Asthma is…
a chronic inflammatory condition of the respiratory system, causing obstruction from mucosal oedema, increase in mucus secretions and bronchospasm.
How many causes of asthma are there?
2 - intrinsic and extrinsic
What is an EXTRINSIC cause of asthma?
- Inflammation mediated by systemic IgE production.
- Caused by foreign bodies such as pollen and dust mites
What is an INTRINSIC cause of asthma?
- Inflammation mediated by localised IgE production
- Triggers unknown, can include exercise, smoking, cold air
- Triggers stimulate parasympathetic response, causing afferent nerves to be stimulated.
- Acetylcholine is released from the efferent nerve endings under the lining of the bronchus causing bronchoconstriction
Phase 1 of the two-phase reaction
Occurs within minutes
- Allergen enters mucous membrane
- Allergen engulfed by dendritic cells, e.g. macrophages
- Dendritic cells bring allergen antigen to T-helper 2 cells
- TH2 releases IL-4 (interleukins) and IL-5
- IL-4: activates plasma cells; stimulating to produce Ig-E antibodies which bind to mast cells
- IL-5: activates eosinophil
Phase 2 of the two-phase reaction
Occurs in 6-8 hours
- Allergen enters mucous membranes
- Allergen antigens bind to Ig-E antibodies on mast cells causing them to degranulate
- Mast cells release inflammatory mediators Histamine and Leukotrienes
- Activated eosinophils release Leukotrienes, proteases and cytokines
- Leukotrienes and cytokines attract WBC
- Histamines and leukotrienes cause; bronchoconstriction
- increase capillary permeability results in increase mucous production
- mucosa fills with fluid, eosinophils and inflammatory mediators, resulting in inflamed mucosa
- increased vascular permeability
NEAR-FATAL asthma signs and symptoms
Raised PaCO₂ and/ or requiring mechanical ventilation with raised inflation pressures
LIFE-THREATENING asthma signs and symptoms
- Altered GCS
- Exhaustion
- Arrhythmia
- Hypotension
- Cyanosis
- Severe wheeze or ‘Silent Chest’
- Poor respiratory effort
- PEF <33% best or predicted
- SpO₂ <92%
ACUTE SEVERE asthma signs and symptoms
- PEF 33-50% best or predicted
- Inability to complete sentences in one breath
- Tachycardia HR >110
- Increased respiratory rate – tachypnoea RR> 25/min
- Use of accessory muscles
- Shortness of breath – dyspnoea
MILD/MODERATE asthma signs and symptoms
- Able to speak in sentences
- Increasing symptoms
- PEF > 50-75% best or predicted
Differentials to consider for asthma
- Anxiety attack
- COPD
- Anaphylaxis
Risk factors for asthma
- Anaphylaxis
- Previous asthma attacks
- Non-compliance with medication
Assessment order
DRA(c)BCDE
DANGER/mechanism of injury/catastrophic bleeding assessment for asthma
- Assess for any potential dangers
- Remove any potential triggers
- Manage any bleeds
RESPONSE assessment for asthma
AVPU - assess
AIRWAY assessment for asthma
- Clear?
* Correct if compromised (consider step-wise approach to airway management if needed)
C-SPINE assessment for asthma
is this a concern based on MOI?
BREATHING assessment for asthma
• Respiration rate? • Wheeze? (What you looking for?) • Accessory muscle use? • Equal and bilateral air entry? • Gain a Peak Expiratory Flow Rate • Assist with ventilation if required (What about Rate/Rhythm/Depth of breathing? What about IPAP? Thorough respiratory assessment.)
CIRCULATION assessment for asthma
- Heart rate?
- Palpable radial pulse?
- Capillary refill?
- Oxygen saturations?
- Blood pressure?
- Skin colour- cyanosis
DISABILITY assessment for asthma
- Temperature
- Blood glucose
- PEARL
- 12 lead ECG
- Alerted GCS? PEFR?
Treatment of asthma
Treat as per JRCALC
- Correct any ABC problems immediately
Stepwise Approach for Asthma Treatment (Mild to Near-Fatal)
- Move patient to a calm, quiet environment
- Encourage use of own inhalers
- Administer high levels of O2 (what saturations you looking for?)
- Administer nebulised salbutamol (5mg – 6/8 litres per minute – no max)
- If no improvement – administer nebulised ipratropium bromide (500mcg – 6/8 litres – max 500mcg)
- Administer hydrocortisone (100mg injected over 2 mins – max 100mg)
- Continuous salbutamol nebulisation (unless clinical side effects occur) or if not clinically indicated.
- Administer adrenaline IM (1:100 – 500mcg – no max)
- Assess for bilateral tension pneumothorax and treat if present
- Pre-alert and convey to A&E with continuous management, treatment and assessment.
What is the nebulised salbutamol dosage for asthma?
5mg – 6/8 litres per minute – no max
What is the nebulised ipratropium bromide dosage for asthma?
500mcg – 6/8 litres – max 500mcg
