Vocal nodules and edema may be due to vibration-induced rises in capillary pressure

Abstract

Hypothesis: Vocal fold vibration may physically raise intravascular pressure to levels high enough to damage capillaries and result in leakage of erythrocytes. This type of injury is commonly seen in benign vocal fold lesions and is not well explained.

Study design: Theoretical, retrospective.

Methods: The relationship of intravascular pressure to vibration frequency and amplitude is derived and confirmed with a physical blood vessel model, then applied to published human measurements to estimate human intravascular pressures.

Results: Vocal fold intravascular pressure is predicted to have a quadratic dependence on both frequency and amplitude. During speaking, the pressure may rise to over 20 cmH2O, and may reach levels far higher for screaming and singing. Such pressure magnitudes are known to trigger inflammatory cascades and can lead to fluid leakage. They also have the potential for pharmacologic control with beta-agonists.

Conclusions: Intravascular pressure likely rises significantly during vocal fold vibration and may lead to the type of injury seen in benign vocal fold lesions. The results support voice therapy aimed at reducing vibratory amplitude. More vibratory amplitude measurements need to be performed in a wider range of subjects before the full range of human vocal fold vascular pressures can be estimated.

Fig. 1

Diagram of a swollen damaged vocal fold blood vessel (not to scale) in relation to the vocal ligament, thyroarytenoid muscle, and laryngeal cartilages. We simplified vessel vibration to lateral motion along the y-direction. The white arrows show the compression of fluid within the vessel from the inertial forces. A indicates the maximum amplitude.

Fig. 2

Physical model simulating the vocal fold vessels with a latex tube driven by an electromagnet.

Fig. 3

(A) Laser calibrated amplitude and frequency measurements of 13 female and 9 male volunteers with no signs, symptoms, or history of voice disorders, taken from a study by Schuster et al. (B) Estimated peak pressure values with respect to frequency when the measurements from (A) are plugged into equation three with sin²= 1. The fluid density of capillary blood was used for ρ, 1040 kg/m³. The mean and standard deviation of the amplitudes in (A) were used to plot the mean and standard deviation of the estimated peak pressure values in (B).

Fig. 4

Pressure plotted with respect to frequency squared and amplitude squared for each trial of the vibrating tube experiment. The trial numbers, linear regression, and theoretical average correspond to Table I. The inset enlarges the boxed area in the main graph.