Pathology of Restrictive Lung Diseases Flashcards
What is the interstitial of the lung?
The connective tissue space around the airways and vessels and the space between the basement membranes of the alveolar walls - capillaries and pneumocytes pushed apart
What can the alveolar wall be thickened by?
Interstitial infiltrate
How is lung compliance affected?
Reduced (stiff lungs)
How is FEV1 and FVC affected?
Both reduced
How is the FV1/FVC ratio?
Normal ratio
What do obstructive lung diseases do to residual volume?
Increase
How does restrictive lung disease affect residual volume?
Reduces it
How does restrictive lung disease affect expiratory reserve volume?
Reduces it
How is gas transfer affected?
Reduced due to diffusion abnormality
Why is gas transfer reduced in restrictive lung diseases?
The distance between alveoli and capillaries is increased as there is increases tissue in the interstitium
What does a diffuse lung disease present as?
Abnormal CXR
Dyspnoea - exertion then rest
Type I respiratory failure
Heart failure
Why do sufferers of restrictive lung disease experience type 1 respiratory failure?
It is much easier for carbon dioxide to diffuse across the thickened alveolar walls than it is for oxygen
What is diffuse avleolar damage associated with?
Major trauma Chemical injury / toxic inhalation Circulatory shock Drugs Infection Auto(immune) disease Radiation idiopathic
What is the evolution of DADs?
Oedema -> Hyaline membranes ->interstitial inflammation -> interstitial fibrosis
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 acute response to parenchymal (interstitial) lung injury?
Diffuse alveolar damage (DAD)
What is another response of parenchymal lung injury, which can also carry on from the acute response?
Chronic response which leads to fibrosis or end-stage honeycomb lung
What are three conditions that arise from the chronic response?
Interstitial Pneumonitis (UIP) Granulomatoud responses: sarcoidosis, hypersensitivity pneumoniitis
What are sarcoidosis?
A multisystem granulomatous disorder of unknown aetiology
Describe the histopathology of sarcoidosis
Epithelioid and giant cell granulomas
Necrosis/caseation unusual
What are the different presentation of sarcoidosis?
- Young adult - acute arthralgia, erythema nodosum, bilateral hilar lymphadenopathy
- Incidental abnormal CXR - no symptoms
- SOB, cough and abnormal CXR
If patient experiences symptoms of sarcoidosis (i.e. presentation 1) when should they resolve?
After 2 years
What treatment is given for sarcoidosis?
Costicosteroids (for SOB, cough)
How is sarcoidosis diagnosed?
Clinical findings
Imaging finding
Serum Ca ++ and ACE
Biospy
What are the antigens for hypersensitivity pneumonitis?
Thermophilic actinomycetes
Bird / animal proteins
Fungi (aspergillus spp.)
Chemicals
What is the acute presentation of hypersensitivity pneumonitis?
Fever, dry cough, myalgia
Chills after Ag exposure
Crackles, tachypnoea, wheeze
Precipitating antibody
What is the chronic presentation of hypersensitivity pneumonitis?
Insidious
Malaise, SOB, cough
Low grade illness
Crackles and some wheeze
What is the histopathology of hypersensitivity pneumonitis?
Immune complex mediated by combine Type II and Type IV hypersensitivity reaction Soft centriacinar epithelioid granuloma Interstitial pneumonitis Foamy histiocytes Bronchiolitis obliterans
What is bronchiolitis obliterans in hypersensitivity pneumonitis?
Obstruction of the smallest airways of the lungs (bronchioles) due to inflammation
What part of the lung is common for hypersensitivity pneumonitis?
Upper zone
Where might UIP be seen?
Connective tissue disorders Drug reaction Post infection Industrial exposure: asbestos Most cryptogenic or idiopathic
What is the histopathology of UIP?
Patchy interstitial chronic inflammation
Type II pneumocyte hyperplasia
Smooth muscle and vascular proliferation
What are clinical signs of UIP?
Dyspnoea Cough Basal crackles Cyanosis Clubbing
What are the investigations for UIP?
CXR PFT (shows restriction) Gas transfer (reduced)
What are other patterns than can cause fibrosis or honey combing of the lung?
Asbestos Silicosis Smoking related fibrosis Cryptogenic organizing pneumonia (COP) Bronchiolitis obliterans organizing pneumonia (BOOP)
What are the levels for Type I and Type II respiratory failure?
Type I - PaO2 < 8kPa (PCO2 normal)
Type II - PaCO2 > 6.5 kPa (PaO2 low)
What are 4 abnormal states associated with hypoxaemia?
Shunt
V/Q mismatch
Diffusion impairment
Alveolar hypoventilation
How does alveolar hypoventilation lead to low PaO2?
Increase PACO2, and thus PaCO2
Increase in PACO2 decrease PAO2, which causes PaO2 to fall
How is a fall in PaO2 due to hypoventilation corrected?
Raising FlO2 (fraction of inspired air which is oxygen)
What is the normal V/Q ratio?
Breath 4min/l, CO is 5l/min so normal V/Q = 0.8
How does diffusion impairment affect equilibrium across alveoli?
Takes longer for blood and alveoli air to equilibrate, particularly for O2 - usually 0.25s, but may take 0.75s in disease
