Efficacy of a Heat Exchanger Mask in Cold Exercise-Induced Asthma: Discussion
The treatment of patients with predominantly EIA symptoms usually involves pretreatment with an inhaled short-acting bronchodilator. This approach is highly effective and is associated with minimal cost and adverse effects, so the benefit of any new device or treatment for EIA should be at least as effective as albuterol pretreatment. We intended to address this question after our initial investigation established the efficacy of this PRHE mask, by taking a small sample of subjects with known EIA and comparing the mask to albuterol pretreatment. comments
While the sample size is small, the cold air exercise-induced declines in FEVX with the mask and albuterol pretreatment exercises were similar (6.3% and 11%, respectively, p = 0.4375), and the decline in FEF25-75 suggested that the mask may be superior to albuterol (10% and 23%, respectively, p = 0.0625). While study 2 demonstrates that the heat exchanger mask is effective at limiting the decline in lung function with cold air exercise, it also suggests that the mask is at least as effective as albuterol pretreatment. While this implies that some patients could try to use this mask in place of albuterol for winter activities, this mask will likely be used in combination with albuterol pretreatment to achieve two goals: to improve symptoms that occur despite appropriate albuterol dosing and to reduce the frequency of albuterol redosing for extended activities in cold dry air.
One of the limitations of this study is the small sample size. While larger studies may be necessary, study 1 results are highly significant. This suggests that the trends toward significance in study 2 probably reflect the limitations of a small sample size, and less likely reflect spurious findings due to chance.
Outliers did not drive these results. In the first study, there were three subjects who demonstrated a > 30% fall in FEV1 during the placebo exercise, who later showed near complete absence of EIA with the active device visit. We believe these data demonstrate the remarkable efficacy of this device. However, even when these three subjects were removed from the analysis, the results were still significant: the mean fall in FEV1 would be 11 ± 2.4% with placebo and 3.8 ± 2.4% with the active device (p < 0.01). The mean fall in FEF25-75 would be 22 ± 3.3% with placebo and 3.6 ± 2.0% with the active device (p < 0.01).