Diffuse Lung Disease Flashcards
What changes occur in the alveolar compartment in diffuse lung disease?
Inflammatory cells
Fibrin
Pulmonary oedema
What changes occur in the interstitial compartment in diffuse lung disease?
Chronic inflammatory cells
Collagen deposition
Fibrosis
What changes occur in the vascular compartment in diffuse lung disease?
Capillary inflammation and leak
Differentiate between airways disease, diffuse lung disease and pulmonary vascular disease in terms of the typical presentation
Airways: wheeze, cough, sputum, dyspnoea
Diffuse: cough, dyspnoea (wheeze unusual)
Vascular: dyspnoea, pleuritic pain, haemoptysis
What is diffuse lung disease?
Label for a common presentation of a number of lung diseases featuring dyspnoea, cough and a CXR featuring diffuse lung involvement
Involves either or both of alveoli and interstitium, including the pulmonary vasculature
What are the 4 layers of the interstitium?
Alveolar cell Epithelial basement membrane Connective tissue (with passing and fixed cell populations, and fluid traffic) Endothelial basement membrane Endothelial cell
Describe 3 processes which can cause diffuse lung disease acutely
Water
Inflammation due to acute inhalation injury, drug toxicity or infection
Blood due to diffuse leakage from inflamed vessels (e.g. in vasculitis)
Describe the acute presentation of diffuse lung disease
"Stiff lungs" Tachypnoea Severe dyspnoea Increased WOB Cough Hypoxia (due to serious V/Q impairment)
What kinds of processes cause a diffuse lung pattern?
Subacute or chronic (presenting over months to years) interstitial disease
List some interstitial diseases
Idiopathic pulmonary fibrosis Sarcoidosis Occupational Extrinsic allergic alveolitis Drugs Radiotherapy Pulmonary fibrosis associated with connective tissue diseases Vasculitis
Investigations for diffuse lung disease
Respiratory function tests (e.g. spirometry, diffusion capacity, lung volumes)
Oximetry
HRCT (+/- CTPA, CTBA)
Bloods: signs of systemic illness and connective tissue diseases
Echo: LV dysfunction, pulmonary HTN
Lung biopsy (not always required)
Expected findings on respiratory testing in diffuse lung disease
Restrictive pattern: reduced FVC, normal or increased FEV1/FVC
Reduced DLCO
Expected findings on oximetry in diffuse lung disease
Normal resting saturation but rapid desaturation on exertion, improved with intranasal oxygen
8 most common diffuse lung diseases (and 2 rarer)
Idiopathic pulmonary fibrosis Sarcoidosis Lymphangitic carcinomatosis Oedema Asbestosis Collagen vascular diseases Silicosis Drugs Rarer: Langerhans' granulomatosis, Farmer's lung
Distinguish between alveolar and interstitial opacity
Alveolar opacity: opacity on CXR associated with fluid filling the air spaces, appears fluffy or cotton wool-like
Interstitial opacity: abnormal appearance of lung interstitium, 4 basic patterns (linear, reticular, nodular, reticulonodular)
Describe the linear pattern of interstitial opacity
Septal lines (Kerley lines)
Describe the reticular pattern of interstitial opacity
Mesh-like appearance with lines in all directions
Describe the nodular pattern of interstitial opacity
Discrete opacities
Describe the linear pattern of interstitial opacity
Mesh-like appearance with lines in all directions
Discrete opacities
What are the 4 “compartments” where lung diseases occur?
Conducting airways
Gas exchange
Interstitium
Vascular
List 3 diseases of the conducting airways
Asthma
COPD
Bronchiectasis
What is the general pathophysiology of alveolar disease?
Alveoli filled with blood, pus or fluid
List 2 diseases of the pulmonary vasculature
PE
Pulmonary HTN
What is the typical pathophysiology and presentation of airways disease?
In asthma/COPD: inflamed narrow airways with active mucous glands, results in a presentation of wheeze, productive cough and SOB
In bronchiectasis: locally damaged dilated airways, results in a presentation of productive cough with large volumes of sputum
What is the typical pathophysiology and presentation of diffuse lung disease?
Diffuse oedema and inflammation, +/- fibrosis involving alveolar and/or interstitium
Presents with cough and SOB (wheeze unusual)
What is the typical pathophysiology and presentation of pulmonary vascular disease?
Narrowing or obstruction of pulmonary vessels
Presents with SOB, pleuritic pain and haemoptysis
What are the clinical signs of idiopathic pulmonary fibrosis?
Fine inspiratory crackles usually basally
Clubbing
List some occupational interstitial lung disease
Asbestosis Other pneumoconiosis (e.g. coal)
Are pleural plaques on XR diagnostic of asbestosis?
No, there must be pulmonary fibrosis due to asbestos exposure (common to have plaques)
List 2 types of extrinsic allergic alveolitis
Bird Fanciers Lung
Farmers Lung
List 6 drugs which may cause interstitial lung disease
Methotrexate Amiodarone Bleomycin Busulphan Cyclophosphamide Nitrofurantoin
Nitrofurantoin
Abx used to treat UTI
Cyclophosphamide
Alkylating agent used in the treatment of cancers, AI disorders and amyloidosis
Busulphan
Alkylating antineoplastic agent
Bleomycin
Antineoplastic agent (used for lymphoma, testicular, ovarian and cervical cancer)
Why is radiotherapy-induced interstitial lung disease easy to diagnose?
Affected area typically confined to radiotherapy port
List 4 connective tissue diseases associated with interstitial lung disease
Systemic sclerosis (scleroderma)
RA
SLE
Anti-Jo 1 +ive polymyositis
List 2 vasculitides associated with interstitial lung disease
Microscopic pulmonary vasculitis
Wegeners associated with pulmonary haemorrhage
How do patients with vasculitis-related interstitial lung disease typically present?
Very unwell
Haemoptysis
AKI with nephritic syndrome
What aspects of Hx are important to ascertain in a patient with suspected interstitial lung disease?
Detailed occupational Hx
Detailed Rx Hx (including CAMs)
Systemic symptoms including LOW, chest pain, fever, joint symptoms, rashes, etc
What signs are important to assess in a patient with suspected interstitial lung disease?
Crackles
Clubbing
Examine for signs of connective tissue disease
Assess for signs of pulmonary HTN
SaO2 (if normal at rest check with exertion)
Signs of pulmonary HTN
Loud +/- palpable P2
Parasternal heave
Elevated JVP
May be peripheral oedema
List 5 Ix which may be appropriate for a patient with suspected interstitial lung disease
Respiratory function tests
High resolution CT chest (HRCT) +/- CTPA/CTBA
Basic bloods (to screen for systemic illness and connective tissue disease)
Echocardiogram
Lung biopsy (transbronchial through bronchoscope or “open” biopsy at thoracoscopic surgery)
What findings on lung function testing would you expect in a patient with interstitial lung disease?
Reduced FVC
Normal/increased FEV1/FVC
(I.e. consistent with restrictive lung disease; however this is not always the case)
When would you use CTBA vs CTPA?
CTBA for large volume haemoptysis (usually from bronchial circulation)
What features may be seen on echo in a patient with interstitial lung disease?
LV dysfunction Pulmonary HTN (especially relevant in connective tissue diseases)
Mrs S, 69 year old woman, presents with progressively worsening exertional dyspnoea over a period of 12 months; believes her breathlessness may even have started 3 years ago
No variation in SOB day-to-day
6/12 of cough productive of sticky jelly-like clear sputum
Some pain and swelling in knuckles of both hands each morning on rising, settling over the day
PHx: 15 year Hx of recurrent UTIs
Rx: nitrofurantoin, paracetamol
~33 pack-year smoking Hx, 1 glass of wine 5/7 per week
SHx: worked as secretary/PA
O/E: inspiratory crackles bilteral lung bases, some swelling of MCP and PIP joints of both hands, no clubbing, SaO2 95% at rest but fell to 91% after 75m of walking
Respiratory function tests: reduced spirometry with non-obstructive pattern, reduced DLCO, desaturates with cruise altitude O2 levels (easily overcome with 1L/min intranasal O2)
HRCT: pattern consistent with IPF
Mx?
Stop nitrofurantoin (potential cause of progressive fibrosis)
Further Ix joint symptoms with specific examination, appropriate connective tissue disease serology tests and XRs
Formal assessment of need for exertional O2
Recommend specialist referral
What is the evidence for treatment of established fibrosis with steroids and immunosuppressive therapy?
Poor evidence base
Describe the natural Hx of pulmonary fibrosis
Variable; may be stable with exacerbations, may be inexorable progression
Differentiate between the linear and nodular patterns of interstitial disease seen on CXR
Linear: thin linear opacities 2-6cm long within lungs, oriented radially towards the hilar and in contact with the lateral pleural surfaces, called Kerley A and Kerley B lines (histologically represents thickening of interstitium)
Nodular: multiple small, discrete, rounded opacities ranging in diameter from 2-10mm, DDx for this pattern includes nodular metastases (usually thyroid, breast or RCC), nodular pneumoconioses and granulomatous diseases