Effect of Vocal Exercises With Straw on Aerodynamic Parameters of Voice (Pressure, Flow) in Dysodic Singers With Nodules

Singers are over-represented in phoniatric consultations; they present increased risk of developing voice disorders whether they are amateurs or professionals. They represent a specific population among phoniatric patients because of their increased sensitivity to the slightest vocal change that makes them consult earlier than non-singers. In addition, their complaints are specific to singing voice.

In phoniatrics, at the CHU Gui de Chauliac in Montpellier, singers (amateurs and professionals) represent one third of phoniatric patients. 80% of them are diagnosed with dysodia. Dysodia refers to singing voice disorders, in the same way as dysphonia refers to speaking voice disorders.

Dysodia results in a variety of symptoms. Acoustic signs are the most numerous: tonal anomalies (lack of accuracy, reduction of vocal range); dynamic anomalies (problem to sing softly or loudly); timbre abnormalities (vibrato problems, strained voice , roughness, difficulties on attacks). Dysodia also results in respiratory disorders, physical signs, psychological consequences and damage to hedonistic properties (loss of comfort, vocal endurance, musicality).

It can reach amateur or professional singers. For professional singers, voice is the main working tool. When they have dysodia, professional difficulties can be temporary or even lead to the loss of work. In addition, dysodia can lead to financial loss and well-documented anxiety. For amateur singers, dysodia hinders their musical practice, thus limiting the recognized benefits of choral singing on cohesion, social integration and personal development.

Prevalence of dysodia is higher among women. This vocal disorder is most often associated with laryngeal pathology. Nodular lesions are most common in singers as in general population. Nodules are the consequence of vocal straining, also known as vocal hyperfunction.

Singing means learning, more or less finely, depending on the level of training and singing style, coordination between breath, vocal fold vibrations and resonators, the so-called pneumo-phono-resonant adaptations. To have balanced phonation, singer must properly dose the air pressure he applies under his vocal folds, have a sufficient flow rate and adapt muscular tension of the vocal folds (neither too strain nor too loose). In this mode of phonation, voice resonates without difficulty. On the other hand, during vocal straining, singer will put too much subglottal pressure decreasing flow rate, which creates a laryngeal tightening and can eventually cause nodules. The pressure threshold required to initiate a sound (phonation pressure threshold) is then increased. Vocal gesture is therefore inappropriate and the voice becomes ineffective.

After diagnosis of dysodia and vocal assessment to identify the patient's difficulties, the patient is referred to speech-language pathologist for voice therapy. According to the vocal difficulties identified, speech therapist defines the therapeutic objectives that will be adapted to each patient and individualized according to the diagnosis, the singer's profile, but also his objectives and his investment. Voice therapy aims not only to prevent the onset or aggravation of vocal disturbances but also to remove or compensate for voice limitations by reconditioning vocal gesture to make it more effective. In the case of nodular lesions, voice therapy therefore aims to reduce vocal straining.

There is no specific therapeutic tool for singers. As in speaking voice, speech-language pathologist uses technical aids as well as indirect and direct therapies. The main technical aid proposed is amplification of voice with a microphone in the event of vocal misuse or abuse, i.e. when the vocal load is too high. Indirect therapy consists of giving vocal hygiene advice, in order to eliminate causes of voice disorder and to establish a vocal economy program with the patient. On the other hand, direct therapy consists in directly modifying vocal gesture through vocal exercises. This therapy is based on the premise that the subject has acquired an inappropriate vocal gesture that the therapist identifies and corrects through vocal exercices. Direct therapy is based on three successive steps: i) rehabilitation of respiratory gesture, ii) work on a vocal emission without associated tension, so as to eventually reduce laryngeal lesions, and iii) awareness of the role of resonance cavities.

Concerning work of vocal emission, to reduce vocal straining, many therapies are based on semi-occluded vocal tract exercises, also called physiological exercises. They include labial and lingual trills (lip and tongue vibration), nasal consonants, voiced fricative consonants, kazoo as well as tubes or straws. Straw exercises are the most reproducible due to the precise calibration of occlusion. Montpellier University Hospital is the national leader in the development of these straw exercises in France, with a particular focus on flow control during the exercises.

The purpose of these exercises is to teach the patient to use proper air pressure and flow while singing. Several studies are investigating effects of these straw exercises on aerodynamic parameters of subglottal pressure, phonation pressure threshold and oral airflow. It appears that:

• straw exercises reduce estimated subglottal pressure. For non-singers, this is true after 15 minutes of exercises as well as after 8 rehabilitation sessions. For singers, results are more variable and concern only singers without voice disorders. No studies have explored effect of straw exercises on estimated subglottal pressure in dysodic singers.
• straw exercises lower phonation threshold pressure (PTP). Most studies find a decrease in PTP after straw exercises, either in non-singer patients with speaking voice disorders or in choristers without voice disorders. No studies have explored effect of straw exercises on PTP in dysodic singers.
• Literature does not provide information on impact of straw exercises on oral airflow. In euphonic subjects (without vocal disorder), whether singers or not, majority of studies find an increase in airflow after straw exercises. Only one study found no difference in airflow after straw exercises, while airflow increased after vocal exercises without straw (vocalized). In dysphonic patients, no difference in flow rate is observed after straw exercises. No studies have explored effect of straw exercises on airflow in dysodic singers.

Thus, no study to date has explored effect of straw exercises on aerodynamic parameters (estimated subglottal pressure, PTP, oral airflow) in dysodic singers. Singers are often targeted as a study population because of their familiarity with semi-occluded exercises but not to further explore singing voice. For example, in a study only one frequency is tested (pitch and comfortable intensity), so singing voice is not further explored. However, the economic and psychological impact of dysodia, particularly among professionals, is well described in the literature.

In this project the investigator want to fill this gap by studying the singing voice effect of straw exercises on the estimated subglottal pressure, PTP and oral airflow in dysodic women singers. Do straw vocal exercises modify aerodynamic behaviour of dysodic women singers with nodules after a rehabilitation session? Based on results of literature for speaking and singing non-pathological voice, the investigator hypothesize that the estimated subglottal pressure and PTP will decrease after straw exercise session while they will remain constant after open mouth exercise session. Meanwhile, the investigator hypothesize that oral airflow will increase following straw exercises while it will remain constant after open-mouth exercises.