The risk of death from asthma peaks during adolescence. There is evidence that some asthmatics have difficulty perceiving airflow obstruction or its severity, but the significance of this risk factor during adolescence is unknown. The long-range goal of the proposed research is to identify and understand the characteristics of respiratory sensation, behavioral style and perception of loaded breathing that may predispose some asthmatic adolescents to life-threatening asthmatic episodes. This application builds on the knowledge, technology, access to asthmatic adolescents and close collaboration developed by a three-center consortium. The specific aims of this project are: (1) to use three established indices of respiratory perception to test for blunted perception on compromised lung function in LTA adolescents, (2) to identify psychological factors that influence respiratory perception in adolescents and (3) to test the importance of key physiologic malfunctions as determinants of respiratory perception. The research design compares a large group of adolescents, as probands with histories of life-threatening asthma events, to matched groups of asthmatic and healthy control subjects. The central hypothesis tested is that some adolescent asthmatics have innate deficiencies in their abilities to assess compromises in respiratory mechanics or gas exchange. Techniques of investigation include assessment of cognition and behavioral style by interview, methacholine bronchial provocation, magnitude estimation of resistive loads and ventilatory responses to hypoxia and hypercapnia. The proposed research is expected to advance the understanding of perceptual abnormalities as risk factors for LTA and to help clinicians identify those adolescents at risk of a life-threatening asthma exacerbation.