Dyspnea frequently accompanies a variety of cardiopulmonary abnormalities. Although dyspnea is often considered a single sensation, alternatively it may encompass multiple sensations that are not well explained by a single physiologic mechanism. To investigate whether breathlessness experienced by patients represents more than one sensation, we studied 53 patients with one of the following seven conditions: pulmonary vascular disease, neuromuscular and chest wall disease, congestive heart failure, pregnancy, interstitial lung disease, asthma, and chronic obstructive pulmonary disease. Patients were asked to choose descriptions of their sensation(s) of breathlessness from a dyspnea questionnaire listing 19 descriptors. Cluster analysis was used to identify natural groupings among the chosen descriptors. We found that patients could distinguish different sensations of breathlessness. In addition, we found an association between certain groups of descriptors and specific conditions producing dyspnea. These findings concur with those in an earlier study in normal volunteers in whom dyspnea was induced by various stimuli. We conclude that different types of dyspnea exist in patients with a variety of cardiopulmonary abnormalities. Furthermore, different mechanisms may mediate these various sensations.

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For each 3-digit number in a protracted sequence of such numbers, Ss responded "old" or "new" depending on whether they did or did not remember having seen that number at an earlier point in the sequence. Each number was presented twice; but the number of other 3-digit numbers intervening between the 1st and 2nd presentation of the same number was manipulated as the independent variable. A trace model yielded theoretical curves that were a close fit to the data obtained. "The fitted curves also made possible the estimation of a lower bound on the amount of information that Ss are able to carry along at any one time during an arbitrarily protracted sequence of three-digit numbers." (28 ref.) From Psyc Abstracts 36:04:4CL02S.

Various theories about the genesis of dyspnea have often assumed that the sensation is similar from patient to patient and is generated by a single underlying mechanism. To investigate whether breathlessness induced in normal volunteers by different stimuli represents one or more than one sensation, we studied 30 subjects in whom breathlessness was induced by each of 8 different stimuli: breath-holding, CO2 inhalation, inhalation of CO2, with ventilation voluntarily targeted below the level dictated by chemical drive, breathing with a resistive load, breathing with an elastic load, voluntary elevation of functional residual capacity, voluntary limitation of tidal volume, and exercise. For each stimulus, subjects were asked to choose description of their sensation(s) of breathlessness from a questionnaire listing 19 descriptors. The responses from this questionnaire were evaluated using cluster analysis to search for relationships among descriptors and to identify natural groupings. We found that distinct groups of descriptors emerged, i.e., subjects could distinguish different sensations of breathlessness. In addition, we found an association between certain descriptor groups and stimuli. We conclude that the term breathlessness may encompass multiple sensations, and, therefore, may not be explainable by a single physiologic mechanism.

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