Asthma Flashcards
Define asthma
Chronic inflammatory disorder of the airways secondary to a type 1 hypersensitivity reaction
When does asthma typically develop?
Childhood
Common to grow out of asthma
What is the nature of the symptoms of asthma?
Variable, recurring
Manifest as reversible bronchospasm –> airway obstruction
What are risk factors for asthma?
Personal/FH of atopy
Antenatal factors - maternal smoking, viral infection during pregnancy (esp RSV)
Low birth weight
Maternal smoking around child
Exposure to high concentrations of allergens, e.g. HDM
Air pollution
What is the hygiene hypothesis?
Increased risk of asthma + other allergic conditions in developed countries due to reduced exposure to infections preventing normal development of the immune system
What other atopic conditions are you more likely to suffer from if you have asthma?
Atopic dermatitis (eczema) Allergic rhinitis (hayfever)
What ENT condition is asthma associated with?
Nasal polyps
What medication are a lot of asthma patients sensitive to?
Aspirin
What are common examples of occupational allergens?
Isocyanates and flour
What is atopy?
Inherited tendency to IgE response to allergens (food allergy, hayfever, asthma, eczema)
What are symptoms of asthma?
Cough - often worse at night
SoB
Wheeze, chest tightness
What are signs of asthma?
Expiratory wheeze on auscultation
Reduced PEFR
What does spirometry measure?
Volume and flow of air during inhalation and exhalation
What is spirometry useful for?
Distinguishing restrictive from obstructive lung disorders
What are restrictive disorders?
Due to restriction to the lungs, e.g. lung fibrosis
What are obstructive disorders due to?
Obstruction to airflow
What is FEV1?
Forced expiratory volume - volume that has been exhaled at the end of the first second of forced expiration
What is FVC?
Forced vital capacity - volume that has been exhaled after a maximal expiration following a full inspiration
What FVC, FEV1 and FEV1% (FEV1/FVC) are typical of asthma?
FEV1 slightly reduced
FVC normal
FEV1% <70%
What are common asthma triggers?
Exercise Cold air Smoke Perfume URTIs Pets Tree/grass pollen Food Aspirin
What investigations should be done in an adult who is suspected of having asthma?
FEV1/FVC ratio
Peak expiratory flow rate
CXR - exclude other pathologies
if spirometry shows FEV1% <70% –> consider full pulmonary function tests, reversibility with beta-agonist and steroids?
If spirometry normal –> PEFR, then consider bronchial provoaction/nitric oxide
Why can fractional exhaled nitric oxide be useful to measure in asthma?
NO is produced by 3 types of nitric oxide synthases (NOS)
One of these is inducible and levels of it rise in inflammatory cells, esp. eosinophils
SO - levels of NO correlate with levels of inflammation
What does the reversibility to bronchodilator test involve?
Baseline, 15 min post 400ug inhaled salbutamol/post-neb 2.5-5mg salbutamol
Significant reversibility if change in FEV >200ml or FEV >15% baseline
How is reversibility to steroids assessed?
Oral corticosteroids
0.6mg/kg prednisolone for 14 days with baseline and 14 day spirometry
What is the most common cause of occupational asthma?
Isocyanates (common in spray paints/foam moulding)
What is the best way to investigate occupational asthma?
Serial measurements of PEFR at work and away from work
All patients >= 5 years old should have what type of test to confirm a diagnosis of asthma?
Objective tests
What is involved in the diagnostic testing of asthma of someone who is >=17 years?
Are symptoms better when away from work? –> if so refer to specialist on basis it may be occupational asthma
All patients should have spirometry with bronchodilator reversibility test + FeNO test
What is involved in the diagnostic testing of asthma of someone who is 5-16 years?
All patients should have a spirometry with bronchodilator reversibility test
FeNO test should be req if normal spirometry or obstructive spirometry with negative BDR test
What is involved in the diagnostic testing of asthma of someone who is <5 years?
Clinical judgement
What FeNO level is considered positive in adults?
> =40 ppb
What FeNO level is considered positive in kids?
> = 35 ppb
What FEV1/FVC ratio is considered obstructive?
<70%
What is a positive reversibility test in an adult?
FEV1 improvement of 12% or more and increase in vol of 200ml+
What is a positive reversibility test in a child?
Improvement in FEV1 of 12% or more
What is the criteria for moderate acute asthma?
PEFR 50-75% best/predicted
Speech normal
RR <25/min
Pulse <100bpm
What is the criteria for severe acute asthma?
PEFR 33-50% best/predicted
Can’t complete sentences
RR >25/min
Pulse >110bpm
What is the criteria for life-threatening acute asthma?
PEFR <33% best/predicted O2 sats <92% Silent chest, cyanosis or feeble resp effort Bradycardia, dysrhythmia or hypotension Exhaustion, confusion or coma Normal pCO2 indicates exhausation
What is the criteria for severe acute asthma in a child?
SpO2 < 92%
PEF 33-50% best or predicted
Too breathless to talk or feed
Heart rate
>125 (>5 years)
>140 (1-5 years)
Respiratory rate
>30 breaths/min (>5 years)
>40 (1-5 years)
Use of accessory neck musclesWhat is the criteria for life threatening acute asthma in a child?
SpO2 <92% PEF <33% best or predicted Silent chest Poor respiratory effort Agitation Altered consciousness Cyanosis
