Respiratory Flashcards
(42 cards)
Define extrinsic allergic alveolitis
• Interstitial inflammatory disease of the distal gas-exchanging parts of the lung caused by inhalation of organic dusts. Also known as hypersensitivity pneumonitis
Aetiology extrinsic allergic alveolitis
• In sensitised individuals, repetitive inhalation of allergens provokes a hypersensitivity reaction, which varies in intensity and clinical course depending on antigen
• In acute phase, alveoli are infiltrated with acute inflammatory cells
• Early diagnosis and prompt allergen removal can halt and reverse disease progression, so prognosis can be good.
o With chronic exposure, granuloma formation and obliterative bronchiolitis
• Antigenic dusts include microbes and animal proteins
o Bacteria
♣ Actinomycetes
• Farmer’s Lung
• Bagassosis
• Mushroom picker’s lung
o Animal proteins (ie Avian proteins)
♣ Pigeon breeder’s lung
♣ Bird Fancier’s lung
• Acute o Present 4-12 hrs after exposure o Reversible episodes of: ♣ Dry cough ♣ Dyspnoea ♣ Malaise ♣ Fever ♣ Myalgia o Wheeze and productive cough may develop if repeat high-level exposure • Chronic o Slowly increasing breathlessness o ↓ exercise tolerance o Weight loss o Exposure is usually chronic, low level and maybe no Hx of previous acute episodes
• Acute o Rapid shallow breathing o Pyrexia o Inspiratory crackles • Chronic o Fine inspiratory crackles o Clubbing (rare)
extrinsic allergic alveolitis
Investigations extrinsic allergic alveolitis
• Immunological response to causative antigen
o Blood checked to determine whether there is antibody to the putative antigen
o Often not diagnostic because may find these in normal individual
• Bloods o FBC ♣ Leukocytosis ♣ Normocytic, normochromic anaemia o ↑ ESR o ↓ Albumin
• CXR o Often can be normal in acute episodes o ACUTE ♣ Patchy, nodular infiltrates o CHRONIC: fibrosis
• CT Chest
o Detects early changes
o Chronic: May show patchy ‘ground glass’ shadowing and nodules, extensive fibrosis
• Pulmonary function tests
o Reversible restrictive defect (low FEV1, low FVC)
o Preserved or increased FEV1/FVC ratio
o Reduced total lung capacity
o Reduced gas transfer during acute attacks
• Bronchoalveolar Lavage
o Increased lymphocytes and mast cells
• Lung biopsy can also be performed
Define ARDS
- Non-cardiogenic pulmonary oedema and diffuse lung inflammation syndrome
- Syndrome of acute and persistent lung inflammation with ↑ vascular permeability – maybe caused by direct lung injury or occur secondary to severe systemic illness
Aetiology ARDS
• Pathophysiology
o Direct lung injury or secondary to systemic illness lung damage release of inflammatory mediators ↑ capillary permeability due to endothelial dysfunction fluid leakage into alveoli as well as ↓ surfactant production impaired gas exchange and ↓ lung compliance
• Common causes o Pulmonary ♣ Pneumonia ♣ Gastric aspiration ♣ Smoke inhalation ♣ Injury ♣ Vasculitis ♣ Contusion o Other ♣ Shock ♣ Septicaemia ♣ Haemorrhage ♣ Multiple transfusions ♣ DIC ♣ Pancreatitis ♣ Acute liver failure ♣ Trauma ♣ Head injury ♣ Malaria ♣ Fat embolism ♣ Burns ♣ Obstetric events: eclampsia, amniotic fluid embolus ♣ Drugs/toxins: aspirin, heroin
- SOB
- Respiratory distress
- Cough
- Acute onset
• Cyanosis
• Tachypnoea
• Tachycardia
• Bilateral widespread fine inspiratory crackles
• Hypoxia refractory to oxygen treatment
Peripheral vasodilation
ARDS
Investigations for ARDS
• Diagnosis is based on 3 criteria:
o Acute onset (within 1 week)
o Bilateral opacities on CXR
o PaO2/FiO2 (arterial to inspired oxygen) ratio of <300
- CXR Bilateral infiltrates
- ABG PaO2/FiO2 (arterial to inspired oxygen) ratio of <300
• Cultures tests for underlying infection
o Sputum
o Blood
o Urine
• Bloods
o Amylase/lipase to check for pancreatitis
- Echocardiography: severe aortic or mitral valve dysfunction
- Pulmonary artery catheterisation: PWCP less than or equal to 18mmHg
- Bronchoscopy: if cause cannot be determined from history, and to exclude differentials
Define asbestosis
• Long term inflammation and scarring of the lungs caused by inhalation of asbestos fibres
Aetiology of asbestosis
• 3 different types of asbestos:
o Chrysotile (white asbestos) is the least fibrogenic.
o Crocidolite (blue asbestos) is the most fibrogenic.
Amosite (brown asbestos) has intermediate fibrogenicity.
• Asbestos commonly used in building trade always ask about OCCUPATION in resp history degree of exposure = degress of pulmonary fibrosis
• Inflammation gradually causes mesothelial plaques in pleura
• Causes ↑ risk of bronchial adenocarcinoma and mesothelioma
• SMOKING ↑ risk
- Dyspnoea on exertion
- Dry non-productive cough
- Fine end–inspiratory crackles heard at bases and moving up as disease gets worse
- Clubbing
Asbestosis
Investigations asbestosis
• CXR
o Lower zone linear interstitial fibrosis
o Pleural thickening
Define mesothelioma
• Aggressive tumour of mesothelial cells that usually occurs in pleura (90%), but sometimes in peritoneum, pericardium or testes.
o Mesothelium is thin epithelium that lines several body cavities including pleura, peritoneum, mediastinum and pericardium
Aetiology mesothelioma
- Associated with occupations exposure to asbestos by relationship is complex
- 90% report prev exposure to asbestos, but only 20% of pts have pulmonary asbestosis
- Latent period between exposure and development of tumour can be up to 45 years
- Malignant pleural mesothelioma rarely spreads to distant sites but most patients present with locally advanced disease
- SMOKING ↑ risk
- SOB
- Chest pain (dull, diffuse, developing)
- Constitutional symptoms: Fever, fatigue, sweats, weight loss
- Dry and non-productive cough
- Abdominal pain
- Occasional palpable chest wall mass
- Diminished breath sounds due to pleural effusion, trapped lung or bronchial obstruction
- Dullness to percussion pleural effusion on affected side
- Abdominal pain/obstruction
Mesothelioma
Investigations for mesothelioma
• Chest X-ray/CT
o Unilateral pleural effusion
o Irregular pleural thickening
o ↓ lung volumes
- MRI and PET
- Pleural fluid: can be sent for cytological analysis and may be blood stained
• Pleural biopsy
o Diagnosis is made on histology, usually following a thoracoscopy (pleural biopsy) – often done post-mortem
o Biopsy of the tumour can be immunostained with a stain that reacts with CALRETININ
Define aspergillus lung disease
• Lung disease associated with Aspergillus fungal infection
• There are five different ways this group of fungi can affect the lungs
o Asthma: type I hypersensitivity (atopic) reaction to fungal spores
o Allergic bronchopulmonary aspergillosis (ABPA): type I and type III hypersensitivity reactions to Aspergillus fumigatus
o Aspergilloma (mycetoma): a fungus ball within a pre-existing cavity (often caused by TB or sarcoidosis)
o Invasive aspergillosis
o Extrinsic allergic alveolitis (EAA): due to sensitivity to Aspergillus clavatus (‘malt worker’s lungs’)
Aetiology aspergillus lung disease
• Aspergilloma
o Growth of an A. fumigates mycetoma ball in pre-existing lung cavity (e.g. post-TB/sarcoidosis, old infarct or abscess)
• Allergic Bronchopulmonary Aspergillosis (ABPA)
o Colonisation of the airways by Aspergillus fumigatus leads to IgE and IgG-mediated immune responses
o Usually occurs in asthmatics and CF patients
o The release of proteolytic enzymes, mycotoxins and antibodies leads to airway damage – this initially causes bronchoconstriction but as inflammation persists, permanent damage occurs causing bronchiectasis
• Invasive Aspergillosis
o Invasion of Aspergillus into lung tissue and fungal dissemination
o This occurs in immunosuppressed patients (e.g. neutropenia, steroids, AIDS) or after broad-spectrum antibiotic therapy
• Aspergilloma o Asymptomatic o May cause cough, haemoptysis (potentially massive), lethargy, weight loss • ABPA o Difficult to control asthma o Recurrent episodes of pneumonia with wheeze, cough, sputum, dyspnoea, fever and malaise • Invasive Aspergillosis o Cough Non-productive o Dyspnoea o Rapid deterioration o Septic picture o Headache o Pleuritic chest pain peripheral lung lesions
- Dullness in affected lung
- ↓ breath sounds
- Wheeze (in ABPA)
- Pleural rub (in IA)
Aspergillus lung disease
Investigations Aspergillus lung disease
Aspergilloma
o CXR
♣ May show a round mass with a crescent of air around it
♣ Usually found in the upper lobes
o CT or MRI - may be used if CXR is unclear
o NOTE: sputum cultures may be negative if there is no communication between the cavity colonised by Aspergillus and the bronchial tree
o Strongly positive serum precipitins
o Aspergillus skin test - +ve in 30%
ABPA o Immediate skin test reactivity to Aspergillus antigens o Aspergillus-specific IgE radioallergosorbent test – RAST o Eosinophilia o Raised total serum IgE o Raised specific serum IgE and IgG to A. fumigatus – serum precipitins o Aspergillus in sputum o CXR • Transient patchy shadows • Segmental collapse or consolidation • Distended mucous-filled bronchi • Signs of complications: ♣ Fibrosis in upper lobes ♣ Bronchiectasis o CT • Lung infiltrates • Central bronchiectasis o Lung Function Tests • Reversible airflow limitation • Reduced lung volumes/gas transfer
Invasive Aspergillosis
o Aspergillus is detected in cultures or by histological examination
o Bronchoalveolar lavage fluid or sputum may be used diagnostically
o Chest CT
• Nodules surrounded by a ground-glass appearance (halo sign)
This is caused by haemorrhage into the tissue surrounding the fungal invasion
Define idiopathic pulmonary fibrosis
• Chronic inflammatory condition of the lungs resulting in fibrosis of alveoli and interstitium
o Fibrosis excess collagen in connective and interstitial tissue causing thickening
Aetiology idiopathic pulmonary fibrosis
• Cause is unknown
• Recurrent injury to alveolar epithelial cells = secretion of cytokines and GFs by pneumocytes, ie TGFb1
o Interstitial tissue between alveoli and capillaries contain fibroblasts and macrophages
♣ Cytokines released cause fibroblast activation, recruitment, proliferation, differentiations into myofibroblasts and ↑ collagen sysnthesis and deposition
o Over time = thickened interstitial layer causing problems with ventilation and oxygenation Alveoli are also stiffer
• This is restrictive disease as there is restricted lung expansion due to fibrosis of interstitium
• Loss of alveoli leading to fluid filled cysts surrounded by thick wall – known as honeycombing
• Certain drugs can produce similar illness (e.g. methotrexate, amiodarone)
• Histological Patterns
o Interstitial pneumonia
• Risk Factors o Age o Male o Smoking o Occupational exposure to metal or wood o Chronic microaspiration o Animal and vegetable dusts
- Gradual-onset, progressive dyspnoea on exertion
- Dry irritating cough
- No wheeze
- Weight loss, fatigue, and malaise can be common
- Take full occupational and drug history
- Clubbing (50%)
- Bibasal fine end expiratory crackles
Idiopathic pulmonary fibrosis
Investigations idiopathic pulmonary fibrosis
• CXR
o Early disease may show ground glass shadowing
o Later stages bilateral lower zone reiculonodular shadowing
o Signs of cor pulmonale
o Honeycombing
• High resolution CT
o More sensitive in early disease than CXR
• Pulmonary function tests
o Restrictive changes (↓ FEV1 and FVC, with preserved or ↑ FEV1/FVC)
o ↓ lung vol, lung compliance, total lung capacity
• Bloods
o ANA and Rheumatoid factor elevated in 1/3 of patients
- Bronchoalveolar Lavage - exclude infections and malignancy
- Lung Biopsy - gold standard for diagnosisbut not always needed, histological changes are referred to as usual interstitial pneumonia (UIP)
