ASTHMA Flashcards
What’s the epidemiology of asthma?
Affects >300 million people worldwide
12% of the UK population have been diagnosed with asthma at some point
Incidence is higher in children than adults
In early childhood, asthma is more common in boys but by adulthood its more common in girls
It accounts for 2-3% of primary care consultations and 60,000 hopsital admissions a year
What proportion of adult-onset asthma is occupational asthma?
Up to 15% - making it the most common industrial lung disease in the developed world
What are the aetiological factors of asthma?
Atopy
Hygiene hypothesis
Aspirin-induced asthma
Occupational asthma
Exercise-induced asthma
What is atopy?
A genetic predisposition to IgE-mediated allergen sensitivity
Atopic individuals are predisposed to allergic asthma, atopic dermatitis and allergic rhinitis
What is the hygeiene hypothesis?
Reduced exposure to infectious pathogens at a young age predisposes individuals to asthma
It’s thought that the developing immune system needs stimuli from infectious agents to adequately develop regulatory T cells and without that stimuli you become more susceptible to allergic disease
What is aspirin-induced asthma?
Ingestion of asthma triggers an asthma attack
These pt exhibit Samter’s triad: asthma, aspirin sensitivity and nasal polyps
What is Samter’s triad?
Asthma
Aspirin sensitivity
Nasal polyps
What is exercise-induced asthma?
In this variant asthma is triggered by strenuous physical activity. The aetiology is complex but exposure to cold air and environmental pollutants contributes.
What is asthma?
a chronic inflammatory condition of the airways that causes episodic exacerbations of bronchoconstriction. This causes reversible airway obstruction that typically responds to bronchodilators
This is caused by hypersensitivity of the airways and can be triggered by environmental factors
What are typical triggers of asthma?
Infections (particularly viral URTI)
Allergies - pollen, dust mites, pet dander, feathers, pests
Smoke, fumes, pollution
Night time/early morning
Exercise
Cold
Mold/damp
Cleaning and disinfectants
Strong emotions
What are risk factors for developing asthma?
Personal or FHx atopy
Male sex for pre-pubertal asthma
Female sex for persistence of asthma from childhood to adulthood
Respiratory infections in infancy
Exposure to tobacco smoke
Premature birth and low birth weight
Obesity
Social deprivation
Exposure to inhaled particulates
Workplace exposure - flour dust, isocyanates etc
Whats the prognosis of asthma?
Male children are more likely to grow out of asthma in the transition to adulthood
The earlier the onset of asthma the better the prognosis however early-onset asthma in atopic children may be associated with a worse prognosis
What are complications of asthma?
Death
Respiratory complications - irreversible airway changes, pneumonia, pulmonary collapse, respiratory failure, pneumothorax and status asthmaticus
Impaired quality of life e.g. fatigue or underperformance and time off school/work
What is status asthmaticus?
repeated asthma attacks without respite, or non-response to appropriate treatment
Outline the pathophysiology of asthma?
EARLY PHASE
Type 1 hypersensitivity reaction - initial sensitisation to allergen -> production of CD4 Th2 cells -> release of IL4 and IL5 -> environmental trigger -> cross‐linking of IgE on the mast cell surface -> release of histamine and production of prostaglandins, leukotrienes, and other enzymes -> eosinophils and mast cells release inflammatory mediators in bronchial walls -> inflammation -> smooth muscle in bronchioles spasm and mucus production in airways increases + vasodilation of pulmonary vascular use increases capillary permeability = oedema
LATE PHASE - delayed by hours
APCs may present a variety of allergenic antigens to chronically activated T helper cells. These cells then secrete multiple cytokines that maintain and intensify the local inflammatory response. Many other inflammatory cells, including mast cells and eosinophils, will respond to the T cells’ cytokines. These inflammatory cells will produce cytokines, which amplify the cellular response and the inflammatory reaction. There is a migration of inflammatory cells from the circulation into the pulmonary vasculature and the airway submucosa. inflammation = intermittent airflow obstruction
CHRONIC
After persistent chronic inflammation the airways lay down fibrous tissue and overtime airway remodelling occurs and manifests as fixed airway obstruction
Whats the pathophysiology of aspirin-induced asthma?
Aspirin inhibits COX-1 which leads to a decrease in prostaglandins and causes an increase in activity in the lipooxygenase pathway which synthesises leukotrienes. = bronchospasms, increased vascular permeability and increased mucin production
What are symptoms of asthma?
Cough
Dyspnoea
Chest tightness
Expiratory wheeze
How do asthma symptoms tend to vary throughout the day?
They are commonly episodic, diurnal (worse at night/early morning) and triggered by exercise, viral infection and exposure to cold air/allergens
What wheeze is typically heard in asthma?
Expiratory polyphonic wheeze - multiple pitches and tones heard over different areas of the lung
Bilateral and wide spread
What are high risk occupations for occupational asthma?
Paint spraying or foam moulding using adhesives - isocyanates
Baking - flour
Wood work - wood dust
Welding - fumes, mists
Healthcare settings - latex, vapours from surgical techniques
Agricultural - grain and poultry dusts
What questions can you ask to assess occupational asthma?
Are symptoms better on days away from work?
Are symptoms better when on holiday?
What are the NICE guidelines for diagnosing asthma?
The advice is to not make a diagnosis clinically without testing once the pt is 5 or older (unlike BTS)
Investigations:
- FeNO
- spirometer with bronchodilator reversibility
And if there is diagnostic uncertainty then peak flow variability and direct bronchial challenge test can be done
What is FeNO?
A device that measures fractional exhaled nitric oxide in the breath of pt
One of the type of nitric oxide is inducible and levels tend to rise in inflammatory cells, particularly eosinophils so the levels typically correlate with levels of inflammation
FeNO> 40ppb is considered positive in adults (35 in children)
How is spirometry useful for diagnosing asthma?
A decreased FEV1/FVC ratio i.e. <70 (obstructive!)
However a normal spirometry result when the person is asymptomatic does not rule out asthma
How do you carry out spirometry with bronchodilator reversibility?
Spirometry is done
You use a reliever inhaler (beta 2 agonist or corticosteroids), wait 15-20 minutes and carry out another spirometry test
How should you interpret the results of bronchodilator revsibility testing?
FEV1 improvement of 12% or more, together with an increase in volume of at least 200mL in response to the bronchodilator is a positive result
An improvement of >400mL in FEV1 is strongly suggested of asthma
When should you offer variable peak expiratory flow to help diagnose asthma?
If the person has normal spirometry or obstructive spirometry and positive BDR with a FeNO level of 39ppb or less
How do you calculate peak flow expiratory variability?
the difference between the highest and lowest readings expressed as a percentage of the average PEF.
How do you use variable peak expiratory flow readings to diagnose asthma?
Pt does peak flow readings at least twice a day (morning and evening) for 2-4 weeks
A value of >20% variability is regarded as a positive result
What is a direct bronchial challenge test?
Pt inhales nebulised histamine or methacholine which provokes bronchoconstriction
eople with pre-existing airway hyperreactivity, such as asthmatics, will react to lower doses of drug.
A provocative concentration causing a 20% drop in FEV1 of 8mg/ml or less is regarded as a positive result
When is direct bronchial challenge test offered?
If diagnostic uncertainty after normal spirometry and either FeNO of 40ppb or more and no variability in peak flow readings OR FeNO of 39ppb or less with variability in peak flow readings
When do you diagnose symptomatic asthmatics?
If there is FeNO of 40ppb or more with either positive bronchodilator reversibility, positive peak flow variability or bronchial hyperreactivity
Or if there is FeNO of 25-39ppb and a positive bronchial challenge test
OR if there is a positive bronchodilator reversibility and positive peak flow variability regardless of FeNO level
How is occupational asthma diagnosed?
Serial measurements of peak expiratory flow are recommended at work and away from work
What are differential diagnoses for asthma?
Bronchiectasis
COPD
Ciliary dyskinesia
Cystic fibrosis
Dysfunctional breathing
Foreign body aspiration
GORD
HF
Interstitial lung disease
Lung cancer
Pertussis
PE
TB
Vocal cord dysfunction
Upper airway cough syndrome
What is complete control of asthma defined as?
No daytime symptoms.
No night-time waking due to asthma.
No need for rescue medication.
No asthma attacks.
No limitations on activity including exercise.
Normal lung function (FEV1 and/or PEF > 80% predicted or best)
Minimal SE from meds
How should you assess a persons baseline asthma status before starting treatment?
Using a validated questionnaire such as the Asthma Control Questionnaire or the Asthma Control Test, and/or lung function tests
When should you arrange specialist referral for asthma?
If occupational asthma is suspected
If a direct bronchial challenge test is needed for diagnosis
If pt needs prophylactic oral antibiotics
If pt experiences 2 asthma attacks within 12 months
How should you manage new asthma diagnosis non-pharmacologically?
Assess person’s baseline asthma status using a questionnaire
Provide self management education and a personalised asthma action plan
Ensure pt has all routine vaccinations
Provide information about sources of information and support
Advise pt to avoid asthma triggering factors
Provide advice on weight loss and smoking cessation
Assess for presence of anxiety or depression
Ensure pt has their own peak flow meter
What is a personalised asthma action plan?
It’s a sheet that explains medications, how to cut risk of asthma attack, what to do if asthma symptoms get worse and the emergency action to take if you’re having an asthma attack
The pt takes it to all asthma appointments
Where can you direct patients for advice, support and information on asthma?
British Lung Foundation
Asthma UK
NHS
What medical management is given for new diagnosis of asthma?
1- SABA when needed
2 - add low-dose ICS daily
3 - SABA + low dose ICS + Leukotriene receptor antagonist
4 - SABA + low-dose ICS + LABA + LTRA
5 - SABA +/- LTRA + maintenance and relieve therapy
6- SABA +/- LTRA + medium dose ICS MART
7 - SABA +/- LTRA + (increase ICS to highest dose or trials an additional drug or seek advice from specialist)
After any medication adjustments in asthma how long should you wait to review the response to treatment?
4-8 weeks