Clinical Features of Asthma Flashcards
What is the definition of asthma?
A disease…
Hyperactive bronchi
Various Stimuli
Effect = narrowing of airways
Outline the prevalence of asthma in children and its distribution between the sexes
10-15% M>F
Outline the prevalence of asthma in adults and its distribution between the sexes
5-10% F>M
Describe the morbidity statistics of asthma
1000 deaths per year in UK on average - often >60 years old and have comorbidities
Describe three confirmed risk factors
Genetics, occupation and lifestyle
In atopic asthma, which parent is more likely to have the greater effect on the occurrence in progeny
Maternal atopy is most influential (3X paternal)
What are the genetic associations of atopic asthma?
- IL-4, IL-5 and IgE for immune response genes
- ADAM33 for airway genes
Give a few examples of occupational asthma stimuli
Isocyanates, colophony, Animal urine proteins
What are the proven effects of maternal smoking to the foetus?
- Decreased FEV1
- Increased airway responsiveness
- Increased prevalence and severity of asthma
- Increase in wheezy illness
Describe The Grandmother Effect - how is this explained
Mother smoked = 50% increased risk
Grandmother smoked = 100% increased chance
Both smoked = 150% increased risk
Suggests epigenetic modification of oocytes in grandmother
What are the four possible risk factors for asthma?
Obesity, Diet, Reduced exposure to microbes, Household pollution
What are the presenting symptoms that should indicate asthma?
Wheeze (must be present) Dyspnoea Chest tightness Cough (usually dry) Sputum (occasionally)
List the potential triggers for asthma
Exercise, cold air, smoke, perfume, URTIs, Pets, Trees, Grass pollen, food, aspirin
How can asthma vary?
Daily - worse at morning and night
Weekly - Better at weekends or on holiday
Annual - Environmental
What is the criteria for diagnosis of occupational asthma?
- Suspicion of work related symptoms
- Working with a recognised sensitiser
- Conformation by conclusive peak flow readings (2 hourly 5 day minimum, 2 pairs of exposed/unexposed periods
How can past medical history aid diagnosis of asthma?
Childhood asthma, eczema etc (atopic diseases)
Drug history - current or past inhalers, beta blockers (bronchospasm) and NSAIDs (inflammation) can also increase risk of asthma
How can social history aid diagnosis of asthma?
Smoking, pets, occupation can all contribute to respiratory inflammation
On examination, what can rule out asthma?
Clubbing, cervical lymphadenopathy, stridor, asymmetrical expansion, dull percussion note (indicates lobular collapse - need for effusion) or crepitations (crackling/rattling indicating bronchiectasis)
Tests for FEV1 and FVC are essentially measures for what?
FEV1 - airway diameter
FVC - lung capacity
If FEV1/FVC is below what percentage is a full lung function test ordered?
70%
What does a LFT consist of?
Helium dilution - tests lung volume
CO transfer - tests gas exchange
What is essentially the purpose of a LFT?
Excludes emphysema and COPD
What is the step after ruling out COPD and Emphysema?
Assess reversibility of symptoms
How is sensitivity to bronchodilator measured?
Spirometry done:
15mins afters 400 micrograms inhaled salbutamol
15 mims after 2-2.5 milligrams of nebulised salbutamol
What percentage margin is considered greatly reversed in response to a bronchodilator?
deltaFEV1 >200ml and deltaFEV1 >15% baseline
What type of drug is salbutamol?
B2 agonist
What is the next step in lung investigation after no/little response to B2 agonist?
Reverseability to oral corticosteroids
What is the drug and dosage and duration of the preferred corticosteroid used? How does this help?
0.6 miligrams/kg Prednisolone 14 days; distinguishes COPD from asthma
If all standard investigations come back normal what is the next step?
Specialist investigation -
Response to metacholine/histamine
Exhaled nitric oxide
What are other useful investigations that can be ordered?
Chest X-Ray: Hyperinflation, hyperlucent (decrease in density due to air trapped)
Atopy investigations: skin prick, total and specific IgE, full blood count (eosinophils)
What criteria are used for objective assessment of asthma?
Ability to speak Heart rate Respiratory rate Peak flow Oxygen saturation/ arterial blood gas
