Asthma Flashcards
Name 4 things chronic asthma is characterised by
- reversible airflow obstruction
- Increase in airway hypperactivity causing bronchoconstriction
- Airway wall inflammation
- Long term structural changes may occur due to chronic inflammation
Name 2 histology features you would see in an asthmatic lung
- More mucus glands: damaged epithelium
2. Thickened/Hypertrophic basement membrane and airway smooth muscle
Which type of asthma (extrinsic or intrinsic) is more common? What are 3 features?
Extrinsic:
- Early onset triggered by environmental allergens
- Often a family history
- Raised IgE and immediate type 1 hypersensitivity reaction to the allergen on skin
What happens in the early, late and prolonged hyperactivity phase of extrinsic asthma?
Early: 15 minutes
Allergen crosslinks 2 IgEs on a MAST cell which then degranulates releasing histamine
Late: Hours
Inflammatory mediators from MAST cells activate macrophages and chemotaxis of PMNs and eosinophils into the mucosa lining the bronchia: release histamine, prostaglandin and PAF
Hyperactivity: Days
Exaggerated response in airways, inflammatory cells in bronchial walls continue damaging epithelial cells
Which age group is likely to have intrinsic asthma? Name 3 things that can induce it
More common in adults, can be induced by excercise, cold or chronic bronchitis
Can perfume cause inflammation?
Perfume is an irritant and can re-trigger symptoms but will not cause them
Name 4 things that can elicit an intial trigger for bronchospasms
- Histamine
- Muscarinic
- Cold air: can cause a bronchospasm through 2 different mechanisms
- Arachadonic acid metabolites
When is asthma most evident in the breathing cycle?
Expiration when the small airways are compressed, often hear a wheeze
When and why would you give an asthmatic patient methacholine?
When measuring responsiveness of the airways; give continous doses of methacholine and measure how much bronchoconstriction occurs with spirometry. Stop when you’ve reached the dose of methacholine that’s made their FEV1 drop by 20%
Can also measure hyper-responsiveness by performing spirometry before exercise with methacholine, making the patient excercise at time intervals and then re-doing spirometry. Then repeat post-bronchodilator
How have researchers justified an increasing prevalence in asthma? Where is it most common?
Although there is a hereditary component, rapid increase indicates environmental triggers such as air pollution, tobacco and fungal spores
More common in developed world
What is the hygiene hypothesis?
Hypothesis that if you’re exposed to more infections as an infant your Th1 becomes active, and theres less chance of your Th2 pathway becoming active and developing asthma, unproved
What are the causal differences between allergic and non allergic asthma?
Allergic asthma: airway inflammation is caused by eosinophils, MAST cells and IgE
Non allergic asthma: (less research done), may be viral induced, ‘aspirin sensitive’ or occupational (welders, farmers, bakers)
When can you diagnose asthma?
If a patient has more than one of the following recurrent symptoms:
- wheeze
- breathlessness
- chest tightness
- cough
- variable airflow obstruction
Describe the tone of an asthmatic wheeze
Polyphonic: Originates in narrowed small airways so has variable intensity and tone
High pitched in expiration and can be on inspiration when severe
What worsens breathlessness in an asthmatic patient, what might occur as a result?
Exercise, worse with acute exacerbation
Tachypnea may occur: Increased resp rate to compensate for decreased tidal volume `
Describe the cough of an asthmatic
Dry, worst a night and exercise induced
What is barrel chest and why does it occur?
Patient’s chest looks like a barrel due to long term obstruction which has caused excessive air to get trapped in the lungs causing hyperinflation
What’s harrison’s sulcus?
A chest wall deformity that morphs the chest wall inward (horizontal lower border of thorax) when patient is trying to use all their respiratory muscles to breathe
Describe the percussion on an asthmatic patient
Hyper-resonant: hollow, high and drum like
Why is peakflow used for monitoring and not diagnosing?
Peak flow is an insensitive indicator of small airway obstruction as there are a wide range of ‘normal values’ in different patients, there’s no ethnicity correction and it’s less reproducible than FEV1
What is often seen in an asthmatic patient’s peak flow over time?
Diurnal variation
What can indicate allergic asthma on a blood test? What else can you analyse?
Eosinophils.
Can also analyse sputum
What asthmatic characteristics are evident on a spirometry graph
Since it’s an obstructive disease you would see a reduced FEV1/FVC ratio and ‘scalloping’ as the expiratory flow rapidly declines and then tapers off
When can spirometry indicate an obstruction?
When the patient is well or unwell (or both)
