RCSI Asthma (Year 1) PDF

RCSI Royal College of Surgeons in Ireland Coláiste Ríoga na Máinleá in Éirinn Asthma Department of Medicine LEARNING OUTCOMES 1. 2. 3. 4. 5. Define Asthma Explain the pathophysiology of asthma List the cardinal symptoms of asthma List the cardinal signs of asthma Explain how each symptom and sig...

RCSI Royal College of Surgeons in Ireland Coláiste Ríoga na Máinleá in Éirinn Asthma Department of Medicine LEARNING OUTCOMES 1. 2. 3. 4. 5. Define Asthma Explain the pathophysiology of asthma List the cardinal symptoms of asthma List the cardinal signs of asthma Explain how each symptom and sign is caused in asthma 6. Develop a differential diagnosis for asthma LEARNING OUTCOME 1 • Define Asthma WHO DEFINITION OF ASTHMA • A chronic inflammatory disease of the airways characterised by reversible intermittent airway obstruction. • This obstruction is due to a combination of three factors: 1. Mucosal inflammation with inflammatory cells, (Eosinophils, Mast cells and Th2 lymphocytes). 2. Neural hyperresponsiveness. 3. Smooth muscle hypertrophy and thickening of the basement membrane, the space below the epithelium. WHY IS ASTHMA IMPORTANT? • 300 million people worldwide. • Affects 10-15% of children & 10% of adults (U.K.)*. • Accounts for large number of hospital presentations. • Higher incidence in Western and Urban societies – This is likely a combination of greater exposure to aetiologies and greater access to diagnosis. • Asthma caused 455,000 deaths [3 deaths per day in UK] in 2019 alone[1]. Most asthma-related deaths occur in low- and lower-middle-income countries, where under-diagnosis and under-treatment is a challenge[2]. • LEARNING OUTCOME 2 • Explain the pathophysiology of asthma PATHOPHYSIOLOGY • All symptoms are related to airway obstruction secondary to airway inflammation & smooth muscle contraction, which is a multicellular process [eosinophils, mast cells and lymphocytes]. • This immune dysregulation is driven by pollution, allergens and viruses. • Smooth muscle surrounding airway becomes oedematous and tightens airway - this reduces amount of air that can pass through leading to wheeze. • Airway epithelium becomes oedematous, erythematous and inflamed. • Inflammatory mediators include: § Type 2 T-helper lymphocytes, IL-4, IL-5, IL-13. § Eosinophils, IgE, Mast cells, Histamine, Leukotrienes. MICROSCOPIC FEATURES • • • • • • Airway infiltration by neutrophils and eosinophils. Mast cell degranulation. Basement membrane thickening. Loss of epithelial integrity. Occlusion of bronchial lumen by mucus. Hyperplasia and hypertrophy of bronchial smooth muscle and goblet cells. Source = RCSI Handbook of clinical Medicine Volume 1 EXTRINSIC ASTHMA [ALLERGIC, EOSINOPHILIC] • • • Predominates in childhood. Individual or family history of atopy (allergy, eczema, hayfever). Increased IgE levels and immediate hypersensitivity on skin testing. Antigen-induced asthma • Commonest type (30-50%) • Airborne allergens - pollens, animal hair, house dust mite Occupation-related • 80 different substances identified, e.g. animal handlers, wood workers. Environmental pollution • Sulphur dioxide, ozone Drug-induced • Aspirin, NSAIDs, Antibiotics & Beta-blockers Viral respiratory tract infections • Children - respiratory syncytial virus [RSV], influenza, rhinovirus Exercise-induced asthma • Cold or humid air increases risk. INTRINSIC ASTHMA [NON-ALLERGIC/ NON-EOSINOPILIC] • Adults • No individual or family history of atopic disease • Skin/inhalation tests negative • Nasal Polyps • Drug hypersensitivity to aspirin & penicillin • Often associated with COPD • Prognosis less good LEARNING OUTCOME 3 • List the cardinal symptoms of asthma ASTHMA SYMPTOMS • Cough (often nocturnal) • Wheeze (intermittent) • Shortness of breath (reversible) • Typically, first onset in childhood but can present as an adult • Strong relationship with rhinitis and eczema (allergy / atopy) ASTHMA: HISTORY IS VERY IMPORTANT SOB • • • • • • • Duration of symptoms (rapidity of onset) Quantify degree of shortness of breath (SOB) Episodic, nocturnal Diurnal variation Precipitating factors (on this occasion) Associated wheeze/ chest tightness/ cough Frequency of b-agonist usage Also • Chest tightness/ Cough/ Wheeze ASTHMA: PAST MEDICAL HISTORY • When was asthma diagnosed? • By whom? And How? • Impact of asthma • Progression over time • Days off work or school/ annum • Precipitating factors ASTHMA: MEDICATION HISTORY • Current inhalers / Oral medications • Adherence • Frequency of b-agonist usage (when well) • Previous inhalers (explore reason for change) ASTHMA: HOW MUCH IMPACT HAS THE CONDITION HAD IN THE PAST • GP / ED visits per year • Number of nebuliser prescriptions per year • Number of courses of oral steroids per year • Number of courses of antibiotics per year • Previous hospital admissions. • Previous Intensive Care Unit (ICU) admissions / Intubation (put on a ventilator machine to help breathing). LEVELS OF ASTHMA CONTROL Characteristic Controlled (All of the following) Partly Controlled (Any measure present in any week) Uncontrolled Daytime symptoms None (twice or less/week) More than twice/week Limitations of activities None Any Nocturnal symptoms/awakening None Any Three or more features of partly controlled asthma present Need for reliever/ rescue treatment None (twice or less/week) More than twice/week Lung function (PEF or FEV1)‡ Normal < 80% predicted or personal best (if known) Exacerbations None One or more/year* * Any exacerbation should prompt review of maintenance treatment to ensure that it is adequate. † By definition, an exacerbation in any week makes that an uncontrolled asthma week. ‡ Lung function is not a reliable test for children 5 years and younger. One in any week† ASTHMA: SYSTEMS REVIEW Medication side effects • Inhaled corticosteroids - oral candidiasis • b-agonists - tremor, palpitations • Oral steroids – obesity, striae, myopathy, glaucoma, osteoporosis, peptic ulcer disease (PUD), diabetes, easy bruising ASTHMA: SUMMARY OF FEATURES • Classic triad: 1. 2. 3. Dyspnoea Wheeze Cough (Non-productive) • Diurnal pattern to symptoms: worse at night / early morning • Presence of identifiable triggers LEARNING OUTCOME 4 • List the cardinal signs of asthma ACUTE ASTHMA EXACERBATION: SEVERITY ASSESSMENT LEARNING OUTCOME 5 • Explain how each symptom and sign is caused in asthma Mechanism of symptoms in asthma Inflammation Altered neural activity & Hyperreactivity Reversible Airway Narrowing Remodelling Cough, Wheeze, Breathlessness ASTHMA: DIURNAL VARIATION • Plasma cortisol levels drop at 12am • Plasma adrenaline levels drop at 4am • Nocturnal symptoms 2-3 am onwards *Generally, symptoms worst in the morning and at night NATURAL HISTORY OF ASTHMA - NOT PRECISELY DEFINED • In majority of patients, it is not progressive (contrast with chronic bronchitis, emphysema cystic fibrosis, bronchiectasis) • Some (minority) patients do develop irreversible changes in lung function • Clinical course is characterised by remissions and exacerbations LEARNING OUTCOME 6 • Develop a differential diagnosis for asthma DIFFERENTIAL DIAGNOSIS Other causes of airway obstruction / wheeze. • • • • • • • COPD Bronchiectasis Cystic fibrosis Airway tumour Goitre (enlarged thyroid) Foreign body Anaphylaxis Other causes of cough • • • • Sinusitis and post-nasal drip Gastro-oesophageal reflux Bronchiectasis LRTI / Pneumonia Other causes of dyspnoea • • • • Pulmonary embolus Pneumothorax Heart failure Acute coronary syndrome KEY POINTS • Asthma is a common condition with variable intermittent airflow limitation due to inflammation of the airways • Episodic shortness of breath, cough and wheeze are the main symptoms • 2 main types – Allergic (eosinophilic) and Non-allergic (noneosinophilic) • Diagnosis and Treatment will be covered at a later stage. Treatment is focused on limiting inflammation and relief of airway obstruction. RESOURCES • UpToDate - Asthma • Global INitiative for Asthma (GINA) Guidelines