A Pilot Study Assessing the Therapeutic Potential of a Vibratory Positive Expiratory Pressure Device (Acapella Choice) in the Treatment of Voice Disorders

Summary

Introduction

Semioccluded vocal tract exercises (SOVTEs) can involve a single source of vibration (eg, vocal folds in the straw exercise) or a dual source of vibration (eg, vocal folds and water bubbling in tube phonation) in the vocal tract. Oftentimes, this secondary source of vibration causes large oscillations in intraoral pressure and has been likened to a "massage effect." This study assesses the implementation of a positive expiratory pressure device (Acapella Choice) as a possible alternative SOVTE, which presents a secondary source of vibration without the need of a water container.

Methods

Twenty-two normophonic participants underwent acoustic, electroglottographic, and aerodynamic assessment before, during, and after phonation with two different established SOTVEs (silicone tube in water and straw in air) in addition to Acapella Choice.

Results

Acapella Choice produced the largest peak-to-peak amplitudes of intraoral pressure oscillation. Straw in air produced the largest static intraoral pressure. Straw in air and Acapella Choice presented significantly larger ranges of static pressures than tube in water phonation. Post-exercise condition showed a statistically larger sound pressure level for Acapella Choice.

Conclusions

Positive expiratory pressure devices, such as Acapella Choice, may be a promising alternative to established SOVTEs as it promotes large oscillatory pressures in the vocal tract without the need for a water container. This exercise also produces larger sound pressure level with no significant changes in glottic contact quotient, indicating improved vocal economy.

Introduction

The therapeutic process often sees clinicians adapting techniques and tools for novel applications. Those engaged in voice rehabilitation are no exception; devices that have been found to have clinical application in dysphonia but which were developed for a different purpose include kazoos,¹ "flow ball" toys,² and variably occluded face masks.3, 4

These devices served to partially narrow and/or elongate the vocal tract, and as such, are forms of semioccluded vocal tract exercise (SOVTE). A common feature of SOVTEs is the increased flow resistance that promotes larger intraoral pressure that, in turn, reduces the transglottal pressure and increases the intraglottal pressure.5, 6, 7 Assuming a constant subglottal pressure, raising the intraglottal pressure causes the vocal folds to separate, reducing adduction. A reduction in the level of vocal fold adduction could be considered advantageous in the treatment of subjects with hyperfunctional voice disorders. In addition, phonation into tubes causes the first acoustic resonance of the vocal tract to lower toward the fundamental frequency increasing the positive reactance of the vocal tract that aids the mechanical vibration of the vocal folds.⁸ This system optimization is further improved by reduced phonation threshold pressure and increased harmonic amplitude caused by faster flow cessation.

SOVTEs using tube phonation can be performed with the distal end of the tube in air or submerged under water. By submerging the distal end of the tube under water, water bubbling is generated adding an oscillatory component to the static intraoral pressure.9, 10, 11, 12 This pressure modulation by the water bubbling is described as producing a "massage effect" on the laryngeal muscles6, 9^,10,13, 14, 15 that supposedly counteracts harmful maladaptations such as hyperfunctional phonation. In SOVTEs involving submersion in water, phonation is achieved once the hydrostatic pressure of the depth of the water is overcome. Hence, the depth of water can be manipulated as part of a therapeutic intervention.

Two distinct methods have been suggested for tube phonation with the distal end submerged under water: Resonance Tube Phonation¹⁶ and LaxVox.¹⁷ Resonance Tube Phonation uses a glass tube submerged under the surface of water in a tank (no volume requirements are prescribed) at about a 45° angle, while LaxVox is implemented via a silicone tube submerged in a water bottle. Due to the flexibility of the silicone tube, no precise angle is prescribed for LaxVox; however, instruction regarding posture and the length and diameter of tube are offered. For more information regarding Resonance Tube Phonation and LaxVox, refer to Simberg and Laine¹³ and Sihvo and Denizoglu,¹⁷ respectively.

Vibratory positive expiratory pressure (PEP) devices are traditionally used to mobilize secretions in the treatment of excessive sputum or secretion retention in conditions such as cystic fibrosis and neurogenic diseases. The PEP devices are variously composed of a mouthpiece attached to a plastic cone containing a metal sphere, which is rhythmically displaced by the airflow (such as the FLUTTER, Aptalis Pharma Inc, Bridgewater, New Jersey) or to a tube with a distal oscillatory arm that closes and opens with airflow (such as Acapella Choice, Smiths Medical ASD, Inc, Rockland, Massachusetts). PEP devices aim to match the frequency of vibration of the ciliary epithelium in the lungs, hence promoting the expectoration of secretions.¹⁸

A practical limitation for implementing Resonance Tube Phonation in water/LaxVox is the evident requirement of an accessible water container. PEP, which would seem to offer an alternative source of oscillatory pressure without such requirements, might therefore have potential as a form of SOVTE.

This study sought to evaluate the physiological effects of a vibratory positive expiratory pressure device, Acapella Choice (Figure 1), on the vocal apparatus with the aim of assessing its implementation as a form of SOVTE. In specific, the oscillatory and static component of the intraoral pressure were assessed and compared to two other well-established SOVTEs, straw phonation in air (henceforth referred to as Straw) and silicone tube in water (henceforth referred to as Tube) on the voices of normal subjects. These exercises were chosen as useful exemplars of techniques not only in common clinical use, but also because they represent a variety of degree of resistance and presence/absence of oscillation.