Breathing and phonation : effects of lung volume and breathing behaviour on voice function
Abstract: Respiration is believed to play a central role in voice function and is thus of relevance to the clinical care of the disordered voice. The overall aim of the present study was to experimentally investigate relationships between the respiratory and phonatory systems. In Studies I, II and III, healthy and vocally untrained subjects were studied with regard to effects of lung volume on the glottal voice source and on vertical laryngeal position during phonation. In Study IV, phonatory breathing behaviours were compared between females with vocal nodules and females with normal voices. Also, five different speech tasks were used in order to investigate the effects of speech material on respiratory measurements. In study V, the inhalatory strategy of expanding the abdominal wall was compared to the paradoxical inward abdominal movement during inhalation, with regard to the effect on vertical laryngeal position in healthy subjects. In study VI, the accuracy with which inhalations can be perceptually detected from audio recordings of reading was investigated. Relative lung volumes, as well as thoracic and abdominal movements, were documented by respiratory inductive plethysmography. Vocal fold vibrations were studied indirectly by inverse filtering of the airflow. Subglottal pressure was estimated from the oral pressure during production of [p] in vowel context. Vertical laryngeal position was measured using two-channel electroglottography. It was found that phonation at high lung volume was associated with a higher subglottal pressure as compared to phonation at low lung volume. Thus, the subjects did not compensate in terms of respiratory muscle activity for the decreasing recoil forces resulting from a decreasing lung volume. The glottal voice source was affected in such a way that the overall glottal adduction was weaker at high lung volume than at low lung volume. In addition, the vertical laryngeal position was lower at high lung volume than at low lung volume. A possible underlying mechanism for these effects is a mechanical linkage between the respiratory apparatus and the larynx in terms of the tracheal pull. Females with vocal nodules were shown to produce speech with a higher SPL than females without nodules. They also inhaled more often and, when shouting, initiated phrases at lower lung volume levels than females without nodules, thus refraining from taking advantage of the increased recoil contributions to PS associated with high lung volumes. The influence of speech task was significant to measurements of respiratory behaviour during phonation. Inhalation with expansion of the abdominal wall was associated with a higher vertical laryngeal position as compared to inhalation with a paradoxical abdominal movement. This effect might be due to postural changes associated with the inhalatory conditions. Finally, inhalations during reading were correctly detected to an average of over 90 percent by untrained listeners. Thus, perceptual detection of inhalations may be an easy method for discovering characteristics of breathing behaviours, which should be further examined.
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