Asthma is a common medical condition that affects the respiratory system. There are various types, and they are controlled differently, but the symptoms in each are similar. Symptoms include shortness of breath, tightness of in the chest, coughing and wheezing. Symptoms may vary from mild to severe, and often increase during respiratory illnesses and infections.
Types of Asthma
The major types of asthma are atopic, non atopic, aspirin induced, occupational and allergic bronchopulmonary asthma.
Most people are familiar with atopic asthma, which is triggered by environmental agents such as dust, pollen, dust mite pellets and contact with animals. Environmental pollution and modern living conditions may have contributed to the recent rise in asthma. There is often a family history, and there may be associated hay fever or eczema. Smoking during pregnancy and around young children may also contribute to them developing asthma.
Environmental agents trigger asthma by irritating the bronchial airways, causing the airways to become inflamed and constrict. Mucus is also produced which further obstructs the airways. The reaction is mediated by the immune system and caused by the production of histamine.
Non Atopic Asthma
Non atopic asthma produces similar symptoms but does not appear to be caused by an immune system reaction. Instead it is associated with recurrent respiratory tract infections and the local irritation and inflammation these cause.
Aspirin Induced Asthma
Aspirin induced asthma often first manifests as rhinitis, with sneezing, eye watering, a runny nose and nasal congestion. Patients can also present with nasal polyps and skin urticaria, as well as typical asthma symptoms. A sensitivity to other non steroidal anti-inflammatory drugs (NSAIDs) drugs such as ibuprofen and beta blockers such as propranolol is also common.
Aspirin induced asthma is linked to a reduction in prostaglandin and thromboxane production, which causes an increase in leukotrienes. Leukotrienes are fatty signalling molecules that cause mucus secretion and bronchial constriction.
Occupational asthma is triggered by various agents in the workplace such as wood dust, flour dust, dust from latex rubber, and dust from animals. However in the UK occupational asthma is most commonly caused by chemicals known as isocyanates. These are found in products such as paints, adhesives, rubbers and pesticides.
If safe alternatives to isocyanates are not available, safety precautions should be taken to minimise exposure. These include installing extractor fans or fume cupboards, wearing breathing equipment and participating in health and safety training. Employers should carry out risk assessments and monitor employees exposed to isocyanates or other hazardous substances.
Allergic Bronchopulmonary Asthma
Allergic bronchopulmonary asthma is specifically due to inhaling Aspergillus fumigates spores, a fungus often found in soil and decaying organic matter. The spores trigger an immune response and typical asthma symptoms. Healthy individuals are able to combat infection, but immunosuppressed patients may develop further conditions which can be serious.
Diagnosis of Asthma
Asthma is typically diagnosed with two tests known as spirometry and peak flow assessment. Spirometry measures the amounts of air an individual can blow out in one second and in one complete breath. These figures are taken together to give a value. Peak flow assessment measures the speed of air blown out from the lungs.