Bio

Bio


I received my Master’s degree in speech language pathology from Purdue University in 2008. I then completed my Clinical Fellowship Year (CFY) at Indiana University Health – Arnett Hospital in Lafayette, Indiana. Following the completion of my Master’s degree, I remained at Purdue and received my PhD in 2012 in laryngeal physiology with M. Preeti Sivasankar, PhD. I then completed postdoctoral training in the Department of Surgery, Division of Otolaryngology – Head & Neck Surgery at the University of Wisconsin-Madison in the laboratory of Susan L. Thibeault, PhD studying vocal fold biology.

I joined the Stanford faculty in 2014 as an Assistant Professor. My clinical interests include the evaluation and treatment of patients with voice, resonance, airway, and swallowing disorders.

My overarching research goal is to use techniques from the basic sciences and human clinical sciences to improve the prevention and management of voice disorders. My research program is directed at improving our understanding of the biologic barriers essential to vocal fold health. Specifically, I investigate how external factors implicated in the development of voice disorders, such as inhaled pollutants, bacteria, and viruses, compromise the function of the vocal fold epithelial and mucus barriers and how these changes may influence voice production. I am also interested in clinical and quality of life outcomes in patients with voice disorders undergoing surgical or behavioral interventions. My ultimate aim is to utilize my research findings to develop novel interventions to prevent and manage voice disorders.

Academic Appointments


  • Assistant Professor - Med Center Line, Otolaryngology - Head & Neck Surgery Divisions
  • Member, Bio-X

Honors & Awards


  • New Investigator Research Grant, American-Speech-Language-Hearing Foundation (2015)
  • The Fall Voice Conference Travel Grant, National Spasmodic Dysphonia Association (2015)
  • National Institutes of Health Extramural Loan Repayment Award for Clinical Research, National Institutes of Health (2013-)
  • Meritorious Poster Submission, American Speech-Language-Hearing Association (2012)
  • Third Place Poster Award, American Laryngological Society (2012)
  • Alumni and Friends Award, Department of Speech, Language, and Hearing Sciences, Purdue University (2010)
  • New Century Scholars Doctoral Scholarship, American-Speech-Language-Hearing Foundation (2010)
  • Wilson Travel Scholarship, Department of Speech, Language, and Hearing Sciences, Purdue University (2010)
  • Student Research Travel Award, American Speech-Language-Hearing Association (2009)
  • Frederick N. Andrews Fellowship, Purdue Graduate School (2008)
  • Outstanding Student Clinician in Speech-Language Pathology, Indiana Speech-Language-Hearing Association (2008)
  • Travel Grant, Purdue Graduate Student Government (2008)
  • Outstanding Student Clinician in Speech-Language Pathology, Indiana Lion’s Club (2007)

Boards, Advisory Committees, Professional Organizations


  • Member, American Speech-Language-Hearing Association (ASHA) (2010 - Present)
  • Member, ASHA, Special Interest Group - 3: Voice and Voice Disorders (2010 - Present)
  • Member, ASHA, Special Interest Group - 13: Swallowing and Swallowing Disorders (2014 - Present)

Professional Education


  • Postdoctoral Fellowship, University of Wisconsin - Madison, Vocal Fold Biology (2014)
  • Ph.D., Purdue University, Vocal Fold Physiology (2012)
  • M.S., Purdue University, Speech Language Pathology (2008)
  • B.S., Purdue University, Speech, Language, & Hearing Sciences (2006)

Teaching

2017-18 Courses


Publications

All Publications


  • Phonomicrosurgery simulation: A low-cost teaching model using easily accessible materials. Laryngoscope Zambricki, E. A., Bergeron, J. L., DiRenzo, E. E., Sung, C. K. 2016; 126 (11): 2528-2533

    Abstract

    To introduce the use of a new phonomicrosurgical trainer using easily accessible materials, and to establish the effectiveness of the model.The model uses a grape imbedded in gelatin, a microscope, and microlaryngeal instruments. The study was designed to test baseline differences in training levels, as well as improvement in performance after training with the simulation model.Thirty subjects enrolled in the Stanford University School of Medicine otolaryngology training program performed microlaryngeal surgery tasks on a grape. Tasks were designed to model both excision of a vocal fold lesion and vocal fold injection. Anonymized video recordings comparing presimulation and postsimulation training were collected and graded by an expert laryngologist. Both objective comparison of skills and subjective participant surveys were analyzed.Objectively, trainees in all groups made statistically significant improvements across all tested variables, including microscope positioning, creation of a linear incision, elevation of epithelial flaps, excision of a crescent of tissue, vocal fold injection, preservation of remaining tissue, and time to complete all tasks. Subjectively, 100% of participants felt that they had increased comfort with microlaryngeal instruments and decreased intimidation of microlaryngeal surgery after completing the simulation training. This appreciation of skills was most notable and statistically significant in the intern trainees.Microlaryngeal surgical simulation is a tool that can be used to train residents to prepare them for phonomicrosurgical procedures at all levels of training. Our low-cost model with accessible materials can be easily duplicated and used to introduce trainees to microlaryngeal surgery or improve skills of more senior trainees.1B. Laryngoscope, 2016.

    View details for DOI 10.1002/lary.25940

    View details for PubMedID 27107403

  • Vocal Tremor: Novel Therapeutic Target for Deep Brain Stimulation. Brain sciences Ravikumar, V. K., Ho, A. L., Parker, J. J., Erickson-DiRenzo, E., Halpern, C. H. 2016; 6 (4)

    Abstract

    Tremulous voice is characteristically associated with essential tremor, and is referred to as essential vocal tremor (EVT). Current estimates suggest that up to 40% of individuals diagnosed with essential tremor also present with EVT, which is associated with an impaired quality of life. Traditional EVT treatments have demonstrated limited success in long-term management of symptoms. However, voice tremor has been noted to decrease in patients receiving deep brain stimulation (DBS) with the targeting of thalamic nuclei. In this study, we describe our multidisciplinary procedure for awake, frameless DBS with optimal stimulation targets as well as acoustic analysis and laryngoscopic assessment to quantify tremor reduction. Finally, we investigate the most recent clinical evidence regarding the procedure.

    View details for PubMedID 27735866

    View details for PubMedCentralID PMC5187562

  • Early Cellular Response to Radiation in Human Vocal Fold Fibroblasts. The Annals of otology, rhinology, and laryngology Erickson-DiRenzo, E., Enos, G., Thibeault, S. L. 2016; 125 (5): 425-432

    Abstract

    Radiation therapy is a common treatment strategy for laryngeal carcinoma. However, radiation is not without adverse side effects, especially toward healthy vocal fold tissue, which can lead to long-term impairments in vocal function. The objective of this preliminary study was to investigate early responses of healthy human vocal fold fibroblasts (VFF) to radiation.VFF were exposed to a single or fractionated dose radiation scheme. Nonradiated VFF served as controls. Morphology of radiated and control VFF was subjectively examined. Quantitative polymerase chain reaction was used to evaluate the effect of radiation on extracellular matrix and inflammatory-related genes. VFF viability was investigated using a LIVE/DEAD and clonogenic assay.Single or fractioned dose radiated VFF were morphologically indistinguishable from control VFF. No significant differences in gene expression were observed following either radiation scheme and as compared to controls. Clonogenic assay revealed reduced VFF viability following the fractionated but not single dose scheme. No changes in viability were detected using the LIVE/DEAD assay.We present one of the first investigations to evaluate early responses of healthy VFF to radiation. Findings will contribute to a growing body of literature seeking to elucidate the biological mechanisms underlying voice changes following radiation therapy for laryngeal carcinoma.

    View details for DOI 10.1177/0003489415615140

    View details for PubMedID 26553661

  • Deep brain stimulation for vocal tremor: a comprehensive, multidisciplinary methodology. Neurosurgical focus Ho, A. L., Erickson-DiRenzo, E., Pendharkar, A. V., Sung, C., Halpern, C. H. 2015; 38 (6): E6-?

    Abstract

    Tremulous voice is a characteristic feature of a multitude of movement disorders, but when it occurs in individuals diagnosed with essential tremor, it is referred to as essential vocal tremor (EVT). For individuals with EVT, their tremulous voice is associated with significant social embarrassment and in severe cases may result in the discontinuation of employment and hobbies. Management of EVT is extremely difficult, and current behavioral and medical interventions for vocal tremor result in suboptimal outcomes. Deep brain stimulation (DBS) has been proposed as a potential therapeutic avenue for EVT, but few studies can be identified that have systematically examined improvements in EVT following DBS. The authors describe a case of awake bilateral DBS targeting the ventral intermediate nucleus for a patient suffering from severe voice and arm tremor. They also present their comprehensive, multidisciplinary methodology for definitive treatment of EVT via DBS. To the authors' knowledge, this is the first time comprehensive intraoperative voice evaluation has been used to guide microelectrode/stimulator placement, as well as the first time that standard pre- and post-DBS assessments have been conducted, demonstrating the efficacy of this tailored DBS approach.

    View details for DOI 10.3171/2015.3.FOCUS1537

    View details for PubMedID 26030706

  • Deep brain stimulation for vocal tremor: a comprehensive, multidisciplinary methodology NEUROSURGICAL FOCUS Ho, A. L., Erickson-DiRenzo, E., Pendharkar, A. V., Sung, C., Halpern, C. H. 2015; 38 (6)

    View details for DOI 10.3171/2015.3.FOCUS1537

    View details for Web of Science ID 000355539900006

    View details for PubMedID 26030706

  • Utility of cell viability assays for use with ex vivo vocal fold epithelial tissue. Laryngoscope Erickson-DiRenzo, E., Sivasankar, M. P., Thibeault, S. L. 2015; 125 (5): E180-5

    Abstract

    Ex vivo models are routinely used to investigate the barrier function of the vocal fold epithelium. However, there are limited reports on assays that can be used to investigate the effect of clinically relevant challenges on vocal fold epithelial tissue viability. Our objective was to determine the utility of two assays routinely used in cell culture-a cellular metabolic activity assay and a cell membrane integrity assay-to investigate the viability of ex vivo porcine vocal fold epithelium.Prospective, ex vivo animal study.Porcine vocal folds were exposed to acrolein, hydrochloric acid, or hydrogen peroxide challenge. An untreated, sham challenge was included as a control. Assays including metabolic activity, cell membrane integrity, and histology were used to determine whether challenges reduced epithelial viability as compared to sham.Cell membrane integrity and metabolic activity assays detected reductions in viability following hydrochloric acid and hydrogen peroxide challenges but not acrolein challenge as compared to sham. No challenge produced significant changes in epithelial appearance as evidenced by light microscopy.Metabolic activity and cell membrane integrity assays are valuable tools that can be used to evaluate the viability of ex vivo vocal fold epithelial tissue following clinically relevant challenges. As viability is reduced, the ability of epithelial tissue to maintain its barrier function is compromised. Accurate assessment of viability may provide us clues into understanding mechanisms underlying vocal fold epithelial injury and disease.NA Laryngoscope, 125:E180-E185, 2015.

    View details for DOI 10.1002/lary.25100

    View details for PubMedID 25511412

  • Deep Brain Stimulation for Essential Vocal Tremor: A Technical Report. Cureus Ho, A. L., Choudhri, O., Sung, C. K., DiRenzo, E. E., Halpern, C. H. 2015; 7 (3)

    Abstract

    Essential vocal tremor (EVT) is the presence of a tremulous voice that is commonly associated with essential tremor. Patients with EVT often report a necessary increase in vocal effort that significantly worsens with stress and anxiety and can significantly impact quality of life despite optimal medical and behavioral treatment options. Deep brain stimulation (DBS) has been proposed as an effective therapy for vocal tremor, but very few studies exist in the literature that comprehensively evaluate the efficacy of DBS for specifically addressing EVT. We present a technical report on our multidisciplinary, comprehensive operative methodology for treatment of EVT with frameless, awake deep brain stimulation (DBS).

    View details for DOI 10.7759/cureus.256

    View details for PubMedID 26180680

  • A preliminary investigation of potential biases in phonation threshold pressure analysis. Journal of voice Sundarrajan, A., Erickson-Levendoski, E., Sivasankar, M. P. 2015; 29 (1): 22-25

    Abstract

    Phonation threshold pressure (PTP) is a voice measure used in both research and clinic. PTP data analysis is susceptible to bias from investigator awareness of experimental hypothesis, and poor investigator training. The objective of this study was to systematically examine the role of these two biases on PTP data analysis.Prospective design.Two trained investigators analyzed PTP datasets. The datasets were identical, but uniquely labeled so that the investigators were not aware that the datasets contained the same data. Each investigator analyzed two datasets. For one dataset, investigators were "blinded" to the experimental hypothesis. For the other dataset, the investigators were "unblinded" and provided a fake experimental hypothesis. Intraclass correlations were used to examine intrarater and interrater reliability.For both investigators, intraclass correlations within the excellent range were obtained for intrarater reliability. In contrast, lower intraclass correlations were obtained for interrater reliability.The high intrarater reliability obtained in this preliminary study suggests that awareness of experimental hypothesis may not significantly bias PTP analysis. Conversely, lower interrater reliability is indicative of differences between investigators analyzing the same data. Our findings contribute to the growing body of literature that seeks to standardize the use of PTP in research and the clinic. Future investigations are needed to identify methods to improve interrater reliability and that quantify the effects of biases on PTP data collection.

    View details for DOI 10.1016/j.jvoice.2014.07.001

    View details for PubMedID 25484262

  • Vocal Fold Ion Transport and Mucin Expression Following Acrolein Exposure JOURNAL OF MEMBRANE BIOLOGY Levendoski, E. E., Sivasankar, M. P. 2014; 247 (5): 441-450

    Abstract

    The vocal fold epithelium is exposed to inhaled particulates including pollutants during breathing in everyday environments. Yet, our understanding of the effects of pollutants on vocal fold epithelial function is extremely limited. The objective of this study was to investigate the effect of the pollutant acrolein on two vocal fold epithelial mechanisms: ion transport and mucin (MUC) synthesis. These mechanisms were chosen as each plays a critical role in vocal defense and in maintaining surface hydration which is necessary for optimal voice production. Healthy, native porcine vocal folds (N = 85) were excised and exposed to an acrolein or sham challenge. A 60-min acrolein, but not sham challenge significantly reduced ion transport and inhibited cyclic adenosine monophosphate-dependent, increases in ion transport. Decreases in ion transport were associated with reduced sodium absorption. Within the same timeline, no significant acrolein-induced changes in MUC gene or protein expression were observed. These results improve our understanding of the effects of acrolein on key vocal fold epithelial functions and inform the development of future investigations that seek to elucidate the impact of a wide range of pollutant exposures on vocal fold health.

    View details for DOI 10.1007/s00232-014-9651-2

    View details for Web of Science ID 000334426600008

    View details for PubMedID 24648011

  • Reducing the negative vocal effects of superficial laryngeal dehydration with humidification. The Annals of otology, rhinology, and laryngology Levendoski, E. E., Sundarrajan, A., Sivasankar, M. P. 2014; 123 (7): 475–81

    Abstract

    Environmental humidification is a simple, cost-effective method believed to reduce superficial laryngeal drying. This study sought to validate this belief by investigating whether humidification treatment would reduce the negative effects of superficial laryngeal dehydration on phonation threshold pressure (PTP). Phonation threshold pressure data analysis may be vulnerable to bias because of lack of investigator blinding. Consequently, this study investigated the extent of PTP analysis reliability between unblinded and blinded investigators.Healthy male and female adults were assigned to a vocal fatigue (n = 20) or control group (n = 20) based on their responses to a questionnaire. PTP was assessed after 2 hours of mouth breathing in low humidity (dehydration challenge), following a 5-minute break in ambient humidity, and after 2 hours of mouth breathing in high humidity (humidification).PTP significantly increased following the laryngeal dehydration challenge. After humidification, PTP returned toward baseline. These effects were observed in both subject groups. PTP measurements were highly correlated between the unblinded and blinded investigator.Humidification may be an effective approach to decrease the detrimental voice effects of superficial laryngeal dehydration. These data lay the foundation for future investigations aimed at preventing and treating the negative voice changes associated with chronic, surface laryngeal drying.

    View details for DOI 10.1177/0003489414527230

    View details for PubMedID 24690983

  • Vocal fold epithelial barrier in health and injury: a research review. Journal of speech, language, and hearing research : JSLHR Levendoski, E. E., Leydon, C., Thibeault, S. L. 2014; 57 (5): 1679–91

    Abstract

    Vocal fold epithelium is composed of layers of individual epithelial cells joined by junctional complexes constituting a unique interface with the external environment. This barrier provides structural stability to the vocal folds and protects underlying connective tissue from injury while being nearly continuously exposed to potentially hazardous insults, including environmental or systemic-based irritants such as pollutants and reflux, surgical procedures, and vibratory trauma. Small disruptions in the epithelial barrier may have a large impact on susceptibility to injury and overall vocal health. The purpose of this article is to provide a broad-based review of current knowledge of the vocal fold epithelial barrier.A comprehensive review of the literature was conducted. Details of the structure of the vocal fold epithelial barrier are presented and evaluated in the context of function in injury and pathology. The importance of the epithelial-associated vocal fold mucus barrier is also introduced.Information presented in this review is valuable for clinicians and researchers as it highlights the importance of this understudied portion of the vocal folds to overall vocal health and disease. Prevention and treatment of injury to the epithelial barrier is a significant area awaiting further investigation.

    View details for DOI 10.1044/2014_JSLHR-S-13-0283

    View details for PubMedID 24686981

  • Influence of Obligatory Mouth Breathing, During Realistic Activities, on Voice Measures JOURNAL OF VOICE Sivasankar, M. P., Erickson-Levendoski, E. 2012; 26 (6)

    Abstract

    Low humidity environments and mouth breathing may contribute to superficial vocal fold dehydration. The purpose of this study was to investigate the effects of obligatory mouth breathing, during daily activities in low- and high-humidity environments, on voice measures. The activities included 15 minutes of obligatory mouth breathing alone, during loud reading and during exercise. The effects of mouth breathing and humidity were compared in subjects who either reported or did not report vocal worsening after heavy voice use.Prospective, between-group, repeated-measures design.Sixty-three healthy adults with normal respiratory function and perceptually normal voice participated in this study. Thirty-one subjects reported symptoms of voice worsening with heavy voice use. Thirty-two subjects who did not report these symptoms participated as controls. Phonation threshold pressure and perceived phonatory effort were measured at baseline and after each obligatory mouth breathing challenge. Ambient humidity was set to either low or high humidity.Obligatory mouth breathing in loud reading and exercise significantly increased phonation threshold pressure when compared with mouth breathing alone. This increase in phonation threshold pressure was observed at low and high humidity, in both subject groups. There were no significant effects for perceived phonatory effort.Obligatory mouth breathing during loud reading and exercise negatively impact phonation threshold pressure. Future investigations that include longer challenge durations, and subjects with voice disorders, are needed to elucidate the underlying mechanisms for increases in phonation threshold pressure.

    View details for DOI 10.1016/j.jvoice.2012.03.007

    View details for Web of Science ID 000311428300028

    View details for PubMedID 22921296

  • Role for Ion Transport in Porcine Vocal Fold Epithelial Defense to Acid Challenge OTOLARYNGOLOGY-HEAD AND NECK SURGERY Erickson-Levendoski, E., Sivasankar, M. P. 2012; 146 (2): 272-278

    Abstract

    The vocal fold epithelium is routinely exposed to gastric contents, including acid and pepsin, during laryngopharyngeal reflux events. The epithelium may possess intrinsic defenses to reflux. The first objective of the current study was to examine whether vocal fold epithelial ion transport is one potential mechanism of defense to gastric contents. The second objective was to determine whether ion transport in response to gastric contents is associated with the secretion of bicarbonate.Prospective design in excised porcine larynges.Laboratory.Porcine vocal folds (N = 56) were exposed on the luminal surface to acid, pepsin, or sham challenges. Ion transport at baseline and following challenge exposure was measured using electrophysiological techniques. To examine specific ion transport mechanisms, vocal folds were pretreated with either a sodium channel blocker or bicarbonate channel blocker.Within 60 seconds of acid but not pepsin exposure, there was a significant increase in ion transport. This rapid increase in ion transport was transient and related to bicarbonate secretion.The current data suggest that porcine vocal folds immediately increase bicarbonate secretion following exposure to acid. Bicarbonate secretion may act to neutralize acid. These findings contribute to the identification of the mechanisms underlying vocal fold defense to reflux and offer implications for the development of treatments for reflux-induced vocal fold injury.

    View details for DOI 10.1177/0194599811428273

    View details for Web of Science ID 000303541300017

    View details for PubMedID 22086905

  • Acute Stress to Excised Vocal Fold Epithelium From Reactive Oxygen Species Combined Otolaryngology Spring Meeting (COSM)/132nd Annual Meeting of the American-Laryngological-Association/Annual Meeting of the American-Otological-Society Alper, R., Fu, X., Erickson-Levendoski, E., Zheng, W., Sivasankar, M. WILEY-BLACKWELL. 2011: 2180–84

    Abstract

    Vocal fold epithelium is exposed to reactive oxygen species from the inhaled environment and from tissue inflammation. The objective of this study was to explore the functional and structural consequences of reactive oxygen species exposure on vocal fold epithelium.In vitro, prospective study design.Hydrogen peroxide (H(2)O(2)), a common reactive oxygen species, was utilized in this study. Freshly excised, viable porcine vocal fold epithelia (N = 32) were exposed to H(2) O(2) or sham challenge for 2 hours. Electrophysiology, western blotting, and light microscopy were used to quantify the functional and structural effects of reactive oxygen species on vocal fold epithelia.Exposure to reactive oxygen species did not significantly alter transepithelial resistance. There was a small, nonsignificant trend for decreased concentration of epithelial junctional complex protein with reactive oxygen species challenge. Minimal changes to the gross structural appearance of vocal fold epithelia were also noted.The stratified squamous epithelia of the vocal folds effectively defend against an acute reactive oxygen species challenge. The current study lays the groundwork for future investigations on the effects of reactive oxygen species on vocal fold epithelia that are compromised from phonotrauma.

    View details for DOI 10.1002/lary.22157

    View details for Web of Science ID 000295228800025

    View details for PubMedID 21898441

  • Investigating the Effects of Caffeine on Phonation JOURNAL OF VOICE Erickson-Levendoski, E., Sivasankar, M. 2011; 25 (5): E215-E219

    Abstract

    A core component of vocal hygiene programs is the avoidance of agents that may dry the vocal folds. Clinicians commonly recommend that individuals reduce caffeine intake because of its presumed dehydrating effects on the voice. However, there is little evidence that ingestion of caffeine is detrimental to voice production. The first objective of this study was to evaluate whether caffeine adversely affects voice production. The second objective was to evaluate if caffeine exacerbates the adverse phonatory effects of vocal loading.Prospective, double-blinded, sham-controlled study.Sixteen healthy adults participated in two sessions where they consumed caffeine (caffeine concentration=480 mg) or sham (caffeine concentration=24 mg) beverages. Voice measures (phonation threshold pressure and perceived phonatory effort) were collected. Subjects then completed a vocal loading challenge and voice measures were obtained again.There were no significant differences in voice measures between the caffeine and sham conditions. Ingestion of caffeine did not adversely affect voice production (P>0.05) or exacerbate the detrimental phonatory effects of vocal loading (P>0.05).Our findings contribute to emerging knowledge on the effects of caffeine on voice production. Recommendations to completely eliminate caffeine from the diet, as a component of a vocal hygiene program, should be evaluated on an individual basis.

    View details for DOI 10.1016/j.jvoice.2011.02.009

    View details for Web of Science ID 000307778900002

    View details for PubMedID 21704493

  • Simulated Reflux Decreases Vocal Fold Epithelial Barrier Resistance Annual Meeting of the American-Laryngological-Association Erickson, E., Sivasankar, M. WILEY-BLACKWELL. 2010: 1569–75

    Abstract

    The vocal fold epithelium provides a barrier to the entry of inhaled and systemic challenges. However, the location of the epithelium makes it vulnerable to damage. Past research suggests, but does not directly demonstrate, that exposure to gastric reflux adversely affects the function of the epithelial barrier. Understanding the nature of reflux-induced epithelial barrier dysfunction is necessary to better recognize the mechanisms for vocal fold susceptibility to this disease. Therefore, we examined the effects of physiologically relevant reflux challenges on vocal fold transepithelial resistance and gross epithelial and subepithelial appearance.Ex vivo, mixed design with between-group and repeated-measures analyses.Healthy, native porcine vocal folds (N = 52) were exposed to physiologically relevant acidic pepsin, acid-only, or pepsin-only challenges and examined with electrophysiology and light microscopy. For all challenges, vocal folds exposed to a neutral pH served as control.Acidic pepsin and acid-only challenges, but not pepsin-only or control challenges significantly reduced transepithelial resistance within 30 minutes. Reductions in transepithelial resistance were irreversible. Challenge exposure produced minimal gross changes in vocal fold epithelial or subepithelial appearance as evidenced by light microscopy.These findings demonstrate that acidic environments characteristic of gastric reflux compromise epithelial barrier function without gross structural changes. In healthy, native vocal folds, reductions in transepithelial resistance could reflect reflux-related epithelial disruption. These results might guide the development of pharmacologic and therapeutic recommendations for patients with reflux, such as continued acid-suppression therapy and patient antireflux behavioral education.

    View details for DOI 10.1002/lary.20983

    View details for Web of Science ID 000280695000014

    View details for PubMedID 20564752

  • Evidence for Adverse Phonatory Change Following an Inhaled Combination Treatment JOURNAL OF SPEECH LANGUAGE AND HEARING RESEARCH Erickson, E., Sivasankar, M. 2010; 53 (1): 75-83

    Abstract

    Voice problems are reported as a frequent side effect of inhaled combination (IC) treatments. The purpose of this experimental study was to investigate whether IC treatments are detrimental to phonation. We hypothesized that IC treatment would significantly increase phonation threshold pressure (PTP) and perceived phonatory effort (PPE), whereas sham treatment would not.Fourteen healthy adults participated in a repeated-measures design in which they received IC and sham treatments in counterbalanced order. PTP and PPE were measured prior to treatments, immediately following treatments, and at 1 and 2 hr following treatments.IC treatment increased PTP, but sham treatment did not. The increase in PTP was maintained for a 2 hr period following administration. PPE ratings were not significantly correlated with PTP.IC treatments can have acute, adverse effects on phonation. Detrimental phonatory effects were elicited in participants with no self-reported voice problems. IC treatments are being increasingly prescribed across the lifespan. The current data increase our understanding of the nature of phonatory deterioration associated with IC treatment and lay the groundwork for increased research effort to develop IC treatments that effectively control respiratory disease while minimizing an adverse effect on phonation.

    View details for DOI 10.1044/1092-4388(2009/09-0024)

    View details for Web of Science ID 000275168300006

    View details for PubMedID 19696437

  • Hypertonic challenge to porcine vocal folds: Effects on epithelial barrier function OTOLARYNGOLOGY-HEAD AND NECK SURGERY Sivasankar, M., Erickson, E., Rosenblatt, M., Branski, R. C. 2010; 142 (1): 79-84

    Abstract

    Dehydration challenges can increase the chemical composition of surface fluid overlying vocal fold epithelia (hypertonic surface fluid). The vocal fold epithelium is posited to act as a barrier, shielding the lamina propria from perturbations in the airway lumen. However, the effects of hypertonic surface fluid on the barrier functions of vocal fold epithelia have not been quantified. We, therefore, sought to investigate whether hypertonic surface fluid compromises epithelial barrier function. We examined the effects of hypertonic surface fluid on vocal fold epithelial resistance, paracellular pathway morphology, and tight junction protein integrity.Ex vivo, between group design.Laboratory.Porcine vocal folds (n = 24) were exposed to hypertonic or isotonic challenge and examined by electrophysiology, transmission electron microscopy, and Western blot analyses.Hypertonic, but not isotonic, challenge significantly reduced transepithelial resistance. This decrease in resistance was observed immediately after the challenge and was consistent with the appearance of dilated paracellular pathway morphology. However, hypertonic challenge did not alter protein levels of occludin, zona occludens-1, E-cadherin, or beta-catenin.Hypertonic surface fluid alters epithelial barrier function in the vocal folds. Specifically, exposure to hypertonic challenges increases epithelial permeability. Given the important role of the vocal fold epithelium in shielding the underlying mucosa from inhaled pathogens and pollutants, our data provide the impetus for future studies on pharmacological treatments aimed at restoring the hydration level and chemical composition of vocal fold surface fluid.

    View details for DOI 10.1016/j.otohns.2009.09.011

    View details for Web of Science ID 000276574200014

    View details for PubMedID 20096227

  • Short-Duration Accelerated Breathing Challenges Affect Phonation Annual Convention of the American-Speech-Language-Hearing-Association Sivasankar, M., Erickson, E. JOHN WILEY & SONS INC. 2009: 1658–63

    Abstract

    Inhaled air must be adequately humidified to prevent vocal fold drying, which is detrimental to phonation. The water content of inspired air is reduced by parameters, such as increased breathing rate and oral route. Accelerated oral breathing challenges induce airway dehydration and are posited to affect airway function. The primary objective of this study was to investigate whether accelerated oral breathing challenges are detrimental to phonation. The secondary objective of this study was to determine whether individuals at increased risk for developing voice problems (i.e., smokers) have greater adverse phonatory effects after accelerated breathing challenge than nonsmoking controls.Prospective study with between-subjects, repeated-measures design.Female smokers (n = 12) and nonsmoking controls (n = 12) participated in this experimental study over 2 days that differed in ambient humidity. Phonation threshold pressures (PTP) were collected prior to and following short-term accelerated and habitual breathing challenges. Respiratory measures were collected during the challenges.Short-term accelerated breathing challenges significantly increased PTP. This increase in PTP with accelerated breathing was transient and not significantly influenced by breathing route, ambient humidity, or smoking status. Likewise, respiratory measures were not affected by breathing route, ambient humidity, or smoking status.During daily activities, such as exercise, individuals may engage in accelerated breathing for prolonged durations. This study demonstrates that even extremely short durations of accelerated breathing may affect phonation.

    View details for DOI 10.1002/lary.20530

    View details for Web of Science ID 000268739500033

    View details for PubMedID 19522007

  • Phonatory Effects of Airway Dehydration: Preliminary Evidence for Impaired Compensation to Oral Breathing in Individuals With a History of Vocal Fatigue JOURNAL OF SPEECH LANGUAGE AND HEARING RESEARCH Sivasankar, M., Erickson, E., Schneider, S., Hawes, A. 2008; 51 (6): 1494-1506

    Abstract

    Airway drying is detrimental to phonation and is posited to exacerbate vocal fatigue. However, limited research has demonstrated the adverse phonatory effects of dehydration in speakers reporting vocal fatigue. We compared the negative phonatory consequences of short-term oral breathing at low, moderate, and high humidity in individuals reporting a history of vocal fatigue and control participants.Females reporting a history of vocal fatigue (N = 8) and matched controls (N = 8) participated in a repeated-measures design over 3 different days.Oral breathing at low and moderate humidity increased phonation threshold pressure (PTP) to a greater extent in individuals reporting a history of vocal fatigue as compared to controls. Conversely, PTP did not increase in either participant group after oral breathing in a humid environment. Perceived phonatory effort (PPE) ratings were poorly correlated with PTP.The emergence of between-group differences in PTP at low and moderate but not high ambient humidity demonstrates that drying challenges might be detrimental to voice production in individuals with a history of vocal fatigue. Based on the phonatory effects of dehydration, we suggest that individuals reporting vocal fatigue may demonstrate impaired compensation to airway drying induced by short-term oral breathing.

    View details for DOI 10.1044/1092-4388(2008/07-0181)

    View details for Web of Science ID 000261196100009

    View details for PubMedID 18664688