A Prospective, Single Arm, Cohort Study of Nocturnal Temperature-controlled Laminar Airflow (TLA) Treatment (Airsonett®) in Patients With Allergic Asthma to Determine the Effect of Long-term Treatment on Exacerbation Frequency.

Asthma affects over 5.4 million people in the UK with nearly 500,00 experiencing severe symptoms and frequent exacerbations that are inadequately controlled with available treatments. The burden of severe asthma on the NHS is enormous accounting for 80% of total asthma cost. In 2009 there were 1131 deaths due to asthma, with those whose asthma remains poorly-controlled facing the greatest risk. Patients with severe asthma bear the greatest burden of asthma morbidity and experience more frequent and severe exacerbations which reduce their quality of life, impair their ability to work and place an enormous burden of anxiety on them and their families. There is also an increased risk of significant depression. 1 in 5 asthmatics in the UK report serious concerns that their next asthma attack will kill them. As highlighted in the 2010 Asthma UK report, 'Fighting for Breath,' these patients also face discrimination from employers, healthcare professional s and society as a whole as a result of their asthma.

Current treatments including oral corticosteroids, 'steroid-sparing' immunosuppressants and monoclonal antibody therapies are often of limited efficacy and have potentially serious side effects (steroids, immunosuppressive agents) or are prohibitively expensive (monoclonal antibodies). The adverse effects of long-term oral steroids include adrenal suppression, decreased bone mineral density, diabetes and increased cardiovascular mortality. The anti-IgE treatment Omalizumab® has been shown to reduce exacerbations by up to 50% and improve quality of life in severe allergic asthma but costs up to £26,640 per year, which is substantially more than the current annual rental cost of a TLA device (£2,088).

Patients with poorly controlled, severe, allergic asthma are left with a significant unmet clinical need and a specific requirement for cost-effective therapies which reduce systemic steroid exposure by reducing the frequency of severe exacerbations.

The Department of Health Outcomes Strategy for COPD and Asthma (2011) recognised the huge burden that poorly-controlled asthma places on people's lives and the NHS, and spelt out the political commitment to improve asthma control and reduce asthma related emergency healthcare needs and deaths. The 2013 British Thoracic Society (BTS) and Scottish Intercollegiate Guidelines Network (SIGN) national asthma guidelines and 2010 WHO consultation on severe asthma have highlighted an urgent need for research in severe asthma, acknowledging the limitations of available treatments in severe asthma and the dearth of clinical trials upon which to base management recommendations. Asthma UK emphasised in its research strategy for 2012 document that new therapies able to reduce symptoms and prevent exacerbations will improve clinical outcomes and patient well-being and reduce the cost of treating severe asthma within the NHS.

More than 70% of severe asthmatic patients are sensitised to common aeroallergens and/or moulds and the level of allergen exposure determines symptoms; those exposed to high allergen levels are at increased risk of exacerbations and hospital admissions. Domestic exposure to allergens is also known to act synergistically with viruses in sensitised patients to increase the risk and severity of exacerbations. Allergen avoidance has been widely recognised as a logical way of treating these patients . In controlled conditions, long-term allergen avoidance in sensitised asthmatics reduces airway inflammation with consequent symptomatic improvement, further supported by high-altitude, clean-air studies. Unfortunately, effective methods of allergen reduction have proved elusive, with current measures unable to reduce allergen load sufficiently to yield a consistent clinical improvement, thus leaving a significant gap in the potential strategies for reducing asthma severity through allergen reduction.