Clinical features of asthma Flashcards
Define asthma
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 are the 3 main characteristics of asthma?
Airflow limitation
Airway hyperresponsiveness to stimuli
Inflammation of the bronchi
What causes the narrowing of airways in asthma?
Inflammation and build up of cellular debris and mucus in the airways. In chronic asthma, there is airway remodelling.
Describe the prevalence of asthma in both children and adults
Children: 10-15%, M>F
Adults: 5-10%, F>M
List some risk factors for asthma
Genetics - atopy
Occupation
Smoking - maternal + grandmother effect
What is atopy?
Atopy is the increased tendency to IgE response to allergens
List some possible risk factors for asthma
Obesity
Diet
Reduced exposure to microbes
Indoor pollution: chemical household products
What environmental agents are linked to atopy and asthma?
House dust mite
Cats
Grass pollen
What are the symptoms of asthma?
Wheeze on expiration SOB Chest tightness Sudden dry cough Sputum occasionally Can be worse at night
Describe some examples of evidence of variable symptoms in asthma
Triggers - cold, smoke, perfume, pets
Daily variation - nocturnal/early morning
Weekly variation - when at work/home only
Annual variation - seasonal allergens
What drugs can increase the severity of asthma?
Aspirin
Beta blockers
NSAIDs
What clinical signs would you seen on examination in asthma patients?
Breathless on exertion
Reversibility of symptoms with treatment
Hyperexpanded chest
Polyphonic wheezes on expiration
What clinical signs on examination would rule out asthma?
Clubbing Cervical lymphadenopathy Stridor Asymmetrical expansion Dull percussion - effusion Crepitations
What investigations would you carry out for asthma?
Full pulmonary function tests Spirometry Carbon monoxide transfer Reversibility to bronchodilator Reversibility to corticosteroids Variability in various peak flow readings CXR - exclude other DD, hyperinflation Skin prick tests Total and specific IgE FBC - eosinophilia in atopy
When is it deemed that reversibility of airflow following the use o bronchodilators is significant enough to diagnose asthma?
FEV1 >200ML
FEV1 >15% baseline
How do you diagnose occupational asthma?
Serial peak flow readings
- every 2 hrs for 5 days
- 2 pairs of exposed vs unexposed periods
Antibodies
Bronchial challenge using nebulised agent
List two specialist investigations for asthma
Airway responsive to metacholine/histamine
Exhaled nitric oxide (higher in asthma)
Describe the effect of metacholine on the airways
When inhaled, it causes the airways to spasm and narrow if asthma is present
How do you assess severe asthma?
Ability to speak HR RR PEF O2 sat/arterial blood gases
Describe moderate asthma
Can speak in full sentence HR <110 RR <25 PEF 50-75% predicted/best SaO2 >92% PaO2 >8kPa
Describe severe asthma
Cant speak in full sentence HR >110 RR >25 PEF 33-50% predicted/best SaO2 > 92% PaO2 > 8kPa
No effect on O2 yet
Describe life threatening asthma
Grunting, impaired consciousness HR >130 RR >25, hypoventilating PEF <33% predicted/best SaO2 < 92% PaO2 < 8kPa Cyanosis, PaCO2 normal but can rise
What are the main differences in asthma in children?
Prevalence and gender : M>F
Severe asthma
Occupational asthma uncommon
What % of UK children are thought to have asthma?
10-15%, 5% on steroids
