22/05/2013 by admin | Respiratory



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%
Severe persistent Daily Frequent <60% >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.

Three characteristics:

  1. 1. Airflow limitation – which is usually reversible spontaneously or with treatment
  2. 2. Airway hyperresponsiveness – to a wide range of stimuli
  3. 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.



Divided into:

  1. Extrinsic – implying a definite external cause
    1. o Atopic individuals who show positive skin-prick reactions to common inhalant allergens.
    2. o Childhood asthma is often accompanied by eczema
    3. o Cause of late-onset asthma in adults is sensitisation to chemicals or biological products in the workplace
  2. Intrinsic or cryptogenic – when no causative agent can be identified
    1. o Often starts in middle age



Respiratory function tests

  1. Measurements of Peak Expiratory Flow (PEF) on waking prior to taking a bronchodilator and before bed after a bronchodilator.
  2. 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

  1. Occupational sensitisers
  2. Cold air/exercise/stress
  3. Atmospheric pollution and irritant dusts, vapours and fumes, animal fur/dander, HDM faeces, pollen, isocyanates (as found in paints and pesticides).
  4. Diet
  5. Drugs
    1. 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.
    2. 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.


Drug treatment:

Step PEFR Treatment
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.

Produce bronchodilation.

Drug Side effects –due to increased sympathetic activity


Caution in:

  1. Hyperthyroidism
  2. Cardiovascular disease
  3. Arrhythmias (and ectopy)
  4. QT prolongation
  5. Hypertension
  6. tremor



Drug Side effects

Administered by inhalation.

Add to regular inhaled corticosteroid treatment.

Role in chronic asthma and useful in nocturnal asthma.



Caution in:

  1. Hyperthyroidism
  2. Cardiovascular disease
  3. Arrhythmias
  4. QT prolongation
  5. Hypertension


Caution in diabetes – risk of ketoacidosis

Side effects:

  1. Fine tremor
  2. Muscle cramps
  3. Palpitations



(mast cell stabaliser = reduce histamine release)

Discontinue if eosinophilic pneumonia occurs

  1. Coughing
  2. Transient bronchospasm
  3. Throat irritation



Block effects of cysteinyl leukotrienes .

May be benefit in exercise-induced asthma and in those with concomitant rhinitis.

MONTELUKAST (‘singulair’)



Rarely Churg-Strauss syndrome is seen in association with taking leukotriene modifiers.

  1. Abdominal pain
  2. Thirst
  3. Hyperkinesia
  4. Headache



Mechanism: more often reserved for COPD
Drug Side effects




  1. Benign prostatic hyperplasia
  2. Bladder outflow obstruction
  3. Angle-closure glaucoma


Side effects:

  1. Dry mouth



Used as bronchodilator in asthma and stable COPD

Metabolised in liver.

Plasma-theophylline concentration is increased in:

  1. Heart failure
  2. Cirrhosis
  3. Viral infections
  4. Elderly


Concentration decreased in:

  1. Smokers
  2. Chronic alcoholics
  3. Drugs inducing liver metabolism


Toxic dose is close to therapeutic dose (TDM required due to narrow TI)



Features with acute severe asthma typically have:

  1. Inability to complete a sentence in one breath
  2. RR >25 breaths per minute
  3. Tachycardia >110 bpm
  4. PEF <50% of predicted normal or best


Features of life threatening attacks are:

  1. A silent chest, cyanosis or feeble respiratory effect
  2. Exhaustion, confusion or coma
  3. Bradycardia or hypotension
  4. PEF <30% of predicted normal or best


Management regimens:


  1. 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:

  1. SA-BDinhaled 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



  1. SA-BDinhaled 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 
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