Asthma Flashcards
Define asthma
Chronic respiratory condition associated with airway inflammation and hyper-responsiveness leading to REVERSIBLE airflow limitation
Define acute asthma exacerbation
Onset of severe asthma symptoms, which can be life-threatening
Asthma symptoms
Cough, wheeze, chest tightness, and shortness of breath, and variable expiratory airflow limitation, that can vary over time and in intensity.
Asthma triggers
Exercise, allergen or irritant exposure, changes in weather, and viral respiratory infections.
Risk factors
Personal or family history of atopic disease (asthma, eczema, allergic rhinitis, or allergic conjunctivitis)
Respiratory infections in infancy e.g. RSV, rhinovirus
Premature birth and LBW
Obesity
Social deprivation e.g. due to damp housing, fungus, air pollution
Exposure to inhaled particulates
Workplace exposures e.g. flour dus, paint
Exposures to tobacco smoke
Complications of asthma
Death
Respiratory complications — irreversible airway changes, pneumonia, pulmonary collapse (atelectasis caused by mucus plugging of the airways), respiratory failure, pneumothorax, and status asthmaticus
Impaired quality of life e.g. time off work/school, fatigue
Briefly describe the anatomy of the airways from trachea to alveoli
Trachea Primary/main bronchus Secondary bronchi Bronchiole Terminal bronchiole Respiratory bronchiole Alveoli duct Alveolar sac
There are 2 major elements in the pathophysiology: inflammation and airway hyper-responsiveness.
Inflammation and airway hyperresponsiveness
The inflammatory reaction is Th1 or Th2 response?
What is this characterised by?
Th2 lymphocytic response. Th2
CD4+ lymphocytes that secrete IL-4, IL-5, and IL-13, TNF-alpha, and the leukotriene LTB4
Mechanism of mucus hypersecretion, oedema and bronchoconstriction
Allergen binds to IgE on mast cells, causing them to degranulate and release inflammatory mediators and chemotactic factors.
This damages the epithelium and causes decreased ciliary function, which stimulates afferent nerves which increase mucus secretion (glands are also hypertrophied) and bronchoconstriction.
History taking for asthma
Presence of more than one variable symptom of wheeze, cough, breathlessness, and chest tightness.
Episodic
Diurnal (worse at night or in the early morning)
Triggers - exercise, viral infection, exposure to cold air or allergens, emotion/laughter (in children), NSAIDs, beta blockers
Is it better on days off from work/on holidays?
PMH - atopy
DH
FH - atopy
SH - high risk job?
Examination findings
Expiratory polyphonic wheeze
Hyperexpansion of the thorax
Atopic dermatitis, eczema, or other allergic skin conditions
Investigations for asthma
No single diagnostic test
Fractional exhaled nitric oxide (FeNO) testing (40 ppb or higher = positive) Spirometry if symptomatic (FEV1/FVC ratio <70%) Bronchodilator reversibility (improvement in FEV1 of 12% or more, increase in 200ml) Variable peak expiratory flow readings (if diagnostic uncertainty) - 20% variability monitoring twice daily for 2-4 weeks Direct bronchial challenge test with histamine or methacholine (specialist test)
Differential diganoses
Bronchiectasis COPD Ciliary dyskinesia Cystic fibrosis Dysfunctional breathing Foreign body aspiration Gastro-oesophageal reflux Heart failure Interstitial lung disease Lung cancer Pertussis Pulmonary embolism (PE) Tuberculosis Upper airway cough syndrome Vocal cord dysfunction
What is complete control of asthma?
No daytime symptoms.
No night-time waking due to asthma.
No need for rescue medication.
No asthma attacks.
No limitations on activity including exercise.
Normal lung function (FEV1 and/or PEF > 80% predicted or best).
Minimal side-effects from medication.
Non-pharm management of asthma
Assess baseline Provide self-management education and a personalised asthma action plan Ensure up to date with vaccinations Provide sources of info/support Advise on avoiding triggers Provide advice on weight loss and smoking cessation Assess for anxiety or depression Ensure has own peak flow meter Explain when and how to use inhalers
How often should people with asthma be followed up?
At least annually
If undergoing treatment adjustment, review after 4-8 weeks
Differential diagnosis for wheeze
Anaphylaxis Vocal cord dysfunction Foreign body aspiration Bronchiolitis Bronchiectasis COPD Tumour causing obstruction Cardiac asthma
Diagnosis of atopy
Skin-prick tests
Blood eosinophilia of 4% or more
Raised allergen-specific IgE
Salbutamol mechanism of action
Short-acting beta-2 agonist
Stimulate B2 adrenergic receptors causing relaxation of bronchial smooth muscle (increase CAMP) and dilation and opening of the airways, acting within minutes.
Salbutamol major side effects
hypokalaemia, fine tremor, anxiety, palpitations, headache, arrythmias and paradoxical bronchospasm (rare), seizure, acute angle-closure glaucoma
Name two short acting beta 2 agonists
Salbutamol
Terbutaline
LABAs - two examples + duration of action
Salmeterol, formoterol
12 hours
Examples of inhaled corticosteroids + mechanism
Beclomethasone, budesonide, fluticasone
They act over days to decrease bronchial mucosal inflammation
Side effects of inhaled corticosteroids
Oral candidiasis, taste altered, headache, voice alteration
Uncommon - anxiety, paradoxical bronchospasm, cataract, vision blurred
Rare - adrenal suppression, glaucoma, growth retardation, sleep disorder
Oral steroids common side effects
Anxiety; behaviour abnormal; cataract subcapsular; cognitive impairment; Cushing’s syndrome; electrolyte imbalance; fatigue; fluid retention; gastrointestinal discomfort; headache; healing impaired; hirsutism; hypertension; increased risk of infection; menstrual cycle irregularities; mood altered; nausea; osteoporosis; peptic ulcer; psychotic disorder; skin reactions; sleep disorders; weight increased
Montelukast mechanism and side effects
Leukotriene receptor antagonist - blocks the effects of cysteinyl leukotrienes (inflammatory mediators) in the airways by antagonising the CystLT1 receptor
SE: abdominal pain, headache, hyperkinesia (in young children), thirst
Theophylline mechanism and side effects
Phosphodiesterase inhibitor -
reduces bronchoconstriction by increasing CAMP levels
SE: arrhythmias, GI upset, fits
Omalizumab mechanism, route, side effects
Anti-IgE (monoclonal antibody)
Given every 2-4 weeks as sub-cut injections
SE: abdominal pain, arthralgia, headache, injection-site reactions, pyrexia, sinusitis, upper respiratory tract infection
BTS/SIGN guidelines steps in adults (5 steps)
- consider moving up if using 3 doses of SABA or more a week
- SABA as required (continue along with all steps)
- Add low dose ICS
- Add LABA
- Increase to medium dose ICS OR add LRTA
- Refer to specialist
BTS/SIGN guidelines steps in children under 5
- consider moving up if using 3 doses of SABA or more a week
- SABA as required (continue along with all steps)
- Very low dose ICS
- Add LTRA
- Increase ICS to low dose
- Refer to specialist, increase ICS to medium, or add theophylline
- Refer to specialist, consider oral steroid
BTS/SIGN guidelines steps in children over 5
- consider moving up if using 3 doses of SABA or more a week
- SABA as required (continue along with all steps)
- Very low dose ICS
- Add LABA
- Increase ICS to low dose (stop LABA if not helping, consider LTRA trial)
- Refer to specialist, increase ICS to medium, or add theophylline
- Refer to specialist, consider oral steroid
What does FEV1 mean?
Forced expiratory volume - volume that has been exhaled at the end of the first second of forced expiration
What does FVC mean?
Forced vital capacity - volume that has been exhaled after a maximal expiration following a full inspiration
Precipitating factors for asthma attack
- Viral infection
- Dust/house dust mite
- Animal dander
- Pollen
- Smoke/pollution
- Exercise
- Atmospheric conditions e.g. lightening
- Medications – aspirin, NSAIDs
Define moderate acute asthma (3)
Increasing symptoms
PEF >50–75% best or predicted
No features of acute severe asthma
Define acute severe asthma
Any one of:
- PEF 33–50% best or predicted
- respiratory rate ≥25/min
- heart rate ≥110/min
- inability to complete sentences in one breath
Define life-threatening asthma
Any one of:
- PEF <33% best or predicted
- SpO2 <92%
- PaO2 <8 kPa
- normal PaCO2 (4.6–6.0 kPa)
- silent chest
- cyanosis
- poor respiratory effort
- arrhythmia
- exhaustion
- altered conscious level
- hypotension
Define near-fatal asthma
Raised PaCO2 and/or requiring mechanical
ventilation with raised inflation pressures
Indications for admission (acute asthma)
1) If life-threatening or near-fatal asthma attack
2) If severe asthma attack and persisting after initial treatment
When can patients with asthma attacks be discharged?
When peak flow is >75% best or predicted one hour after initial treatment
Treatment of asthma attack
Oxygen (aim 94–98% sats)
Salbutamol nebs (oxygen driven) 5 mg, repeat every 20–30 minutes
Ipratropium bromide nebs 0.5mg 4-6 hourly
Prednisolone 40-50 mg daily for at least 5 days
IV magnesium sulphate - ONLY DONE WITH SENIOR
When to refer acute asthma to ICU
Refer any patient:
- requiring ventilatory support
- with acute severe or life-threatening asthma, who
is failing to respond to therapy (deteriorating PEF, persisting or worsening hypoxia, hypercapnia, ABG analysis showing decreased pH or raised H+, exhaustion, feeble respiration, drowsiness, confusion, altered conscious state, resp arrest)
Monitoring when in hospital with acute asthma
- Regular peak flow
- Oxygen saturations
- ABG
- Serum potassium and glucose
- ECG – watch for arrhythmias
Follow up after asthma attack
Inform GP within 24 hours from discharge - need GP apt within 48 hours
Keep under specialist supervision if near-fatal attack
If severe attack, specialist follow up for at least one year after admission - first apt within 4 weeks
What measures should be taken prior to discharge to prevent acute asthma recurrence?
Check inhaler technique Need steroid (inhaled and oral) and bronchodilator therapy, their own PEF meter and personalised asthma action plan
Pharmacological interventions to prevent asthma exacerbations
Inhaled corticosteroids
Leukotriene receptor antagonists
Non-pharmacological interventions to prevent asthma exacerbations
Buteyko breathing technique
Smoking cessation
Weight reduction
