Interstitial Lung Diseases Flashcards
what is pulmonary Interstitium?
the space between the alveolar epithelium and endothelial basement membrane. Fibroblasts and connective tissue lie here. This is where gas exchange occurs.
is pulmonary Interstitium visible radiographically?
The pulmonary Interstitium is not normally visible radiographically (chest x ray/ CT scan).
It only becomes visible when there is disease present (i.e. oedema, fibrosis, tumour) which increases its volume & attenuation
what are the 3 subdivisions that the Interstitium is composed of?
double check if we need to know this?
Bronchovascular Region: surrounds bronchi, arteries, & veins from the lung root to the level of respiratory bronchiole.
Parenchymal region: situated below the alveolar & capillary basement membranes.
Subpleural Region: situated beneath the pleura & in the interlobular septae
what does gas exchange require?
Functioning alveoli (alveoli that allow for gas exchange)
Alveolar ventilation
Pulmonary circulation (blood circulating around alveoli)
what are the 3 things that impairment of gas exchange could come from?
- Impaired ventilation:
Central (due to impairment in nervous system)
Mechanical (swallowed something/blockage) - Impaired circulation: blockage of circulation around alveolus
- Abnormal alveoli structure: prevents gas exchange from happening.
when determining the effect of lung disease or pulmonary fibrosis, what is the main things that need to be measured?
what would you see in a spirometry of interstitial lung disease?
restrictive spirometry
due to effects of fibrosis in the interstitium and stiffness:
Low FVC
Normal/high FEV1/FVC
the other important measures are lung volumes:
there’s a reduction in TLC and RV
what is the difference between intrapulmonary and extrapulmonary restrictive spirometry
Intrapulmonary - effect the interstitium/ gas exchange
* Fibrosis
* Inflammation/Infection - pneumonia
* Sarcoidosis
* Atelectasis
- FVC, FEV1 decrease
- Ratio normal or raised
- Slope of curve increase
- TLC/RV decrease
- Diffusion decrease
Extrapulmonary
* Pleural cavity - pleural thickening (due to asbestos)
* Neuromuscular
* Chest wall
* Obesity - splinting of diaphragm
- FVC, FEV1 decrease
- Ratio normal
- Slope of curve normal or
decrease - TLC/RV decrease
- Diffusion normal
what is pulmonary fibrosis and when does it occur?
Pulmonary fibrosis: scarring of the Interstitium
Usually occurs after inflammation - formation of fibrous tissue (scaring).
As a result of pulmonary fibrosis the lungs become stiff –> increasing the work of breathing, and gas exchange across the alveoli is impaired.
what would the results of pulmonary fibrosis spirometry be?
You get restrictive spirometry:
Low FVC
Normal/high FEV1/FVC ratio
low RV
low TLC
DLCO is low
what is Interstitial lung disease (ILD)?
Interstitial lung disease (ILD): is an umbrella term for a whole range of diseases that causes fibrosis in the Interstitium.
what are the 8 types of interstitial lung disease?
- Cryptogenic fibrosing alveolitis (CFA):
- Cause unknown.
- Also known as idiopathic pulmonary fibrosis
- Usual interstitial pneumonitis - Non-specific interstitial pneumonitis
- RB-ILD (respiratory bronchiolitis associated interstitial lung disease)
- DIP (desquamative interstitial pneumonia)
- COP (cryptogenic organising pneumonia)
- LIP (Lymphoid interstitial pneumonia)
- Extrinsic ‘Allergic’ Alveolitis (EAA)
- Sarcoidosis
what is the aetiology of pulmonary fibrosis?
Pulmonary fibrosis can be widespread throughout the lungs or restricted to the upper or lower zones.
The causes vary…
how do you work out the cause of pulmonary fibrosis?
We can work out the cause of pulmonary fibrosis using the following:
Autoantibody screen - provides evidence for/against connective tissue disease
Drug history - to see if a drug has caused fibrosis
Take occupational and exposure history
what is the incidence rate of pulmonary fibrosis?
Approx 50/ 100,000 (30,000+)/yr
* 8/ 100,000 ( 5,000/yr) Idiopathic Pulmonary Fibrosis (IPF)
* ~ 40% autoimmune rheumatic / connective tissue diseases (CT-ILDs)/ sarcoidosis
* ILD found in 10%-40% patient with Rheumatoid arthritis;
* 70-90% Systemic sclerosis
* ~ 40% idiopathic of which ~50% IPF
what are some clinical features of pulmonary fibrosis?
Symptoms (may not occur until disease is more advanced):
Dry cough (usually presents first)
Dyspnoea (shortness of breath)
Fine end inspiratory crepitations (crackling) at base of lungs
Usually occurs in middle age
Occurs in men > women
what are the signs of pulmonary fibrosis on a chest X ray?
what are the signs of pulmonary fibrosis on a CT scan?
how do you manage pulmonary fibrosis?
Management depends on cause, histology, severity and rapidity of progression.
Example:
UIP (usual interstitial pneumonia) 🡪 pirfenidone or nintendanib
Autoimmune disease 🡪 immunosuppression
Lung transplantation 🡪 if patient is becoming hypoxic because you can’t treat inflammation.
PFTs (pulmonary function test) are then used to monitor patients to see how they are responding to treatment.
Depends on cause, histology, severity & rapidity of
progression.
*IPF pirfenidone or nintendanib
*Progressive pulmonary fibrosis
nintendamib
* Autoimmune disease immunosuppression
* Transplantation
* Monitor using PFTs
Depends on type and cause!
* COP – corticosteroids
* Smoking-related ILD – respiratory bronchiolitis ILD (RB-ILD)
/desquamative interstitial pneumonia (DIP) – smoking
cessation
* Hypersensitivity pneumonitis – avoidance of causative
agent, corticosteroids
* CTD-ILD – immunosuppression – corticosteroids,
cyclophosphamide
* Sarcoidosis - corticosteroids
why may biopsies of the lung be required?
how are they performed?
Biopsies are required if:
It is not clearly UIP on a high-resolution CT scan.
No clear cause on antibody tests/history etc.
Biopsies can be performed using
Bronchoscopic washings (BAL) + transbronchial biopsy (collect cells)
Surgery (VATS): Wedge of lung taken out and sent to pathology.
what are the types of interstitial lung disease?
UIP = Usual interstitial pneumonitis
NSIP = non-specific interstitial pneumonitis
what is Usual interstitial pneumonitis?
UIP = Usual interstitial pneumonitis
Occurs in basal region of the lung
Presents in the peripheral/sub-pleural regions
Not much ground-glass change seen on CT (as it is an established fibrosis)
Honeycombing seen
Blood test will be negative for antibodies etc.
what is non-specific interstitial pneumonitis?
Anything non-specific (see a mix of fibrosis, honeycombing, +/- ground glass change, not mainly in lower zones) will be labelled as this.
Generally better prognosis than classical UIP
Causes: lots e.g. exposure to asbestos, autoimmune diseases etc.