- What is severe asthma?On the left is a lung cast taken from a normal healthy lung whereas the one on the right is taken from a case of fatal asthma. The reduced branching in the cast of the fatal asthma victim is obvious and is caused by thick mucus plugs that prevent the casting material from reaching the distal portions of the lung. These plugs are major barriers that prevent medication from reaching deep into the lungs severely reducing its efficacy.
Asthma is a chronic respiratory disease that is characterized by shortness of breath, tightness in the chest, cough and wheezing. These symptoms are due to narrowing of the airways as a result of muscle contraction and mucous plugs. An attack results in reduced airflow to and from the lungs. Severity of the disease and attacks range from mild to severe cases where emergency medical treatment may be required.
Severe asthma is difficult to control, leading to an increased risk of frequent, severe attacks, or even death. Severe asthma includes three groups: untreated severe asthma, due to undiagnosed asthma or unavailability of therapy, difficult-to-treat severe asthma (due to adherence issues, inappropriate or incorrect use of medicines, environmental triggers or co-morbidity), and treatment-resistant severe asthma, including asthma for which control is not achieved despite the highest level of recommended treatment.
- What causes asthma?
Although the cause of asthma is unknown, it has been associated with several risk factors, including family history and exposure to environmental factors during pregnancy and the first few years of life. An asthma attack can be triggered by many factors including allergens, physical activity, cold, smoke and even certain medications such as non-steroid anti-inflammatories and beta-blockers.
Asthma is extremely prevalent yet under-diagnosed and under-treated worldwide. The United States is home to over 25 million people diagnosed with the disease with Canada having similar per capita numbers. Asthma symptoms are reported in over 20% of North American children aged 13-14 with rates climbing around the 30% mark for children of the same age group in Australia, New Zealand and the UK. Approximately 180,000 people die of their disease globally. Those that die are often young and succumb before they access medical care. In untreated cases of severe asthma, death is rapid, with most deaths (80%) occurring within 1 hour of onset of symptoms. In these life-threatening situations, conventional asthma treatment with inhaled bronchodilators increasingly fails to relieve symptoms, as the medication is unable to penetrate the obstructed airways.
- Treatment Gap
Issues with Current Rescue Treatment
Although there are many different treatments available the current treatments do not effectively satisfy the medical need. This is especially true in cases of severe acute asthma where the majority of fatalities occur rapidly (under an hour) in young individuals who die prior to receiving any medical attention.
Salbutamol/albuterol, the current gold standard for bronchodilators in asthma therapy is not always an effective rescue treatment as it only achieves its maximum dilatory effect after several minutes and it has no indications of mucus plug removal or penetration. The inability to penetrate obstructed airways severely limits the effectiveness of any conventional medication as only a small portion of the lung ever receives the intended treatment. The major challenge for treating asthma and preventing death is to open obstructed airways rapidly, allowing the delivery of oxygen and conventional medication into the lungs.
Casts of lungs prepared in the laboratories of Dr Francis Green illustrate differences between normal healthy airways and diseased abnormal airways.
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