Define asthma
Asthma is a chronic inflammatory airway disease characterised by reversible, intermittent airway obstruction and hyper-reactivity
(expiration is the problem not inspiration)
What types of hypersensitivity is associated with asthma?
● Type 1 hypersensitivity
What are the 3 factors that contribute to airway narrowing in asthma?
o Bronchial muscle contraction, triggered by a variety of stimuli
o Mucosal swelling/inflammation, caused by mast cell and basophil degranulation leading to inflammatory mediators
o Increased mucus production
What are the 3 common triggers of airway inflammation/ exacerbate symptoms in asthma?
- Allergies
- Exertion
- Colds
Describe the aetiology of asthma
individuals with a GENETIC SUSCEPTIBILITY who encounter ENVIRONMENTAL EXPOSURES can experience the reversible airflow obstruction (ASTHMA)
What are the non-environmental risk factors for asthma?
- Family history of atopy (allergic rhinitis/hay fever and atopic dermatitis/eczema)
- Atopy (tendency for T lymphocytes to drive production of IgE on exposure to allergens)
- Low birth weight
- Not being breastfed
- Maternal smoking around child
- Antenatal - infection with RSV during pregnancy
- Males (more common pre-pubertal) and females (more common post-puberty)
- Samter’s triad- asthma, recurring nasal polyps, and sensitivity to aspirin/other NSAIDs
What are the environmental risk factors for asthma?
- House dust mites
- Pollen
- Pets
- Cigarette smoke
- Viral respiratory tract infections
- Aspergillus fumigatusspores
- Occupational allergens e.g. flour, spandex, epoxy resin, isocyanates (most common cause found in spray paint and foam moulding )
What are symptoms of asthma can be picked up from the history?
- Episodic history
- intermittent dyspnoea (breathlessness)
- Wheeze
- Breathlessness
- Cough (worse in the morning and at night) -diurnal variation
- Sputum
Summarise the epidemiology of asthma
● Affects 10% of children
● Affects 5% of adults
● Prevalence appears to be increasing
What signs of asthma can be found on physical examination?
- Tachypnoea (abnormally rapid breathing.)
- Use of accessory muscles
- Prolonged expiratory phase
- Polyphonic expiratory wheeze on auscultation
- Hyperinflated chest and hyper-resonant percussion, decreased air entry
- Harrison’s sulcus in chronic asthma (an indentation on the chest roughly along the 6th rib, which is usually bilateral but can also occur unilaterally)
- Pulsus paradoxus- fall of SBP >10mmHg on inspiration, occurs during acute asthma attack
What are the different ways in which an acute attack can be characterized
Based on severity:
1. Moderate:
- Worsening symptoms
- Peak flow 50-75%
- normal speech
- RR < 25
- pulse < 110
2. Severe (any one of)
= Peak flow 33-50%
- RR more than or equal to 25
- HR more than or equal to 110
- Unable to complete sentences in one breath
3. Life-threatening (any one of)
- Reduced conscioussness
- Exhaustion (normal pCO2 in an acute asthma attack indicates exhaustion)
- Arrythmia
- Low BP
- Cyanosis
- Silent chest
- Poor respiratory effort
- Peak flow < 33%
- SpO2 < 92%
- PaO2< 8 KPa
- “Normal” PaCO2
4. Near fatal
one or both:
- High PaCO2
- Mechanical ventilation
What other diseases can be associated with asthma?
Acid reflux (asthma can lead to lower oesophageal sphincter relaxing), polyarteritis nodosa, Churg Strauss syndrome (eosinophilic granulomatosis with polyangitis)
What investigations are used to monitor ACUTE asthma?
- Basic obs (RR and 02sat), pulse oximetry
- Peak expiratory flow and bedside spirometry :
- Moderate: 50-75%
- Severe: 33-50%
- Life-threatening: <33% - Bloods:
- ABG (respiratory failure, acidosis, arterial C02is low in asthma due to hyperventilation, if high transfer to HDU - indicates failing respiratory effort)
- FBC - raised WCC if infective exacerbation, Hb to check for anaemia
- CRP
- U&Es
- Blood and sputum cultures
- Charcot-Leyden crystals are eosinophilic granules present in sputum - CXR- to exclude other diagnoses (e.g. pneumonia, pneumothorax), may see hyperextended chest
What investigations are used to monitor CHRONIC asthma?
-1. FeNO (fractional exhaled nitric oxide):
- FIRST
- Inflammatory cells produce nitric oxide (>40ppb)
- Peak flow: variability > 20%
2. Spirometry :
- FEV1% (FEV1/FVC) <70%
- Bronchodilator Reversibility: 12%
3. PEFR (Peak expiratory flow rate)
- Used if spirometry does NOT show variability
- Often shows diurnal variation
- PEFR varies by at least 20%for 3 days in a week over at least 2 weeks or PEFR increases by at least 20%
4. Airway hyperreactivity testing: histamine or methacholine direct bronchial challenge
5. Allergy testing (skin prick tests and RAST (radioallergosorbent) testing)- for allergic asthma
6. Bloods - check:
- Eosinophilia
- IgE level
- Aspergillus antibody titres
7. Curschmann spirals can be seen on histology, which are where shed epithelium becomes whorled mucous plugs
How is chronic asthma managed?
Start on the step that matches the severity of the patient’s asthma, moving up if needed or down if control is good for >3 months
STEP 1:
● Inhaled short-acting beta-2 agonist e.g. salbutamol used as needed for symptom relief, AND regular inhaled low-dose steroids e.g. beclometasome or Budesonide
● If needed > 1/day or night-time symptoms, then move onto step 2
STEP 2:
● Step 1 + inhaled long-acting beta-2 agonist (LABA) e.g. salmeterol by inhaler
● If benefit but inadequate control with LABA, increase step 1 steroid dose OR add a 4th drug
● If no response to LABA, stop LABA and increase steroid dose
STEP 3: – refer to specialist at this point
● Increase inhaled steroid dose
● Add 4th drug (e.g. leukotriene antagonist (montelukast), slow-release theophylline or beta-2 agonist tablet)
STEP 4:
● Add regular oral steroids – prednisolone at lowest possible dose
● Refer to specialist asthma care
How is an acute asthma attack managed?
- Oxygen (target sats 94-98%)
- Salbutamol Nebulisers
- Ipratropium Bromide Nebulisers
- Oral Prednisolone (or IV Hydrocortisone if severe/if patient unable to swallow)- pts should take 40-50mg prednisolone for > or equal to 5 days following an acute asthma episode
- IV Magnesium Sulfate (only in asthma exacerbation, not COPD)
- NIV shouldn’t be used in acute asthma exacerbations. If needed, mechanical ventilation should be used.
When can a patient be discharged from asthma management?
When:
- PEF > 75% predicted
- Diurnal variation < 25%
- Inhaler technique checked
- Stable on discharge medication for 24 hours
- Patient owns a PEF meter
- Patient has steroid and bronchodilator therapy
- Arrange follow-up
What advice should be given to patients managing their asthma?
- Teach proper inhaler technique
- Explain important of PEFR monitoring and inhaler adherence
- Avoid provoking factors
- Smoking cessation and weight loss
- WRITTEN self-management action plans are an effective way to prevent severe detoriation (self-management and education is very important, zone 1 = well controlled, zone 2 = asthma getting worse, zone 3 = severe, zone 4 = medical alert/emergency)
- Emergency advice in written action plan.
What complications may be associated with asthma?
- Growth retardation
- Chest wall deformity (e.g. pigeon chest - pectus carinatum)
- Recurrent infections
- Pneumothorax
- Respiratory failure
- Death
What is the different between asthma and COPD?
Athma:
- reversible with salbutamol
- usually onset < 35 years
- episodic symptoms
- can be related to atopic history
COPD:
- non- reversible
- usually onset > 35 yeats
- chronic dyspnoea with sputum production
- high relation with smoking (passive/ active) or pollution
What is atopy?
Atopy is a predisposition to an immune response against diverse antigens and allergens
Describe the pathophysiology of asthma
- Allergen/ trigger in environment
- Picked up by APC cells on their MHC II
- The APC activates Th2 cells
- Th2 proliferate and produce the cytokines: IL-4= activation of B cells that release IgE, IL-5= increases eosinophil numbers (inflammation), IL-13= production of mucus
What is the role of IgE in asthma?
- IgE antibodies respond- bind to mast cells and basophils
- Mast cells released cytokines (histamine)
- These cytokines contract the smooth muscle around airways= airway tightening
What are the main 3 targeted interleukins in asthma? what do they do?
IL-4: activation of B cells that released IgE
IL-5: Increases eosinophil numbers
IL-13: production of mucus
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Asthma36
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COPD23
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Respiratory Arrest10
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Respiratory Failure54
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Pneumothorax15
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Pneumonia23
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Tuberculosis15
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Acute bronchitis6
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Allergic disorder11
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Asbestos- related lung disease9
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Bronchiectasis14
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COVID-194
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Fibrotic lung disease10
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Influenza7
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Lower Respiratory Tract Infection9
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Upper respiratory tract infection8
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Occupational lung disease11
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Lung cancer11
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Sarcoidosis6
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Asthma COPD overlap syndrome6
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Developmental delay24
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Toddler Diarrhoea5
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Constipation16
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Cerebral Palsy16
