Quantification of dyspnea confirmed by voice pitch analysis

Previous efforts to quantitate dyspnea are reviewed. In this study, the voice was recorded at each level of exercise on 44 healthy male subjects exercised to maximum oxygen consumption (MVO2) by incremental treadmill testing. The fundamental frequency (FO) was compared to the physical changes noted during exercise associated with dyspnea at each level of oxygen uptake (VO2) and minute ventilation (VE). FO increased linearly with VO2 and VE. FO at MVO2 was about 1.66 times FO at rest; the slope of the increase was an individual characteristic. The sum of the graded signs of dyspnea codes (dyspnea sum index, DSI) also agreed with the measured voice changes, VO2, VE and the subjective assessment of dyspnea by the subject. Equations for predicting MVO2 from submaximal exercise are given which tested favorably against the actual MVO2. Because resting FO was most affected by anxiety, the equation predicting MVO2 from FO was not as reliable as from DSI. FO is a function of elastic properties of the vocal folds, which change in response to increased VE by permitting air to pass through "air shunts" of the arytenoid aperture. This creates a falsetto characteristic to the voice and is perceived as a stress quality. FO is a measurement reflecting many changes in the larynx with stress of exercise and perceived dyspnea. The laryngeal changes during exercise are reviewed, and the basis for the correlation between qualities of the voice and quantities such as FO are suggested.