Asthma Flashcards
What is asthma? What contriibutes to airway narrowing?
Recurrent episodes of dyspnoea, cough and wheeze caused by reversible airway obstruction
Airway narrowing occurs due to:
Bronchial muscle contraction
Mucosal swelling/inflammation caused by mast cell and basophil degranulation resulting in release of inflammatory mediators
Increased mucus production
Symptoms of asthma?
Cough - often nocturnal Wheeze Intermittent dyspnoea Sputum Diurnal variation - symptoms/peak flow may vary over the day - marked morning dipping of peak flow reduced exercise tolerace Disturbed sleep May have acid reflex Other atopic disease - eczema, hay fever, allergy or FHx
Precipitants of asthma?
Cold air, exercise, emotion, allergens (house dust mite, pollen, fur) infection, smoking, passive smoking, pollution, NSAIDs, beta blockers
What should you ask about in asthma history?
Precipitants Nocturnal cough - disturbed sleep, pillows Sputum Diurnal variation Exercise tolerance - quantify Acid reflux Other atopic disease - eczema, hay fever, allergy Family history Pets Carpets Days off work/school - may indicate trigger Occupation! Ddx - aspirin/beta blocker
What are signs of asthma?
Tachypnoea Expiratory wheeze on auscultation Reduced PEFT Hyperinflated chest Hyper-resonant percussion Reduced air entry
Signs of severe asthma?
Inability to complete sentences
HR>110bpm
RR>25/min
PEF 33-50% predicted
How is asthma diagnosed?
Spirometry - measures volume and flow of air during exhalation and inhalation Obstructive pattern FEV1<80% FVC - normal or reduced FEV1:FVC < 70%
With bronchodilator reversibility test
All patients should habe a FeNO test
Then trial asthma treatment
If successful continue on minimum effective dose
IF unsuccessful assess inhaler technique/compliance
What tests for acute asthma?
Bedside: PEF Sputum culture Bloods: FBC U&E CRP Cultures ABG
What tests for chronic asthma?
PEF monitoring Spirometry Imaging: CXR - hyperinflation Other: Skin prick test to identify allergens
What are the ddx for airway obstruction?
COPD
Pulmonary oedema
Large airway obstruction - foreign body/ tumour
SVC obstruction - wheeze and dyspnoea not episodic
Pneumothorax
PE
Bronchiectasis
What symptoms lower the probability of asthma?
Dizziness, light-headedness Chronic productive cough without wheeze Normal examination when symtpomatic Change in voice Syntoms only with cold Significant smoking hx Cardiac disease normal PEF when symptomatic
What will spirometry show in asthma? Reversibility testing?
Obstructive pattern
FEV1 < 80%
FVC normal or low
FEV1:FVC ratio < 70%
Reversibility testing
In adults, a positive test is indicated by an improvement in FEV1 of 12% or more and increase in volume of 200 ml or more
In children, a positive test is indicated by an improvement in FEV1 of 12% or more
What are risk factors for asthma?
- personal or family history of atopy
- antenatal factors: maternal smoking, viral -infection during pregnancy (especially RSV)
- low birth weight
- not being breastfed
- maternal smoking around child
- exposure to high concentrations of allergens (e.g. house dust mite)
- air pollution
- ‘hygiene hypothesis’: studies show an increased risk of asthma and other allergic conditions in developed countries. Reduced exposure to infectious agents in childhood prevents normal development of the immune system resulting in a Th2 predominant response
What is the FeNO test?
Franctional exhaled nitric oxide
Nitric oxide is produced by 3 types of nitric oxide synthase
One type is inducible and levels tend to rise in inflammatory cells, particularly eosinophils
Levels of NO typically correlate with levels of inflammation
in adults level of >= 40 parts per billion (ppb) is considered positive
in children a level of >= 35 parts per billion (ppb) is considered positive
How is reversibility tested for?
Bronchodilator reversibility (BDR) test
In adults, a positive test is indicated by an improvement in FEV1 of 12% or more and increase in volume of 200 ml or more
In children, a positive test is indicated by an improvement in FEV1 of 12% or more
