7.1 & 7.2 Pathology, Diagnosis and Management of Restrictive Lung Disease Flashcards
What percentage of pulmonary syndromes are restrictive? What about obstructive?
Restrictive: 20%
Obstructive: 80%
Using a (not very accurate) acronym, explain five causes of restrictive lung disease
PAINT
P: Pleural
A: Alveolar
I: Interstitial
N: Neuromuscular
T: Thoracic cage
What are the three overarching groups of extrinsic restrictive lung disease?
- Decreased muscle tone of respiratory pump
- Chest wall/rib cage deformities
- Space-occupying
List a type of disease that falls under “loss of respiratory pump muscle tone” restrictive diseases
Neuromuscular disease
List two restrictive chest wall/rib cage deformities
- Obesity
- Scoliosis
List two space-occupying restrictive lung defects
- Pleural effusion
- Pneumothorax
Provide a brief explanation of intrinsic restrictive lung diseases
- Reduced distensibility of the lungs
- Compromised expansion
- Reduced TLC
Is cough more likely in extrinsic or intrinsic lung disease?
Intrinsic
What unique conditions may be present in extrinsic vs intrinsic lung disease?
Intrinsic: Connective tissue disease
Extrinsic: Neuromuscular
Diffusing capacity in intrinsic vs extrinsic lung disease
Extrinsic: may be normal
Intrinsic: Usually reduced
Which type of respiratory failure is more likely to be present in intrinsic vs extrinsic restrictive lung disease?
Intrinsic: Type 1
Extrinsic: Type 2
List some of the main diagnostic features of restrictive lung disease
- Cough (with intrinsic)
- Systemic features (e.g. malaise, joint symptoms, rash with connective tissue disease)
- Muscle weakness/neurological symptoms (intrinsic OR extrinsic)
- Exposure/Past history
Spirometry findings of restrictive lung disease
- Reduced FEV1 and FVC; preserved ratio
- Or: reduced FVC alone; increased ratio
Lung volume test findings during restrictive lung disease
- Always low TLC (and likely low other volumes)
ABG findings in intrinsic vs extrinsic restrictive lung disease
- May be hypoxia (caused by V/Q mismatch and increased pulmonary shunting with intrinsic)
- Or hypercapnia (more common with extrinsic)
List two conditions that can decrease chest wall compliance
- Obesity
- Kyphoscoliosis
What does it mean that anatomical dead space increases in idiopathic pulmonary fibrosis?
The amount of conducting airway increases relative to lung volumes
What happens to the amount of alveolar dead space present during idiopathic pulmonary fibrosis?
It increases
Why does exercise worsen hypoxaemia in patients with idiopathic pulmonary fibrosis?
- Lower capillary transit time
- Cannot recruit enough lung volume to oxygenate the blood
Why does awake hypercapnia only occur in end-stage restrictive intrinsic lung disease?
The respiratory muscles fail due to overwhelming mechanical load from severely reduced compliance
How can neuromuscular and chest wall respiratory disorders cause cor pulmonale?
- Hypoxaemia
- Pulmonary vasoconstriction -> increased pulmonary vascular resistance
- Right heart failure
Most common space-occupying lesion leading to restrictive lung disease
Pleural effusion
List two gas exchange abnormalities in restrictive lung disease
- Intrapulmonary shunt
- Alveolar dead space (in heart failure)
Define interstitial lung disease
Disease that affects lung interstitium (as opposed to airways)
Summarise ILD pathophysiology
- Inflammation of parenchyma
- Collagen in interstitium
- Irreversible pulmonary fibrosis
- Decreased lung compliance
- Decreased inspiratory capacity
- Thickened alveolar septae
List some occupational/inhaled exposures that can cause interstitial lung disease
- Silica
- Asbestos
- Beryllium
- Birds
List some pneumotoxic drugs
- Antibiotics
- Chemo
- Antiarrhythmic
- Statins
What are pneumoconioses?
Group of lung diseases caused by inhalation of certain dusts
Is lung fibrosis better or worse than lung inflammation?
Worse; irreversible scarring
Define occupational lung disease
- Lung diseases that arise as a result of occupational exposure to dust, fumes, smoke, or other agents
Screening history questions for occupational lung disease
- What kind of work (exactly)
- Do they think breathing problems are related to work?
- Do symptoms get better when you are away?
- Have you been exposed to fumes, gases, or dusts in the past?
History questions to ask IF occupational exposure to substances was present
- Type of substance
- Frequency, quantity duration
- Route of exposure
- Protective equipment?
- Similar symptoms in coworkers?
Non occupational exposures that can cause lung disease
- Smoking
- Pets
- Home environment
- Hobbies/recreation
What are the two types of work related asthma?
- Occupational asthma
-Work exacerbated asthma
What are the two classifications of occupational asthma? Which is more common?
- Sensitiser-induced (immunological)
- Irritant-induced (non-immunological;l epithelial asthma)
Sensitiser induced is more common (~90%)
How can peak flow measurements be used in diagnosis of occupational asthma? What are the limitations of this?
- If peak flow decreases during work and increases after work, then it is indicative of work related asthma
- However, this does not differentiate between sensitiser-induced and irritant-induced
What percentage of COPD cases are linked to occupational exposures?
15%
What are the three main types of occupational interstitial lung disease?
- Pneumoconiosis
- Granulomatous
- Hypersensitivity pneumonitis
What characterises granulomatous lung disease?
Granuloma formation
What is hypersensitivity pneumonitis? What substances can trigger it?
- Parenchymal inflammation as an allergic reaction to inhaled substances
- Substances include bacteria, fungi, animal proteins, low molecular weight chemicals
Does asbestos-related disease have a long or short delay before onset? How long or short is it?
Long. Over 25 years.
List some common industries that can lead to asbestos exposure
- Insulation
- Cement production
- Dockyard work
- Railway carriage maintenance
What main three types of disease are caused by asbestos exposure?
- Interstitial lung disease
- Pleural disease
- Malignancy
What are pleural plaques? What are they made of? Do they increase cancer risk?
- Collagen components with a linear, banded, or nodular appearance.
- There is no accepted correlation between pleural plaques and cancer risk
Describe pleural thickening. Under what circumstances can it cause dyspnoea? Under what circumstances could it indicate cancer?
- Fibrosis involving the visceral and parietal pleura
- May reduce lung volumes and cause dyspnoea
- If in conjunction with chest wall pain, may indicate malignancy
What is pleural mesothelioma?
Cancer that forms in the tissue covering your lungs and chest wall
Symptoms of benign asbestos-related pleural effusion. Is this always the case?
- Pleuritic chest pain
- Dyspnoea
- Chronic cough
- Fever
However, asymptomatic in a majority of cases
Describe benign asbestos pleural effusions. How long before onset of interstitial lung disease do they occur?
- Usually small and unilateral
- They occur years before the onset of interstitial lung disease
Correlation between amount of asbestos exposure and earlier onset of benign pleural effusions
- Largely unclear
- Earlier onset may be correlated with higher amounts of exposure
What is pulmonary asbestosis?
Pulmonary fibrosis caused by inhalation of asbestos fibres
Does the classification of substances as carcinogens inform treatment at an individual level?
No; only at a population level
What is the most common form of cancer in never smokers and asbestos exposure patients?
Adenocarcinoma
What is adenocarcinoma?
Cancer in epithelial tissue of glands
What type of respiratory failure is more common in interstitial lung disease? Why?
Type 1; the respiratory pump can still remove CO2, the problem is at the level of gas exchange and O2 transport inward.
What is meant by ground-glass opacity?
Areas of hazy greyness that do not obscure underlying structures.
What is reticulation on a CT scan?
“Like a net”
What histological findings on biopsy support a diagnosis of interstitial pneumonia? Will there be more fibrosis or inflammation?
- Identification of tissue at varying stages of fibrosis within the same sample.
- There will be more fibrosis than inflammation
What is the gold standard for IPF diagnosis?
Multidisciplinary diagnosis
Criteria for IPF diagnosis
- Common clinical features and exclusion of other causes
- Histological pattern of UIP
A patient has inhaled a gas/particulate that could damage their lungs. Generally, which zone(s) of the lungs are most likely to be damaged as a result?
The upper lung zones
List some clinical findings of ILD on examination
- Clubbing
- Cough
- Fine inspiratory crackles
What could high attenuation on lung CT indicate?
Consolidation
What could low lung attenuation on lung CT indicate?
Emphysema
List some types of conditions that favour the upper lung zones
- Pneumoconiosis
- Smoking-related diseases
- Hypersensitivity pneumonitis
List some conditions that favour the lower zones of the lungs
- Pulmonary oedema
- Aspiration
- Usual interstitial pneumonia
Consolidation vs ground-glass-opacity
Consolidation: Cannot see underlying vessels
Gound-glass: can see underlying vessels
Describe treatment of interstitial lung disease
- Remove irritant
- Treat exacerbations
- Steroids may help reverse inflammation
- Lung transplantation
- Medico-legal aspects
- Ongoing monitoring
What is lung consolidation?
It indicates that the normal, air-filled spaces of the lung are filled with the products of disease
List five broad categories of restrictive lung disease
- Occupational
- Autoimmune
- Treatment related
- Sarcoidosis
- Idiopathic
Asbestosis pathology
- Fibrosis of lower lung lobes
- Fibrosis/collagen plaques of surrounding pleura
Asbestosis pathophysiology
- Asbestos fibres have a toxic effect on cells
- Release of inflammatory mediators leads to fibrosis
Mesothelioma pathology
- Starts as small nodules (typically on parietal pleura)
- Over time, grows larger and joins together, forming larger tumour
- Can invade surrounding structures, such as the chest well
Treatment of neuromuscular breathing disease
- Respiratory therapy
- Home education
- Physiotherapist for exercise
Does fibrosis commonly result from chronic or acute inflammation?
Chronic
What are the signs and symptoms that result from inflammation of the lung interstitium?
Interstitial fibrosis -> decreased compliance, and thickened alveolar membrane (leading to impaired diffusion)
Signs:
- End-inspiratory fine crackles
Symptoms:
- Dyspnoea
Symptoms caused by inflammation of bronchi
- Excess mucus production
- Productive cough
- Dyspnoea