Restrictive Thoracic Disease Flashcards
What are causes of thoracic restriction outwith the lungs?
- Skeletal: vertebrae (e.g. kyphoscoliosis), ankylosing spondylitis, ribs (e.g. multiple rib fracture)
- Muscle weakness: intercostal or diaphragmatic (due to myopathy, neuropathy, myelopathy) e.g. Myasthenia Gravis, Guillian Barre, Motor Neurone Disease, Poliomyelitis
- Abdominal obesity/ascites - compression of diaphragm into thoracic cage, cannot contract and descend as effectively
What is myopathy?
Disease of the muscle
What is neuropathy?
Disease of the nerves
What is myelopathy?
Disease of the spinal cord
What are examples of diseases that cause muscle weakness?
- Myaesthenia Gravis
- Guillan Barre
- Motor neurone disease
- Poliomyelitis
What is ascites?
Build up of fluid in abdominal cavity
What does thoracic restriction result in?
- Chronic alveolar hypoventilation with decreased PaO2 (hypoxia) and increased PaCO2 (hypercapnia)
- Reduced lung volumes
What are the causes of thoracic restriction originating from within the lungs?
- Acute DPLD (interstitial lung disease)
- Episodic DPLD
- Chronic DPLD due to occupational or environmental agents/drugs
- Chronic DLPD with evidence of systemic disease
- Chronic DLPD with no evidence of systemic disease
What is DPLD?
Interstitial lung disease
What is lung interstition?
Area between alveoli
What is restrictive thoracic disease?
Occurs due to disease within the lungs
What are examples of diseases that cause thoracic restriction?
- Disease of alveolar structures (walls/lumen) e.g. DPLD
* Pathophysiology - impaired exchange of O2, but not CO2
What does Alveolar-Arteriolar barrier determine?
How effectively oxygen is transferred across alveolar epithelium into red blood cells where it binds to haemoglobin
Why is CO2 exchange unimpaired due to pathophysiology?
- Alveolar ventilation is normal
* CO2 is very soluble and blown off (normal PaCO2)
What are causes of DPLD?
- Fluid in the alveolar air spaces
- Consolidation of alveolar air spaces
- Inflammatory infiltrate of alveolar walls (i.e. alveolitis)
- Drug-induced alveolitis
- Toxic gas/fumes
- Pulmonary fibrosis
- Autoimmune (multi-system)
- Dust-disease (pneumoconiosis)
- Carcinomatosis
- Eosinophilic allergic response
What is ARDS?
Adult respiratory distress syndrome (shock lung) caused by leaky pulmonary capillaries
What are causes of consolidation of alveolar air spaces?
- Infective pneumonia (most common cause)
- Pulmonary infarction (pulmonary emboli)
- BOOP (bronchiolitis obliterans organising pneumonia)
What causes fluid to build up in alveolar air spaces?
- Cardiac Po oedema (in alveolar walls and lumen) due to raised Po venous pressure e.g. due to left ventricular failure
- Non cardiac Po oedema - normal Po venous pressure with leaky Po capillaries due to sepsis or trauma
What causes BOOP?
- Rheumatoid disease
- Drugs
- Cryptogenic (unknown cause)
What are the 2 causes of granulomatous alveolitis?
- Extrinsic allergic alveolitis
* Sarcoidosis
What is extrinsic allergic alveolitis?
Hypersensitivity type 3 reaction due to extrinsic antigen (not allergen as not mediated by IgE)
What are examples extrinsic allergic alveolitis?
- Farmer’s lung
* Avian
What inflammation is caused by extrinsic allergic alveolitis and sarcoidosis?
No eosinophilic inflammation - gives lymphocytic inflammation, causing formation of granulomas
What is sarcoidosis?
A disease that results in granulomatic lymphocytic inflammation
What is the cause of sarcoidosis?
No known cause
What drugs can induce alveolitis?
- Amiodarone
- Bleomycin, Methotrexate
- Gold
What toxic gas can cause DPLD?
Chlorine
What are examples of autoimmune diseases that cause DPLD?
- Systemic lupus erythematosus (SLE)
- Polyarteritis
- Wegeners
- Churg-Strauss
- Bechet’s
What is pneumoconiosis?
Dust-disease - usually associated with fibrosis
What are the 2 types of pneumoconiosis?
- Fibrogenic
* Non-fibrogenic
What are causes of fibrogenic pneumoconiosis?
- Asbestosis
* Silicosis
What are causes of non-fibrogenic pneumoconiosis?
- Siderosis (Iron)
- Stanosis (Tin)
- Baritosis (Barium)
What are glandular adenocarcinomas that metastasise via blood and lymphatics to the lungs?
- Bronchial adenocarcinoma
- Breast adenocarcinoma
- Prostate adenocarcinoma
- Colon adenocarcinoma
- Stomach adenocarcinoma
What are clinical signs of DPLD?
- Breathless on exertion
- Cough but no wheeze (wheeze indicated airway obstruction)
- Finger clubbing
- Inspiratory lung crackles
- Central cyanosis (if hypoxaemic)
- Pulmonary fibrosis as end stage response to chronic inflammation
How is DPLD diagnosed?
- History e.g. occupation, drugs, pets
- Reduced lung volumes - decreased FEV1 and FVC, FEV1/FVC ratio normal >75%
- peak flow normal
- Reduced gas diffusion (DLCO)
- Arterial oxygen desaturation (PaO2, SaO2)
- Antibodies (avian, fungal)
- ACE and Ca raised in sarcoidosis
- CXR
- Echocardiogram to exclude heart failure and diagnose secondary pulmonary hypertension
- High resolution CT scan (can be used to stage disease)
- Sputum/bronchoalveolar lavage
- Transbronchial or thorascopic lung biopsy
What is PaO2?
Partial pressure of oxygen in arterial blood
What is SaO2?
The volume of oxygen bound to haemoglobin in arterial blood
What is the treatment for DPLD?
- Remove trigger factor
- Treat reversible alveolitis e.g. immuno-suppressives
- Systemic steroids - ICS not effective, treated with Azathioprone
- IPF treated with anti-fibrotic agents e.g. pirfenidone, nintendanib
- Oxygen if hypoxaemic
- Lung transplantation (last resort)
Why are inhaled corticosteroids not effective in treating interstitial lung disease?
Not a high enough concentration in distal lung
Do anti-fibrotic agents destroy collagen?
No, they only prevent further deposition of collagen
Why are pirfenidone and nintendanib not first line treatments?
Horrible side effects
What are clinical signs of sarcoidosis?
- Erythema
- Bilateral hilar lymphadenopathy (viewed on CXR)
- Lung infiltrates (viewed on CXR)
