Restrictive lung disease Flashcards
What is a restrictive lung disease?
Where lung volume is lower due to restriction of expansion of the lung due to either intrinsic or extrinsic disorders
What are intrinsic lung diseases?
Alterations to the lung parenchyma
What are extrinsic lung diseases?
Disorders that compress the lungs or limit expansion, can be pleural, chest wall related or neuromuscular
What is the lung parenchyma?
The alveolar regions of the lung
What are the important cellular components of the lung parenchyma?
Alveolar type 1 and 2 epithelial cells, fibroblasts, alveolar macrophages and the interstitial space
What is the function of alveolar type 1 cells?
The gas exchange surface
What is the function of alveolar type 2 cells?
Surfactant to reduce surface tension, stem cells for repair
What is the function lung parenchyma fibroblasts?
Produce ECM
What is the function of alveolar macrophages?
Phagocytise foreign material, surfactant
What is the lung parenchyma interstitial space?
Space between the alveolar epithelium and capillary endothelium
What does the lung parenchyma interstitial space contain and what is its function?
Contains lymphatic vessels, fibroblasts and ECM. Provides structural support to the lung and is very thin to facilitate gas exchange
What are the six classifications of interstitial lung diseases (ILD)?
Idiopathic, autoimmune related, exposure related, those with cysts or airspace filling, sarcoidosis and others
Different patterns of fibrosis influence survival of ILD, which pattern decreases survival the most?
UIP
What are the signs and symptoms associated with ILD?
Progressive breathlessness, non-productive cough, limitation in exercise tolerance, occupational and exposure history, medication history (drug induced ILD) and family history of ILD ( up to 20% of idiopathic ILDs are familial)
What is found on clinical examination of a patient with ILD?
Low oxygen saturations, fine bilateral inspiratory crackles, digital clubbing
What investigations are undertaken to diagnose ILD?
Blood tests, pulmonary function tests, 6 minute walking test, high resolution CT scan, invasive testing - bronchoalveolar lavage (BAL), surgical lung biopsy
What parameters are looked at in diagnostic blood testing for ILD?
Anti-nuclear antibody, rheumatoid factor, anti-citrullinated peptide (CCP)
Outline the physiology of ILD
Scarring makes lung stiff decreasing compliance, decreasing lung volume, decreasing diffusing capacity of lung for carbon monoxide, lowering arterial PO2
What is the expected FEV1:FVC ratio of a patient with ILD?
Normal or raised
What is idiopathic pulmonary fibrosis (IPF)?
Progressive scarring lung disease of unknown cause,
What is the average decline in forced vital capacity (FVC) associated with IPF?
150-200mls per year
What are the proposed mechanisms of IPF?
Predisposing factors such as genetic susceptibility, environmental triggers and cellular ageing
What are the characteristic features of IPF on a CT scan?
Subpleural honeycombing and traction bronchiectasis. Basal predominance in coronal plane
Is immunusupression used to treat IPF?
No, has been shown to be harmful
What treatment is given to slow disease progression in IPF
Antifibrotics
What is hypersensitivity pneumonitis?
ILD caused by immune-mediated response in susceptible and sensitised individuals to inhaled environmental antigens, involves the small airways and parenchyma
What are the two classifications of HP and how are they different?
Acute HP - intermittent, high level exposure, abrupt symptom onset, flu-like syndrome
Chronic HP - long-term, low-level exposure, is either non-fibrotic or fibrotic
Which type of chronic HP has the higher mortality?
Fibrotic
Outline how immunological dysregulation drives HP
Antigen exposure and processing by the innate immune system causes an inflammatory response mediated by T-helper cells and antigen-specific immunoglobulin antibodies. This leads to accumulation of lymphocytes and formation of granulomas
What will be heard on auscultation of a patient with HP?
Inspiratory ‘squeaks’ caused by the coexisting bronchiolitis
How is HP treated?
Complete antigen removal/ avoidance, corticosteroids, immunosuppressants
What is systemic sclerosis associated ILD
Autoimmune connective tissue disease characterised by immune dyes regulation and progressive fibrosis that affects the skin, with variable internal organ involvement
How is SSc associated ILD classified?
Based on skin involvement: can be limited cutaneous SSc or diffuse cutaneous SSc
Limited cutaneous SSc is more associated with _____, whereas diffuse cutaneous SSc is more commonly associated with _______
Limited cutaneous more associated with pulmonary hypertension whereas diffuse cutaneous SSc more associated with ILD
What is the most common type of ILD?
IPF
