Vocal Fold Surface Hydration: A Review

Abstract

Vocal fold surface liquid homeostasis contributes to optimal vocal physiology. In this paper we review emerging evidence that vocal fold surface liquid is maintained in part by salt and water fluxes across the epithelium. Based on recent immunolocalization and electrophysiological findings, we describe a transcellular pathway as one mechanism for regulating superficial vocal fold hydration. We propose that the pathway includes the sodium-potassium pump, sodium-potassium-chloride cotransporter, epithelial sodium channels, cystic fibrosis transmembrane regulator chloride channels, and aquaporin water channels. By integrating knowledge of the regulating mechanisms underlying ion and fluid transport with observations from hydration challenges and treatments using in vitro and in vivo studies, we provide a theoretical basis for understanding how environmental and behavioral challenges and clinical interventions may modify vocal fold surface liquid composition. We present converging evidence that clinical protocols directed at facilitating vocal fold epithelial ion and fluid transport may benefit healthy speakers, those with voice disorders, and those at risk for voice disorders.

Climate, vocal folds, and tonal languages: Connecting the physiological and geographic dots

“…Independent of its desiccation, cold air inhaled via the nasal cavity yields greater bronchoconstriction and increased nasal fluid (27), two factors that promote oral breathing. Oral breathing, even of nondry air, promotes the desiccation of the vocal tract and the evaporation of the airway surface liquid of the vocal cords, and the latter has been shown to yield a variety of difficulties vis-à-vis precise phonation (14). The effects of breathing cold air on the vocal tract and the larynx have been supported by numerous studies of those active outdoors in frigid contexts (28,29).…”

“…Fundamental frequency is impacted by hydration or dehydration according to a variety of metrics obtained from in vivo and ex vivo laboratory studies. Increased hydration is associated with heightened vocal fold viscosity and facility of phonation (14). In contrast, dehydration of the vocal folds is associated with increased phonation threshold pressure (PTP) and increased perceived phonation effort (PPE) (14), although the extent of PTP increase remains a matter of inquiry (15).…”

“…Increased hydration is associated with heightened vocal fold viscosity and facility of phonation (14). In contrast, dehydration of the vocal folds is associated with increased phonation threshold pressure (PTP) and increased perceived phonation effort (PPE) (14), although the extent of PTP increase remains a matter of inquiry (15). Laryngeal dehydration is also associated with alterations to the ionic composition of the vocal fold surface liquid, more specifically an increase in Na + concentration and associated modulation to vocal fold elasticity (16,17).…”

“…In short, under both laboratory and naturalistic conditions, the inhalation of very cold and arid air yields short-term and long-term desiccating effects on the vocal tract and the vocal cords. And desiccation of the vocal cords has been clearly tied to imprecision of phonation (14).…”

Effect of systemic isotretinoin treatment on voice

“…The mucus layer (sol layer, 10 μm in depth) which is a highly delicate structure on the surface of VFs is essential for healthy phonation. [12] It has been reported by Witt et al [13] that superficial dehydration of the VFs may decrease the amplitude and frequency of the mucosal wave. The amount of energy distribution during vibration of VFs increases with viscosity; therefore, more aerodynamic energy is required to maintain the same phonatory status.…”