Restrictive (Interstitial) Lung Diseases Flashcards
What is the interstitium of the lung?
The connective tissue space around the airways and the vessels and the space between the basement membranes of the alveolar walls
Features of restrictive, diffuse interstitial lung disease
Reduced lung compliance - stiff lungs
Low FEV1 and Low FVC but FEV1/FVC normal ratio
Reduced gas transfer (diffusion abnormality)
Ventilation/perfusion imbalance
Presentation of diffuse lung disease
Discovery on abnormal CXR
SOB on exertion or rest
Type I resp failure
HF
Pathology of parenchymal (interstitial) lung injury
Acute response
- diffuse alveolar damage (DAD)
Chronic response
- Usual interstitial pneumonitis (UIP)
- granulomatous responses (sarcoidosis, hypersensitivity pneumonitis)
- other patterns
Fibrosis or end stage honeycomb lung
What is diffuse alveolar damage associated with?
Major trauma
Chemical injury / toxic inhalation
Circulatory shock
Drugs
Infection
Autoimmune disease
Radiation
Idiopathic
What does idiopathic mean?
Without a known cause
Evolution of DAD
Exudative stage ( up to 7 days following the injury)
- oedema
- hyaline membranes damage
Proliferative stage (7 days onwards)
- interstitial inflammation
- interstitial fibrosis
What does DAD stand for?
Diffuse alveolar damage
Histological features of DADs
Protein rich oedema
Fibrin
Hyaline membranes
Denuded basement membranes
Epithelial proliferation
Fibroblast proliferation
Scarring; interstitium and lung spaces
What is sarcoidosis?
A multisystem granulomatous disorder of unknown aetiology
Histology of sarcoidosis
Epithelioid and giant cell granulomas
Necrosis/caseation very unusual
Little lymphoid infiltrate
Variable associated fibrosis
Who gets sarcoidosis?
Young adults
F > M
Organ involvement in sarcoidosis
Lymph nodes
Lung
Spleen
Liver
Skin, eyes, skeletal muscle
Bone marrow
Salivary glands
Presentation of sarcoidosis
Acute arthralgia (polyarthralgia)
Erythema nodosoum
Bilateral hilar lymphadenopathy
Swinging fever
Asymptomatic - accidental abnormal CXR
SOB
Cough
Lupus pernio
Hypercalcaemia
Treatment of sarcoidosis
Corticosteriods
Diagnosis of sarcoidosis
Clinical findings
Imaging
Serum calcium +++ and ACE
CXR
PFTs
Biopsy
Bloods / urinalysis / ECG/ Eye exam
Bronchoscpy including biopsies
Kveim test
Tuberculin test
Antigens in hypersensitivity pneumonitis
Thermophilic actinomycetes
- micropolyspora faeni
- thermoactinomyces vulgaris
Presentation of hypersensitivity pneumonitis
Acute presentation
- fever
- dry cough
- myalgia
- chills 4 - 9 hours after Ag exposure
- crackles
- tachypnoea
- wheeze
Chronic presentation
- insidious
- malaise
- SOB
- cough
- low grade illness
- crackles and some wheeze
Does acute hypersensitivity pneumonitis have a precipitating antibody?
Yes
What can hypersensitivity pneumonitis lead to?
Resp failure
Gas transfer low
Pathology / histology of hypersensitivity pneumonitis
Immune complex mediated combined Type III and Type IV hypersensivity reaction
Soft centraacinar epitheliod granulomata
Interstitial pneumonitis
Foamy histocytes
Bronchiolitis obliterans
Upper zone disease
What may unusual interstitial pneumonitis (UIP) be seen in?
Connective tissue diseases; especially scleroderma and rheumatoid disease
Drug reaction
Post infection
Asbestos exposure
Cryptogenic or idiopathic (idiopathic pulmonary fibrosis (IPF) and cryptogenic fibrosing alveolitis (CFA)
Histology of UIP
Patchy interstitial chronic inflammation
Type II pneumocyte hyperplasia
Smooth muscle and vascular proliferation
Evidence of old and recent injury
- temporal heterogenicity
- spatital heterogenicity
Proliferating fibroblastic foci
Presentation of idiopathic pulmonary fibrosis
Clinical syndrome
SOB (chronic)
Cough (chronic)
Basal crackles
Cyanosis
Pneumonitis
Clubbed or crackles
Progressive disease; most dead within 5 years
Restrictive PFT and reduced gas transfer
Who gets idiopathic pulmonary fibrosis?
60 - 70 y/o
M > F
What would a CXR of idiopathic pulmonary fibrosis show?
Basal / posterior
diffuse infiltrates
Cysts
“Ground glass”
Prognosis of idiopathic pulmonary fibrosis
Poor
- some fulminant
- some steroid response
What happens beyond the terminal bronchiole?
Diffusion
Normal Pa02
10.5 - 13.5 kPa
Normal PaCO2
4.8 - 6.0 kPa
What is type I Resp failure?
PaO2 < 8kPa (PaCO2 normal or low)
What is type II resp failure?
PaCO2 > 6.5kPa (Pa02 usually low)
What are the 4 abnormal states Assosiated with hypoxaemia?
Alveolar hypoventilation
Shunt
Ventilation/perfusion imbalance (V/Q)
Diffusion impairment
Pathology of alveolar hypoventilation
Hypoventilation increases PaCO2 and thus increases PaCO2
Increased in PaCO2 decreases Pa02 which causes Pa02 to fall
Fall in PaO2 due to hypoventilation is corrected by raising FIO2.
What is FIO2?
Fraction of inspired air which is oxygen
Normal V/Q
4/5 or 0.8
What is the commonest cause of hypoxaemia encountered clinically?
Low V/Q
Why does Low V/Q in some alveoli airse?
Due to local alveolar hypoventilation due to some focal disease
What does hypoxaemia due to low V/Q respond well to?
Even small increases in Fi02
What does gas flow through a membrane depend on?
Thickness and surface areas of membrane
Gas pressure across it
CO2 diffusion vs O2 diffusion
CO2 20x faster due to greater solubility
Do diseases impairing gas diffusion usually change CO2 levels?
No
What does diffusion impairment lead to?
Longer for blood and alveolar air to equibrillate, particularly for O2
How long does equilibrillation usually take?
0.25 seconds
What is the capillary transit time?
0.75 seconds
What can correct hypoxaemia?
Increasing FiO2
What is a shunt?
Blood passing from R to L side of the heart WITHOUT contacting ventilated alveoli
When do you get pathological shunts?
AV malformations
Congenital heart disease
Pulmonary disease
What is the physiological definition of restriction?
FVC < 80% of the predicted normal
What is FVC affected by normally?
Age
Size
Ethnicity
What is the marker of restriction?
Vital capacity
Possible systems causing restriction
- Lungs
- Pleura
- Nerve or muscle
- Bone
- Other
Lung causes of restriction
Interstitial lung disease
- Idiopathic pulmonary fibrosis
- sarcoidosis
- hypersensitivity pneumonitis
Pleural causes of restriction
Pleural effusions
Pneumothorax
Pleural thickening
What is a pleural effusion?
Fluid in pleural space
What is a pneumothorax?
Air in pleural space
Skeletal causes of restriction
Kyphoscoliosis
Ankylosing spondylitis
Thoracoplasty (elderly)
Rib fractures
Muscle causes of restriction
Amyotrophic lateral sclerosis
Sub diaphragmatic causes of restriction
Obesity
Pregnancy
What occurs in the interstitium?
Gas diffusion
What are interstitial lung diseases?
> 200 diseases causing thickening of the interstitium and can result in pulmonary fibrosis
What are the top 3 interstitial lung diseases?
Sarcoidosis
Idiopathic pulmonary fibrosis
Hypersensitivity pneumonitis
What is sarcoidosis?
Multisystem granulomatous disease of unknown aetiology
What is the histological hallmark of sarcoidosis?
Non caseating granuloma
What is the most common interstitial lung disease?
Sarcoidosis
Presentation of sarcoidosis
Lung effects
Anterior / posterior uveitis
Erythema lodosum
Pink lesions
Skin manifestation of cardiod
Stages of sarcoidosis (pulmonary)
Stage 1 - 4
Remission rate of each stage of sarcoidosis in the lungs based on CXR
Stage 1 - 55-90%
Stage 2 - 40 - 70%
Stage 3 - 10-20%
Stage 4 - 0%
Treatment of sarcoidosis with mild disease no vital organ involvement, normal lung function and few symptoms
NO treatment
Treatment of sarcoidosis if have erythema nodosum / arthralgia
NSAIDs
Treatment of sarcoidosis if skin lesions / anterior uveitis / cough
Topical steroids (inhalers / drops / cream)
Treatment of sarcoidosis if cardiac, neurological, eye disease not responding to topical treatment or hypercalcaemia
Systemic steroids
What % of sarcoidosis patients sustain permanent or extra pulmonary complications?
10 - 20%
Pulmonary Complications of sarcoidosis
Progressive resp failure
Bronchiectasis
Aspergilloma, haemoptysis
Pneumothorax
What do a lot of patients with idiopathic pulmonary fibrosis have previous problems of?
HF / heart problems
Median survival of idiopathic pulmonary fibrosis
3 years
Treatment of idiopathic pulmonary fibrosis
Oral anti fibrotic
Pirfendone
Nintedanib
Double lung transplant (consider < 65 y/o)
Palliative care
Common occupation / hobbie when dealing with hypersensitivity pneumonitis
Bird feather dust
Farmers - mould and dusty hay
Malt workers lung
What zones of the lungs does sarcoidosis cause fibrosis in?
Upper lobes
Investigation for idiopathic pulmonary fibrosis
High resolution CT
Causes of pulmonary fibrosis of the upper zones
Hypersensitivity pneumonitis (extrinsic allergic alveolitis)
Coal workers pneumoconiosis
Silicosis
Sarcoidosis
AS (rare)
Histiocytosis
TB
Causes of pulmonary fibrosis of the lower zones
Idiopathic pulmonary fibrosis
Most connective tissue disorders (except AS) e.g. SLE
Drug induced
- amiodarone
- methotrexate
Asbestosis
What is lupus pernio? What does it look like?
Cutaneous manifestation of sarcoidosis
Most frequently affects
- cheeks
- nose
- cheeks
- lips
- ears
- digits
Not painful or itchy
What diagnosis would a facial rash and lymphadenopathy make you think of?
Sarcoidosis
Presentation of idiopathic pulmonary fibrosis
Progressive exertional SOB
Bibasal fine end inspiratory creps on auscultation
Dry cough
Clubbing
What is raised in sarcoidosis?
ACE levels
What can acute sarcoidosis mimic?
Other types of arthritis
Indications for corticosteroid treatment in sarcoidosis
Parenchymal lung disease
Uveitis
Hypercalcaemia
Neurological or cardiac involvement