This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The purpose of this study is to test the hypothesis that the mucosa of the respiratory tract is sensitive to environmental temperatures and functions as a thermostat to regulate its own blood flow. The investigators postulate that the airway epithelium senses and reacts to falling temperatures during the conditioning of inspired air by the production of vasoactive substances such as nitric oxide which in turn increases bronchial blood flow and provides a sufficient reserve of heat and water to condition the inspired air and prevent freeze injury. These experiments seek to establish a relationship between level of thermal stress in the airways and augmentation of bronchial blood flow. The independent variable of thermal stress primarily varied by temperature and relative humidity of inspired air (21 degrees Celsius and 50% relative humidity, -5 degrees Celsius and 1% relative humidity, 30 degrees Celsius and 100% relative humidity) and level of ventilation 10, 30, 60 L/min. Forty subjects, 20 asthmatic and 20 controls will be subjected to isocapnic 'hyperventilation'. The study will be done in 3 study visits on separate days. Each study session will be the same, except for the temperature of the inhaled gas during the isocapnic breathing challenge. Each subject will have baseline spirometry, nitric oxide and bronchial blood flow measurements made.
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