Clinical features of asthma Flashcards
What is the definition of asthma?
A disease characterised by an increased responsiveness of the trachea and bronchi to various stimuli and manifested by a widespread narrowing of airways that changes in severity either spontaneously or as a result of therapy.
What 2 paths can airway inflammation mediated by the immune system go down?
- Widespread narrowing of airways
- Increased airway reactivity > Airway narrowing > Spontaneously or Stimuli.
Is asthma more common in males or females in children?
More common in males
Is asthma more common in males or females in adults?
More common in females
What are proven risk factors for asthma?
- Genetic: Atopy
- Occupation
- Smoking
Features of Atopy in asthma
- Inherited tendency to IgE response to allergens.
- Strongest risk factor: personal, familial atopic tendency, Maternal atopy most influential.
Which two groups of genetic association genes are linked to asthma?
- Immune response genes: IL-4, IL-5, IgE
2. airway genes: ADAM33
What changes can maternal during pregnancy cause?
- Decreased FEV1
- Wheezy illness
- Increased responsiveness
- Increased asthma and severity
What are possible risk factors for asthma?
- Obesity
- Diet
- Reduced exposure to microbes/microbial products.
- Indoor pollution: chemical household products
Clinical aspects of asthma
- It is a reversible obstruction
- Daily symptom variability
- Family history
- No smoking
- Allergy, rhinitis, eczema maybe.
What is the most important aspect when diagnosing asthma?
HISTORY
Symptoms: wheeze, short of breath (dyspnoea), severity chest tightness (pain), cough, paroxysmal, usually dry sputum.
What are evidence of variable symptoms?
- Triggers :exercise, cold air, smoke, perfume, URTI’s, pets, tree, grass pollen, food, aspirin.
- Daily/ weekly/ Annually variation
- PMH
- Drugs
- FMH
- PSH
What examination findings is usually unhelpful in clinic?
- Breathless on exertion
- Hyperexpanded chest
- Polyphonic wheezes
What findings mean its probably not asthma?
- Clubbing, cervical lymphadenopathy
- Stridor- hard inspiratory wheeze, blocking of trachea or proximal bronchi.
- Assymetrical expansion
- Dull percussion note
- Crepitations
What evidence are you looking for in an essential investigation for asthma?
- Airflow obstruction
- Variability and/or reversibility of airflow obstruction
Examples of essential investigations for asthma?
- If obstructed: Full pulmonary function testing
- Reversibility to bronchodilator
- Reversibility to oral corticosteroids
- If normal spirometry: variability to airflow obstruction.
Features of full pulmonary function testing
- Effectively excluding COPD/emphysema
- Lung volumes (helium dilution)
- Carbon monoxide gas transfer (transfer of CO to Hb across alveoli)
Features of reversibility to bronchodilator
- Response to bronchodilator
- Significant reversibility: FEV1>200ml & FEV1>15% baseline
- no bronchoconstriction, no reversibility
- severe bronchoconstriction, no reversibility
Features of reversibility to corticosteroids
- Response to corticosteroids (anti-inflammatory)
- Useful if obstructed, reversibility, variability.
- Separates COPD from asthma
Features of airflow obstruction
Analysis subjective:
- morning/nocturnal dips
- decline over weeks/days
- variability > 20%
Diagnosis of occupational asthma
- Suspicion from work related symptoms.
- Working with recognised occupational sensitiser
- Confirmation- serial peak flow readings, antibodies, bronchial challenge, positive response to colophony.
Specialist investigations for asthma
- Airways responsiveness to methacholine/histamine.
- Exhaled nitric oxide (NO)
Give substances that you know will cause bronchoconstriction
Useful investigations for asthma
- Chest X-Ray
- Skin prick testing (atopic status)
- Total and specific IgE (atopic status)
- Full blood count
Moderate symptoms of asthma
- Able to speak, complete sentences
- HR <110
- RR <25
- PEF 50 - 75% predicted or best
- SaO2 > 92% (no need for ABG)
- PaO2 > 8kPa
