Asthma Flashcards
What is Asthma?
Chronic inflammatory disease of the small airways with:
- intermittent airway obstruction (due to bronchoconstriction)
- hyper-reactivity
- variable expiratory airflow limitation
Inflammation reversible (spontaneously/with treatment)
What is the inflammatory reaction that occurs and what cells and signalling molecules are used?
- macrophage presents antigen to Th2 cell (T lymphocyte)
- Th2 cell releases cytokines- amplify immune response which attract inflammatory cells
- Mast cells - release histamine, prostaglandins, leukotrienes, cytokines
- Eosinophils - leukotrienes and cytokines
- B cells - IgE antibody to the allergen
- Airway epithelial damage – shedding and
subepithelial fibrosis, basement membrane
thickening - Mucus plugging in fatal and severe asthma
What are the 2 types of responses seen in asthma?
Immediate response - type 1 hypersensitivity reaction to a trigger
- <20 mins in duration
- Bronchoconstriction
Late phase response- type 4 hypersensitivity reaction
- 3-12 hrs after immediate
- Airway inflammation
- mucosal swelling
- thickened bronchial walls
- mucus overproduction
- bronchoconstriction
- epithelium shedding- thicker mucus
What does poor long term control cause ?
- smooth muscle hyperplasia and hypertrophy
- Increased numbers of mucus secreting goblet cells
- Thickening of basement membrane
Main triggers of asthma ?
- Infections
- Cold
- Allergen- pets, HDM, Pollen
- Stress
- Exercise
- Occupational irritants
- Smoking
- Drugs- aspirin and beta blockers
Differentials for Asthma
COPD
Pulmonary fibrosis
Pneumothorax
PE
Infection- Bronchitis- can cause wheeze
Allergy
Cardiac disease
How does it present and symptoms ?
- Episodic symptoms
- Dry cough typically worse at night
- Wheeze and SOB
- Chest tightness
- History of atopic conditions like eczema or hayfever
- Family history of asthma
What signs do you find on examination ?
- Expiratory wheeze on auscultation
-reduced peak expiratory flow rate (PEFR) - Increased RR
- Tachycardia
- Decreased oxygen sats
What investigations would you do ?
All should have:
- Spirometry with reversibility testing
- Fractional exhaled nitric oxide
- Peak flow variability
- CXR
- FBC
If spirometry or Peak flow do not show reversibility and variability:
- Direct bronchial challenge with histamine or methacholine
What are typical spirometry results ?
- FEV1 - significantly reduced
- FVC normal
- FEV1% (FEV1/FVC) < 70% (obstructive)
- Reversibility testing with bronchodilator
- in adults, a positive test is indicated by animprovement in FEV1 of 12% or moreand increase in volume of 200 ml or more
- in children, a positive test is indicated by animprovement in FEV1 of 12% or more
When is fractional exhaled nitric oxide test used?
- Should be performed if equipment is available.
- NICE recommend a FeNO test for all adults with suspected asthma
- FeNO can be used as part of the diagnostic process in people with an intermediate probability of asthma, although it is not essential
- FeNo testing can be used to follow patients over time, monitor adherence to treatment, and to guide treatment decisions
fractional exhaled nitric oxide test how does it work?
- nitric oxide is produced by 3 types of nitric oxide synthases (NOS).
- one of the types is inducible (iNOS) and levels tend to rise in inflammatory cells, particularly eosinophils
- levels of NO therefore typically correlate with levels of inflammation.
- FeNO values
- in adults level of >= 40 parts per billion (ppb) is considered positive
- in children a level of >= 35 parts per billion (ppb) is considered positive
BTS guidelines on when to treat asthma and what probability must it be for investigations?
- High probability of asthma clinically: Try treatment
- Intermediate probability of asthma: Perform spirometry with reversibility testing
- Low probability of asthma: Consider referral and investigating for other causes
Management of chronic asthma: overview
- Avoid and remove triggers- secondary prevention
- Advise exercise
- Smoking cessation
- Use self-management plan
- Pharmacological- secondary prevention
- Assess and teach inhaler technique
- Yearly flu jab
- Yearly asthma review
Pharmacological treatment of chronic asthma: step wise approach
Step 1: SABA- salbutamol- reliever
Step 2: ICS (are considered if using b2 agonist 3x a week, symptomatic ≥3x a week, waking one night a week with symptoms)
Step 3: ICS and LABA- salmeterol
Step 4: Increase ICS to high dose or Add Leukotriene receptor antagonist (montelukast)
Step 5: Specialist care, LAMA (tiotropium), oral theophylline or oral steroids
