- Created by: BeckiSweet95
- Created on: 26-11-19 16:46
What is Asthma?
- Most common childhood disease.
- Chronic inflammatory disorder of the bronchi.
- Characterized by episodic, reversible bronchospasm, caused by a bronchoconstrictor response to various stimuli.
- Triggers differ dependent on the person.
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What is Bronchoconstriction?
- The lining of the bronchioles become swollen and inflamed.
- The lumen narrows due to inflammation causing airway oedema.
- Bronchioles produce excess mucus to trap the antigen - this can cause mucus plugs.
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What is the Pathophysiology of Asthma?
- Inhaled antigen causes an immune response.
- The blood vessels become leaky, allowing IgE and eosinophils to travel to the tissues.
- Antigen activates dendritic cells and macrophages. These are antigen-presenting cells (APC), they present the antigen to T helper cells.
- Macrophages begin to engulf and eliminate the antigen.
- Th1 cells activate lymphocytes (T cells, B cells and natural killer cells). They also contribute to bronchoconstriction.
- Th2 cells activate IgE cells and eosinophils. They are also needed for the proliferation and differentiation of B cells.
- Eosinophils release neuropeptides which cause tissue injury and airway hyperresponsiveness.
- IgE cells bind to an antigen and then bind to mast cells causing the mast cells to release histamine.
- Histamine causes inflammation and contributes to bronchoconstriction.
- Airway obstruction via inflammation increases airflow resistance and decreases flow rate. This can trap air.
- Trapped air leads to decreased diffusion in the alveoli. This causes VQ mismatch.
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What are the Risk Factors for Asthma?
- Exposure to allergens/irritants
- Genetics - If a parent has asthma, the child will be more susceptible to it.
- Exercise - During exercise breathing is fast and through the mouth. This causes cold, dry air to reach the lungs which can irritate the airway.
- Stress - Makes inflammatory response more prominent to environmental triggers.
- Recurrent Respiratory Infections -
- Recurrent infections with episodes of wheezing during early life are a risk factor for later asthma diagnosis.
- Damage to epithelial barrier causes a risk of severe infections.
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What are the Symptoms of Asthma?
- Cough - An irritant causes the bronchial tubes to constrict, prompting a non-productive cough.
- Wheezing - Narrowing of the lumen and excess mucus production can cause mucus obstructions in the airway. These causing a 'wheeze' sound as air is inspired/expired.
- Tachycardia - Heart rate increases to compensate for lack of oxygen being transported to the blood.
- Tachypnoea - As the airway narrows, less oxygen is inspired. When CO2 levels rise, the pH of the blood drops. This sends a message to the medulla to increase the respiratory rate to get a higher level of oxygen into the body.
- Shortness of Breath - The lungs can't hold as much air due to inflammation and mucus build-up.
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What are the Treatments for Asthma?
- Respiratory Assessment - Chest observed for pattern of breathing, symmetry of movement and accessory muscle usage. A doctor will listen to chest for wheezing, stridor and air entry/exit.
- ECG - monitor heart rate (side effect of salbutamol is tachycardia).
- Blood gasses - monitor oxygen and carbon dioxide levels in the blood.
- Peak flow - measure how quickly air can be expelled from the lungs (indicates a narrowing of the bronchioles).
- Inhaled Corticosteroids - taken daily to reverse inflammation of the airway.
- Salbutamol Inhaler - taken PRN (as needed). Opens the airway during symptomatic episodes.
- Oxygen - given during asthma exacerbation. Reverses hypoxia.
- Magnesium Sulfate - given during asthma exacerbation. Relaxes bronchiole muscles and expands the airway.
- Education - Children and parents taught correct inhaler technique and receive advice on avoiding triggers.
- Follow Up - Follow up with GP who continues to monitor the patient and prescribe medications. Asthma clinic review to check symptom management.
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