Speaking-related dyspnea in healthy adults

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.