Respiratory Flashcards
(116 cards)
Define acute respiratory distress syndrome.
Syndrome of acute and persistent lung inflammation with increased vascular permeability.
- Acute onset
- Bilateral infiltrates consistent with pulmonary oedema
- Hypoxaemia - PaO2 /FiO2 < 200mmHg regardless of the level of positive end-expiratory pressure (PEEP)
- No clinical evidence for increased left atrial pressure (pulmonary capillary wedge pressure PCWP <18mmHg)
- ARDS is the severe end of the spectrum of acute lung injury (ALI)
Explain the aetiology /risk factors of acute respiratory distress syndrome.
Severe insult to the lungs or other organs induces the release of inflammatory mediators, increased capillary permeability, pulmonary oedema, impaired gas exchange and reduced lung compliance.
Causes:
- Sepsis
- Aspiration
- Pneumonia
- Pancreatitis
- Trauma / Burns
- Transfusion - massive, transfusion-related lung injury
- Transplantation (bone marrow, lung)
- Drug overdose / reaction
- Alcohol misuse
- Smoke inhalation
- Drowning
- E-cigarette and vaping product use
Summarise the epidemiology of acute respiratory distress syndrome.
1 in 6000 per year in UK
Recognize the presenting symptoms of acute respiratory distress syndrome.
- Rapid deterioration of respiratory function
- Dyspnoea
- Respiratory distress
- Cough
- Symptoms of aetiology
Recognize the signs of acute respiratory distress syndrome on physical examination.
- Cyanosis
- Tachypnoea
- Tachycardia
- Widespread inspiratory crepitations
- Hypoxia refractory to oxygen treatment
- Bilateral signs
- May be asymptomatic in early stages
Identify appropriate investigations for acute respiratory distress syndrome and interpret the results.
- CXR
- Bloods
- Echocardiography
- Pulmonary artery catheterisation
- Bronchoscopy
CXR
- Bilateral alveolar and interstitial shadowing
Bloods
- FBC
- U&E
- LFT
- ESR / CRP
- Amylase
- Clotting
- ABG
- Blood culture
- Sputum culture
- Plasma BNP < 100pg/mL may distinguish between ARDS and heart failure (cannot exclude if critically ill)
Echocardiography
- Severe aortic or mitral valve dysfunction or low left ventricular ejection fraction favours haemodynamic oedema over ARDS
Pulmonary Artery Catheterisation
- PCWP <18mmHg
- High PCWP does not exclude ARDS as patients may have concomitant left ventricular dysfunction
Bronchoscopy
- If cannot determine from history
- Exclude differentials - e.g. diffuse alveolar haemorrhage
- To lavage fluid for microbiology - mycobacteria, Legionella pneumophila
- For cytology - eosinophils, viral inclusion bodies, cancer cells
Diffuse Alveolar Haemorrhage
- Frothy blood in airways
- Haemosiderin-laden macrophage from lavage fluid
Define arterial blood gas.
A collective term applied to three separate measurements = pH, PCO2 and PO2.
They are generally made together to evaluate acid-base status, ventilation and arterial oxygenation.
Summarise the indications for an arterial blood gas.
- Respiratory failure - both acute and chronic states
- Any illness that may lead to a metabolic acidosis - e.g. cardiac failure, liver failure, renal failure, hyperglycaemic states (DM), multiorgan failure, sepsis, burns, poisons/ toxins
- Ventilated patients
- Sleep studies
- Severely unwell patients from any cause - affects prognosis.
Identify the possible complications of an arterial blood gas.
- Local haematoma
- Arterial vasospasm
- Arterial occlusion
- Air or thrombus embolism
- Local anaesthetic anaphylactic reaction
- Infection at the puncture site
- Needle-stick injury to healthcare personnel
- Vessel laceration
Define asbestos-related lung disease (including asbestosis and mesothelioma).
Asbestosis - diffuse interstitial fibrosis of the lung as a consequence of exposure to asbestos fibres
Mesothelioma - a tumour of the mesothelial cells that usually occurs in the pleura, and rarely in the peritoneum or other organs, associated with asbestos exposure but relationship is complex
Explain the aetiology / risk factors of asbestos-related lung disease (including asbestosis and mesothelioma).
Asbestosis
- Caused by inhalation of asbestos fibers
- Commonly sued in building trade for fireproofing, pipe lagging, electrical wire insulation and roofing felt
- Degree of asbestos exposure is related to degree of pulmonary fibrosis.
- Onset occurs after 10+ years following initial exposure
- Increases risk of bronchial adenocarcinoma & mesothelioma
Risk factors:
- Occupational exposure
- Longer duration of exposure
- Smoking history
- Indirect exposure
Mesothelioma
- Long latency period (20-40 year latency)
- Few long-term survivors, high lethal malignancy
Risk factors:
- Asbestos exposure during home maintenance and renovation
- 60-85 years
- Male sex
Summarise the epidemiology of asbestos-related lung disease (including asbestosis and mesothelioma).
Asbestosis & Mesothelioma
- 90% report previous exposure to asbestos
- 20% of patients have pulmonary asbestosis
- Latent period between exposure and development of tumour is up to 45 years
- Incidence in the US is 3200 per year (for malignancy)
Recognize the presenting symptoms of asbestos-related lung disease (including asbestosis and mesothelioma).
Asbestosis
- Asymptomatic
- Shortness of breath (dyspnoea), especially on exertion
- Cough
- Presence of risk factors
Mesothelioma
- Chest pain
- Dyspnoea
- Presence of risk factors
Recognize the signs of asbestos-related lung disease (including asbestosis and mesothelioma) on physical examination.
Asbestosis
- Clubbing
- Fine end-inspiratory crackles
- Pleural plaques
Mesothelioma
- Weight loss
- Finger clubbing
- Recurrent pleural effusions
Signs of Metastasis
- Lymphadenopathy
- Hepatomegaly
- Bone pain / tenderness
- Abdominal pain /obstruction - peritoneal malignant mesothelioma
Identify appropriate investigations for asbestos-related lung disease (including asbestosis and mesothelioma) and interpret the results.
Asbestosis
- CXR (PA and lateral)
- Pulmonary function tests
- High-resolution CT chest
- Lung biopsy
- Bronchial lavage
Results:
- Pleural abnormalities
- Pleural plaques with/without calcification
- Diffuse pleural thickening
- Benign pleural effusion
- Rounded atelectasis
- In concordance with or in absence of parenchymal fibrosis
Mesothelioma
- CXR (PA and lateral)
- CT chest (with contrast)
- Histology following thoracoscopy
- Thoracentesis
- Pleural biopsy
- Video-associated thoracoscopic surgery
- Immunohistochemistry
Results:
- Pleural thickening / effusion
- Bloody pleural fluid
Define Aspergillus lung disease.
Lung disease associated with Aspergillus fungal infection.
Explain the aetiology/risk factors of Aspergillus lung disease.
Inhalation of the ubiquitous Aspergillus (usually Aspergillus fumigates) spores produce 3 different clinical pictures:
- Aspergilloma - growth of an A.fumigatus mycetoma ball in a pre-existing lung cavity (e.g. post-TB, old infarct or abscess)
- Allergic BronchoPulmonary Aspergillosis (ABPA)
- Invasive Aspergillosis - invasion into lung tissue and fungal dissemination (secondary to immunosuppression - e.g. neutropenia, steroids, haematopoietic stem cell/ solid organ transplantation, AIDS)
ABPA
- Aspergillus colonization of airways
- IgE and IgG mediated immune repsonses
- Proteolytic enzymes and mycotoxins released by fungi
- CD4/Th2 cells produce IL-4 and IL-5
- Eosinophilic inflammation
- IL-8 mediated neutrophilic inflammation
- Airway damage and central bronchiectasis
Summarise the epidemiology of Aspergillus lung disease.
Uncommon
Elderly
Immunocompromised
Recognize the presenting symptoms of Aspergillus lung disease.
Aspergilloma
- Asymptomatic
- Haemoptysis (may be massive)
ABPA
- Difficult to control asthma
- Recurrent episodes of pneumonia
- Wheeze
- Cough
- Fever
- Malaise
Invasive Aspergillosis
- Dyspnoea
- Rapid deterioration
- Septic picture
Recognize the signs of Aspergillus lung disease on physical examination.
- Tracheal deviation in large aspergillomas
- Dullness in affected lung
- Reduced breath sounds
- Wheeze (ABPA)
- Cyanosis (invasive aspergillosis)
Identify appropriate investigations for Aspergillus lung disease and interpret the results.
Aspergilloma
- CXR - round opacity with a crescent of air around it (in upper lobes)
- CT or MRI imaging (if CXR does not clearly delineate a cavity)
- Cultures of sputum - if no communication between cavity and bronchial tree
NB: Aspergillus is a common colonizer of an abnormal respiratory tract.
ABPA
- Immediate skin test reactivity to Aspergillus antigens
- Eosinophilia
- High serum total IgE
- High serum specific IgE and IgG to Aspergillus fumigatus or precipitating serum antibodies to Aspergillus fumigatus
- CXR
- CT - lung infiltrates, central bronchiectasis
- Lung function tests - reversible airflow limitation, reduced lung volumes/ gas transfer in progressive cases
CXR
- Transient patchy shadows
- Collapse
- Distended mucus-filled bronchi producing tubular shadows = gloved fingers
- Signs of complications
- Fibrosis in upper lobes (TB)
- Parallel-line shadows and rings (bronchiectasis)
Invasive Aspergillosis
- Detection in cultures or histologic examination (septated hyphae with acute angle branching)
- Risk factors
- Suggestive clinical findings
- Microscopic evidence of septate hyphae of examination of bronchoalveolar lavage fluid/sputum / positive serum galactomannan / beta-D-glucan assay
- Chest CT - nodules surrounded by ground-glass appearance (halo) = haemorrhage into tissue surrounding area of fungal invasion
Define asthma.
Chronic inflammatory airway disease characterized by variable reversible airway obstruction, airway hyper-responsiveness and bronchial inflammation.
Explain the aetiology/risk factors of asthma.
Genetic Factors:
- Family history (twin studies)
- Atopy - tendency of TH2 cells to drive production of IgE on exposure to allergens
- Multiple chromosomal locations (genetic heterogeneity)
Environmental Factors:
- House dust mite
- Pollen
- Pets - e.g. urinary proteins, furs
- Cigarette smoke
- Viral respiratory tract infection
- Aspergillus fumigatus spores
- Occupation allergens (isocyanates, epoxy resins)
Early Phase (Up to 1h)
- Exposure to inhaled allergens in a pre-sensitized individual
- Cross-linking of IgE antibodies on mast-cell surface
- Release of histamine, PgD2, leukotrienes, TNF-alpha
- Smooth muscle contraction = bronchoconstriction
- Mucous hypersecretion
- Oedema
- Airway obstruction
Late Phase (After 6-12h)
- Recruitment of eosinophils, basophils, neutrophil and TH2 lymphocytes and products
- Perpetuation of inflammation and bronchial hyper-responsiveness
- Structural cells (e.g. bronchial epithelial cells, fibroblasts, smooth muscle, and vascular endothelial cells) release cytokines, profibrogenic and proliferative GFs
- Contribute to inflammation and altered function
- Contribute to the proliferation of smooth muscle cells and fibroblasts = airway remodelling
Summarise the epidemiology of asthma.
10% of children 5% of adults Increasing prevalence W > M 1000-2000 deaths from acute asthma per year