Asthma Flashcards
What is the definition of asthma?
chronic inflammatory airway disease characterised by intermittent airway obstruction and hyper-reactivity.
What are the 2 types of asthma?
- Allergic/ eosinophilic: allergens and atopy
- Non-allergic/ non-eosinophilic: e.g. exercise, cold air and stress
Epidemiology of asthma
- 3 deatsh a day in the UK
- Commonly starts in childhood between the ages 3-5 years and may either worsen or improve during adolescence
- Peak prevalence between 5-15 years
- 60k hospital admissions a year
- 160k diagnosed a year
RFs for asthma
Eczema
Allergic rhinitis
Family history
Allergens
Viral upper respiratory tract infection
Occupational exposure
What is there an excessive reaction from in asthma?
Th2 cells against specific allergens
What do allergens from environmental triggers get picked up by?
picked up by dendritic cells and presented to Th2 cell. This leads to production of cytokines e.g. (IL-3, IL-4, IL-5, IL-10, IL-13)
leads to the production of IgE antibodies which coat mast cells and stimulate them to release granules containing histamines, leukotrienes and prostoglandins
Results in activation of eosinophils which promote immune response by releasing more cytokines and leukotrienes.
What happens minutes after the exposure to allergen?
- Bronchospasm
- leads to constriction of the airway as more mucus is produced in response
What is there an increase of in asthma?
- Vascular permeability + addition of immune cells from the blood.
- A few hours after exposure immune cells release chemical mediators that physically damage the endothelium of lungs.
- Initially inflammatory changes reversible - but over years become irreversible - thickens epithelial basement mebrane reducing airway diameter
What cytokines do the T cells release?
Allergens + microbes and pollutants attack airway epithelial cells releasing dendritic cells
Th17 - IL-17, CXCL8
Th1 - IFNg, TNFa
Both activate neutrophils
Th2 - IL-4, IL-13 (Activates B cells), IL-5
ILC2 - IL-5 (which activates Eosinophil), IL-13 which activates airway smooth muscle cells
What activates TH2 and ILC2 cells?
Cytokines IL-33, 25 and TSLP from airway epithelial cells
Genetic factors of asthma
- Genetic susceptibilitypredisposes patients toairway hyper-responsiveness, triggered by environmental factors such as viral infection, allergens (the main cause in children), cold and exercise
- Genes controlling the production of cytokines IL-3,-4,-5,-9 & -13
- ADAM33 is associated with airway hyper-responsiveness and tissue remodelling
Asthma ages
causes of childhood asthma diagnosed before age 12 are thought to be due to a stronger genetic influence, whereas later onset asthma is more likely to be largely due to environmental factors.
Signs of asthma
- Diurnal PEFR variation: worse at night and early morning
- Dyspnoea and expiratory wheeze due to change from laminar to turbulent flow
-
Samter’s triad
- Nasal polyps
- Aspirin insensitivity
- Asthma
Symptoms of asthma
- Episodic shortness of breath: diurnal variation (worse at night and early morning)
- Dry cough
- Wheeze and ‘chest tightness’
- May be sputum
- History of exposure to a trigger
- Nocturnal symptoms
Primary investigations of asthma:
- Fractional exhaled nitric oxide (FeNO):>40 ppb is positive in adults
-
Spirometry:FEV1/FVC <70% suggests obstruction. If obstruction is found, BDR should be carried out
- Bronchodilator reversibility (BDR): improvement of FEV1 by ≥12%andincrease ≥200ml in volume post-bronchodilator
What other investigations should you consider for asthma?
Peak flow rate
Allergy testing
Chest X-ray
Key drugs in asthma
- SABA(short-acting beta-agonist); e.g. salbutamol
- ICS(inhaled corticosteroid); e.g. beclomethasone.
- LTRA(leukotriene receptor antagonist); e.g. montelukast
- LABA(long-acting beta-agonist); e.g. salmeterol
- MART(maintenance and reliever therapy); this iscombinedfast-acting LABA and ICS for symptomatic relief and maintenance in a single inhaler.
Management of Asthma
- SABA
- SABA + low dose ICS
- SABA + ld ICS + LTRA
- SABA + ld ICS + LABA - consider stopping LTRA depending on response
- SABA +/- LTRA - switch ICS/LABA to MART
- SABA+/-LTRA - increase dose of ICS within MART
- SAVA +/- LTRA + one of the following - increase ICS to high dose or trial and additional drug
Treatment step down and monitoring
- Aim is to use lowest effective doses of medication to manage symptoms
- BTS guidelines recommend stepping down treatment approximatelyevery 3 months
- Patients withstable asthmaare usually reviewed formally on anannual basis, whilst those with recenttreatment escalationor frequent exacerbationsshould be reviewedmore frequently
- A specific step-down regimen isnotdescribed (e.g. step 4 to step 3), but step-down requires consideration of factors such as patient preference, treatment duration and side-effect profile
- Reduction of inhaled corticosteroids: 25-50% at a time
Other things to do with asthma
- Each patient should have an individual asthma self-management programme
- Yearly flu jab
- Yearly asthma review
- Advise exercise and avoid smoking
Complications of asthma
- Asthma exacerbations:typically triggered by an upper respiratory tract infection, pneumonia, or exposure to a trigger, e.g. an allergen or occupational exposure
- Pneumothorax
- Oral thrush: due to steroid medication
What is an asthma exacerbation?
acute or subacute episode of progressive worsening of symptoms of asthma, including shortness of breath, wheezing, cough, and chest tightness.
Epidemiology of asthma
Asthma is responsible for 60,000 admissions in the UK every year
Key triggers of an asthma exacerbation
- Known diagnosis of asthma
- Allergen exposure:pollen, dust mite, pets
- Occupationalexposures:plastics, foam, glue, flour
- Viral infection
- Smokingexposure
- Pollution
- Exercise
General clinical manifestations of asthma exacerbations
- Progressively worsening shortness of breath
- Use of accessory muscles
- Fast respiratory rate (tachypnoea)
- Symmetrical expiratory wheeze on auscultation
- The chest can sound “tight” on auscultation with reduced air entry
Moderate asthma exacerbations
PEFR 50-75%
Severe asthma exacerbation
- PEFR 33-50%
- Respiratory rate ≥ 25
- Heart rate ≥ 110
- Inability to complete sentences in one breath
Life-threatening asthma exacerbation
- PEFR < 33%
- SpO2< 92%
- PO2< 8 kPa
- PCO2normal (4.0-6.0 kPa)
Near fatal asthma exacerbations
High pCO2 (> 6.0 kPa) and/or requiring ventilation with raised inflation pressures.
Investigations of asthma
- Peak flow expiratory rate (PEFR)
- ABG:patients will initially have respiratory alkalosis. Abnormal or high PCO2is an extremely concerning sign as it implies patient is tiring.
- Inflammatory markers:raised CRP and WCC may suggest an infective trigger
- CXR:hyperexpansion +/- a focus of infection
Management of asthma exacerbations
- Moderate asthma: treated in primary care with
- Inhaled salbutamol
- 5-day course of prednisolone
- Severe or life-threatening exacerbation: treatment in hospital
Immediate management of asthma exacerbations
Oxygen:
Nebulised bronchodilators: salbutamol 5mg first line
Ipratropium bromide 0.5mg can be given additionally every 4-6 hours
Corticosteroids:
Prednisolone 40mg
100mg hydrocrotisone IV
If patient does not respond to treatment in asthma what do you do?
- IV bronchodilator:magnesium sulphate (first-line)
- ICU admission:if the patient is not responding to the above therapy, they may need ICU admission for further IV bronchodilation (salbutamol or aminophylline) and possible intubation
Complications of asthma exacerbations
- Intubation:those who fail to respond to medical therapy will require ICU admission and intubation
- Death:respiratory failure can lead to death. Three people die from asthma everyday in the UK
OSHITME for asthma exacerbation
Oxygen
Nebulised salbutamol
IV hydrocortisone/ prednisolone
Ipratropium bromide
IV theophylline
IV MgSO4
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