Asthma Flashcards
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
