Asthma Flashcards
Why is asthma important?
-Common
-Kills people
-Can recognise, control and fix disease
Factors that predispose asthma not resolving in adolescence/ returning later in life
-Airway hyperresponsiveness
-Sensitisation to house dust mite
-Female sex
-Smoking at age 21
Describe genetic risk asthma
-Atopy
=Increased allergic hypersensitivity (inhaled allergens)
=Often have raised IgE and positive skin prick tests
=Atopic dermatitis and allergic rhinitis (IgE mediated)
=May also be sensitive to aspirin, nasal polyps
Describe environmental risk factors for asthma
-Influence susceptibility to development of asthma in predisposed individuals
-Precipitate asthma exacerbations
-Allergens
-Hygiene hypothesis
=Exposure to infections early in life influences immune system along non-allergic pathway
-Antenatal factors: maternal smoking, viral infection during pregnancy (especially RSV)
-Low birth weight
-Not being breastfed
-Maternal smoking around child
-Exposure to high concentrations of allergens (e.g. house dust mite)
-Air pollution
-Occupation (bakery, construction…)
Pathophysiology of asthma
-Chronic inflammatory disorder of the airways secondary to type 1 hypersensitivity
-Th2 lymphocyte driven
-Many cells and cellular elements play role
=Eosinophils (IL-5 from Th2 stimulated)
=Mast cells (releases histamine, leukotrienes, cytokines)
=B cells (produce IgE to stimulate mast cell)
=Neutrophils
-Increased mucus production
-Bronchospasm/ constriction
-Swelling and irritation of airways
How does inflammation manifest in asthma?
-Increased hyper-responsiveness
=Acute bronchoconstriction= turbulent airflow= wheeze
-Swelling of airway (increased permeability of airway)
-Mucus plug formation (goblet cell hypersecretion)
-Airway wall remodelling/ thickening of basement membrane
Asthma history
-Presence of more than one variable symptom of wheeze, cough, breathlessness, and chest tightness.
=Symptoms are commonly episodic, diurnal (worse at night or in the early morning), and/or triggered or exacerbated by exercise, viral infection, and exposure to cold air or allergens.
=In children, symptoms may also be triggered by emotion and laughter.
=In adults, symptoms may be triggered by use of non-steroidal anti-inflammatory drugs and beta-blockers.
=Ideally, expiratory polyphonic wheeze (with multiple pitches and tones heard over different areas of the lung when the person breathes out) will be confirmed on auscultation.
=Note: Occupational asthma may be suggested by adult-onset asthma, where symptoms improve when not at work. High-risk occupations include laboratory work, baking, animal handling, welding, and paint spraying. Check for possible occupational asthma by asking:
==Are symptoms better on days away from work?
==Are symptoms better when on holiday?
-Personal/family history of other atopic conditions, particularly atopic eczema/dermatitis and/or allergic rhinitis.
How do we diagnose asthma?
-Breathlessness
-Cough (often worse at night)
-Wheeze (expiratory on auscultation)/ chest tightness
-Variable airflow obstruction
=Spirometry initial test (presence and severity)
==FEV1 significantly reduced, FVC normal, FEV1% <70
-PEF if spirometry not available- reduced PEFR
=Fractional inhaled nitric oxide FeNO
FeNO testing
should be used where possible to confirm eosinophilic airway inflammation to support an asthma diagnosis in people aged 17 years and older. This test may be available in some primary care practices or may require referral to a specialist centre. In steroid-naive adults, a FeNO level of 40 parts per billion (ppb) or higher is considered a positive result.
=Consider FeNO testing in children and young people (aged 5 to 16 years) if there is diagnostic uncertainty after initial assessment, and they have either normal spirometry or obstructive spirometry with a negative bronchodilator reversibility (BDR) test (see below). A FeNO level of 35ppb is considered a positive result in this group.
==Approximately 1 in 5 people with a negative result will have asthma.
==Approximately 1 in 5 people with a positive result will not have asthma.
==Be aware that the results of FeNO tests may be affected by empirical treatment with inhaled corticosteroids.
Provoking factors for asthma
-Inhaled aeroallergens
-Exercise
-Anxiety/ stress
-Temperature change
-Cigarette smoke
-Foods, additives (preservatives, colouring agents)
-Occupational agents (isocyanates)
-Drugs (NSAIDs, b blockers)
Features that increase the probability of asthma
-1+ of the following
=Wheeze, breathlessness, chest tightness, cough (worse at night and early morning/ response to exercise, allergen exposure and cold air/ after taking aspirin or b blockers/ family history of asthma or atopy)
=Widespread wheeze heard on auscultation of the chest
=Unexplained low FEV1 or PEF
Features that lower probability of asthma
-Prominent dizziness, light-headedness, peripheral tingling
-Chronic productive cough in the absence of wheeze or breathlessness
-Repeatedly normal physical examination of chest when symptomatic
-Voice disturbance
-Symptoms with colds only (bronchial hyperactivity syndrome)
-Significant smoking history (>20 pack-years)
-Cardiac disease
-Normal PEF or spirometry when symptomatic
How to test for airflow obstruction
- Basic spirometry
=Reduction in FEV1
=FEV1: FVC ratio less than 70% - Reversibility testing/ treatment trials
=Nebulized bronchodilators (or steroids)
->400mls improvement/ symptom scores
=in adults, a positive test is indicated by an improvement in FEV1 of 12% or more and increase in volume of 200 ml or more
=in children, a positive test is indicated by an improvement in FEV1 of 12% or more - Monitor peak flow/ PEF monitoring- variability 20% after monitoring at least twice daily for 2-4 weeks is regarded as a positive result
- Assessment airway responsiveness
=Useful in patients with normal lung function
=Histamine challenge= induce bronchoconstriction - CXR, blood eosinophil, IgE, skin prick tests
Diagnosis algorithm in asthma
Patients >= 17 years
patients should be asked if their symptoms are better on days away from work/during holidays. If so, patients should be referred to a specialist as possible occupational asthma
all patients should have spirometry with a bronchodilator reversibility (BDR) test
all patients should have a FeNO test
Children 5-16 years
all children should have spirometry with a bronchodilator reversibility (BDR) test
a FeNO test should be requested if there is normal spirometry or obstructive spirometry with a negative bronchodilator reversibility (BDR) test
Patients < 5 years
- diagnosis should be made on clinical judgement
FeNO
in adults level of >= 40 parts per billion (ppb) is considered positive
in children a level of >= 35 parts per billion (ppb) is considered positive
Differentials of intermediate probability without airflow obstruction (from additional investigation)
-Chronic cough syndrome
-Hyperventilation
-Vocal cord dysfunction
-Rhinitis
-Gastroesophageal reflux
-Heart failure
-Pulmonary fibrosis
Differentials of intermediate probability WITH airflow obstruction (from additional investigation)
-COPD
-Bronchiectasis
-Inhaled foreign body
-Lung cancer
-Sarcoidosis
-Obliterative bronchiolitis
Aims of asthma management/ control
-No daytime symptoms
-No nighttime awakening to asthma
-No need for rescue medications
-No exacerbations
-No limitations on activity including exercise
-Normal lung function (FEV1 and/or PEF>80% predicted or best)
=With minimal side effects
Non-pharmacological management
-Avoid/ remove provoking factors
=Aeroallergen
=Food allergen
=Tobacco smoke
=Obesity
=Aspirin/ b-blockers
Describe short-acting beta agonists
-Inhaled short-acting B2-agonist
=Salbutamol and terbutaline
=B2-adrenergic receptors
=Bronchodilator activity
=First-line, typically used if patient develops symptoms
-Relatively B2 selective but cardiac effects (B1)
=Tachycardia, vasodilation, arrhythmia. Relax smooth muscle of the airways
-Systemic effects
=Hypokalaemia, tremor, insomnia
