Respiratory JC015: Shortness Of Breath In A Construction Site Worker: Occupational Lung Diseases, Pulmonary Fibrosis, Workman's Compensation Flashcards
Interstitial lung diseases
- Aka Pulmonary fibrosis
- Heterogeneous —> Different pathological processes —> Different treatment
Types:
1. Inhaled substances
- Inorganic: **Silicosis, **Asbestosis
- Organic: ***Hypersensitivity pneumonitis
- ***Drug-induced
- Antibiotics
- Chemotherapy
- Immune-checkpoint inhibitor
- Antiarrhythmic
- Statins - Connect tissue disease
- ***Systemic sclerosis
- RA - Infection
- Atypical pneumonia
- Pneumocystis pneumonia
- TB
- Chlamydia
- RSV - Idiopathic
- ***Idiopathic pulmonary fibrosis
- Sarcoidosis - Malignancy
- Lymphangitis carcinomatosis - Radiation
Pulmonary Interstitium
Microscopic space between Alveolar epithelium (gas exchange unit) and Capillary endothelium (vascular compartment)
—> Crucial for gas exchange
***Pathophysiology of ILD / Pulmonary fibrosis
Key site of injury and pathogenesis:
- ***Alveolar-capillary interface
Pathophysiology:
Formation of lung fibrosis (Scarring of lung tissue)
—> **Thickening of interstitium
—> Loss of thin elastin-rich connective component containing capillary blood vessels
—> **Blockade of effective gas exchange across alveolus
—> Worsening dyspnea
- Acute and Chronic diseases processes
- Many differently causes / patterns
Early stage:
- ***Alveolitis (injury with inflammatory cell infiltration)
Late stage:
- ***Fibrosis (uncontrolled persistent inflammation)
Effect:
1. ↑ in Interstitial tissue (in response to external stimulus) —> **↓ Lung compliance (less distensible) —> Restrictive deficit
2. **Hypoxia
3. **Pulmonary hypertension
4. **Cor pulmonale
5. HF
Chronic Interstitial Lung Diseases
- IPF / UIP
- Sarcoidosis
- Hypersensitivity pneumonitis
- Pneumoconiosis
- CT diseases
Idiopathic Pulmonary Fibrosis (IPF) / Usual Interstitial Pneumonia (UIP)
Definition:
- Progressive interstitial fibrosis of ***unknown cause
- Variable association with inflammation
- Clubbing
- Chronic
- ***Progressive decline in lung function (e.g. FVC)
- Ultimately fatal
Usual Interstitial Pneumonia pattern (UIP)
- a form of IPF
- NOT equate to diagnosis of IPF
Diagnosis:
IPF is diagnosed only if known causes of ILD are ***excluded
—> Environmental exposure: Asbestosis
—> CT disease
—> Drug toxicity
—> Chronic hypersensitivity pneumonitis
Pathology:
- Local **persistent inflammation —> Fibrosis at **Subpleural + **Basal segments (Location of terminal bronchiole, alveoli)
- Terminal lung structures replaced by dilated spaces surrounded by fibrous walls —> **↓ Compliance + ***↓ DLCO
Epidemiology:
- Presentation at ***advanced age
- No gender difference
Risk factors:
- **Smoking
- **Environmental pollutants (e.g. exposure to metal / wood dusts, hairdressing, raising birds
- Undiagnosed GERD (repeated micro-injury)
- Familial pulmonary fibrosis (<5%)
Prognosis:
- Poor
Diffuse Parenchymal Lung Diseases (DPLD)
Same as Interstitial Lung Disease
***DPLD = ILD
Broad term, classified according to etiology:
- DPLD of known etiology (HP, drugs, collagen-vascular)
-
**Idiopathic Interstitial Pneumonia (IIP)
- Chronic fibrosing —> **IPF, ***NSIP
- Smoking related —> RBILD, DIP
- Acute / Subacute —> AIP, COP
(Very rare IIPs: LIP, PPFE) - Granulomatous DPLDs (Sarcoidosis)
- Other forms of DPLD (Eosinophilic pneumonia, LAM, HX etc.)
Terminology
IPF: Idiopathic pulmonary fibrosis
NSIP: Nonspecific interstitial pneumonia
RBILD: Respiratory bronchiolitis–associated interstitial lung disease
DIP: Desquamative interstitial pneumonia
AIP: Acute interstitial pneumonia
COP: Cryptogenic organizing pneumonia (previous known as Bronchiolitis obliterans with organizing pneumonia (BOOP) (SpC Medicine))
LIP: Idiopathic lymphocytic interstitial pneumonia
PPFE: Idiopathic pleuroparenchymal fibroelastosis
Examples of drugs that can cause ILD / Pulmonary fibrosis
Anti-cancer drugs
- ***Bleomycin
- Immune-checkpoint inhibitors (i.e. Immunotherapy)
Cardiac drugs
- ***Amiodarone
Antibiotics
- Cephalosporin
- **Sulfasalazine
- **Nitrofurantoin
***Illicit drugs (esp. inhalational drugs)
- Cocaine
- Heroin
Miscellaneous:
- **High flow oxygen
- **Inhalation / Aspiration of fat-containing substances (e.g. drugs containing mineral oils, certain laxatives, petroleum jelly)
- ***Radiotherapy
***Clinical features of ILD
- ***Dyspnea exacerbated by exertion
- ***Cough: dry, non-productive + persistent
- Fatigue (∵ poor gas exchange)
- ***Tachypnea (often laboured)
- Loss of appetite + Weight loss
- Chest pain
- Fever
- ***Central cyanosis
- ***Cor pulmonale
- Respiratory insufficiency + failure
S/S:
- >50 yo
- Dry, non-productive cough on exertion
- Progressive exertional dyspnea (SOB with exercise)
- Dry, inspiratory bibasilar “Velcro-like” crackles (i.e. **Fine crackles) —> **not change with coughing (vs Bronchiectasis / Pneumonia)
- **Clubbing
- Abnormal lung function test —> **Restriction pattern (FEV1/FVC >80%) + ***Impaired gas exchange (↓ DLCO)
***Initial assessment of patients with Suspected ILD
- History:
- Medical / Drug
- **CT disease symptoms
- **Environmental / Occupational exposure
- Smoking
- Family
- Gastric reflux - Examination:
- ***Clubbing
- Fever
- Eye signs
- Rashes
- Arthritis
- Hepatosplenomegaly
- Crackles - Investigations (Tailored towards S/S):
- **CXR
- Oximetry
- **Spirometry
- **Blood tests: **Arterial blood gas, **AutoAb (to rule out CT disease)
- Urinalysis
- **ECG - Refer to chest physician
- Further assessment:
- **High resolution CT chest (HRCT: best mode of investigation to diagnose ILD)
- Bronchoscopy +/- Lavage
- **Transbronchial biopsy (only if history / imaging not conclusive of diagnosis / malignancy cannot be ruled out)
- Surgical lung biopsy
- Detailed pulmonary function test
- ECG - Discussion at multidisciplinary meeting, review management plan
Diagnosis of UIP and IPF
- ***Exclusion of known / environmental / occupational causes (can be difficult)
- ***Exclusion of collagen vascular diseases (can be difficult)
- HRCT scan techniques
- Local expertise in ILD
- Multidisciplinary discussion
UIP pattern vs NSIP pattern
Based on HRCT
UIP:
1. Subpleural, Basal predominance
2. **Reticular abnormality (Network)
3. **Honeycombing +/- Traction bronchiectasis
4. Absence of features consider to be inconsistent with UIP pattern
NSIP:
1. More **ground glass opacity (Hazy patches)
2. Reticulation usually comes with a **Peribronchovascular distribution
3. Less Honeycomb changes and Traction bronchiectasis
***Management of ILD
Medical treatment:
1. Occupational exposure
- avoid that environment
- Drug cause
- discontinue drug - Some idiopathic / CT-based causes (associated with **systemic sclerosis)
- may be treated with **Nintedanib (newer targeted kinase) -
**Systemic glucocorticoid
- no longer recommended as 1st line (esp. in IPF with UIP patttern)
- used in **acute exacerbation - ***Immunosuppressant
- some patients may respond - ***Supplemental O2
- patients with hypoxaemia (in form of ambulatory O2 / LTOT therapy) -
**Sildenafil
- in advanced IPF
- vasodilator to relieve effects of **pulmonary hypertension
- 10mg QDS
Surgical treatment:
1. ***Lung transplantation
- most effective
- but severe risks of its own
Supportive care:
1. Supplemental O2
2. Patient education
3. Pulmonary rehabilitation
4. Vaccination (Influenza + ***Pneumococcal polysaccharide vaccine)
5. Palliative
Monitoring:
1. Regular follow-up ***lung function tests (FVC, TLC, DLCO, Kco)
—> information on disease progression
- ***Flexible bronchoscopy +/- BAL +/- Transbronchial biopsy (TBBx) (not necessarily needed)
—> exclude infection / malignancy - Thoracoscopic VATS biopsy (Video-assisted thoracoscopic surgery)
- more invasive but more reliable
- generates far more tissue - ***6-minute Walk Test (6MWT)
- functional assessment of exercise tolerance
- assess how long patient can walk - Breathlessness score
- grade + assess symptoms - Multi-disciplinary approach
- physiotherapist
- pulmonary rehab
- occupational therapist
Spirometry
Suggestive but NOT diagnostic of restrictive lung physiology
Restrictive pattern:
- ***Narrowing of Flow-volume loop
Obstructive pattern:
- Shortening of Flow-volume loop
Diagnosis also depends on Measurement of lung volume
—> ***↓ in ALL volumes
—> ↓ VC, RV, FRC, TV, TLC (in different extent)
Nintedanib
- Inhibitor of VEGF and Multiple angiokinase
- Small molecule like Pirfenidone
- VEGFR, FGFR, PDGFR inhibitor
- Developed as anti-vascular anti-cancer therapy
Hypersensitivity Pneumonitis (Extrinsic Allergic Alveolitis)
?A form of IPF (Mentioned in lecture but not sure)
Chronic inflammatory disease
- Small airways
- Interstitial involvement
- Occasional granuloma
**Allergic origins
- Reaction to Organic dust / Inorganic dust
- **Type 3 / Type 4 hypersensitivity
Example:
- **Farmer’s lung: Thermophilic bacteria
- **Bird / Pigeon Fancier’s lung: Avian proteins
- ***Malt Worker’s lung: Fungi (Beer brewery)
Investigations:
- Precipitins (Ab that can precipitate when bind to Ag) / ***Ab often detectable in serum samples
- Unusual cases come to biopsy
- CT: Small airway sepsis-like changes
Pneumoconiosis
Lung disease caused by **mineral dust exposure
1. **Asbestosis
2. ***Silicosis
3. Coal worker’s lung
Disease severity depends on:
1. Particle size
2. Reactivity of particles
3. Clearance of particles
4. Host response
5. Duration of exposure
Asbestos:
- a Silicate
- Serpentine (curved) fibres: relatively safe
- ***Amphibole (straight) fibres: highly dangerous to man (more immunogenic)
Detrimental effects of inhaling dusts
- COPD
- Asthma
- ***Extrinsic Allergic Alveolitis (EAA) / Hypersensitivity Pneumonitis
- Fibrosing Alveolitis
- ***Pneumoconiosis
- ***Cancer
- Heart disease: Cardiorespiratory failure
- Other problems
***Silicosis (矽肺病)
Occupational lung disease
Etiology:
- Inhalation of ***crystalline silica dust
Pathology:
- Inflammation + Scarring in form of **Nodular lesions in **upper lobes of lungs —> Pulling of structures upwards
- ***Hilar lymphadenopathy (“eggshell” calcification) —> widening of mediastinum
Occupational risk factors
- Stone mining + cutting
- Pneumatic drill worker
- Caisson worker
- Jade polisher, Gemstone cutter
- Ceramic workers
- Manual labourer in construction sites
Clinical features:
1. Dyspnea exacerbated by exertion
2. Cough: dry + persistent
3. Fatigue (∵ poor gas exchange)
4. Tachypnea (often laboured)
5. Loss of appetite + Weight loss
6. Chest pain
S/S:
- >50 yo
- Dry, non-productive cough on exertion
- Progressive exertional dyspnea (SOB with exercise)
- Dry, inspiratory bibasilar “Velcro-like” crackles (i.e. ***Fine crackles) —> not change with coughing
- Clubbing
- Abnormal lung function test —> Restrictive pattern + Impaired gas exchange
Occupational risk factors: Asbestosis and Malignant pleural mesothelioma
Handling of ***asbestos products (石綿) (incorporated into construction work, commercial / household products)
Construction works:
- Demolition of fireproof coatings / bricks / pipes
—> shipyard workers, seamens
Commercial / Household:
- Demolition work
- Insulation wall layers with broken asbestos brick in floorings / roofings
***Asbestosis (石綿肺)
- ***Diffuse interstitial fibrosis
- Develops after prolonged / heavy exposure
Pathogenesis:
Chronic inflammation
—> Fibroblasts proliferate in interstitium
—> Fibrosis
—> **Bronchiolar epithelium extend to line airspaces + Collapsed / **Amputated distal airway
—> Obstruction of usual gas exchange
End stage:
- Acini “simplified” —> Cystic space
- Bronchiolar epithelium grow into cystic space
- Honeycomb lung
Pathological features:
1. Interstitial fibrosis
2. **Obliteration of some air spaces
3. **Cystic dilatation of others (non-functional)
4. Chronic inflammatory cells (not always present)
5. **Asbestosis bodies
6. Abnormal pleural shadows on CXR
- **not conforming to any pulmonary Parenchymal anatomy
- **Pleural thickening (calcified)
- **Asbesto / Pleural plaque
Management of Silicosis and Asbestosis
- ***Irreversible with no cure
- Treatment on alleviating symptoms + preventing complications
- Silica and Asbestos: WHO Type 1 carcinogens
- Stop further exposure
- Silica
- Lung irritants (including tobacco smoking) - Cough suppressant
- Antibiotics (if lung infection)
- TB prophylaxis (if positive tuberculin skin test / IGRA)
- Prolonged anti-TB drugs (Multi-drug regimen) (for active TB)
-
**Monitor for malignancy
- **Mesothelioma: primary malignant neoplasm of mesothelial tissue (cancer derived from lining (mesothelium) of pleura, pericardium, peritonium) due to dust of Asbestos
Occupation safety clinic
Evaluation of compensation
Must be HK resident
Once diagnosed with **Pneumoconiosis, **Mesothelioma
Referred to Pneumoconiosis Medical Board (Shau Kei Wan Chest Clinic)
—> Evaluate degree of lung function impairment
—> Stratified by ***FVC measurement
From CPRS L67
Pathological features of IPF:
1. Interstitial fibrosis (stained pink)
- ↓ compliance —> stiff, rigid lung
- reduced capillaries —> ↓ gas exchange —> impaired perfusion
- alveolar fibrosis —> ↓SA + ↓ diffusion capacity —> VQ mismatch
- Obliteration and cystic dilation of air space
Gross appearance (restrictive pattern):
1. Rigid shrunken lung (sense/fibrosis)
2. Thickened alveolar wall (***pinhole alveolar space)
3. Honeycomb lung (End stage changes)
S/S:
1. Dry cough
2. SOB but no wheeze
3. Chronic hypoxia —> cyanosis
4. Coarse lines and nodules on CXR
5. Risk of lung cancer
Effects of chronic hypoxia
1. Pulmonary vasoconstriction
- Early: reversible
- Late: irreversible structural change: increased fibroblast and smooth muscle cell —> thickening of tunica media and intima
2. Polycythaemia: increased blood viscosity
3. Pulmonary hypertension (type 3)
4. Right ventricular hypertrophy / dilatation (systemic venous congestion)
5. Cor pulmonale
