Asthma is a common chronic inflammatory lung disease of the airways characterised by variable, reversible and recurring symptoms, airflow obstruction and bronchospasm.
|Severity||Symptom frequency||Nighttime symptoms||%FEV1 of predicted||FEV1 Variability|
|Intermittent||<1 per week||≤2 per month||≥80%||<20%|
|Mild persistent||>1 per week but <1 per day||>2 per month||≥80%||20–30%|
|Moderate persistent||Daily||>1 per week||60–80%||>30%|
10-15% of population
Total of 300 million worldwide
More common in developed countries = ‘hygiene hypothesis’.
P/c Cough, expiratory wheeze and dyspnoea (nocturnal dyspnoea common), chest tightness, reduced O2 sats, eosinopjillia, mucus plugs, tachycardic/tachypnoeic, reduced breath sounds…
Asthma attack = tachycardia, rhoncus (=course rattling somewhat like snoring caused by bronchila secretions), accessory muscles, intercostals recession, paradoxyical pulse.
- 1. Airflow limitation – which is usually reversible spontaneously or with treatment
- 2. Airway hyperresponsiveness – to a wide range of stimuli
- 3. Inflammation of the bronchi – with eosinophils, T lymphocytes and mast cells with associated plasma exudation (=inflammatory), oedema, marked smooth muscle hypertrophy, mucus plugging and epithelial damage.
- Extrinsic – implying a definite external cause
- o Atopic individuals who show positive skin-prick reactions to common inhalant allergens.
- o Childhood asthma is often accompanied by eczema
- o Cause of late-onset asthma in adults is sensitisation to chemicals or biological products in the workplace
- Intrinsic or cryptogenic – when no causative agent can be identified
- o Often starts in middle age
Respiratory function tests
- Measurements of Peak Expiratory Flow (PEF) on waking prior to taking a bronchodilator and before bed after a bronchodilator.
- Spirometry is useful, especially in assessing reversibility.
Diagnosed by >15% improvement in FEV1 or PEF following the inhalation of a bronchodilator (i.e. REVERSIBLE [labile obstruction]. FIXED IRREVERSIBLE obstruction = COPD).
Aetiology – cause, risk factors
- Occupational sensitisers
- Cold air/exercise/stress
- Atmospheric pollution and irritant dusts, vapours and fumes, animal fur/dander, HDM faeces, pollen, isocyanates (as found in paints and pesticides).
- o NSAIDs (particularly aspirin and propionic acid derivatives). Drugs lead to an imbalance in the metabolism of arachidonic acid due to inhibiting of COX pathway.
- o Beta-blockers. Inhibition of beta2 receptors lead to bronchoconstriction and airflow limitation in asthmatic patients.
Complex – ‘weep and sweep’
Varying clinical severity is dependent on interplay between airway inflammation and airway wall remodelling.
Inflammatory component is driven by Th2-type (CD4+) T lymphocytes which facilitate IgE synthesis.
|1. Occasional symptoms, less frequent than daily||100% predicted||As required bronchodilators (salbutamol PRN). If used more than once daily, move to step 2.|
|2. Daily symptoms||<80% predicted||Anti-inflammatory drugs. Sodium cromoglicate or low-dose inhaled corticosteroids (beclomethasone OD)
If not controlled, move to step 3
|3. Severe symptoms||50-80% predicted (<60% severe)||High-dose inhaled corticosteroids up to 2000ug daily|
|4. Severe symptoms uncontrolled with high-dose inhaled corticosteroids||50-80% predicted||Add regular long-acting beta2 agonists (eg salmeterol – s/s – may inc risk of death in asthma?!)|
|5. Severe symptoms deteriorating||<50% predicted||Add prednisolone 40mg PO daily|
|6. Severe symptoms deteriorating in spite of prednisolone||<30% predicted||Hospital admission|
|Group: SHORT ACTING BETA-2 AGONISTS (increase adrenaline therefore BRONCHODILATE).|
|Mechanism: Used for mild to moderate symptoms of asthma.
|Drug||Side effects –due to increased sympathetic activity|
|Group: LONG ACTING RELIEVERS|
|LONG ACTING BETA2 AGONISTS (LABA’s):
Administered by inhalation.
Add to regular inhaled corticosteroid treatment.
Role in chronic asthma and useful in nocturnal asthma.
Caution in diabetes – risk of ketoacidosis
(mast cell stabaliser = reduce histamine release)
|Discontinue if eosinophilic pneumonia occurs
Block effects of cysteinyl leukotrienes .
May be benefit in exercise-induced asthma and in those with concomitant rhinitis.
|Rarely Churg-Strauss syndrome is seen in association with taking leukotriene modifiers.
|Group: OTHER AGENTS WITH BRONCHODILATOR ACTIVITY|
|Mechanism: more often reserved for COPD|
Used as bronchodilator in asthma and stable COPD
Metabolised in liver.
|Plasma-theophylline concentration is increased in:
Concentration decreased in:
Toxic dose is close to therapeutic dose (TDM required due to narrow TI)
Features with acute severe asthma typically have:
- Inability to complete a sentence in one breath
- RR >25 breaths per minute
- Tachycardia >110 bpm
- PEF <50% of predicted normal or best
Features of life threatening attacks are:
- A silent chest, cyanosis or feeble respiratory effect
- Exhaustion, confusion or coma
- Bradycardia or hypotension
- PEF <30% of predicted normal or best
- SA-BD (beta-2 agonist: salbutamol PRN)inhaled steroid (beclomethasone 200-400mcg/d)leukotriene receptor agonist (monteleukast)refer to respiratory doctors
5-12 years old:
- SA-BD inhaled steroid (beclomethasone 200-400mcg/d)Long acting beta-2 agonist (LABA: salmeterol)leukotriene (monteleukast) or theothyllineinhaled steroid (beclomethasone 800mcg/d)additional daily oral steroid (prednisolone) refer to respiratory doctors
- SA-BD inhaled steroid (beclomethasone 200-800mcg/d)Long acting beta-2 agonist (LABA: salmeterol)leukotriene (monteleukast) or theothyllineinhaled steroid (beclomethasone up to 2000mcg/d)additional daily oral steroid (prednisolone) refer to respiratory doctors