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Professional voice users are a diverse group of individuals with high vocal demands and unique health considerations. This group includes vocal performers, teachers, lawyers, professors, orators, clergy, and call-center workers. Professional voice users are essentially vocal athletes, with the same career-ending implications and potential setbacks during long and busy careers. They are often highly attuned to small changes in vocal function with significant functional impact due to their high vocal demands. In addition, vocal performers and orators may have formal voice training, increasing their sensitivity to minor changes in vocal biomechanics. Management of voice disorders in this population requires special consideration encompassing a detailed history, finer points of laryngeal imaging, specialized voice therapy, and occasionally meticulous phonomicrosurgical techniques.
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ANATOMY AND PHYSIOLOGY
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Voice production for both speech and song is a complex process of fluid dynamics affecting the air column extending from the lungs to the lips and involving multiple body systems. The larynx serves as a transformer in converting aerodynamic energy from the lungs into the acoustic energy of voice. This relies, in part, upon the laryngeal structural anatomy, but also more broadly upon the entire respiratory tract, mucous membranes and musculature of the oral cavity and oropharynx, and upper body musculoskeletal system. The process begins with the action of the intercostal and abdominal muscles acting along with the natural recoil of the chest wall to create a pressure gradient forcing air from the lungs up into the trachea and subglottis. This forced air is the power source for phonation. When the vocal folds (VF) are closed, pressure within the subglottis rises. As the subglottic pressure overcomes the closing force of the VF, the VF are pushed laterally and a mucosal wave is entrained across their surface. The VF then recoil and close, momentarily stopping airflow until the subglottic pressure once again overcomes the VF closing force. A proper balance must be achieved between subglottic pressure and the closing forces of the VF to maintain stable airflow and an ongoing glottal cycle. This requires complex muscular action and coordination of several muscles within the upper torso. With stable airflow, a steady phonatory cycle of the VF opening and closing occurs. As the closing part of the cycle interrupts the airflow, sound waves (acoustic energy) are translated forward into the oropharynx. The upper airway then acts as a resonator amplifying and manipulating the basic acoustic signal. Finally, articulation in the oral cavity modifies this sound into speech and song.
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The laminar structure of the VF with its varying rheologic properties is crucial to maintaining proper mechanics of phonation. To achieve this transformation efficiently, the epithelial cover must easily slide over the stiffer underlying VF structures. The dynamic relationship between tissue layers principally relies on the viscoelastic properties of the superficial lamina propria. This unique layer consists of a high concentration of hyaluronic acid, a loose network of elastin fibers, and a ...