Asthma PDF

Asthma Asthma trajectories - Variable pathways – early onset (mostly atopic) - Post puberty – resolution/new development. - Adult onset –late onset asthma. - Why do we need to know this? o People often ask – will my child grow out of their asthma? § T...

Asthma Asthma trajectories - Variable pathways – early onset (mostly atopic) - Post puberty – resolution/new development. - Adult onset –late onset asthma. - Why do we need to know this? o People often ask – will my child grow out of their asthma? § They may or may not. The respiratory tract Respiration – mechanism - Inspiration: contraction of diaphragm and external intercostal muscles increase the thoracic cavity space and decrease intra-pleural pressure- allowing air to rush in due to pressure diEerential. - The diaphragm then relaxes, increasing intra-pleural pressure – triggering passively the process of expiration. - The inspiration-expiration cycle allows gas exchange. Respiration – control - This is managed by the CNS respiratory control system. o The central neural respiratory generator. o The sensory input system (thoracic neural receptors, peripheral (carotid and aortic bodies) and central medullary chemoreceptors), and o The muscular eBector system. ASTHMA PATHOGENESIS AND PATHOPHYSIOLOGY What is asthma? - Asthma is a chronic obstructive lung disease, which can be controlled but not cured. - In clinical practice, i.e., for a diagnosis. Asthma is characterised by both the following: o A respiratory of symptoms (cough, wheeze, dyspnoea, or chest tightness) which vary over time and intensity as well as. o Excessive variation in expiratory airflow function. - Asthma is also associated with airway inflammation and airway hyper-responsiveness. Current understanding of asthma development - Asthma may be a result of gene-environment interactions that occur as early as in-utero. Risk factors that impact onset, development, progression Asthma triggers - House dust mites - Mould - Pets - Pollen - Cigarette smoke - Exercise - Smoke - Chemicals - Stress - Emotions - Hormonal changes (women) - Respiratory infections. (common cold =80% of bad asthma exacerbations) - Weather (e.g. thunderstorms) - Medications, occupational exposures. Asthma pathophysiology - Repeated infections/ exposures disrupt airway epithelial barrier → danger signalling and chemokine secretion. - Immature dendritic cells (DC) recruited to airway mucosa – act as antigen presenting cells (APCs) - Allergen linked APCs then migrate to local lymph nodes and stimulate naïve T helper Cells to diEerentiate to T helper Type 2 (TH2) cells. - Cytokines linked to Th2 cell response drive inflammation (majority of asthma cases) – eosinophils are the main driver. Changing concepts in pathophysiology of asthma. - Even with first episode of asthma, the lung will be damaged and start remodelling it. Counselling on patients to control their asthma using snit-inflammatory is very important as controlling the asthma will at least reduce the amount of remodelling of the lung. Asthma management Asthma Diagnosis - History (family history, symptoms, symptoms pattern) - Physical examination (wheeze) - Considering other diagnoses. - Documenting variable airflow limitation (spirometry – pre-pose bronchodilator variability. Asthma treatment decisions à exacerbation à 위독, 악화 Assessing Asthma control Risk factors for asthma flare-ups. Asthma treatment principles - Bronchodilators (relievers) o Short acting beta agonists (SABAs) o Long-acting beta agonists (LABAs) o Short or long-acting muscarinic antagonists (SAMA/LAMA) - Anti-inflammatory agents (preventers) o Inhaled corticosteroids (ICS) à omnipotent. o Leukotriene receptor antagonists (LTRA) o Targeted biologic agents. - If symptoms more than twice a month à need to be on preventer à inhaled corticosteroids. - Most children can be treated by SABA. à You can add on ICS or montelukast. - No ICS+LABA combination allowed for 1-5 years children. Reliever medications – schedule 3 - Short acting beta 2 agonists (SABAs) o Salbutamol o Terbutaline - Salbutamol - Formulation type: (pressurised metered dose inhaler or pMDI and Autohaler) - Formulation strength: 100 µgs/puE x 200 doses in inhaler. - Time to action: 1-2 minutes. - Elimination half-life: 2.7-5 hours. - Dose: 1-2 puEs (100-200 µgs) every 4-6 hours ONLY when needed or 5-15 minutes pre- exercise. - Inhaler use is important – as inappropriate inhalation technique can lead to systemic absorption. - Precautions o Risk factors for angle – closure glaucoma - inhaled salbutamol may rarely precipitate acute angle-closure crisis, especially if used with ipratropium. - Pregnancy and breastfeeding: safe to use. - Side eBects: o Skeletal muscle tremor, Peripheral arteriole dilation – compensatory in blood pressure, Tachycardia, Headache, Nausea, Insomnia, Hyperactivity in children, Paradoxical bronchospasm (first time use-check), Potentially serious hypokalaemia – more likely with high doses or oral route. pMDIs usage steps The role of spacers – usage steps Reliver medications – schedule 3 (Terbutaline) - Terbutaline formulation: (Dry Powder Inhaler DPI) - Formulation strength: 500 µgs/puE x 120 doses in inhaler. - Time to action: 5-30 minutes. - Elimination half-life: excreted mainly unchanged in the urine. Practically all of an administered dose of terbutaline is eliminated after 72 hours. Duration of action ¬4-5 hours. - Dose: 1–3 inhalations (500–1500 micrograms) when required, or 5–15 minutes before exercise. Repeat 3 or 4 times daily as necessary. - Inhaler use is important – as inappropriate inhalation technique can lead to systemic absorption, or NO DOSE! - Precautions o Risk factors for angle – closure glaucoma - inhaled salbutamol may rarely precipitate acute angle-closure crisis, especially if used with ipratropium. Dry Powder Inhalers- Turbuhalers Teach back method – key steps. Salbutamol vs terbutaline - No clinical diEerence in eEect. - However, for S4 versions terbutaline is no longer subsidised by PBS. - Dry powder inhalers may need a higher inspiratory flow generation (though most people even with severe asthma etc. can use these inhalers). - Dry powder inhalers more environmentally friendly – lower carbon footprint. Key roles for pharmacist SABA use issues - There is increased risk of severe flare-ups in patients using as needed SABAs in the absence of inhaled corticosteroids or with poor adherence to inhaled corticosteroids. à This should be a key discussion point for S3 requests for SABAs. SABA use issues Key roles for pharmacists in dispensing S3 Relievers– no emergency situation. - Check asthma control (how?) - Check if patient has been prescribed preventers (if Sx > 2 per month) - Check patient is adherent to preventers (how?) - Check level of SABA usage (no of puEs/day or cannisters bought per year) – info gathering/pharmacy records if you record sales. - Check if patient knows appropriate technique for using their SABA inhaler. - Check if there may be comorbid conditions (AR, OSA, GORD – refer if needed). - Check if patient has an asthma action plan. Asthma first aid Information gathering à poorly controlled asthma Management options - Provide Reliver PuEer Yes/No. - Demonstrate puEer technique. - Provide Bisolvon Dry Cough Liquid Yes/No –Why? - GP referral Preventer need education. - Awareness about what do in a serious asthma flare-up (including what a serious flare up may be) Suggest Symptom diary for GP visit. - Provide information on asthma management (Asthma Australia) 1800Asthma or 1800 278 462. - Record key counselling provided if possible.