Objectives


  1. Discuss in broad terms the likely causes of asthma
  2. Speculate on a) the rise in incidence of asthma; b) its underdiagnosis
  3. Describe what happens to the lungs during the development of reversible obstructive lung disease (asthma)
  4. Compare and contrast chronic obstructive pulmonary disease and asthma in terms of morbidity and mortality, causes, clinical features, effects on respiratory physiology, potential approaches to management
  5. Discuss factors influencing patient adherence/compliance.



What is Asthma?



Asthma


Asthma is a disease which affects the lungs, causing narrowing of the airway resulting in difficulty breathing (dyspnea,) shortness of breath, coughing and wheezing. Asthma affects some 10-15% of children and 5-10% of adults, although in urban areas the figures rise markedly. (25% of children.) The disease causes inflammation of the bronchioles giving rise to hyper-sensitivity of the bronchi and hyperplasia and hypertrophy of mucous producing goblet cells.

What are the causes of Asthma?





The disease may be described as:

Extrinsic(Allergic)
Atopic (increased tendency to produce IgE in trivial circumstances.) Airway hyperreactivity - increased response to non-specific stimulae - Most commonly dust mite faeces. Childhood onset and associated with allergic rhinitis and excema Eosinophilia test positive - eosinophils usually respond to parasites or helminths, here they respond to allergen and are the primary cause of inflammation in asthma. Eosinophils degranulate when they reach the airway epithelium and release chemicals which kill epithelial cells and increase mucous secretion. Confirmed by simple biopsy. Skin Prick Test positive to discover allergen.


Intrinsic
Not necessarily atopic. Also known as Adult onset Asthma, is related to perennial rhinitis (annual running/stuffed up nose.) Accounts for approx 10% of adults with asthma. Aetiology is unknown although similar prevalence of eosinophils in inflammation.


Occupational
Certain chemicals - eg. Toluene Diisocyanate used in paint/adhesive/foam manufacture and flour/grain in farmers. - are known to have sensitizing effects on the respiratory systems which may allow allergic reactions to occur when the chemical is next inhaled, giving asthma like symptoms.


What are the physiological symptoms of Asthma?





Narrowing of airways - inflammation + muscle constriction + hypersecretion of mucous. Constricted Muscles - histamine is released from basophils to dilate blood vessels to allow leucocytes to enter the blood stream, also has the effect of constricting airway muscles, perhaps to reduce anatomical dead space thereby increasing functional oxygen concentration in gas exchange areas, to increase movement to blood. Triggers attach in asthmatics. Damaged Airway passage wall -the airways are damaged by the action of eosinophils destroying epithelial tissue and their overpopulation due to a hypersensitive response. Inflammation - due to eosinophils, mast cells, lymphocytes and basophils responding to allergens and epithelial damage.
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How is Asthma Treated?




Asthma can be treated by administering medicine during each attack, or by taking medicine to prevent attacks from occuring. Bronchodilators are used during and attack as they are fast-acting and provide instant relief. Corticosteroids can be used to reduce inflammation - the root problem in asthma- in the long term, preventing attacks from ever occuring.

Bronchodilators widen airways and anti-inflammatories reduce eosinophil proliferation, reducing inflammation.

Relief Medicine - Bronchodilators

Relief from shortness of breath or wheezing can readily be achieved with bronchodilators such as beta 2 agonists (Salbutamol- Trade name Ventolin.) The are
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These can be taken with inhalers, but must be held in the lungs for 10 seconds after breathing in, thus for some people (especially the elderly) a spacer may be used (see right) - this allows the whole breath to be taken gradually, rather than in a fast burst by letting the dose mix with air in the tube before inhalation.Alternatively a nebuliser can be used which produces a long, continuous inhalation up to the full dosage. It is recommended that asthmatics use their inhaler no more than 3 times per day (three puffs, not three attacks!)... The underlying cause of asthma is bronchiole inflammation and the inhaler merely manages this short term but does not treat the inflammation. Patients using an inhaler more than 3 times per day should ideally be on steroid or non-steroidal anti-inflammatory medicines which is the key to long-term asthma management.

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Prophylactics - Anti-Inflammatories


Current inflammation treatment protocols recommend prevention medications such as an inhaled corticosteroids, which helps to suppress inflammation and reduces the swelling of the lining of the airways, in anyone who has frequent (greater than twice a week) need of relievers or who has severe symptoms. If symptoms persist, additional preventive drugs are added until the asthma is controlled. With the proper use of prevention drugs, asthmatics can avoid the complications that result from overuse of relief medications.

If severe attacks persist, oral steroids can be given, although this involves a much higher does and can lead to several effects associated with steroid overuse.Side effects: High doses of steroids (especially oral) can be associated with weight gain and/or Addison's disease - caused when cessation of steroid use does not give the adrenal gland adequate time to begin producing naturally produced steroids again. - glucocorticoids (such as cortisol) are produced in the adrenal gland and regulate the immune response, stress and blood glucose leading to associated disorders such as hypertension, night sweats, hyperthyroidism or diabetes.



More people in the UK - 5.1 million - suffer from asthma than anywhere else in Europe.

Twenty times as many people died from COPD (30,634) than from asthma (1,521) in the UK in 1999.