RESUMO
PURPOSE: To reveal the qualities and intensity of speaking-related dyspnea in healthy adults under conditions of high ventilatory drive, in which the behavioral and metabolic control of breathing must compete. METHOD: Eleven adults read aloud while breathing different levels of inspired carbon dioxide (CO(2)). After the highest level, participants provided unguided descriptions of their experiences and then selected descriptors from a list. On a subsequent day, participants read aloud while breathing high CO(2) as before, then rated air hunger, physical exertion, and mental effort (with definitions provided). Recordings were made of ventilation (with respiratory magnetometers), end-tidal partial pressure of CO(2), transcutaneous PCO(2), oxygen saturation, noninvasive blood pressure, heart rate, and the speech signal. RESULTS: Unguided descriptions were found to reflect the qualities of air hunger, physical exertion (work), mental effort, and speech-related observations. As CO(2) stimulus strength increased, participants experienced increased perception of air hunger, physical exertion, and mental effort. Simultaneous increases were observed in ventilation, tidal volume, end-inspiratory and end-expiratory volumes, expiratory flow during speaking, nonlinguistic junctures, and nonspeech expirations. CONCLUSION: Two qualities of speaking-related dyspnea--air hunger and physical exertion--are the same as those reported for many other types of nonspeech dyspnea conditions and, therefore, may share the same physiological mechanisms. The mental effort quality associated with speaking-related dyspnea may reflect a conscious drive to balance speech requirements and ventilatory demands. These findings have implications for developing better ways to evaluate and manage clients with respiratory-based speech problems.