Efficacy of a Heat Exchanger Mask in Cold Exercise-Induced Asthma: Conclusion
In fact, the efficacy of this mask may have been underestimated in both studies with the inclusion of data from the subjects needing early albuterol rescue after placebo exercise. Their maximal decline in FEV1 may have been much greater in that visit, had we not prevented further decline in lung function with albuterol administration.
While all subjects stated that they experienced symptoms of asthma in cold air prior to enrollment and had positive methacholine challenge results, more than half of the study 1 subjects had a decrement in FEV1 with placebo exercise that was < 10%. Nevertheless, the heat exchanger device prevented lung function decline in this population, as well as in those with more significant lung function decline. This gives the device broad applicability to the general asthma population, and may suggest that there is a disconnect between EIA symptoms and change in FEV1. add comment
The use of a mask that heats inspired air to ameliorate symptoms related to cold weather is not new. Several PRHEs already exist, and some have been studied in cold air. The Qxtec PRHE device is a plastic heat exchanger module embedded within a mesh pocket overlying the mouth opening of a fleece facemask. The module is composed of multiple folds of desiccant-coated plastic that provides a large surface area for rapid heat and moisture transfer, and requires no power source. As the user exhales, heat and moisture are trapped within the device; as the user inhales, cold air is warmed and humidified as it travels across the material. As the imbedded desiccant traps exhaled water vapor, it is warmed further by the exothermic transition from gas to liquid. According to the unpublished data from the manufacturer (L. Bagby, MBA; DMCE Engineering; Arvada, CO; September 2003), at steady-state exercise in cold air, inspired air at
– 40°C can be warmed to as high as 15°C, and exhaled air temperature drops from 37°C to – 23°C as it leaves the device. Humidification data were not supplied by the device manufacturer, and the authors did not have the ability to measure inhaled air humidity in front of and behind the device during exercise. What is unique to this device is its light weight, ease of use, and lack of external power source. The proposed mechanism of action of this device also addresses both temperature and humidity, both of which are believed to play a role in exercise-induced bronchoconstriction.