A device that provides cooled, filtered airflow while patients sleep improved quality of life in patients with atopic asthma, according to the findings of randomized controlled trial conducted in six European countries.
The benefits of treatment with the device, Protexo, developed by Airsonett, seemed "greatest in patients with a combination of high asthma intensity and poor asthma control, who represent a significant area of unmet need," said Dr. Robert J. Boyle of the pediatrics department at Imperial College London, and his coinvestigators.
A total of 312 patients with atopic asthma were randomized to use the device, which filters and cools the air near the user’s nighttime breathing zone, or an identical placebo device. The active therapy arm received temperature-controlled laminar airflow (TLA) treatment, which is proposed to decrease exposure to allergens.
The primary end point of the phase III study was an improvement of at least 0.5 points on the Asthma Quality of Life Questionnaire. Secondary end points included fractional exhaled nitric oxide (FENO); IgE levels and blood eosinophil count; and airflow obstruction as measured by forced expiratory volume in 1 second (FEV1), forced expiratory flow at 50% of vital capacity (FEF50), and peak expiratory flow (PEF). Subgroup analyses were done by age, treatment intensity at baseline, symptom control at baseline, and a combination of treatment intensity and symptom control (Thorax 2011 [doi:10.1136/thoraxjnl-2011-200665).
Participants were enrolled between April 2008 and February 2009, and the two groups had similar demographic and clinical characteristics at baseline. Patients were aged 7-70 years (mean 24 years), had a history of asthma for at least 1 year (mean approximately 13 years), had a demonstrated allergy to pets or dust mites, and were on daily corticosteroids. A little over half of the participants were male. Patients continued using asthma medications as needed during the study and underwent medical assessment at 1, 3, 6, 9 and 12 months.
Of the active treatment group, 76% reached the primary end point at 1 year, compared with 61% of the placebo group, a significant difference (95% confidence interval 3%-27%, P = .02). Findings were similar for the subgroup analysis of patients aged 12 years and older (74% vs. 60%; 95% CI 1%-28%, P = .06). The greatest difference was seen in TLA recipients who had both high treatment intensity and low symptom control at baseline, compared with similar patients who received placebo (75% vs. 50%; 95% CI 4%-47%, P = .009).
Regarding the secondary outcomes, use of the treatment device was linked to a greater decrease in FENO, with a mean difference of –7.1 parts per billion, compared with use of the placebo device (95% CI –13.6 to –0.7, P = .03). The treatment group also saw a smaller increase in cat-specific IgE levels relative to baseline, compared with the placebo group (8% vs. 35%), and smaller increases in IgE levels specific to dust mites and dog allergens (differences not significant). No significant differences were found between groups in total IgE level change, eosinophil count, FEV1, FEF50, or PEF. There also were no differences in medication use or exacerbation rates.
Although previous studies have found no benefit to avoiding allergens in asthma, this study "found that exposure control using TLA treatment at night has an impact on overall asthma-related quality of life," Dr. Boyle and his colleagues wrote. The researchers theorized that "the reason that nocturnal TLA is successful where so many other approaches have failed may be the profound reduction in inhaled aeroallergen exposure." They suggested that "the clinical effects of TLA can be explained by its ability to break the persistent body convection and thereby reduce aeroallergen exposure."
Because the patient cohort encompassed a wide range of ages and residents of several countries, the authors said that "the clinical effects of nocturnal TLA treatment appear to be applicable to a broad patient group." However, they noted that it may be of most benefit in "patients with uncontrolled atopic asthma despite high treatment intensity, where guidelines recommend stepping up treatment."
There were no treatment-related adverse events in either group.
The study was funded by Airsonett. The researchers reported having no other financial conflicts.