Depression of salivary epidermal growth factor by smoking.

reduction in the forced expiratory volume in one second after exercise was calculated using the pre-exercise value as the baseline value. Statistical significance was calculated with Student's paired t test. The study was approved by the research ethical committee of the Faculty of Medicine, Queen's University, Belfast. The table shows the percentage reduction in forced expiratory volume in one second with and without using the mask. Only one patient (case 6) showed no improvement with the mask. The mean reduction in the group was 33-7% (SE 3 2%) without the mask and 9-1% (6 1%) with it (p<0 01). Most patients felt heat on their face but none complained of difficulty in breathing through the mask. Comment Our results show that a mask retaining heat and moisture effectively controlled exercise induced asthma in most of our asthmatic subjects. Previous work has shown that humidification of air can prevent the reduction in the forced expiratory volume.' Storing exhaled air in a mask such as the one we used is a practical way to humidify and heat air, thus making both water and heat available for the next inspiration. The mask might be more beneficial in cold weather, which classically precipitates the development of exercise induced asthma.4 The increased dead space from the mask does not play an important part during exercise. We found that even with the mask the forced expiratory volume in one second decreased by 9-1% after exercise. This reduction is, however, similar Reduction in forced expiratory volume in one second (FEV,) after exercise with and without a mask in 10 asthmatic patients