Asthma Flashcards
What is asthma?
Chronic inflammatory disease of the airways
- Involves airway inflammation, structural remodelling and contraction of bronchial smooth muscle
What are the key features of asthma?
- Wheeze, SoB, chest tightness and cough that varies over time and in intensity
- Variable expiratory airflow limitation
What makes asthma different from COPD?
The variability of the expiratory airflow
What are structural features of asthmatic airways?
- Bronchial hyper responsiveness
- Mucous cell metaplasia → plugs the airways
- Thickening of the bronchial wall
- Bronchoconstriction
- inflammation
What are the 5 asthma phenotypes?
1) Allergic asthma
2) Non-allergic asthma
3) Late-onset asthma
4) Asthma with fixed airflow limitation
5) Asthma with obesity
Describe the features of allergic asthma
- Most easily recognised
- Usually commences in childhood
- Associated with past/family history of allergic disease
- Usually presents with eosinophilic airway inflammation
- Good response to ICS
Describe the features of non-allergic asthma
- Sputum may be neutrophilic, eosinophilic or with few inflammatory cells
- Less response to ICS bc tend to work on Th2 cells so if this is not present, doesn’t really work
Describe the features of late onset asthma
- More common in women
- Tendency to non allergic phenotype so higher doses of ICS required
Describe the features of asthma with fixed airflow limitation
- Long standing asthma
- Airflow limitation thought to be due to airway wall remodelling rather than inflammation
Describe the features of asthma with obesity
- Prominent respiratory symptoms
- Little eosinophilia
What are the main characteristic features of asthma?
1) Variable airways narrowing → airflow obstruction that is reversible (spontaneously or with treatment)
2) Non-specific airways hyper responsiveness to innocuous stimuli e.g. cold air, irritants, pollutants → bronchoconstriction (airway resistance)
3) Mucosal inflammation
4) Airways remodelling
What decreases after someone with asthma is exposed to a stimulus, and then increases as time goes on?
FEV1
Describe the inflammatory features of an asthmatic airway
1) Inflammatory infiltrate → inflammatory cell recruitment i.e. Th2 cells, mast cells and eosinophils
2) Mucosal oedema → bronchial microvascular leak
3) Mucus hypersecretion → blockage of airways by mucus plugs
4) Bronchial smooth muscle contraction → action of inflammatory mediators
Describe the remodelling features of an asthmatic airway (persistent alterations in airway structure)
1) Epithelial cell damage → leaky epithelium
2) Reticular BM thickening
3) Airway smooth muscle thickening
4) Submucosal mucus gland hypertrophy
What two important roles does the epithelium play in asthma?
Barrier and immunity
What type of hypersensitivity is involved in the early response to asthma?
Type I
What type of hypersensitivity is involved in the late response to asthma?
Type IV
What are the two types of asthma-associated risk factors?
1) Host factors (predisposition)
2) Environmental factors (precipitate asthma exacerbations)
What are host asthma risk factors?
1) Genetic
2) Atopy → positive skin prick tests - type I
What are environmental asthma risk factors?
1) Allergens
2) Occupational sensitisers e.g. vehicle spray painting, baking → occupational asthma
3) Air pollutants
4) Respiratory viruses (common cold)
5) Exercise
6) Drugs e.g. aspirin, NSAIDs
7) Tobacco smoke
What does asthma (airway inflammation, structural remodelling, contraction of bronchial smooth muscle) lead to?
Airways hyper responsiveness and airflow obstruction
What happens during an asthma attack?
Air gets in but the same amount of air can’t get out
What is the most common cause for asthma exacerbations?
Virus → most common = rhinovirus (common cold)
What is a flare up or exacerbation?
An acute or sub-acute worsening of symptoms and lung function compared with the patient’s usual status
What are the steps of management of worsening asthma?
1) Self-management with a written asthma action plan
2) Management in primary care
3) Management in the emergency department and hospital
What patients are at an increased risk of asthma-related death?
1) Any history of near-fatal asthma requiring intubation and ventilation
2) Hospitalisation or emergency care for asthma in last 12 months
3) Not currently using ICS, or poor adherence with ICS
4) Currently using or recently stopped using OCS → indicating severity of recent events
5) Overuse of SABAs, especially if more than 1 canister/month
6) Lack of written asthma action plan
7) History of psychiatric disease or psychosocial problems
8) Confirmed food allergy in patient with asthma
What do you do for patients who are at an increased risk of asthma-related death?
Flag them for more frequent review
Until when do you follow up all patients regularly after an exacerbation?
Until symptoms and lung function returns to normal
Why do you follow up all patients regularly after an exacerbation?
- Patients are at an increased risk during recovery from an exacerbation
- Exacerbations often represent failures in chronic asthma care, and they provide opportunities to review the patient’s asthma care and management
What do you check at a follow up visit from someone who had an asthma exacerbation?
1) The patient’s understanding of the cause of the flare up
2) Modifiable risk factors e.g. smoking
3) Adherence with medications, and understanding of their purpose
4) Reliever should be used as-needed rather than routinely
5) inhaler technique skills
6) Written asthma action plan
In what patients do acute asthma exacerbations frequently occur?
In patients who are not well controlled day-to-day → often due to avoidable factors e.g. poor adherence to ICS, smoking
What does acute asthma treatment consist of?
1) Repeated high dose inhaled (or nebulised) salbutamol ± ipratropium
2) Systemic steroids (oral prednisolone or IV hydrocortisone)
3) Oxygen if reduced O2 saturations
4) IV magnesium as a single dose
What are features of moderate acute asthma?
1) Increasing symptoms
2) PEF > 50-75% best or predicted
3) No features of acute severe asthma
- SATS don’t fall
What are features of acute severe asthma?
Any of one of:
1) PEF 33-50% best or predicted
2) RR > 25
3) HR > 110
4) Inability to complete sentences in one breath
What are features of life-threatening asthma?
1) PEF < 33% best or predicted
2) SpO2 < 92
3) PaO2 < 8 kPa
4) Normal PaCO2 (4.6-6)
5) Silent chest
6) Cyanosis
7) Poor respiratory effort
8) Arrhythmia (cause of death)
9) Exhaustion
10) Altered consciousness level
11) Hypotension
What is near-fatal asthma?
Defined as raised PaCO2 and/or required mechanical ventilation with raised inflation pressures
