diffuse alveolar damage syndrome

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18
Q

what changes occur in DADS

A

changes are related to alveolar epithelium and capillary endothelium

results in leaky vessels

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19
Q

what is DADS associated with

A 
major trauma e.g. cardiac arrest
chemical injury/toxic inhalation
circulatory shock 
drugs 
infection - DADS can complicate the effects of an infection
autoimmune disease
radiation

can also be idiopathic

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20
Q

what are the 2 stages of DADS

A

exudative stage - oedema (0-2 days following injury) due to leaky capillaries, plasma proteins precipitate in the lungs and form a layer (1-14 days)

proliferative stage (7 days) - interstitial inflammation and fibrosis

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21
Q

histological features of DADS

A

protein rich oedema
fibrin
hyaline membranes
denuded basement membranes

(lung is trying to repair itself after the damage but isn’t good at it)

epithelial proliferation
fibroblast proliferation
scarring - interstitium and airspaces

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22
Q

sarcoidosis

A

a multisystem granulomatous disorder of unknown aeitology

most likely affects lymph nodes and lungs

most likley one to encounter in clinical practice

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23
Q

histopathology of sarcoidosis

A

epithelioid and giant cell granulomas - accumulation of macrophages
necrosis/caseation (cheese like appearance) is very unusual
little lymphoid infiltrate
variable associated fibrosis

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24
Q

incidence of sarcoidosis

A 
commonly affects young adults 
f>m
3-4/100 000 in UK
20/100 000 in african-americans in USA
low in equatorial regions 
it is a disease of temperate climates
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25
Q

organ involvement in sarcoidosis (% cases)

A 
lymph nodes - almost 100
lung - >90
spleen - 75
liver - 70 
skin, eyes, skeletal muscle - 50
bone marrow - 20
salivary glands - up to 50
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26
Q

sarcoidosis presentation

A
  1. young adult, acute arthralgia, erythema nodosum, bilateral hilar lymphadenopathy
  2. incidental abnormal CXR/CT, asymptomatic
  3. SOB, cough, abnormal CXR

most (esp 1) resolve after 2yrs
2 and 3 may resolve, persist or progress

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27
Q

what is arthralgia

A

joint pain

28
Q

what is erythema nodosum

A

nodular eruptions over the skin

29
Q

what is the treatment for sarcoidosis

A

corticosteroids

30
Q

sarcoidosis diagnosis

A

clinical findings
imaging findings
serum Ca++ and ACE
biopsy (only needed in relatively few patients)

31
Q

what is hypersensitivity pneumonitis

A

granulomatous response

caused by inhalation of organic antigens

32
Q

what antigens cause hypersensitivity pneumonitis

A 
thermophilic actinomycetes (fungus): micropolyspora faeni, thermoactinomyces vulgaris 
bird/animal proteins - faeces, bloom 
fungi: aspergillus spp
chemicals
others e.g. drugs
33
Q

what is hypersensitivity pneumonitis also known as

A

extrinsic allergic alveolitis

34
Q

acute presentation of hypersensitivity pneumonitis

A

fever, dry cough, myalgia
chills 4-9hrs after antigen exposure
crackles, tachyopnoea, wheeze
precipitating antibody

high dose of the antigen can lead to infection-like presentation

35
Q

chronic presentation of hypersensitivity pneumonitis

A

insidious
malaise, SOB, cough
low grade illness
crackles and some wheeze

can lead to resp failure, low gas transfer

36
Q

histopathology of hypersensitivity pneumonitis

A

immune complex mediated combined type III and IV hypersensitivity reaction
soft centriacinar epithelioid granulomata
interstitial pneumonitis
foamy histiocytes
bronchiolitis obliterans

37
Q

why is hypersensitivity pneumonitis an upper zone disease

A

the parts of the lung most affected are the areas where the inhaled material first lands

laminar flow –> diffusion point, inhaled material is no longer carried and is deposited
centriacinar regions of the lung are where most pathology occurs

38
Q

which condition is most likely to progress to severe pulmonary firbosis

A

usual interstitial pneumonitis

can be fatal and lead to resp failure
poor prognosis

39
Q

where may usual interstitial pneumonitis (UIP) be seen

A 
connective tissue disease - esp scleroderma and rheumatoid disease
drug reaction 
post-infection - viruses
indusrtial exposure - asbestos 
others
40
Q

what generally causes UIP

A

most are cryptogenic or idiopathic (generally cannot determine a possible cause)

Idiopathic pulmonary fibrosis (IPF) or cryptogenic fibrosing alveolitis (CFA)

don’t say the patient has UIP, say they have IPF/CFA

41
Q

histopathology of UIP

A

patchy interstitial chronic inflammation
type II pneumocyte hyperplasia
smooth muscular and vascular proliferation
evidence of old and recent injury (temporal and spatial heterogeneity)
proliferating fibroblastic foci

42
Q

what is the importance of proliferating fibroblastic foci in UIP

A

they aren’t unique to UIP
manifestation of the repair and fibrosis process
they are both a very important part of the pathological process

43
Q

clinical example of idiopathic UIP

A

> 50, m>f
clinically show: dyspnoea, cough, basal crackles, cyanosis, clubbing
progressive disease - most dead in 5yrs
restrictive PFT and reduced gas transfer

44
Q

what would a CXR oF UIP show

A

basal/posterior
diffuse infiltrates
cysts
‘ground glass’

45
Q

what is the prognosis for UIP

A

some fulminant
some steroid responsive

overall poor prognosis

pulmonary fibrosis confers an increased risk of developing lung cancer

46
Q

appearance of the lung in UIP

A

basal and posterior fibrosis and scarring with honeycombing

creation of cystic spaces in the lung - byproduct of the attempt of the lung tissue to repair itself which has failed

47
Q

normal pulmonary gas exchange

A

air flow in airways is laminar or turbulent, depends on pressure difference

beyond terminal bronchiole - diffusion

48
Q

how saturated is the blood leaving the capillary bed and why

A

98% saturated for FIO2 of 0.21

Hb affinity for oxygen

49
Q

normal PaO2

A

10.5-13.5 kPa

50
Q

normal PaCO2

A

4.8-6 kPa

51
Q

type I respiratory failure

A

PaO2 <8 kPa

PaCO2 normal or low

52
Q

type II respiratory failure

A

PaCO2 >6.5kPa

PaO2 usually low

53
Q

what are the 4 abnormal states associated with hypoxaemia

A

alveolar hypoventilation
shunt
ventilation/perfusion imbalance
diffusion impairment - generally doesn’t lead to CO2 retention

54
Q

alveolar hypoventilation

A

amount of air moved in and out of lungs
hypoventilation increases PACO2 and thus increases PaCO2
PACO2 rise decreases PAO2 which causes PaO2 to fall
fall in PaO2 due to hypoventilation is corrected by raising FIO2

55
Q

V/Q mismatch

A

normal V/Q is 0.8
low V/Q is COMMONEST cause of hypoxaemia encountered clinically
low V/Q in some alveoli arises due to local alveolar hypoventilation due to some focal disease
hypoxaemia due to low V/Q responds well to small increases in FIO2

56
Q

what does gas flow through a membrane depend on

A

thickness and SA of the membrane and gas pressure across it

57
Q

how much faster does CO2 diffuse than O2 and why

A

20x

greater solubility

58
Q

does diffusion impairment change CO2 levels

A

diseases impairing gas diffusion usually do no change CO2 levels

it means it takes longer for blood and alveolar air to equilibrate, particularly for oxygen

59
Q

how long does equilibration normally take

A

normally 0.25s

in disease equilibration may take close to 0.75s

60
Q

how long does capillary transit time take

A

0.75s at rest

the time RBC spend in the alveolar capillary network

61
Q

when may PaO2 falls occur in diffusion impairment disease

A

on exercise as capillary transit time falls

exercise can precipitate hypoxaemia in interstitial lung disease

62
Q

how can hypoxaemia by diffusion impairment be corrected

A

increasing FIO2

increases PAO2 therefore increasing rate of diffusion

rarely clinically the sole cause of hypoxaemia

63
Q

define shunt and normal values

A

blood passing from R to L side of heart w/o contacting ventilated alveoli

normally 2-4% shunt

64
Q

when can pathological shunt occur

A

AV malformations
congenital heart disease
pulmonary disease

65
Q

do large shunts respond to increases in FIO2

A

they respond poorly

blood leaving the normal lung is already 98% saturated

respiratory system year 1 (25 decks)

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