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The Effects of Hard Voice Onset on Objective Voice Function in Patients With Laryngopharyngeal Reflux

  • Xinlin Xu
    Affiliations
    Department of Otolaryngology, Head and Neck Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, China

    Department of Voice, Zhongshan Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, China
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  • Xueqiong Huang
    Affiliations
    Department of Otolaryngology, Head and Neck Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, China
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  • Jiajie Tan
    Affiliations
    Department of Otolaryngology, Head and Neck Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, China
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  • Hugo Stevenson
    Affiliations
    Division of Otolaryngology−Head and Neck Surgery, Department of Surgery, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin
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  • Peiyun Zhuang
    Correspondence
    Address correspondence and reprint requests to Peiyun Zhuang, Department of Voice, Zhongshan Hospital of Xiamen University, School of Medicine, Xiamen University, Hubin South Road 201-209, Xiamen 361004, China
    Affiliations
    Department of Voice, Zhongshan Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, China
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  • Xiangping Li
    Correspondence
    Xiangping Li, Department of Otolaryngology, Head and Neck Surgery, Nanfang Hospital, Southern Medical University, 1838 Guangzhou Avenue North, Guangzhou 510515, China.
    Affiliations
    Department of Otolaryngology, Head and Neck Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, China
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Open AccessPublished:April 01, 2022DOI:https://doi.org/10.1016/j.jvoice.2022.02.027

      Summary

      Objective

      Laryngopharyngeal reflux (LPR) causes laryngopharyngeal hypersensitivity and laryngeal muscle hyperfunction, which may result in hard voice onset in patients with LPR. The purpose of this study is to examine the incidence of hard voice onset in patients with LPR and the effects of hard voice onset on objective voice function in patients with LPR.

      Methods

      Forty patients with confirmed LPR were enrolled in the LPR group, and 40 healthy subjects were enrolled in the non-LPR group. Subjects underwent laryngeal high-speed videoendoscopy, and the presence or absence of hard voice onset in each subject was determined by two experienced laryngologists based on whether glottal closure was complete or incomplete before vocal fold vibration. Based on the results, the subjects with LPR were divided into a hard voice onset group and a non-hard voice onset group. The voice onset time (VOT) was measured and compared between the hard and non-hard voice onset groups within the LPR group. Laryngeal aerodynamic assessment was also carried out on the LPR group, and subglottal pressure, phonation threshold pressure (PTP), glottal resistance, and mean flow rate were measured. The voice acoustic signals of subjects were additionally analyzed in the LPR group, and the fundamental frequency, jitter, shimmer, and noise-harmony ratio were determined. The kappa statistic, chi-square test and independent-samples t test in SPSS were used for statistical analysis.

      Results

      The two laryngologists had substantial inter-rater consistency on the evaluation of hard voice onset and non-hard voice onset, with a kappa statistic of 0.71. In the LPR group, 42.5% of patients had hard voice onset (17/40), significantly more than in the non-LPR group (8/40, 20%) (P < 0.05). The VOT in the LPR group was significantly longer than in the non-LPR group (P < 0.05). Within the LPR group, the VOT, PTP and shimmer were significantly greater in the hard voice onset group than in the non-hard voice onset group (all P < 0.05). The other laryngeal aerodynamic parameters and acoustic parameters were not significantly different between the hard voice onset group and the non-hard voice onset group (P > 0.05).

      Conclusion

      Changes in vocal production may occur in LPR patients, causing them to be more susceptible to hard voice onset. The patients with hard voice onset require longer VOT and greater PTP to initiate phonation.

      Key Words

      INTRODUCTION

      Vocal onset is determined by the initiation process of vocal fold vibration. Complete glottal closure before vocal fold vibration produces a hard voice onset while incomplete glottal closure before vocal fold vibration produces a soft or breathy voice onset.
      • Baken R.J.
      • Watson B.C.
      Research note: vocal attack time-extended analysis.
      Hard voice onset is considered a poor vocalization method, since excessive delays in vocal onset after vocal fold adduction causes patients to experience vocal fatigue.
      • McDonnell M.
      • Sundberg J.
      • Westerlund J.
      • et al.
      Vocal fold vibration and phonation start in aspirated, unaspirated, and staccato onset.
      ,
      • Woo P.
      High-speed imaging of vocal fold vibration onset delay: normal versus abnormal.
      Laryngopharyngeal reflux disease (LPRD) is an umbrella term for a series of signs and symptoms that occur as a result of abnormal gastroesophageal reflux above the upper esophageal sphincter muscles, which causes atypical inflammation and mucosal lesions in the laryngopharyngeal region.
      • Li J.R.
      • Xiao S.F.
      • Li X.P.
      • et al.
      Explanation of the experts consensus on diagnosis and treatment of laryngopharyngeal reflux disease (2015).
      Laryngopharyngeal reflux (LPR) causes laryngopharyngeal hypersensitivity and laryngeal muscle hyperfunction,
      • Yeakel H.
      • Balouch B.
      • Vontela S.
      • et al.
      The relationship between chronic cough and laryngopharyngeal reflux.
      which may cause changes in vocal production.
      LPRD is known to affect vocal function, with 50%-78% of patients with voice hoarseness found to also suffer from LPRD.
      • Lechien J.R.
      • Khalife M.
      • Huet K.
      • et al.
      Perceptual, aerodynamic, and acoustic characteristics of voice changes in patients with laryngopharyngeal reflux disease.
      ,
      • Lechien J.R.
      • Saussez S.
      • Harmengnies B.
      • et al.
      Laryngopharyngeal reflux and voice disorders: a multifactorial model of etiology and pathophysiology.
      Hard voice onset derived from LPR could further cause poor vocal function in patients with LPRD. To objectively measure vocal function, laryngeal aerodynamic parameters and voice acoustic assessments (fundamental frequency (F0), jitter, shimmer, and noise-harmony ratio (NHR)) were taken from patients with LPR. We chose aerodynamic parameters that are indicative of vocal function. Phonation threshold pressure (PTP) is defined as the minimum subglottal pressure required to initiate phonation, and is related to both tissue properties and glottal configuration,
      • Mau T.
      • Muhlestein J.
      • Callahan S.
      • et al.
      Phonation threshold pressure and flow in excised human larynges.
      as well as being unaffected by the phonation of different vowels.
      • Tattari N.
      • Forss M.
      • Laukkanen A.M.
      • et al.
      The efficacy of the NHS waterpipe in superficial hydration for people with healthy voices: effects on acoustic voice quality, phonation threshold pressure and subjective sensations.
      PTP is flexible for clinical use,
      • Plexico L.W.
      • Sandage M.J.
      Influence of vowel selection on determination of phonation threshold pressure.
      and is a potential diagnostic indicator of glottal closure.
      • Jen J.H.
      • Chan R.W.
      • Wu C.H
      • et al.
      Phonation threshold pressure/flow for reflecting glottal closure in unilateral vocal fold paralysis.
      Other aerodynamic parameters include subglottal pressure (SGP), mean flow rate (MFR) and glottal resistance (GR), GR being the ratio of subglottal pressure to glottal flow.
      • Alipour F.
      • Jaiswal S.
      Glottal airflow resistance in excised pig, sheep, and cow larynges.
      In this paper, we investigated the incidence of hard voice onset in LPR patients and the effects of hard voice onset on vocal function by analyzing laryngeal high-speed videoendoscopy videos of LPR patients, their laryngeal aerodynamic parameters, and the acoustic parameters of their voice.

      STUDY SUBJECTS AND GROUPING

      Forty LPR patients who were treated at Zhongshan Hospital, Xiamen University from July 2020 to January 2021 were enrolled in the LPR group. The ages of patients ranged from 18 to 60 years, and mean age was 33.54 years. There were 14 males and 26 females. Inclusion criteria were as follows: suspected LPR patients with reflux symptom index (RSI) scores >13 and reflux finding scores (RFS) >7 underwent oropharyngeal 24-hour Dx pH monitoring, and the patients with a positive Ryan score (Ryan score >9.41 when pH <5.5 in a standing position or Ryan score >6.8 when pH <5 in a recumbent position) were included in an empirical therapy of proton pump inhibitor treatment. The patients with at least 50% improvement in symptoms after proton pump inhibitor treatment were enrolled in the LPR group. Patients with the following conditions were excluded: acute laryngopharyngitis, vocal fold hyperplastic lesions, sulcus vocalis, vocal fold paralysis, unilateral pharyngeal pain or discomfort, chronic rhinitis, chronic tonsillitis, or any history of surgery performed on the head, neck, or chest.
      Forty healthy subjects were included in the non-LPR group and underwent stroboscopy. The subjects were selected from hospital staff, students at Xiamen University, and caregivers. Subjects did not possess cases of vocal fatigue or abnormal vocal function, RSI ≤13 and RFS≤7. The exclusion criteria were the same as the LPR group.
      To investigate the effects of hard voice onset on objective voice function in patients with LPR, the subjects with LPR were then divided into a hard voice onset group and a non-hard voice onset group.
      This study was approved by the medical ethics committee of Zhongshan Hospital, Xiamen University, and all subjects signed the informed consent form.

      STUDY METHODS

      Laryngeal high-speed videoendoscopy

      The laryngeal high-speed videoendoscopy system was jointly developed by Laryngograph Ltd. (United Kingdom) and Beijing Freeber Technology Co. Ltd. (China). This system uses a 70° rigid endoscope for high-speed videoendoscopy of vocal fold vibration through an intraoral approach, and the high-speed video sampling frequency (f) was set at 4000 Hz.
      The patient was seated comfortably in a raised chair and used both hands to gently pinch the tip of the tongue and pull it downwards during the intraoral approach. The endoscope was inserted to be just within the threshold of the laryngeal vestibule and adjusted so that the vocal folds were exactly at the center of the viewing window. Then, the subject was instructed to repeatedly inhale and stably produce at a comfortable frequency and sound intensity the vowel /i/ for high-speed videoendoscopy. The length of the recorded video was 8 s.

      Hard voice onset and non-hard voice onset judgement

      Digital videokymography was used to analyze the initiation process of vocal fold vibration. Two laryngologists, each with 7 years’ experience, assessed the vocal onset of the subjects. Hard voice onset refers to complete glottal closure without gaps before the start of vocal fold vibration, and non-hard voice onset refers to an incomplete glottal closure before vocal fold vibration (Figure 1).
      FIGURE 1
      FIGURE 1Two voice onset types in digital videokymography: the left figure shows hard voice onset, and the right figure shows non-hard voice onset.

      Voice onset time measurement

      Voice onset time (VOT) refers to the time between adduction of the vocal folds to the first stable vocal fold vibration during vocalization. Calculation method: The video frame number when the vocal folds are at the adduction phase (A1) and the video frame number when the first stable vocal fold vibration occurs (A2) were determined within the high-speed footage, and the frame difference between the two states was calculated. This frame difference was divided by the high-speed video sampling frequency (f) to obtain the VOT. The formula for VOT is shown in (1).
      t = 1000*(A2-A1)/f
      (1)


      t is the voice onset time in ms, A1 is the number of video frames when the vocal folds are at the adduction phase before voice onset, A2 is the number of video frames when the first stable vocal fold occurs, and f is the high-speed video sampling frequency in Hz.

      Objective voice function assessment

      Laryngeal aerodynamic assessment

      The phonatory aerodynamic system (PAS, Model 6600, KayPENTAX Inc, USA) was used for aerodynamic assessment of the subjects.
      A 3-mm-diameter tube for continuous measurement of subglottal pressure was inserted approximately 2 cm into the subject's mouth. A face mask was used to seal around the mouth and nose to avoid air leakage. The subject was then instructed to repeatedly produce /pa/ 6-8 times at a loudness of 76±3 dB using a comfortable pitch. SGP and GR were calculated at the bilabial stop phase of phonation. To measure PTP, the subject was instructed to produce /pa/ repeatedly, starting at an almost inaudible whisper, 6-7 times per breath. They then were directed to gradually increase their loudness until the voicing of the /a/ began to be obvious. The pressure was measured during the bilabial stop phase immediately before that point.
      • Smitheran JR
      • Hixon TJ
      A clinical method for estimating laryngeal airway resistance during vowel production.
      Subjects were also directed to rest between trials to avoid the confounding variable of vocal fatigue. This was repeated 10 times, with PTP obtained as the average between trials. SGP, GR, and PTP were measured three times in each patient, and mean values were calculated for analysis.
      Glottic airflow was measured with a paper tube. The subject's mouth made a tight seal around the circumference of the tube, and the subject's nose was clamped to prevent velopharyngeal leakage. The subject was then instructed to produce the vowel /a/ three times using a comfortable pitch and loudness, with each phonation lasting 4-5 seconds. The flow rate was collected, and the mean flow rate (MFR) was measured.
      • Guo Y.Q.
      • Lin S.Z.
      • Xu X.X.
      • et al.
      Role of aerodynamic parameters in voice function assessment.
      Measurements were repeated three times, and the mean values were calculated for analysis.

      Voice acoustic assessment

      The Multi-Dimensional Voice Program (MDVP) Model 5105 in the KayPENTAX multi speech software was used for voice acoustic analysis. The subject was placed in an environment with background noise <45 dB. The subject's mouth was 30 cm away from the microphone, and the microphone angle was 30°. The subject was instructed to produce /a/ using a comfortable and consistent pitch and loudness. Acoustic signals were collected to analyze the F0, jitter, shimmer, and NHR. Measurements were repeated three times, and the mean values were calculated for analysis.
      • Hong Y.J.
      • Xu X.X.
      • Lin S.Z.
      • et al.
      The observation of vocal polyp by phonomicrosurgery and vocal fold recovery.

      Statistical methods

      SPSS 25 was used for statistical analysis. The kappa statistic was used to evaluate the inter-rater reliability of the two laryngologists identifying vocal onset movement asymmetry. The chi-square test was used for comparative analysis of the numbers of people with and without hard voice onset between the LPR group and the non-LPR group. The independent-samples t test was used to compare the measurement data between the hard voice onset group and the non-hard voice onset group within the LPR group.

      RESULTS

      Higher incidence of hard voice onset in LPR patients than in non-LPR controls

      The two laryngologists had good inter-rater consistency on the evaluation of hard voice onset and non-hard voice onset, with a kappa statistic of 0.71. In the LPR group, 17 patients had hard voice onset (42.5%), and in the non-LPR group, 8 subjects had hard voice onset (20%). The incidence of hard voice onset was significantly higher in the LPR group than in the non-LPR group (P < 0.05) (Table 1). The VOT in LPR group (135.37±72.9) was significantly longer than in the non-LPR group (95.6±54.42) (P = 0.01).
      TABLE 1Comparison of the Presence/Absence of Hard Voice Onset in the LPR Group and the Non-LPR Group
      Hard Voice OnsetNon-Hard Voice Onset
      LPR group1723
      Non-LPR group832
      χ24.71
      P-value0.03

      Longer VOT in subjects with hard voice onset with LPR

      The mean VOT of the hard voice onset group was 194.61 ms, which was significantly higher than that (89.4 ms) of the non-hard voice onset group (P < 0.05) (Figure 2). Additionally, the mean RFS was found to be significantly lower in the hard voice onset group than in the non-hard voice onset group (P < 0.05), and the mean RSI score was lower but not significantly lower in the hard voice onset group than in the non-hard voice onset group (P > 0.05) (Figure 3).
      FIGURE 2
      FIGURE 2VOT histogram of the hard voice onset group and the non-hard voice onset group with LPR. LPR, laryngopharyngeal reflux; VOT, voice onset time.
      FIGURE 3
      FIGURE 3RSI and RFS histograms of the hard voice onset group and the non-hard voice onset group with LPR. LPR, laryngopharyngeal reflux; RFS, reflux finding scores; RSI, reflux symptom index.

      Greater PTP in subjects with hard voice onset than in subjects without hard voice onset with LPR

      Among aerodynamic parameters, the PTP was found to be significantly greater in the hard voice onset group than in the non-hard voice onset group (P < 0.05). The other laryngeal aerodynamic parameters (SGP, GR, PTW, and MFR) and the acoustic parameters were not significantly different between the two groups (P > 0.05) (Figure 4).
      FIGURE 4
      FIGURE 4Histograms of the aerodynamic parameters of the hard voice onset group and the non-hard voice onset group with LPR. LPR, laryngopharyngeal reflux.

      Hard voice onset affected acoustic parameters in subjects with LPR

      Among acoustic parameters, shimmer was significantly greater in the hard voice onset group than in the non-hard voice onset group (P < 0.05), and jitter was not significantly greater in the hard voice onset group than in the non-hard voice onset group (P > 0.05). The F0 and NHR were also not significantly different between the two groups (P > 0.05) (Figure 5).
      FIGURE 5
      FIGURE 5Histograms of the acoustic parameters of the hard voice onset group and the non-hard voice onset group with LPR. LPR, laryngopharyngeal reflux.

      DISCUSSION

      More than 50% of patients who present to otolaryngology departments with voice hoarseness were found to also have LPRD.
      • Lechien J.R.
      • Saussez S.
      • Harmengnies B.
      • et al.
      Laryngopharyngeal reflux and voice disorders: a multifactorial model of etiology and pathophysiology.
      Vocal fold edema caused by the back flow of gastric contents into the larynx is often considered to be the primary factor affecting vocal fold vibration and causing voice hoarseness in patients with LPRD.
      • Lechien J.R.
      • Akst L.M.
      • Hamdan A.L.
      • et al.
      Evaluation and management of laryngopharyngeal reflux disease: state of the art review.
      ,
      • Mesallam T.A.
      • Stemple J.C.
      • Sobeih T.M.
      • et al.
      Reflux symptom index versus reflux finding score.
      However, recent data has cast doubt on this hypothesis, particularly in cases of mild and moderate LPRD with mild or no edema.
      • Lechien J.R.
      • Khalife M.
      • Delvaux V.
      • et al.
      Pathophysiology, assessment and treatment of laryngopharyngeal reflux.
      • Lechien J.R.
      • Huet K.
      • Khalife M.
      • et al.
      Impact of laryngopharyngeal reflux on subjective and objective voice assessments: a prospective study.
      • Lechien J.R.
      • Finck C.
      • Huet K.
      • et al.
      Voice quality as therapeutic outcome in laryngopharyngeal reflux disease: a prospective cohort study.
      There was no significant correlation between acoustic parameters and laryngoscopic signs in LFR patients.
      • Lechien J.R.
      • Schindler A.
      • De Marrez L.G.
      • et al.
      Instruments evaluating the clinical findings of laryngopharyngeal reflux: a systematic review.
      Three months after anti-reflux treatment, voice hoarseness was improved in LPR patients, but the laryngoscopic signs were not significantly improved.
      • Lechien J.R.
      • Saussez S.
      • Karkos P.D.
      Laryngopharyngeal reflux disease: clinical presentation, diagnosis and therapeutic challenges in 2018.
      These studies showed that the mechanism by which LPR causes voice hoarseness is not only dependent on vocal fold edema but also other factors that affect vocalization.
      • Lechien J.R.
      • Khalife M.
      • Huet K.
      • et al.
      Perceptual, aerodynamic, and acoustic characteristics of voice changes in patients with laryngopharyngeal reflux disease.
      LPR causes laryngeal mucosal hypersensitivity, and LPR patients often present with throat clearing and chronic cough,
      • Li X.
      • Lin S.
      • Wang Z.
      • et al.
      Gastroesophageal reflux disease and chronic cough: A possible mechanism elucidated by ambulatory pH-impedance-pressure monitoring.
      ,
      • Dabirmoghaddam P.
      • Rahmaty B.
      • Erfanian R.
      • et al.
      Voice component relationships with high reflux symptom index scores in muscle tension dysphonia.
      and secondary muscle tension dysphonia.
      • Schneider S.L.
      • Clary M.S.
      • Fink D.S.
      • et al.
      Voice therapy associated with a decrease in the reflux symptoms index in patients with voice complaints.
      ,

      Chen, W., P. Woo, and T. Murry, Vibratory onset of adductor spasmodic dysphonia and muscle tension dysphonia: a high-speed video study.J Voice. in press.

      Changes in laryngeal motion in LPR patients may cause hard voice onset.
      • Maryn Y.
      • Poncelet S.
      How reliable is the auditory-perceptual evaluation of phonation onset hardness?.
      This study shows that the incidence of hard voice onset was significantly higher in LPR patients than in healthy controls, supporting observations that LPR patients are more susceptible to hard voice onset.
      The types of phonation onsets are mainly thought to consist of soft, breathy, and hard voice onsets.
      • DeJonckere P.H.
      • Lebacq J.
      In Vivo quantification of the intraglottal pressure: modal phonation and voice onset.
      Among these vocalization methods, hard voice onset requires more adduction strength in the vocal folds, tighter glottal closure, and compression from supraglottic structures, and it is considered a poor vocalization method as it carries a risk of phonotraumatic injury when vocal folds vibrate.
      • DeJonckere P.H.
      • Lebacq J.
      In Vivo quantification of the intraglottal pressure: modal phonation and voice onset.
      • Deguchi S.
      Mechanism of and threshold biomechanical conditions for falsetto voice onset.
      • Uygun M.N.
      • Aydinli F.E.
      • Aksoy S.
      • et al.
      Turkish standardized reading passage for the evaluation of hard glottal attack occurrence frequency.
      Hard voice onset is a prominent cause of benign vocal fold hyperplastic lesions. The frequency of hard voice onset is significantly higher in patients with vocal nodules and laryngeal muscle tension dysphonia than in normal subjects,
      • DeJonckere P.H.
      • Lebacq J.
      In Vivo quantification of the intraglottal pressure: modal phonation and voice onset.
      ,
      • Uygun M.N.
      • Aydinli F.E.
      • Aksoy S.
      • et al.
      Turkish standardized reading passage for the evaluation of hard glottal attack occurrence frequency.
      and patients with hard voice onset may have poorer voice quality.
      • Chen W.
      • Woo P.
      • Murry T.
      Spectral analysis of digital kymography in normal adult vocal fold vibration.
      The results of this paper showed that hard voice onset had mild effects on the voice quality of LPR patients. Specifically, shimmer was greater in the hard voice onset group than in the non-hard voice onset group, but jitter, F0, and NHR were not significantly different between the two groups. The prominence of this vocalization method in LPR patients may make them more susceptible to voice disorders.
      Laryngeal high-speed videoendoscopy records vocal fold motion and vibration at a speed of >2000 frames per second and can directly observe the statuses of the vocal folds before and after stable vibration.
      • Chen W.
      • Woo P.
      • Murry T.
      Spectral analysis of digital kymography in normal adult vocal fold vibration.
      Laryngeal high-speed videoendoscopy is more accurate in visualizing the mucosal wave than the pseudocycles of stroboscopy. The sampling frequency of laryngeal high-speed videoendoscopy in this paper was 4000 frames per second. VOT refers to the time from glottal closure to the start of vocal fold vibration. Woo et al employed laryngeal high-speed videoendoscopy to analyze the VOT between subjects with normal and abnormal vocal fold vibration onset delay. They found that the mean VOT values of normal and abnormal subjects were 62 ms and 203 ms, respectively.
      • Woo P.
      High-speed imaging of vocal fold vibration onset delay: normal versus abnormal.
      The mean VOT values of patients without hard voice onset and patients with hard voice onset in this paper were 89.4 ms and 194.61 ms, respectively, which were similar to the results of previous studies.
      • Woo P.
      High-speed imaging of vocal fold vibration onset delay: normal versus abnormal.
      ,
      • Maryn Y.
      • Poncelet S.
      How reliable is the auditory-perceptual evaluation of phonation onset hardness?.
      PTP refers to the minimum subglottal pressure required for vocalization and can reflect the effort of vocalization.
      • Jiang J.
      • O'Mara T.
      • Conley D.
      • et al.
      Phonation threshold pressure measurements during phonation by airflow interruption.
      The patients with hard voice onset required greater PTP during vocalization, indicating that it is more difficult to initiate vocalization with hard voice onset. It is easiest for subglottal pressure to drive vocal fold vibration when vocalizing with a soft onset with incomplete glottal closure prior to exhalation.
      • DeJonckere P.
      • O'Mara T.
      • Lebacq J.
      Intraglottal aerodynamics at vocal fold vibration onset.
      The other aerodynamic parameters were not significantly different between the hard voice onset group and the non-hard voice onset group in this experiment. This may be because the other aerodynamic parameters are generated during continuous vocal fold vibration and were not correlated with initiation of vocal fold vibration.
      There are some limitations of this paper. The LPR patients selected were precluded for having vocal fold hyperplastic lesions by our basis of selection, but hard voice onset is one of the main causes of vocal fold hyperplastic lesions. In addition, LPR occurs in 75% of patients with vocal polyps.
      • Wang L.
      • Tan J.J.
      • Wu T.
      • et al.
      Association between laryngeal pepsin levels and the presence of vocal fold polyps.
      Therefore, the incidence of hard voice onset in LPR patients might be underestimated, and more clinical observations are required for confirmation. There are still some questions that necessitate future research, like the role of voice therapy on the vocal function of LPR patients with hard voice onset and whether voice therapy could ease the treatment cycle for LPR.

      CONCLUSIONS

      Changes in vocal production may occur in LPR patients, potentially increasing their susceptibility to hard voice onset. The patients with hard voice onset require longer VOT and greater PTP to initiate phonation. These results provide theoretical evidence for targeting and correcting hard voice onset as a treatment method for vocal fatigue in LPR patients.

      Statement of Ethics

      These studies were approved by the ethics committee of Zhongshan Hospital of Xiamen University. Informed written consent was obtained from each patient.

      Conflict of interest

      The authors had no conflict of interest to declare.

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