Laryngeal vibratory mechanisms: the notion of vocal register revisited.

This study, focused on the laryngeal source level, introduces the concept of laryngeal vibratory mechanism. Human phonation is characterized by the use of four laryngeal mechanisms, labeled M0-M3, as evidenced by the electroglottographic (EGG) study of the transition phenomena between mechanisms with a population of men and women, trained and untrained singers. Macroscopic and local descriptions of the EGG signal are analyzed during the production of glissandos and held notes with different mechanisms. The transition from one mechanism to another of higher rank is characterized by a jump in frequency, a reduction of EGG amplitude, and a change in the shape of the derivative of the EGG (which may correspond to a reduction of the vibratory mass). These characteristics are used to identify a transition between two mechanisms, in complement with acoustic spectrographic analyses. The pitches of transitions between the two main mechanisms M1 and M2 and the range of the frequency-overlap region are described in detail. The notion of vocal register is revisited in the light of these concepts of laryngeal mechanism. The literature on vocal registers is reviewed, and it is shown that the confusion often cited with respect to this notion may be related to the heterogeneity of the approaches and methods used to describe the phenomena and to the multiplicity of descriptors. Therefore, the terminology of the registers is organized depending on their relation to the four laryngeal vibratory mechanisms.

Use of reaction time in the temporal analysis of normal swallowing.

This study was performed to establish the swallowing trigger by using the reaction time from an auditory stimulus. With this stable temporal starting point, we described the chronology of the different acoustic, electrophysiologic, and respiratory events that occurred during swallowing in a population of normal adults. We studied the swallowing reaction time (SRT) in 18 subjects aged 23 to 73 years by using acoustic, electroglottographic (EGG), and aerodynamic recordings. The chronology (the beginning of EGG activity, apnea, and respiratory sound and release) was identified in 91% of the recordings. The average SRT was 264 ms and the average swallowing duration was 977 ms, without any significant difference with respect to gender. The swallowing sound produced during apnea was composed of either two or three components. The reaction time procedure also demonstrated that the first sound component was unstable. By using this procedure for studying swallowing, we were able to stabilize the chronology of the different events, improve the subjects' attention, and establish a fixed benchmark for performing temporal measurements.

[Laryngeal registers as shown in the voice range profile]. / Phonétogramme par registre laryngé.

Voice range profile (VRP) is a well-known vocal test. Usually, it consists of a single diagram based on the whole voice range. When practised separately in each individual laryngeal mechanism, VRP may offer much information on both the relative development of the different mechanisms used by the subject and the extension of the common area between two consecutive mechanisms. We present the results obtained from 42 subjects of both sexes who have different singing technique levels: professional singers, student and amateur singers, as well as subjects without any experience in singing. For each mechanism, the global VRP area and the dynamic range were computed. Results are discussed in relation to sex category and vocal training of subjects. Exploring systematically VRP for each mechanism gives new and valuable information on register managing in singing practice.

Laryngeal paralysis: distinguishing Xth nerve from recurrent nerve paralysis through videoendoscopic swallowing study (VESS).

Distinction between unilateral recurrent laryngeal nerve paralysis and Xth nerve paralysis is a rarely addressed issue in the literature. However, it may be crucial to examine the cause of the paralysis and to perform the appropriate investigation. The videoendoscopic swallowing study has been demonstrated to be a useful tool in assessing pharyngeal function. Since in unilateral Xth nerve paralysis the pharynx is impaired on the same side as the vocal fold immobility, it may be easily detected by videoendoscopic swallowing study. The rotation of the posterolateral pharyngeal wall toward the opposite side during swallowing is a sign of impaired motor pharyngeal branches. To demonstrate the usefulness of the videoendoscopic swallowing study in distinguishing unilateral Xth nerve from isolated recurrent nerve paralysis, a series of six patients were studied prospectively. Diagnosis of Xth nerve paralysis focused the investigation toward the high neck or the skull base area. Paralysis of the Xth nerve was suspected in all cases and diagnosis was achieved in five cases by the workup performed. Videoendoscopic swallowing study is a cost-effective and easily available tool which should be performed in all cases of vocal fold paralysis.

Role of medialization in the improvement of breath control in unilateral vocal fold paralysis.

A prospective study was performed on 18 adults to analyze disturbances of voice and respiratory function in unilateral vocal fold paralysis and the role of medialization in the improvement of breath control. In addition to physical examination, an acoustic and aerodynamic analysis, as well as patient self-assessment, were performed both before and after medialization (14 fat injections, 4 thyroplasties) to evaluate voice and both phonatory breath control and respiratory function outcome. Preoperative and postoperative results, at short, middle, and long term, were compared to data from 14 control subjects and evaluated by statistical analysis. Preoperative acoustic and aerodynamic parameters were significantly disturbed in comparison to controls. Independently of the pulmonary status, medialization induced an improvement in most of the parameters at short and long terms, whereas a diminished effect was observed at middle term. Phonatory breath control, as evaluated by maximum phonation time, mean flow rate, and expired volume, was statistically improved, with the best results being obtained in women. From the questionnaire, it was clear that voice, as well as phonatory breath control and respiratory function, showed considerable improvement, although some difficulties persisted during effort. This study demonstrates that there is a disturbance of phonatory breath control and respiratory function in adult unilateral vocal fold paralysis. Improvement following medialization supports the concept that the respiratory dysfunction seen beforehand is most probably the result of air escape rather than laryngeal obstruction. Although medialization may provoke an extrathoracic obstruction, its feature of variability appears to improve breath control.