Restrictive (Interstitial) Lung Diseases Flashcards
What is the interstinum of the lung?
The connective tissue space around the airways and vessels and the space between the basement membrane of the alveolar walls
What is true of normal alveolar wall?
Most of the alveolar epithelial and interstitial capillary endothelial cell basement membranes are in direct contact
How does restrictive lung diseases affect compliance?
Reduced lung compliance (stiff lungs)
How are FEV1 and FVC values affected by restrictive lung diseases?
- Low FEV1
- Low FVC
- FEV1/FVC ratio remains normal
How is gas transfer affected in restrictive lung disease?
- Reduced gas transfer
- Diffusion abnormality
How is ventilation/perfusion affected by restrictive lung disease?
- Ventilation/perfusion imbalance
- When small airways affected by pathology
How is diffuse lung disease normally discovered?
Discovery of abnormal chest X-ray
What is the main symptom of restrictive lung disease?
- Dyspnoea
- Shortness of breath on exertion progresses to shortness of breath at rest
What do people with restrictive lung disease often develop?
- Type I respiratory failure
- Heart failure
What normally starts the process of restrictive lung disease
Parenchymal lung injury
How can a parenchymal lung injury progress?
- Acute response
- Chronic response
- Acute response which progresses to a chronic response
What are the ‘3’ responses to a chronic response?
- Usual interstitial pneumonitis (UIP)
- Granulomatous responses
- Other patterns
What is an example of an acute response?
Diffuse alveolar damage (DAD)
What are other names for DAD?
- ARDS
- Shock lung
What are the causes of DAD?
- Major trauma
- Chemical injury/toxic inhalation
- Circulatory shock
- Drugs
- infection
- Autoimmune disease
- Radiation
- Idiopathic
What are the histological features of DAD?
- Protein rich oedema
- Fibrin
- Hyaline membranes
- Denuded basement membranes
- Epithelial proliferation
- Fibroblast proliferation
- Scarring- interstitium and airspaces
What are examples of granulomatous responses?
- Sarcoidosis
- Hypersensitivity pneumonitis
What is sarcoidosis?
A multisystem granulomatous disorder of unknown aetiology
What is the histopathology of sarcoidosis?
- Epithelioid and giant cell granulomas
- Necrosis/caseation very unusual
- Little lymphoid infiltrate
- Variable associated fibrosis
Who is commonly affected by sarcoidosis?
- Young adults
- Females more than males
Where are the most common sites of sarcoidosis?
- Inter-thoracic lymph nodes
- Lungs
How does sarcoidosis usually present in a young adult?
- Acute arthralgia
- Erythema nodosum
- Bilateral hilar lymphadenopathy
How is sarcoidosis diagnosed in a patient who is asymptomatic?
Incidental abnormal chest X-ray
How might sarcoidosis present?
- Shortness of breath
- Cough
- Abnormal chest X-ray
How is sarcoidosis normally diagnosed?
- Based on clinical findings
- Image findings
- Serum Ca+ and ACE
- Biopsy
What is hypersensitivity pneumonitis?
Group of immunologically mediated lung diseases in which a hypersensitivity response occurs in a sensitised individual to an inhaled antigen.
What antigens can cause hypersensitivity pneumonitis?
- Thermophilic actinomycetes (micropolyspora faeni) (thermoactinomyces vulgaris)
- Bird/animal proteins (faced, bloom)
- Fungi (aspergillus spp)
- Chemicals
- Others
What is the acute presentation for hypersensitivity pneumonitis?
- Fever, dry cough, myalgia
- Chills 4-9 hrs after Ag exposure
- Crackles, tachyopnoea
- Precipitating antibody
What is the chronic presentation for hypersensitivity pneumonitis?
- Insidious
- Malaise, shortness of breath, cough
- Low grade illness
- Crackles and some wheeze
What can hypersensitivity pneumonitis lead to?
Respiratory failure
How is gas transfer affected in hypersensitivity pneumonitis?
Gas transfer is low
What is the histopathology of hypersensitivity pneumonitis?
-Immune complex mediated type III and type IV hypersensitivity reaction
-Soft centriacinar epithelioid granulomata
-Interstitial pneumonitis
-Foamy histiocytes
-Bronchiolitis obliterans
Upper zone disease
What are other names for Usual interstitial pneumonitis?
- Cryptogenic fibrosing alveolitis
- Idiopathic pulmonary fibrosis
What can cause UIP?
-Connective tissue diseases
-Drugs
-Asbestos
-Viruses
Most are cryptogenic or idiopathic
What are the main connective tissue diseases in which UIP is seen?
- Scleroderma
- Rheumatoid disease
What is the histopathology of UIP?
- Patchy interstitial chronic inflammation
- Type II pneumocyte hyperplasia
- Smooth muscle and vascular proliferation
- Evidence of old and recent injury
- Proliferating fibroblastic foci
What can be seen in UIP in the histopathology in terms of evidence of old and recent injury?
- Temporal heterogeneity
- Spatial heterogeneity
Who is usually affected by idiopathic pulmonary fibrosis (UIP)?
- Elderly
- Males more than females
What is usually the pathology of idiopathic pulmonary fibrosis?
Usual interstitial pneumonitis
What are the symptoms and signs of idiopathic pulmonary fibrosis?
- Dyspnoea
- Cough
- Basal crackles
- Cyanosis
- Clubbing
What is the prognosis of idiopathic pulmonary fibrosis?
- Progressive disease
- Most dead within 5 years
- Some fulminant
- Some steroid responsiveness
What can be seen on the chest X-ray of a patient with idiopathic pulmonary fibrosis?
- Basal/posterior
- Diffuse infiltrates
- Cysts
- ‘Ground glass’
How is gas transfer affected by idiopathic pulmonary fibrosis?
Reduced gas transfer
What are other pattern responses?
- Non-specific interstitial pneumonia (NSIP)
- Asbestos
- Silicosis
- Bronchiolitis obliterans organising pneumonia (BOOP)
- Cryptogenic organising pneumonia (COP)
What is airflow in airways dependent on?
Pressure differences
How saturated is the blood leaving the capillary bed if the FIO2 is 0.21?
98%
How soluble is CO2?
Very soluble and rapidly equilibrates between blood and air
What are the normal values for PaCo2?
4.8-6.0kPa
What are the normal values for PaO2?
10.5-13.5kPa
What are the 2 kinds of respiratory failure?
- Type I: PaO2<8kPa (PaCO2 normal or low)
- Type II: PaCo2>6.5kPa (PaO2 usually low)
What are the 4 abnormal states associated with hypoxaemia?
- Alveolar hypoventilation
- Shunt
- Ventilation/perfusion imbalance V/Q
- Diffusion impairment
Why does alveolar hypoventilation lead to hypoxaemia?
- Hypoventilation increases PAO2 and thus increases PaCO2
- Increase in PACO2 decreases PAO2, which causes PaO2 to fall
How is the fall in PaO2 due to hypoventilation corrected?
Raising FIO2
What is the commonest cause of hypoxaemia?
Low V/Q
Why does low V/Q arise in some alveoli?
Due to local alveolar hypoventilation due to some focal disease
What does hypoxaemia due to low V/Q respond to?
Responds well to even a small increases in FIO2
What does gas flow through a membrane depend on?
- Thickness of membranes
- Surface area of membranes
- Gas pressure across membranes
How does the diffusion of CO2 differ to that of O2?
It diffuses 20 times faster due to its greater solubility
What do diseases impairing gas diffusion usually not do?
Change the CO2 levels
What does diffusion impairment do?
Mean it takes longer for blood and alveolar air to equilibrate, particularly for oxygen
How long does equilibration normally take?
0.25 seconds
How long does capillary transit usually take?
0.75 seconds
Why may hypoxaemia be corrected by increasing FIO2?
- This increases PAO2
- Increase in rate of diffusion
How does the time to equilibrate differ in disease states?
- May take closer to 0.75 seconds
- PaO2 maintained at rest
- Serious falls in PaO2 on exercise
What is shunt?
Blood passing from right to left side of heart without contacting ventilated alveoli
When does pathological shunt occur?
- AV malformations
- Congenital heart disease
- Pulmonary disease
What do large shunts respond poorly to?
Increases in FIO2
