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Phonation threshold pressure predictions using viscoelastic properties up to 1,400 Hz of injectables intended for Reinke's space


  • This work was performed at The University of Iowa, Iowa City, Iowa, and was supported by NIH Grant No. DC004224 and No. DC008047 from the National Institute on Deafness and Other Communication Disorders. Cymetra samples were provided by LifeCell Corp. as per study review board request. Carbomer samples and nominal funding for labor were provided by Cytophil, Inc. as part of a preclinical trials contract with The University of Iowa. Cytophil, Inc. was not involved in developing the purpose, experimental design, analysis, results, or discussion of the study. The authors have no other funding, financial relationships, or conflicts of interest to disclose.



Viscoelastic properties of numerous vocal fold injectables have been reported but not at speaking frequencies. For materials intended for Reinke's space, ramifications of property values are of great concern because of their impact on ease of voice onset. Our objectives were: 1) to measure viscoelastic properties of a new nonresorbing carbomer and well-known vocal fold injectables at vocalization frequencies using established and new instrumentation, and 2) to predict phonation threshold pressures using a computer model with intended placement in Reinke's space.

Study Design:

Rheology and phonation threshold pressure calculations.


Injectables were evaluated with a traditional rotational rheometer and a new piezo-rotary vibrator. Using these data at vocalization frequencies, phonation threshold pressures (PTP) were calculated for each biomaterial, assuming a low dimensional model with supraglottic coupling and adjusted vocal fold length and thickness at each frequency. Results were normalized to a nominal PTP value.


Viscoelastic data were acquired at vocalization frequencies as high as 363 to 1,400 Hz for six new carbomer hydrogels, Hylan B, and Extracel intended for vocal fold Reinke's space injection and for Cymetra (lateral injection). Reliability was confirmed with good data overlap when measuring with either rheometer. PTP predictions ranged from 0.001 to 16 times the nominal PTP value of 0.283 kPa.


Accurate viscoelastic measurements of vocal fold injectables are now possible at physiologic frequencies. Hylan B, Extracel, and the new carbomer hydrogels should generate easy vocal onset and sustainable vocalization based on their rheologic properties if injected into Reinke's space. Applications may vary depending on desired longevity of implant. Laryngoscope, 2010