Asthma a Clinical Perspective Flashcards
What is the epidemiological burden of asthma?
1,000 deaths a year from asthma - most of which are preventable
9-10% of adults have asthma in the UK
35% of adults with asthma have had an attack within the last year
Costs the NHS £1bn per year.
What is the clinical definition of asthma?
Chronic inflammatory conditions of the airways, characterised by bronchial hypersensitivity to variety of stimuli leading to variable airway obstruction from mainly bronchoconstriction.
What level of variation in symptoms is characterisic of asthma?
A PEFR variation of more than 20%.
What is the basic pathological description of asthma?
(allergic)
Chronic eosinophilic bronchitis
Airwayf inflammation with cellular infiltrate by Th2, mast cells and eosinophils
Large and small airway involvement
Cytokine production - PAF, IL5 and leukotrines contribute to inflammation and airway remodelling.
What are some different phenotypes of asthma?
Cough variant - cough is only symptoms
Eosinophilic - type 2 response, with eosinophil infiltrate
Non-eosinophilic - severe, absent eosinophils, harder to treat
Occupational - exposure to inhaled irritants at work
Chronic asthma with fixed airflow obstruction - may be a result of COPD overlap
Exercise-induced bronchospasm - narrow when exercise.
What causes the airway obstruction in asthma?
Inflammatory cell infiltration
Mucus hypersecretion and plugging
Smoot muscle contraction.
What are the long term changes seen in smooth muscle in asthmatics?
Hypertrophy
Hyperplasia
Leads to thickened smooth muscle layers in the bronchi.
Apply Pouiselles law to asthma.
Asthma leads to a reduction in the diameter of the airway lumen
R = 1/r4
Small reduction in airway radius leads a large reduction in resistance to airflow (x factor of 4 )
How common is misdiagnosis of asthmatics?
1/3 are misdiagnosed
How does gender influence asthma?
More common in boys than girls
As adults higher prevalence and higher mortality in women compared to men.
What are some potential triggers to asthma?
Weather
LRTi - influenze, RSV, parainfluenza
Food
Pollution
Cigarette smoke
Emotion.stress
Mould/damo
Pets
Exercise
Dust
Pollen
Drugs including NSAIDs
How does acute asthma present?
SOB
Cough +/- green phlegm
Chest pain/tightness
Difficulty completing sentences
Wheeze.
How does chronic asthma present?
Coughing and wheezing - most common in childhood
Breathlessness, chest tightness or pressure, may also have chest pain
Poor school performance and fatigue may indicate from sleep deprivation from nocturnal symptoms.
What investigations should be orders when a patient presents with an acute exacerbation of asthma?
ABC
PEFR
Chest X-ray
Bloods - eosinophil, wbc, CRP,
ABG
What are the diagnostic criteria for moderate acute asthma?
Increasing symptoms
PEF 50-70% best or predicated
no features of acute severe asthma
What is the diagnostic criteria for acute severe asthma?
PEF 33-50% best or predicted
Respiratory rate of 25 bpm or more
Heart rate of 110 bpm
Inability to complete sentences in one breath.
What is the diagnostic criteria for life threatening asthma?
May present with any one of
PEF 33% or below of best or predicted
SpO2 less than 92%
PaO2 - less than 8kPa
Normal PaCO2
Silent chest
Cyanosis
Poor respiratory effort
Arrythmia
Exhasation
Altered consciousness level
Hypotension.
What is the diagnostic criteria of near fatal asthma?
Raised PaCO2 and/or requiring mechanical ventilation with raised inflation pressures.