Restrictive (Interstitial) Lung Diseases Flashcards
is pathological material stretchable?
no, not functional, lungs become stiff, none stretching and none complying
can the damaged tissue be localised?
yes
respiratory failure (type 1) + chronic hypoxia =
heart failure
1 disease -> 1 outcome?
no, many diseases can lead to same outcome
how likely is UIP going to progress to fibrosis, scarring or “end-stage honeycomb lung”
very likely
how common is sarcoidosis?
most common granulomatous disorder
is it a lung disease?
no, multi-system granulomatous disorder
how does its pathology vary across systems?
it doesen’t
usually associated with fibrosis?
not much, although variable
what is the aetiology of sarcoidosis?
unknown
what organs are most likely to be involved?
lymph nodes and lung
do most patients with sarcoidosis progress to end stage fibrosis?
no
what is thermophilic actinomycetes? responsible for what?
antigen on mouldy hay, responsible for farmer’s lungs (hypersensitivity reaction)
how do you treat UIP?
you can’t you’re fucked
what is the most likely reason for end-stage fibrosis of the lung?
UIP
what is the interstitium of the lung?
the connective tissue space around the airways and vessels and the space between the basement membranes of the alveolar walls
how close are pneumocytes and endothelial cells basement membranes in a normal alveolar wall?
direct contact
why might alveolar wall thicken?
interstitial infiltrate
what are the outcomes of restrictive/ diffuse/ interstitial lung disease on compliance, FEV1, FVC, V/Q ratio and gas transfer?
- reduced compliance (stiff lungs)
- low FEV1 and low FVC but FEV1/FVC normal ratio
- reduced gas transfer (diffusion abnormality)
- V/Q imbalance (when small airways affected by pathology)
what is are the symptoms for diffuse lung disease?
- discovery of abnormal CXR
- dyspnoea (shortness of breath on exertion, at rest)
what might chronic dyspnoea lead to?
type 1 respiratory failure
what are the two possible responses to interstitial lung injury?
acute or chronic response
what condition is an outcome of an acute response to interstitial lung injury?
diffuse alveolar damage
what are diffuse alveolar damage’s causes?
- major trauma
- chemical injury/ toxic inhalation
- circulatory shock
- drugs
- infection
- autoimmune disease
- radiation
- idiopathic
how many stages are there to DADS?
2 (exudative and proliferative)
what are the histological features of DADS?
- protein rich oedema
- fibrin
- hyaline membranes
- denuded basement membranes
- epithelial proliferation
- fibroblast proliferation
- scarring - interstitium and airspaces
what is the histopathology of sarcoidosis?
- epithelioid and giant cell granulomas
- necrosis/ caseation very unusual
- little lymphoid infiltrate
- variable associated fibrosis
who does sarcoidosis commonly affect?
young adults, F>M
what are the symptoms/signs of a sarcoidosis that will self-resolve?
- affects young adult
- acute arthralgia
- erythema nodosum
- bilateral hilar lymphadoenopathy
what are the symptoms/signs of a sarcoidosis that will persist or progress?
incidental abnormal CXR, no symptoms, SOB, cough, abnormal CXR
how do you treat sarcoidosis?
corticosteroids
what is the aetiology of hypersensitivity pneumonitis?
antigen exposure
what antigens cause hypersensitivity pneumonitis (HP)?
- Thermophilic actinomycetes (Micropolyspora faeni Thermoactinomyces vulgaris) - bird / animal proteins (faeces, bloom) - fungi (Aspergillus spp) - chemicals - others
what is the acute presentation of HP?
- fever, dry cough, myalgia
- chills 4-9 hours after Ag exposure
- crackles, tachypnoea, wheeze
- precipitating antibody
what is the chronic presentation of HP?
insidious, malaise, SOB, cough, low grade illness, crackles and some wheeze
what is the histopathology of HP?
immune complex mediated combined type III and type IV hypersensitivity reaction, soft centriacinar epithelioid granulomata, interstitial pneumonitis, foamy histiocytes, bronchiolitis obliterans, upper zone disease
what is the aetiology of usual interstitial pneumonitis (UIP)?
connective tissue diseases (esp. scleroderma and rheumatoid disease) drugs, infection, industrial exposure to asbestos, others
what is the histopathology of UIP?
patchy interstitial chronic inflammation, type II pneumocyte hyperplasia (damage to alveolar epithelium), smooth muscle and vascular proliferation, evidence of old and recent injury (temporal heterogeneity, spatial heterogeneity), proliferating fibroblastic foci
what does temporal heterogeneity mean?
can see disease at different stages of evolution
what does spatial heterogeneity mean?
the disease is not in the same quantities everywhere in the lung
what is the incidence of UIP?
elderly >50, M>F
what are the symptoms of idiopathic pulmonary fibrosis (UIP)?
dyspnoea, cough, basal crackles, cyanosis, clubbing
what is the prognosis for patients with idiopathic pulmonary fibrosis?
poor (most dead in 5 years)
what exposures could lead to end-stage fibrosis?
NSIP, asbestos, silicosis, COP, BOOP, smoking related fibrosis
what is normal FIO2?
0,21
how fast does O2 equilibrate between blood and air (essentially, how long does it take to uptake O2)?
0,25s
how fast does CO2 equilibrate between blood and air (essentially how long does it take to dump CO2)?
negligible (very high solubility)
what four abnormal states are associated with hypoxaemia?
- alveolar hyperventilation
- shunt
- ventilation/ perfusion imbalance (V/Q)
- diffusion impairment
what are the values for normal PaO2?
10,5-13,5kPa
what are the values for normal PaCO2?
4,8-6,0kPa
what are the values for PaO2 and PCO2 in type 1 respiratory failure?
PoO2 < 8kPa (PaCO2 normal or low)
what are the values for PaO2 and PCO2 in type 2 respiratory failure?
PaCO2 > 6,5 kPa (PaO2 usually low)
what are the outcomes of hypoventilation?
increase in PACO2, thus increase in PaCO2, increase in PACO2, decreases PAO2, causing PaO2 to fall
how is hyperventilation corrected?
raising FIO2
what is the commonest cause of hypoxaemia encountered clinically?
low V/Q
why does low V/Q arise?
local alveolar hypoventilation due to some focal disease
how does hypoxaemia respond to small increases in FIO2?
well
how better is CO2 at diffusing that O2?
20 times
do diseases which impair gas diffusion usually affect CO2 levels? why?
no, because increased diffusion abilities
which gas is affected by diffusion impairment?
O2
what factors do diffusion depend on?
surface area, thickness, gas pressure across the membrane
how long does capillary transit time last normally? (maximum time spend collecting O2)
0,75s
how may O2 equilibration time vary during disease?
may take close to 0,75s
how may this increase be pathological?
serious falls in PaO2 may occur on exercise (when exertion, capillary transit time reduces -> hypoxia for those with interstitial lung disease)
what is a shunt?
blood passing from right to left side of heart without contacting ventilated alveoli (within the heart, bypasses the lung)
what percentage of blood normally passes through shunt? may this explain an Hb saturation of less that 100%?
2-4% (yes)
when do you get pathological shunts?
AV malformations, congenital heart disease and pulmonary disease
how well do large shunts respond to FIO2 increase?
poorly (blood leaving normal lungs is already 98% saturated, it’s just that large quantities of blood are not even going through to the lungs)
