Chronic obstructive pulmonary disease (COPD) has a major impact on medical statistics in the United States. For example, the chronic respiratory diseases are the most rapidly increasing of the top ten leading causes of death, rising at a rate of 1.4% per year. The major complaint of patients with COPD is dyspnea (breathlessness), but the role of respiratory sensations in the disordered breathing of patients with lung disease is poorly understood. There have been many psychophysical studies, in normals and in patients with lung disease, designed to assess the sensory impact of respiratory loads using both threshold detection and magnitude scaling techniques. Clinical rating scales and exercise tests have been used also to quantify the experience of unpleasant respiratory sensations. However, no consensus has emerged either about the physical stimuli underlying respiratory sensations or about which sensory attributes underlie psychophysical decisions. This confusion relates in part to limitations associated with behavioral measures of respiratory sensations. For example, magnitude scaling requires that the subject attend to a single sensory aspect of breathing closely specified by the experimenter. In other sensory modalities, recordings of sensory and cognitive brain responses have contributed to the understanding of perceptual processing, and to the identification of central processing abnormalities in patient populations. Accordingly, the specific aim of the present application is to examine both sensory and cognitive brain responses elicited by various breathing maneuvers. Studies are proposed to determine the nature of central, respiratory-related signals elicited by static, flow-resistive, and elastic loads added to breathing. Effects of changes in the background level of mechanical impedance on central processing are also of interest. Central nervous system activity (evoked potentials) recorded with surface electrodes will be compared among young and old adults and patients with COPD. Both exogenous (i.e., short-latency, somatosensory evoked potentials) and endogenous potentials (i.e., long-latency, human information processing signals) will be examined. Such activity will be correlated with behavioral responses for standard psychophysical scaling tasks. In this way, the relationship between perception of respiratory sensations, and central processing of respiratory loads, will be examined. These findings could prove useful clinically in the identification of central correlates of aberrant perceptual responses to respiratory loads in patients with obstructive lung disease, and to greater understanding of the problem of breathlessness in these patients.
