Asthma

Question 1

Asthma

Answer 1

A chronic respiratory disorder characterised by variable airway obstruction and hyper-responsiveness to stimuli.

Question 2

Reasons for narrowing of airways

Answer 2

• Spasm: Bronchial smooth muscle spasm.
• Swelling: Swelling of bronchial mucosa.
• Secretion: Excess viscous mucus secretion

Question 3

Asthma Symptoms

Answer 3

Wheezing
Shortness of breath
Chest tightness
Dry cough.

Question 4

Asthma Attack

Answer 4

• same symptoms plus
• itching
• Anxiety and sweating

Question 5

Asthma Pathophysiology

Answer 5

• Usually mediated by immunoglobulin E (IgE) and precipitated by an allergic response to an allergen (e.g., pollen, animal dander, polution).
• Leads to the release of inflammatory mediators such as histamine leukotrienes, and prostaglandins, which cause bronchospasm, triggering an asthma attack.
• If untreated, eosinophils, T helper cells and mast cells migrate into the airways.
• Mucus production by goblet cells is plugging the airway and, together with increased airway tone and hyper responsiveness, causes the airway to narrow, further exacerbating symptoms.
• Airway remodelling —chronic inflammation causes bronchial smooth muscle hypertrophy, formation of new vessels and interstitial collagen deposition. Results in persistent airflow obstruction, similar to COPD.
• Lipoxygenase products: Most potent chemical mediators in asthma. Leukotrienes are 1000 times more potent stimulators of bronchial constriction than histamine.
• Asthmatics have an imbalance in arachidonic acid metabolism, leading to relative increases in lipoxygenase products.
• COX is downregulated in favour of LOX leading to ↑leukotrienes.

Question 6

Asthma: Causes and Risk Factors

Answer 6

Th2 dominance
Hygiene hypothesis
Antibiotics - pre or post-natal exposure
No breastfeeding
Early weaning
Obesity
Preservatives - sulphites
Molybdenum deficiency - sulphite sensitivity
Food colourings
Female sex hormone fluctuations

Question 7

Asthma: Causes and Risk Factors - Obesity

Answer 7

Obesity: Increases risk, symptoms and frequency / severity of attacks.
Factors implicated in obese asthma include:
* Lung function: Changes in mechanical properties of lungs and chest wall significantly ↓ lung capacity
* Diets that promote obesity: (↑ saturated fat and sugar, ↑ omega 6:3 , low fibre and antioxidants) increase asthma
* Microbiome changes: Obesity is linked with low Bacteroidetes bacteria (major producer of SCFAs). Alterations in circulating SCFAs increase allergic airway disease.
* Systemic inflammation: ↑ cytokines released from adipose tissue contribute to airway hyper responsiveness and remodelling.

Question 8

Asthma: Causes and Risk Factors - Female sex hormones fluctations

Answer 8

• Raised oestrogen (oestrogen favours Th2)
• HRT
• Perimenstrual asthma a cyclical worsening of asthma during the luteal phase (building of oestrogen) and / or first few days of menstruation.

Question 9

Extrinsic Asthma

Answer 9

Extrinsic (allergic / atopic) asthma (60–90% of cases):
* Involves an IgE mediated response.
* Common triggers include pollen, mould, dust mites, pet dander.

Question 10

Intrisic Asthma

Answer 10

Intrinsic (non-allergic) asthma (10–40% of cases):
* More common in females, typically develops later in life.
* Bronchial reaction, IgE can sometimes be involved.
* Possible triggers cold temperatures, humidity, stress, exercise, pollution, irritants in air such as smoke, and respiratory infections