Grant: Travel Awards - Institute Community Support

We take deep inspirations unconsciously at a rate of about 1 every 6 minutes. The deep inspiration stretches the lungs, which also tends to elongate and dilate the airways embedded within the lungs. Oppositely, one special lung tissue, called the airway smooth muscle, is encircling the airways and sometimes contracts to constrict the airway lumen. This is especially concerning in patients with asthma, where respiratory symptoms occur due to excessive airway constriction caused by exaggerated contraction of the airway smooth muscle. It was previously demonstrated that the stretch inflicted by a deep inspiration relaxes the airway smooth muscle and thus accounts for the respiratory relief afforded by a deep inspiration. Obviously, the depth of the deep inspiration determines the magnitude of the stretch and the extent by which it is relaxing the airway smooth muscle. Interestingly, this relaxing response to a stretch is lost in asthma. The mechanisms liable for this aberrant response may contribute to excessive airway narrowing in asthma. Beyond the magnitude of the stretch, the frequency with which the deep inspirations are taken may also influence the contraction of airway smooth muscle. In this study, we have stretched the airway smooth muscle from sheep after different time intervals in order to determine whether the time elapsed without stretches influences the relaxing effect of a subsequent stretch. The preliminary results show that changing the time elapsed between stretches greatly influences its relaxing effect on the airway smooth muscle. These results are relevant to asthma as they may link the excessive airway constriction seen in asthma to a naturally abnormal frequency of deep inspirations.