Wheezing and Chronic Asthma in Adults Flashcards
What is the definition of asthma?
A chronic inflammatory disorder of the airway characterised by bronchial hyperreactivity to a variety of stimuli, leading to a variable degree of airway obstruction, some of which may become irreversible over many years
What is the UK prevalence of asthma?
10-15%
What is the pathophysiology of asthma?
Chronic eosinophilic bronchitis/bronchiolitis
Airway inflammation is seen, with cellular infiltration by T2 helper cells, lymphocytes, eosinophils, and mast cells. There is large and small airway involvement, and cytokine production. Degranulation of mast cells releases:
- Chemotactic factors - ECF-A, PAF - causes inflammatory cells to flood into the airways and release inflammatory mediators
- Spasmogens - such as histamine, which causes bronchoconstriction, increased vascular permeability and mucus hypersecretion
https://www.youtube.com/watch?v=fEKc37vrQ_I
Why does airway obstruction occur in asthma?
Combination of:
- Inflammatory cell infiltration
- Mucus hypersecretion with mucus plug formation
- Smooth muscle contraction
What irreversible changes can occur in someone with asthma?
- Basement membrane thickening
- Collagen deposition
- Epithelial desquamation
- Airway remodelling - smooth muscle hypertrophy and hyperplasia
What are proven risk factors for the development of asthma?
- Atopy
- Occupation
- Smoking
What are possible risk factors for the development of asthma?
- Obesity
- Diet
- Reduced exposure to microbes - hygeine hypothesis
- Indoor pollution
- Environmental allergens
What is atopy?
A form of allergy in which there is a hereditary or constitutional tendancy to develop hypersensitivity reactions (e.g. hayfever, asthma, atopic eczema) in respone to allergenes. Individuals with this predisposition - and the conditions provoked in them by contact with allergens - are said to be atopic
In atopic individuals, what is the immunilogical reaction that occurs when exposed to an allergen?
React to antigen challenge by producing specific IgE from B-cells. This leads to the formation of IgE-antigen complexes that bind to mast cells, basophils and macrophages, leading to the release of preformed mediators such as histamine, IL5 and chemotactic factors
What is the hygeine hypothesis?
This suggests that asthma may be a by product of modern first world cleanlines. Early exposure to bacterial endotoxin switches off allergic responses by reducing T2 mediated pathways, and, when this exposure is lost, the likelihood of developing allergic disease such as asthma, increases considerably.
What are the symptoms of asthma?
- Cough
- SOB
- Wheeze
- Chest tightness
What are classical features of the symptoms seen in those with asthma?
- Variable/intermittent
- Worse at night
- Triggered by specific things- pollens, cats, dog dander
- Triggered by non-specific things - cold, perfumes, bleaches
- Episodic attacks
- Can be exercise induced
If someone presented with symptoms of asthma, and you found that there was weekly variation in symptoms, what would you suspect to be the problem?
Occupational asthma
What causes the symptom of wheezing?
Airway narrowing allows airflow-induced oscillation of airway walls, producing acoustic waves. As the airway lumen becomes smaller, the airflow velocity increases, resulting in vibration of the airway wall and the tonal quality.
What phase of the breathing cycle does wheeze normally occur in?
Expiratory phase
What signs might you see on examination in someone with asthma?
- Tachypnoea
- Expiratory wheeze
- Chest deformity/hyperinflation
What is a monophonic wheeze?
A wheeze with a single note that starts and ends at different points in time. The classic example is caused by a tumour in the bronchi. The pitch and timing is fixed as the tumour itself is static.
A child with a fixed foreign body may have a monophonic wheeze.
If, when examining someones chest, you heard the following, what would you think of as part of a DDx?
Wheeze can be heard
- Asthma
- COPD
- Foreign body aspiration
- Respiratory tract infections
When is wheezing regarded as pathological?
On normal quiet expiration or inspiration
What is the correlation between length and pitch of wheeze and degree of obstruction?
Longer and more high pitched the wheeze, the more severe the obstruction is
If someone presented with symptoms of asthma, what else would you ask abou tint the history?
- Nasal symptoms - obstruction, rhinorrhoea, hyposmia
- Atopic dermatitis/eczema
- Hay fever
- Allergies
- Reflux/GORD
- Triggers - exercise, menstruation
- Social situation/stress
- Aspirin sensitivity
- Family history
If you suspected someone had asthma, what test could you initially do?
Simple spirometry
What would be suggestive of an obstructive cause of symptoms on simple spirometry?
- FEV1/FVC <70%
- FEV1 < 80% predicted
What is the diagnosis of asthma based on?
- Symptoms - dry cough, wheeze, dyspnoea
- Day-to day peak flow variation - >15% variability or B2 agonist responsiveness
- Airway hyperresponsiveness
If simple spirometry point towards someone having an obstructive airway disease, what essential investigations would you do?
- Peak flow recording
- Full spirometry
- Bronchodilator reversibility testing
- Steroid reversibility
What is involved in peak flow recording?
https://www.youtube.com/watch?v=jdA8KU_D9JU
Peak expiratory flow rate (PEFR) is a person’s maximum speed of expiration, as measured with a peak flow meter, a small, hand-held device used to monitor a person’s ability to breathe out air.
The patient takes a deep breath in and exhales as rapidly as possible. The rate rises rapidly to reach the peak calue early in exhalation and then declines slowly until exhalation ic complete.
If someone had symptoms of asthma and had normal simple spirometry on admission, what investigations might you consider doing?
- PEFR diary - for 2 weeks
- Methacholine/histamine challenge
- Exhaled nitric oxide testing
What would be the first line management for someone newly diagnosed with asthma?
Step one of BTS guidelines
- Regular preventer - low dose ICS
- Short acting B2 agonist
What is the mechanism of action of ß2 agonists?
β2 agonists work by mimicking the effect of norepinephrine on β2 receptors. This produces sympathetic effects on tissues containing β2 receptors; in this case bronchodilation of the airways
What medications do you add to inhaled SABA’s and ICS in step 2 of the BTS guidelines for treatment of chronic asthma?
Give Add on LABA to ICS and SABA - normally as combihaler
If you were considering starting someone on step 3 of the BTS guidelines for treatment of asthma, what would you do (patient currently on SABA and inhaled corticosteroids, and a LABA)?
Assess control with LABA, then consider increasing steroids or adding additiona therapies
When trailing a LABA as part of step 2/3 of the BTS guidelines for treatment of chronic asthma, how would you proceed if there was a good response to LABA therapy?
Continue with LABA
When trailing a LABA as part of step 3 of the BTS guidelines for treatment of chronic asthma, how would you proceed if there was a benefit to LABA therapy, but the response was inadequate?
Continue with LABA, and increase steroid dose to 800 mcg/day
OR consider
Continue LABA and ICS at same dose and add LTRA, S-R Theophylline or LAMA
When trailing a LABA as part of step 3 of the BTS guidelines for treatment of chronic asthma, how would you proceed if there was no response to LABA therapy?
Stop LABA and increase steroid dose to 800 mcg/day.
If you were considering moving someone to step 4 of the BTS guidelines for treating chronic asthma, what changes/additions to SABA + ICS +/- LABA therapy would you make?
Increase inhaled steroid up to 2000 mcg/day
Addition of a fourth drug
- Leukotriene receptor antagonist
- SR theophylline
- B2 agonist tablet
How do leukotriene receptor antagonists work?
The leukotriene receptor antagonists block the effects of leukotrienes at the LTC4, LTD4 and LTE4 receptors in the airways, decreasing both the early and late responses to inhaled allergens.
What is the action of xanthines?
Administration of xanthines results in dilatation of the airways and is a useful drug in the treatment of airway obstruction (especially asthma). There is also evidence to suggest that xanthines have anti-inflammatory / immunomodulatory and broncho-protective effects that are mediated by other molecular mechanisms.
If you were considering moving to step 5 of the BTS guidelines for the treatment of chronic asthma, what would you change/add to treatment of SABA + ICS +/- LABA + LRA/THEO/B2Tablet?
- Maintain high dose of steroids
- Add daily steroid tablet in the lowest dose
- Consider other treatments - Monoclonal Antibody (Omlizumab)
