Asthma

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  • Asthma
    • What is Asthma?
      • A chronic inflammatory disorder of the bronchi
      • Characterized by episodic, reversible bronchospasm
        • Caused by a bronchoconstrictor response to various allergens/irritants
      • Clinical diagnosis based on recognition of characterized symptoms without other explanations
    • Pathophysiology
      • When an antigen is inhaled this causes an immune response.
      • Airway becomes leaky due to inspired antigen - allows white blood cells to the tissues
        • Antigen exposure triggers activation of dendritic cells and macrophages
          • Macrophages engulf and eliminate the antigen.
          • Antigen presenting cells (APC), present the antigen to T helper cells.
            • Th2 cells stimulate activation of IgE and eosinophils
              • Eosinophils cause tissue injury through release of neuropeptides
                • Contribute to bronchial hyperresponsiveness
              • IgE cells bind to the antigen, and then bind to the surface of mast cells
                • Mast cells are then activated and release histamine
                  • Histamine causes bronchoconstriction and airway oedema.
                    • Bronchioles produce excess mucus to trap the antigen.
                      • Can cause mucus plugs which obstruct the airway
                        • Airway obstruction via inflammation increases airflow resisttance and decreases flow rate
                          • This can trap air which causes decreased diffusion in the alveoli, resulting in VQ mismatch.
            • Th1 and Th2 cells contribute to bronchoconstriction.
              • Th1 activate lymphocytes and produce proteins
              • Th2 are needed for differentiation and proliferation of B cells
      • When asthma is not managed well, epithelial tissue can peel away
        • This reduces cilliated epithelium, meaning mucus is not moved away
      • Airway remodelling causes the smooth muscle in the bronchioles to become thickened
        • Lumen is now narrowerer than usual
    • Risk Factors
      • Exposure to allergens/irritants
      • Genetics
        • If a parent has asthma, their child will be more susceptible to it
      • Excercise
        • Excercise causes people to breathe more quickly through their mouths
          • Cold, dry air travels to the lungs
            • This irritates the airway, causing smooth muscle to tighten, increasing the chances of an asthma flare up
      • Stress
        • Can make the inflammatory response more prominent to environmental triggers
      • Frequent respiratory infections
        • Recurrent respiratory infections with wheezing episodes during early life are a risk factor for development of asthma in later life.
        • Infections are linked with asthma exacerbation.
          • If there is damage to the epithelial barrier, this is a risk of more severe infections
    • Treatments
      • Respiratory Assessment
        • Chest observed for pattern of breathing, symmetry of chest movement and sounds such as wheezing
      • Monitoring
        • ECG
          • Monitor heart rate.  Side effect of salbutamol is tachycardia
        • Blood Gas
          • Monitor oxygen and carbon dioxide in the blood
        • Peak flow
          • Measure how quickly air can be expelled from the lungs
            • Indicates narrowing of the bronchiolles
      • Medications
        • Inhaled corticosteroids taken daily
          • Reverse inflammation of the airway
        • Sulbutamol inhaler
          • Opens the airway during symptomatic episodes
        • Ocygen
          • Reverse hypoxia during attack
        • Magnesium sulfate
          • Given during an attack.  Relaxes bronchiolle muscles and expands the airway
      • Education
        • Correct inhaler technique
        • Advice on avoiding triggers
      • Follow Up
        • GP
          • Monitor patient
          • Prescribe medications
    • Symptoms
      • Cough
        • Inflammation of bronchial tubes prompts a non-productive cough
      • Wheeze
        • Narrowing of the lumen and obsturction caused by excess mucus production causes the wheeze sound
      • Tachycardia
        • Heart rate increases to compensate for lack of oxygen in the blood
      • Tachypnoea
        • Respiratory rate increases in attempt to increase oxygen in the blood.
      • Shortness of breath
        • The lungs can't hold as much air due to inflammation and mucus buildup
    • Child Development

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