Pulmonary Pathophysiology - Restrictive Lung Disease Flashcards
Restrictive lung disease definition
Diseases in which the expansion of the lung is restricted either because of alterations in the lung parenchyma, diseases of the pleura, chest wall or neuromusculature
Lung parenchyma definition
Gas exchanging lung tissue
Blood gas barrier diagram
Structure of type I collagen in alveolar wall
Forms type 1 collagen cable to support structure
Diffuse interstitial pulmonary fibrosis: alternate names
Idiopathic interstitial fibrosis
Interstitial pneumonia
Cryptogenic fibrosing alveolitis
Pathology of diffuse interstitial pulmonary fibrosis
Thickening of interstitium of alveolar wall
Initial infiltration with lymphocytes and plasma cells
Later fibroblasts lay down thick collagen bundles
Alveoli may contain cellular exudate ‘desquamation’
Eventually architecture is destroyed ith extensive scarring, dilated air spaces and ‘honey-combing’
Scarring definition
End result of many pathological processes
Due to laying down of collagen
Clinical features of Diffuse Interstitial Pulmonary Fibrosis
Not common
SOB with rapid shallow breathing
Reduced exercise tolerance
Dry cough
Signs of diffuse interstitial pulmonary fibrosis
Fine crepitations
Finger clubbing
Reduced chest movements
Radiological features of diffuse interstitial pulmonary fibrosis
CXR - small lungs with reticular pattern
Honey-comb appearance in late disease / on CT scan
Ventilatory mechanics and volume changes in restrictive lung disease
Low FEV1 and low FVC
Normal or increased FEV/FVC ratio
All lung volumes reduced
Reduced lung compliance
Changes to calibre of alveoli / small airways in pulmonary fibrosis
Calibre increases due to radial traction forces
Therefore have higher initial flow rates
Gas exchange changes in diffuse interstitial pulmonary fibrosis
Reduced PaO2
Normal or low PaCO2
PaO2 falls on exercise
Reduced diffusing capacity
Pulmonary circulation changes in diffuse interstitial pulmonary fibrosis
Many capillaries are obliterated by fibrosis
Pulmonary vascular resistance increases
Pulmonary hypertension - especially on exercise
Possible trigger for breathing with diffuse interstitial pulmonary fibrosis
?stimulation of J receptors causing rapid shallow breathing
Especially in context of normal or low PaCO2
Primary cause of arterial hypoxaemia in diffuse interstitial pulmonary fibrosis
V/Q mismatch
Diseases which can cause interstitial pulmonary fibrosis
Sarcoidosis
Hypersensitivity pneumonitis
Collagen diseases
Drugs
Oxygen toxicity
Poisons
Features of Sarcoidosis
Characteristic non caseating granulomas
Affects several organs
Probable immunological basis
Can cause interstitial pulmonary fibrosis
Features of Hypersensitivity pneumonitis
Disease of lung parenchyma due to hypersensitivity to inhaled organic dusts
Exposure is heavy
Acute disease causes SOB, fever and cough
Longstanding disease can cause interstitial pulmonary fibrosis
Examples of causes of Hypersensitivity pneumonitis
Farmer’s lung - spores in mouldy hay
Bird breeder’s lung
Collagen disease example
Systemic scleroderma
Drugs which can cause interstitial pulmonary fibrosis
Bleomycin
Busulfan
Poison example which can cause interstitial pulmonary fibrosis
Paraquat - a weed killer
Causes of restrictive lung disease outside of the lung
Pleural diseases
Chest wall diseases
Neuromuscular diseases
Pleural diseases which can cause restrictive lung disease
Pneumothorax
Pleural effusion
Pleural thickening
Chest wall diseases which can cause restrictive lung disease
Scoliosis
Ankylosing spondylitis
Neuromuscular diseases which can cause restrictive lung disease
Polio
Guillain-Barre syndrome
Myasthenia gravis
Muscular dystrophy
