Acute Asthma Flashcards
Asthma is a common obstructive chronic respiratory condition.
What is asthma characterised by?
Asthma is characterised by recurrent episodes of dyspnoea, cough and wheeze caused by a reversible airway obstruction.
What are the 3 main underlying pathology in asthma which lead to airway narrowing?
- Bronchial muscle contraction triggered by various stimuli => airflow limitation
- Mucosal inflammation caused by mast cell and basophil degranulation resulting in the release of inflammatory mediators
- Increased mucus production
* In chronic asthma inflammation may be accompanied with irreversible airflow limitation due to airway wall remodelling.
Who does asthma affect?
Asthma commonly starts in childhood between 3-5 years => may worsen or improve during adolescence.
Westernised life-style / Developed countries
What is the atopic triad?
Who does this commonly affect?
Atopic triad:
=> Atopic Dermatitis,
=> Atopic Asthma,
=> Allergic Rhinitis
Atopic asthma is a childhood onset wheezing illness caused by inhaled allergic triggers.
What are the most common allergens in atopic asthma?
Dust mite
Animal danders particularly cats
Pollens
Fungi
Which age group does non-atopic asthma affect?
What extrinsic factors lead to asthma in this?
Middle aged individuals
Extrinsic causes:
Sensitisation to occupational agents
Intolerance to NSAIDs
Beta-adrenoreceptor blocking meds => block protective effect of endogenous catecholamines.
*Extrinsic causes must be considered in all cases of asthma and avoided.
What are the underlying theories behind allergic asthma?
Explain hygiene hypothesis in detail.
- Early childhood exposure to allergens and maternal smoking = major influence in IgE production
- Hygiene hypothesis: growing up in a ‘clean’ environment predispose towards IgE response to allergies
Conversely, growing up in a ‘dirtier’ environment allows the immune system to avoid allergic response
=> early life exposure to inhaled and ingested products of micro-organisms as seen in developing countries => reduces the risk of developing asthma/allergies.
*allergens involved in asthma similar to ones involved in rhinitis
What are the precipitating factors for asthma?
Exercise-induced
Cold air
Smoking & passive smoking
Emotions
Drugs i.e. NSAIDs, beta-adrenoceptor blocker
Environment exposure i.e. pollen, house dust-mite, fur
Irritants, dust, vapour, fumes
Atmospheric pollution
Viral infections i.e. rhinovirus, parainfluenza virus, RSV
Occupational sensitisers
Genetic factors
How does exercise or cold air induce asthma?
Exercise induced wheeze is driven by the release of histamine, prostaglandin and leukotrienes from mast cells.
Why are beta-adrenoceptor blockers contraindicated in asthma?
The airways have a direct parasympathetic innervation to produce broncho-constriction via beta2 receptors.
Non-selective beta-blockers i.e. propranolol => broncho-constriction and reduced airflow therefore, should be avoided in asthma.
Beta-1 receptor blockers may be given i.e. atenolol if needed in asthmatic patients
There are two broad types of occupational sensitisers.
I. Low molecular weight compounds i.e.
=> found in spray painting, welding, electronics industry,
=> wood dust,
=> bleaches and dyes,
=> complex metals i.e. nickel, platinum and chromium.
II. High molecular weight compounds
=> Antibiotics
=> Latex
=> Allergens from animals & insects inc. farmers, poultry workers, seafood processing industry, laboratory workers
INFO CARD
Occupational asthma depends on level of exposure.
Atopic individuals develop occupational asthma more quickly => development of specific IgE antibodies
Non-atopic individuals can also develop occupational asthma when exposed to occupational sensitisers for a longer time than atopic individuals.
What are the signs and symptoms of asthma?
Symptoms:
Wheezing attacks
Intermitted dyspnoea
Cough [nocturnal] => usually predominant feature in children and nocturnal cough may be the presenting symptom
Sputum
Signs:
Tachypnoea
Audible wheeze
Hyper-inflated chest
Hyper-resonant percussion
Reduced air entry
Widespread, polyphonic wheeze
What are the clinical features of a severe attack?
Inability to finish sentences
Pulse >110bpm
Respiratory rate >25/min
Peak expiratory flow: 30-50% predicted
What are the clinical features of a severe life-threatening attack?
Silent chest
Confusion
Exhaustion
Cyanosis <92% O2 sats
Bradycardia
Peak expiratory flow <33% predicted
Near fatal = high CO2
What are the 7 important information to establish during history-taking a suspecting asthma patient?
- Diurnal variation: vary throughout the day but marked peak flow drop is common during morning
- Exercise: quantify tolerance
- Disturbed sleep: quantify as nights per week (sign of severe asthma)
- Acid reflux: 40-60% of people with asthma have reflux => treating it improves spirometry but not symptoms
- Other atopic disease: eczema, hay-fever or family Hx?
- Home (especially bedroom): pets? carpets? feather pillows or duvet? soft furnitures i.e. floor cushions?
- Job: 15% of cases are job related, more for paint sprayers, food processors, welders and animal handlers.
If symptoms get better during weekends or holidays then work may be the trigger => ask patient to measure their peak flow at intervals at work and at home (at the same time of day) to confirm
How is initial diagnosis of asthma made in children?
High probability of asthma => trial asthma treatment
=> if successful, continue at minimum effective dose
=> if unsuccessful, assess inhaler technique/compliance
=> no further improvement = refer
Intermediate probability => lung function tests/atopy
=> if lung function test +ve, start asthma trial
=> if lung function test -ve, investigate/treat other cause/refer
Low probability => consider alternative cause
How is initial diagnosis of asthma made in adults?
Clinical investigation i.e. spirometry or peak flow
High probability of asthma => asthma treatment
=> if successful, continue at minimum effective dose
Intermediate probability
=> FEV1/FVC <0.7 = asthma treatment
=> FEV1/FVC >0.7 = consider alternative cause / refer
