Airway Disease Flashcards
What is asthma?
An obstructive condition characterized by IgE hypersensitivity inducing mast cell degranulation and airway obstruction from Th2 cell mediated sensitisation by interacting with dendritic cells, mediated by IL-4 and IL-5.
This results in bronchial wall oedema and mucous gland hypersecretion and bronchoconstriction due to inflammation.
What are the clinical features of asthma?
Cough, shortness of breath
Wheeze and Chest tightness.
These are typically, variable, worst at night and assoicated with allergic triggers and non-allergic triggers such as cold air and exercise. Predominately, cough may be the only symptom.
It is important to rule out nasal symptoms, GERD associatd with hoarse voice, throat clearing and acid in mouth, aspirin sensitivity, family history and social situations
What are the main cytokines involved in asthma pathophysiology?
- IL-4
- IL-5
What are the clinical presentations of asthma in an emergency department?
- Dyspnoea
- Wheezing breath sounds
- Hyper-resonance to percussion
Obstruction to airflow creates air trapping and hyper-inflation o the lungs with a barrel chest
What are the triggers for asthma attacks?
Aspirin, a non-selective COX inhibitor which induces arachidionic acid metabolites to enter the lipo-oxygenate pathway involving pro-inflammatory leukotrienes that induce bronchoconstriction.
- Beta blockers
- Viral upper respiratory tract infections
*Cold air
*Exercise
*Allergies
What complications are associated with asthma?
- Respiratory failure type 2
- Pneumothorax: hyperfinaltion can cause the lungs to rupture and air to leak from parenchyma into the pleural cavity
- Silent chest, with short inspiration and long expiration.
- Pulsus paradoxus may occur due to negative intrapleural pressure and lung hyperinflation and cause a septum shift which impedes ventricualr filling during inspiration
What is status asthmaticus?
A medical emergency characterized by hypoxaemia, hypercapnia, and secondary respiratory failure. There is an acute bronchospastic phase after allergen exposure, followed by a later inflammatory phase of airway swelling and oedema due to eosinophilic mediation.
On examination, patients are typically tachycardia, tachypnoea and conversationally dyspnoeic.
What are common triggers for asthma attacks?
- Aspirin
- Beta-blockers
- Viral upper respiratory infections
- Cold air
- Exercise
- Allergies
What are the clinical features of asthma?
- Cough
- Shortness of breath
- Wheeze
- Chest tightness
What is the atopic triad associated with asthma?
- Urticaria
- Asthma
- Dermatitis
What are the diagnostic tests for asthma?
- CXR: usually normal but may show hyperinfaltion
- 12 lead ECG: typically normal
- ABG: may show respiratory acidosis
- Peak flow tests Shows day-to-day variability and airway hyperresponsivenes
- Pulmonary function tests such as FEV1/FVC ratio, where a reduced ratio indicates obstructive lung disease and is reversible following administration of a bronchodilator
- Diffusion limitation capacity for carbon monoxide, where normal or increased indicates asthma
- FBC for eosinophil count, sputum analysis for eosinophilia and biomarkers such as FINO.
What is used to test bronchial hyperreactivity?
Methacholine can be used to test bronchial hyperreactivity following administration, which will show a reduced FEV1, because it is a parasympathomimetic bronchoconstrictor.
What des a peak flow less than 40% indicate?
Peak expiratory flow less than 40% indicates asthma exacerbation.there should be day to day variability with response to treatment, with reduced FEV1
What is the significance of a reduced FEV1/FVC ratio?
Indicates obstructive lung disease.
What is the role of methacholine in asthma diagnosis?
Used to test bronchial hyperreactivity.
What are the types of asthma management?
- Bronchodilators
- Anti-inflammatories
- Leukotriene receptor antagonists
- Anti-histamines
What is the aetiology of asthma?
Atopic, associated with IgE-antigen complexes
Non-eosinophilic disease, which is assoicated with a poorer response to corticosteroid
Genetics
Hygeine hypothesis, where reduced exposure in early life to endotoxins increases the allergic Th2 mediated response that creases allergen sensitivity in later life
Environment
What is occupational asthma?
Occupational asthma occurs after sensitisation where
Immunological: repeated exposure to the allergen
Non-immunological: exposure to high concentrations of allergen.
It should be screened in patients by assessing whether symptoms worsen at work and improve on weekends/holidays away from work. They should be referred to an occupational asthma specialist. Management includes early diagnosis and removal from exposure. Their PEF should. Be recorded every 2hous from waking to sleep for 4 weeks
What characterizes brittle asthma?
Brittle asthma is a rare form of severe asthma characterised by wide variation of PEF, despite heavy dose of steroids
What are the types of brittle asthma?
- Type 1: maintained PEF variability, affecting females between 15 and 55, assoicated with skin prick test positivity and food intolerance.
- Type 2: acute exacerbations requiring mechanical ventilation for respiratory insufficiency and are mainly free of symptoms otherwise
What is difficult/refractory asthma?
Characterized by continuous corticosteroid use with frequent exacerbations and poor bronchodilator response. There is a poor bronchodilator response to B2 agonists and they fail to completely reverse their airflow obstruction following a course off oral a prednisolone. They require high dose inhaled corticosteroids with long acting inhaler B2 agonists.
How should steroid resistant patients with refractory asthma be managed?
Patients that are steroid resistant in this group should be manage with alternative medication such as macrolide antibiotics which have an anti-inflammatory effect, at reducing airway reactivity and eosinophil inflammation.
What should be assessed in a clinical history for asthma?
- Wheeze
- Cough
- Breathlessness
- Chest tightness
These will be worse during the night or early morning and is seasonal - Triggers
- Family history of asthma and allergic rhinitis
How to assess morbidity for asthma?
-> have you experienced difficulties sleeping due to asthma?
-> have usual asthma symptoms occured during the day?
-> have these asthma symptoms interfered with normal activities?
What are the initial objective tests for asthma?
Initial Objective tests for asthma diagnosis include eosinophil count, Fractional exhaled nitric oxide (FeNO), spiromotry and to assess for reversible bronchodilation with peak expiratory flow.
-> results of spirometry and FeNO may be altered and appear normal for those taking inhaled corticosteroids
What are the objectiv tests for asthma diagnosis in adults?
Measure blood eosinophil count or FeNO
Measure bronchodilators reversibility with spirometry -> increase by 12% or more in FEV1 after using bronchodilator indicates asthma
Peak expiratory flow measured twice daily for 2 weeks-> variability over 20% indicates asthma
What are the tests for diagnosing asthma in children 5-16 years old?
Measure FeNO level -> over 35 ppl indicates asthma
Reversible bronchodilators test with spirometry -> FEV1 increase of 12% or more indicates asthma
Measurement of PEF twice daily to assess variability -> 20% or more indicates asthma
Skin prick testing for positive sensitisation response to house dust mite
Measure total IgE level and blood eosinophil count
How to diagnose asthma in children under 5?
Perform typical objective tests, however, if not possible, treat with inhaled corticosteroids and review on regular basis, with attempting tests every 6 to 12 months
What should be assessed in patinets with uncontrolled asthma?
Alternative diagnosis/comorbidity
Suboptimal adherence or inhaler technique
Smoking
Occupational exposures
Psychosocial factors
Environmental factors such as season, air pollution or indoor mould exposure
What are the steps for managing intermittent asthma?
Step 1: SABA for symptomatic relief.