Quantification of dyspnea confirmed by voice pitch analysis
Mohler, J.G.
Bulletin Europeen de Physiopathologie Respiratoire 18(6): 837-850
1982
ISSN/ISBN: 0395-3890 PMID: 6927538 Document Number: 186338
Previous efforts to quantitate dyspnea are reviewed. Here, the voice was recorded at each level of exercise on 44 healthy men exercised to maximum O2 consumption (M.ovrhdot.VO2) by incremental treadmill testing. The fundamental frequency (Fo) was compared to the physical changes noted during exercise associated with dyspnea at each level of O2 uptake (.ovrhdot.VO2) and minute ventilation (.ovrhdot.VE). Fo increased linearly with .ovrhdot.VO2 and .ovrhdot.VE. Fo at M.ovrhdot.VO2 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, .ovrhdot.VO2, .ovrhdot.VE and the subjective assessment of dyspnea by the subject. Equations for predicting M.ovrhdot.VO2 from submaximal exercise are given, which tested favorably against the actual M.ovrhdot.VO2. Because resting Fo was most affected by anxiety, the equation predicting M.ovrhdot.VO2 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 .ovrhdot.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.