Clinical Aspects Of Airway Disease Flashcards
At what age does asthma occur?
Any
Most common in childhood (3-5yrs)
Is asthma common?
10-15% of UK population
Incidence increasing worldwide
Does asthma have a high mortality?
1000-2000 people/yr die from acute asthma
What 3 factors can bring on asthma?
- Genetic
- Environmental
- Acute
What are the causes and triggers of asthma?
- Environmental allergen e.g. moulds, dust, grass pollen, pet hair
- Viral infections e.g. rhinovirus, parainfluenza virus, RSV
- Cold air
- Emotion
- Irritant vapours & fumes
- Genetic factors
- Drugs e.g. NSAIDs, beta-blockers
- Atmospheric pollution e.g. sulphur dioxide, ozone, particulates
- Exercise
- Occupational sensitizers
What are the 2 types of asthma?
- Extrinsic/atopic: result of inappropriate adaptive immune response to an inhaled Ag so associated with atopy esp. eczema & hayfever (eosinophilic inflammation)
- Intrinsic/non-atopic: triggered by factors not related to allergies so no personal/family history of asthma/atopy (neutrophilic inflammation)
OFTEN OVERLAP
What is the difference between the onsets of the 2 types of asthma?
- Extrinsic/atopic: typical onset in childhood
2. Intrinsic/non-atopic: typical onset in middle age often following an upper airway infection
What are the 2 phases of extrinsic asthma?
Sensitisation
Effector
What is the pathophysiological features of asthma?
Airway obstruction (reversible)
Airway hyperresponsiveness
Airway inflammation
What happens inside the airways in asthma?
- Mucus accumulation due to increased goblet cells in mucosa & hypertrophy of submucosal glands
- Mucus plug with eosinophils & desquamated epithelial cells
- Hypertrophy & hyperplasia of SMCs so muscle layer thickened
- Thickened basement membrane
- Oedema due to dilated blood vessels
- Chronic inflammation due to recruitment of IS cells e.g. eosinophils, macrophages, neutrophils, lymphocytes & mast cells
What nerve reflex is involved in asthma?
Cholinergic reflex
Activated via sensory nerve irritation & causing SM to constrict
What are the 3 phases of asthma pathogenesis?
- Immediate/early: Allergen stimulates IgE production from B cells & IgE-sensitized MCs produce histamine, tryptase, PDG2, LTC4/D4 & PAF which constricts SM
- Late: Th2 cells produce IL-3, IL-5, GM-CSF & TNF whilst eosinophils release ECP + MCP & neutrophils release proteases + PAF -> vascular leak, cell infiltration & mucus secretion
- Re-modelling (chronic): SM hypertrophy, SM/epithelial cell hyperplasia, epithelial damage & BM thickening
What are the main problems of the early/acute and the late/chronic asthma response?
Acute: transient bronchial constriction due to factors released by IgE-sensitized histamine
Chronic: infiltration of inflammatory immune cells like T cells, eosinophils & neutrophils
What is asthma?
Chronic inflammatory condition with often acute exacerbations called “asthma attacks”
Closely associated with ‘atopy’/allergy
What are the symptoms of asthma?
Cough Wheeze Chest tightness SOB Worst at night often
What are signs of asthma during exacerbation?
Difficulty completing sentences Wheeze (audible) Tachypnoea Tachycardia Use of accessory muscles Reduced breath sounds (if severe)
Why do patients with asthma get woken in the morning by wheezing?
Cyclical secretion of steroids i.e. cortisol exacerbate airway narrowing
How is asthma diagnosed?
- Trial of treatment & assess response (can also give irritant e.g. Ag or histamine)
- Reversibility on spirometry before/after salbutamol
- Diurnal variation on peak flow monitoring
- Fractional exhaled NO (FeNO)
BUT NO GOLD STANDARD TEST