Asthma - Full summary Flashcards
What is asthma?
Asthma is an episodic, chronic respiratory disorder, characterised by airway obstruction caused by inflammation and hyper-responsiveness of the bronchial smooth muscle
What are the 2 main classes of asthma?
Type II High (Atopic)
Type II Low (Non-atopic)
What are some common triggers of type II high asthma?
Pollen
Dust mites
Animal dander (FEL D1 proteins in cat saliva)
What are some common triggers of type II low asthma?
Cigarette smoke
Respiratory infection
Response to cold air
Emotional distress
Exercise
What 3 things make up the atopic triad?
Eczema
Allergic rhinitis
Asthma
What occurs in first contact to an allergen in type II high asthma?
The allergen stimulates the release of TSLP from the bronchial epithelium
This activates dendritic cells
This stimulates Th2 and B cells
Th2 cells release Interleukin 4, 5 and 14
This stimulates the release of IgE from B cells
Eosinophils and mast cells take up IgE
What occurs in second contact with an allergen in type II high asthma?
Eosinophils and mast cells release leukotrienes, cytokines and histamines
Mast cells also stimulate the production of arachidonic acid from membrane phospholipids, via the enzyme phospholipase A2
Arachidonic acid is then broken down into leukotrienes
This all causes bronchial smooth muscle inflammation and damages nerve fibres endings, increasing sensitivity of the bronchial smooth muscle
What are some changes that can occur to the bronchioles in chronic asthma?
Hyperplasia and hypertrophy of the smooth muscle
Pulmonary oedema
Increased mucus secretion
Sub-epithelial fibrosis, decreasing lung compliance
What occurs in aspirin sensitive asthma?
Both cyclooxygenase and 5-lipoxygenase breakdown arachidonic acid, COX into prostaglandins and lipoxygenase into leukotrienes
Aspirin blocks the enzyme cyclooxygenase, so more leukotrienes are produced
Leukotrienes stimulate increased mucus production, decreased mucus transport, damage to sensory nerve fibres (C-fibres) and increase contraction of airway smooth muscle
What are some symptoms and signs of asthma?
Intermittent episodes of:
- Dry cough
- Chest tightness
- Dyspnoea
- Diurnal variability
- Expiratory polyphonic wheeze
- Wheezing upon exhalation on auscultation
- Hyperressonance upon percussion
- Family history of atopic conditions
What is the name given to a severe asthma episode?
Status asthmaticus (Asthma attack)
What are some signs of a severe episode of asthma?
The patient may be unable to speak or can only use short phrases
They may be using accessory muscles during breathing
What are some examples of accessory muscles during breathing and what do they do?
Pectoralis major - Pull ribs up and outwards towards the humorous
Pectoralis minor - Pulls ribs 3-5 up towards the coracoid process of the scapula
Sternocleidomastoid - Pulls sternum and clavicle up towards the mastoid process of the temporal bone
Scalenus anterior, medius and posterior - Pulls rubs 1 and 2 up towards the cervical vertebrae
How can the severity of asthma be classified?
Using peak flow measurements
A peak flow metre is used 3 times and the highest measurement is used
The actual score is then divided by the normal score for that persons height, gender, weight and age, all multiplied by 100 to get a percentage normal value
Severity is the determined using the percentage:
>75% - Mild
50-75% - Moderate
33-50% - Severe
<33% - Life threatening
What are some red flag features that may be suggestive of conditions other than asthma?
Prominent systemic features - myalgia, fever, weight loss
Unexpected clinical findings - crackles, finger clubbing, cyanosis
Persistent, non-variale dyspnoea
Chronic sputum production
Unexplained restrictive spirometry
Chest X-ray shadowing
What are some conditions that can mimic asthma?
COPD
Hypersensitivity pneumonitis
Inducible Laryngeal Obstruction (ICO)
Allergic Broncho-Pulmonary Aspergillosis
Dysfunctional breathing
Bronchiolitis
Gastroesophageal reflux disease
Churg-Strauss syndrome
What is hypersensitivity pneumonitis?
A type III and IV hypersensitivity reaction to an air-born allergen
What is Inducible Laryngeal Obstruction?
A condition that results in the adduction of the vocal cords together, resulting in stridor (loud inspiration) and wheezing (Loud expiration)
Patients will often complain of something being stuck in their throat
What are some common triggers of Inducible Laryngeal Obstruction?
Strong smells
Cold air
Smoking
Exercise
What is Allergic broncho-pulmonary aspergillosis?
An allergic response to aspergillum fungus in the lungs, causing mucus plugging and proximal bronchiectasis
It presents with wheezing and high serum levels of IgE and eosinophils
How is allergic broncho-pulmonary aspergillosis usually treated?
Using steroids and possible Itraconazole (Anti-fungal)
How does bronchiolitis usually present?
It usually presents in children under 2 years old, with asthma like symptoms following an upper respiratory infection
How does gastroesophageal reflux disease differ from asthma?
Though Gastroesophageal reflux disease can cause a chronic cough and wheezing, it often occurs in obese adults who will respond well to proton pump inhibitors
What is Churg-Strauss syndrome?
A small vessel vasculitis that, like asthma, is associated with wheezing and eosinophilia, however, unlike asthma, it also causes skin purpura and peripheral neuropathy
