Restrictive (Interstitial) Lung Diseases Flashcards by Rassa Kapite

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

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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

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Presentation of diffuse lung disease

Discovery on abnormal CXR
SOB on exertion or rest
Type I resp failure
HF

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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

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What is diffuse alveolar damage associated with?

Major trauma
Chemical injury / toxic inhalation
Circulatory shock
Drugs
Infection
Autoimmune disease
Radiation
Idiopathic

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What does idiopathic mean?

Without a known cause

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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

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What does DAD stand for?

Diffuse alveolar damage

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Histological features of DADs

Protein rich oedema
Fibrin
Hyaline membranes
Denuded basement membranes
Epithelial proliferation
Fibroblast proliferation
Scarring; interstitium and lung spaces

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What is sarcoidosis?

A multisystem granulomatous disorder of unknown aetiology

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Histology of sarcoidosis

Epithelioid and giant cell granulomas
Necrosis/caseation very unusual
Little lymphoid infiltrate
Variable associated fibrosis

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Who gets sarcoidosis?

Young adults
F > M

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Organ involvement in sarcoidosis

Lymph nodes
Lung
Spleen
Liver
Skin, eyes, skeletal muscle
Bone marrow
Salivary glands

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Presentation of sarcoidosis

Acute arthralgia (polyarthralgia)
Erythema nodosoum
Bilateral hilar lymphadenopathy
Swinging fever
Asymptomatic - accidental abnormal CXR
SOB
Cough
Lupus pernio
Hypercalcaemia

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Treatment of sarcoidosis

Corticosteriods

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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

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Antigens in hypersensitivity pneumonitis

Thermophilic actinomycetes
- micropolyspora faeni
- thermoactinomyces vulgaris

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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

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Does acute hypersensitivity pneumonitis have a precipitating antibody?

Yes

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What can hypersensitivity pneumonitis lead to?

Resp failure
Gas transfer low

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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

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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)

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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

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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

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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?

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

1. Lungs 2. Pleura 3. Nerve or muscle 4. Bone 5. 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