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Umatani M, Ogawa M, Hosokawa K, Kato C, Okajima E, Iwahashi T, Inohara H. The Feasibility of Gastroesophageal Manometry for Continuously Evaluating the Degree of Expiratory Effort During Successful Crescendo Phonation. J Voice 2021; 37:470.e7-470.e16. [PMID: 33707030 DOI: 10.1016/j.jvoice.2021.02.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2020] [Revised: 01/23/2021] [Accepted: 02/01/2021] [Indexed: 10/22/2022]
Abstract
OBJECTIVES This study aimed to assess the feasibility of gastroesophageal manometry for continuously evaluating the degree of expiratory effort by measuring the pressures in the digestive tract during crescendo phonation. METHODS Each of 18 healthy nondysphonic speakers had a probe with a four-channel gastroesophageal manometer inserted through the nasal cavity to place four pressure sensors in the hypopharynx, cervical-/thoracic esophagus, and stomach, and was asked to gradually increase the vocal loudness during sustained phonation of the vowel /e:/ (vowel-crescendo task), while the sound pressure level and the pressures were simultaneously recorded. RESULTS 50% of the successful vowel-crescendo task samples with a gradual and adequate sound pressure level increase showed a concomitant gradual increase in both the intra-thoracic-esophageal/intra-gastric pressure values from approximately -5 mmHg /6 mmHg to -10 mmHg/20 mmHg, respectively. The maximum pressure value was the highest in the intra-gastric pressure followed by the intra-thoracic-esophageal and intra-cervical-esophageal pressures in order. However, most of the samples showed less than one of atypical pressure changes, such as fluctuations in the intra-thoracic-esophageal and intra-gastric pressure changes and dispersion in the intra-cervical-esophageal and intra-hypopharyngeal pressure values (perhaps due to the peristaltic motions, and the contact of the sensors to the membranous wall). CONCLUSION These results show that, during successful crescendo phonation, gastroesophageal manometry reveals a gradual increase in the intra-thoracic and intra-abdominal pressures with increasing the vocal intensity, even though showing some systematic errors, suggesting the usefulness of gastroesophageal manometry for continuously evaluating the degree of expiratory effort without influence by the laryngeal condition.
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Affiliation(s)
- Masanori Umatani
- Department of Otorhinolaryngology - Head and Neck Surgery, Osaka University Graduate School of Medicine, Suita, Japan
| | - Makoto Ogawa
- Department of Otorhinolaryngology - Head and Neck Surgery, Osaka University Graduate School of Medicine, Suita, Japan; Department of Otorhinolaryngology, JCHO Osaka Hospital, Osaka, Japan.
| | - Kiyohito Hosokawa
- Department of Otorhinolaryngology - Head and Neck Surgery, Osaka University Graduate School of Medicine, Suita, Japan
| | - Chieri Kato
- Department of Otorhinolaryngology - Head and Neck Surgery, Osaka University Graduate School of Medicine, Suita, Japan
| | - Eri Okajima
- Department of Otorhinolaryngology - Head and Neck Surgery, Osaka University Graduate School of Medicine, Suita, Japan
| | - Toshihiko Iwahashi
- Department of Otorhinolaryngology - Head and Neck Surgery, Osaka University Graduate School of Medicine, Suita, Japan
| | - Hidenori Inohara
- Department of Otorhinolaryngology - Head and Neck Surgery, Osaka University Graduate School of Medicine, Suita, Japan
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Jiang J, Stern J, Chen HJ, Solomon NP. Vocal Efficiency Measurements in Subjects with Vocal Polyps and Nodules: A Preliminary Report. Ann Otol Rhinol Laryngol 2016; 113:277-82. [PMID: 15112969 DOI: 10.1177/000348940411300404] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Vocal efficiency is a quantitative measure of the ability of the larynx to convert subglottal power to acoustic power. On the basis of the scant previous literature and clinical intuition, we tested the hypothesis that vocal efficiency, as an indicator of the functional status of the larynx, is abnormally reduced in persons with vocal nodules and polyps. Because the most difficult aspect of obtaining measures of vocal efficiency has been the determination of subglottal pressure, we applied a noninvasive airflow interruption technique for this purpose. Subjects with normal voices (n = 22), vocal polyps (n = 14), and vocal nodules (n = 16) phonated at different intensities into a mask connected by way of piping to a flow meter, a pressure transducer, and an acoustic microphone. Inflation of a balloon-type valve located within the piping provided interruption of phonation. The intraoral pressure plateau occurring during flow interruption was used to estimate subglottal pressure. Subglottal power and acoustic power were determined, and their quotient provided a measure of vocal efficiency. The vocal efficiency in the normal subjects averaged 1.15 × 10−5 at 70 dB, 3.17 × 10−5 at 75 dB, 7.52 × 10−5 at 80 dB, and 1.41 × 10−4 at 85 dB. The vocal efficiency in the patients with vocal polyps averaged 3.62 × 10−6 at 70 dB, 8.34 × 10−6 at 75 dB, 2.10 × 10−5 at 80 dB, and 4.26 × 10−5 at 85 dB. The vocal efficiency in the patients with vocal nodules averaged 4.32 × 10−6 at 70 dB, 1.57 × 10−5 at 75 dB, 4.26 × 10−5 at 80 dB, and 8.34 × 10−5 at 85 dB. As compared to the normal subjects, the patients with laryngeal polyps or vocal nodules had significantly reduced vocal efficiency. These results provide quantitative verification of the clinical impression of inefficient phonation in patients with mass lesions of the vocal folds.
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Affiliation(s)
- Jack Jiang
- Department of Surgery, Division of Otolaryngology-Head and Neck Surgery, University of Wisconsin Medical School, Madison, Wisconsin 53706, USA
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Hoffman MR, Rieves AL, Surender K, Devine EE, Jiang JJ. Evaluation of auditory and visual feedback for airflow interruption. J Voice 2012; 27:149-54. [PMID: 23280384 DOI: 10.1016/j.jvoice.2012.10.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2012] [Accepted: 10/04/2012] [Indexed: 11/30/2022]
Abstract
INTRODUCTION Clinical application of mechanical interruption methods for measuring aerodynamic parameters has been hindered by relatively high intrasubject variability. To improve the intrasubject reliability, we evaluated the effect of auditory and visual feedback on subject performance when measuring aerodynamic parameters with the airflow interrupter. METHODS Eleven subjects performed four sets of 10 trials with the airflow interrupter: no feedback (control); auditory feedback (tone matching subject's F0 played over headphones); visual feedback (real-time feedback of sound pressure level, frequency, and airflow); and combined auditory and visual feedback. Task order was varied across subjects. The effect of each feedback method on mean and coefficient of variation (CV) of subglottal pressure (Ps), mean flow rate (MFR), and laryngeal airway resistance (RL; Ps/MFR) compared with that of the control trials was determined using paired t tests. Feedback methods were compared against each other using one-way repeated measures analysis of variance. RESULTS Each feedback method significantly decreased CV of RL compared with that of the control trials (auditory feedback: P=0.005; visual feedback: P=0.008; and combined feedback: P<0.001). Auditory feedback (P=0.011) and combined feedback (P=0.026) also decreased CV of MFR. Mean MFR was significantly higher during trials with visual feedback compared with that of the auditory feedback. CONCLUSIONS Each feedback method improved the intrasubject consistency when measuring RL. Feedback appeared to have a greater effect on MFR than Ps. Although there is no clear optimal feedback method, each is preferable to not providing any feedback during trials. Evaluating new methods of visual feedback to further improve MFR and thus RL measurement would be valuable.
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Affiliation(s)
- Matthew R Hoffman
- Division of Otolaryngology-Head and Neck Surgery, Department of Surgery, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA
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Chapin WJ, Hoffman MR, Rieves AL, Jiang JJ. Comparison of labial and mechanical interruption for measurement of aerodynamic parameters. J Voice 2010; 25:337-41. [PMID: 20189755 DOI: 10.1016/j.jvoice.2010.01.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2009] [Accepted: 01/06/2010] [Indexed: 11/24/2022]
Abstract
OBJECTIVES/HYPOTHESIS To directly compare the mechanical and labial interruption techniques of measuring subglottal pressure (P(s)), mean flow rate (MFR), and laryngeal resistance (R(L)). METHODS Thirty-four subjects performed 10 trials with both mechanical and labial interruption. P(s) and MFR were recorded, whereas R(L) was calculated by dividing P(s) by MFR. Coefficients of variation were calculated to compare intrasubject precision. A subset of 10 subjects performed the tasks twice with 30 minutes between sessions. Bland-Altman plots were used to determine intrasubject repeatability for each of the methods. RESULTS Mechanical interruption produced coefficients of variation for P(s), MFR, and R(L) of 0.0995, 0.127, and 0.129, respectively. Labial interruption produced coefficients of variation of 0.102, 0.147, and 0.169, respectively. P values were 0.824 for P(s), 0.159 for MFR, and 0.043 for R(L). The Bland-Altman plots revealed comparable repeatability between the two methods. The 95% confidence intervals of the Bland-Altman plots for mechanical interruption were (-0.050, 0.072), (-0.543, 1.832), and (-2.498, 10.528) for MFR, P(s), and R(L). Confidence intervals for labial interruption were (-0.018, 0.031), (0.057, 2.442), and (-3.267, 10.595) for MFR, P(s,) and R(L). CONCLUSIONS Mechanical interruption produced higher precision when measuring R(L) because of more reliable airflow measurements. Mechanical and labial interruption showed comparable repeatability. Further research into using mechanical interruption clinically is warranted.
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Affiliation(s)
- William J Chapin
- Division of Otolaryngology-Head and Neck Surgery, Department of Surgery, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
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Hoffman MR, Baggott CD, Jiang J. Reliable time to estimate subglottal pressure. J Voice 2008; 23:169-74. [PMID: 18207358 DOI: 10.1016/j.jvoice.2007.09.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2007] [Accepted: 09/13/2007] [Indexed: 11/27/2022]
Abstract
Measuring subglottal pressure (P(s)) with complete interruption can be problematic due to unsteady plateaus in supraglottal pressure data traces during balloon valve interruption. Subjectively determining when the graph plateaus neglect the effects of laryngeal, auditory, and other physical reflexes may alter patient effort and glottal configuration. If the P(s) estimation was made at a consistent time before the onset of reflexes, the recorded pressure would not be dependent on subjective analysis by a clinician, and intrasubject data would be more precise. Previously collected data using the airflow interruption system have shown consistency at approximately 150 milliseconds after balloon valve inflation. To evaluate the validity of estimating P(s) at this point, a theoretical and a physical model were applied. A theoretical ideal gas model of capacitance calculated the time necessary for supraglottal pressure to equilibrate with P(s). Using a mechanical pseudolung which served as a constant pressure source, known subresistor pressures were compared to the pressure measured by the interruption device. Both models confirmed the validity of measuring P(s) consistently at 150 milliseconds into the 500-millisecond interruption. In human trials testing 25 subjects, mean intrasubject standard deviation using this optimal time constant was 0.66+/-0.37cm H(2)O, and 1.11+/-0.48cm H(2)O when performing plateau analysis (P<0.0005). This novel modification to the clinically feasible interruption model for P(s) estimation demonstrates a marked improvement in the reliability of balloon valve interruption while maintaining the validity demonstrated in previous studies.
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Affiliation(s)
- Matthew R Hoffman
- Department of Surgery, Division of Otolaryngology-Head and Neck Surgery, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706, USA
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Baggott CD, Yuen AK, Hoffman MR, Zhou L, Jiang JJ. Estimating subglottal pressure via airflow redirection. Laryngoscope 2007; 117:1491-5. [PMID: 17762273 DOI: 10.1097/mlg.0b013e318063e89e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Subglottal pressure (SGP) is a valuable parameter in the research and clinical assessment of laryngeal function. The lungs serve as a constant pressure source during sustained phonation, and that pressure, SGP, can be used to determine the efficiency with which the larynx converts aerodynamic power to acoustic power. As the larynx serves as an aerodynamic transducer, the vocal efficiency (Ve) coefficient, defined as acoustic power (dB) divided by aerodynamic power (SGP x glottal airflow) has been shown to reliably reflect vocal health. However, current SGP measurement techniques are hesitantly used because of either an invasive nature or the requirement of intensive patient training. This study tests a novel device that has been designed to noninvasively estimate SGP through mechanical airflow redirection, producing a numeric output on completion of the trial, which lasts only a few seconds. The novelty of this design lies in the ease of use for both the patient and the clinician. Multiple mechanical airflow redirections occlude the airway for only 135 ms, which is predicted to limit the effect of confounding laryngeal reflexes that may occur during the trials. Additionally, the airflow redirection into a retention device allows for the pneumatic in-trial comparison of the estimated SGP with the pressure achieved by the patient, providing a numeric output to the clinician on completion.
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Affiliation(s)
- Christopher D Baggott
- Department of Surgery, Division of Otolaryngology-Head and Neck Surgery, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53792-7375, USA
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Jiang JJ, Tao C. The minimum glottal airflow to initiate vocal fold oscillation. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2007; 121:2873-81. [PMID: 17550186 DOI: 10.1121/1.2710961] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Phonation threshold flow (PTF) is proposed as a new aerodynamic parameter of the speech production system in this study. PTF is defined as the minimum airflow that can initiate stable vocal fold vibration. Because the glottal airflow can be noninvasively measured, it is suggested that the aerodynamic parameter PTF may be more practical for clinical vocal disease assessment. In order to investigate the relationship between PTF and phonatory system properties, the stability of the body-cover vocal fold model was analyzed. The study has theoretically shown that PTF is a sensitive aerodynamic parameter dependent on tissue properties, glottal configuration, and vocal tract loading. It was predicted that PTF can be reduced by decreasing tissue viscosity, decreasing mucosal wave velocity, increasing vocal fold thickness, or decreasing prephonatory glottal area. Furthermore, it was predicted that a divergent glottis or low vocal tract resistance lead to a reduced PTF. Also discussed is the potential significance of PTF in investigating the energy distribution in a vocal fold vibration system and related clinical applications.
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Affiliation(s)
- Jack J Jiang
- Department of Surgery, Division of Otolaryngology Head and Neck Surgery, University of Wisconsin Medical School, Madison, Wisconsin 53792-7375, USA.
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Neumann K, Gall V, Schutte HK, Miller DG. A new method to record subglottal pressure waves: potential applications. J Voice 2003; 17:140-59. [PMID: 12825647 DOI: 10.1016/s0892-1997(03)00037-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Rapid subglottal pressure changes related to the glottal cycles influence the aerodynamics of phonation. Various methods to measure these have been developed, but are not practical for routine phoniatric use. For that reason, a noninvasive measurement tool is necessary. This article presents a technique that uses a microphone positioned at the skin of the jugular fossa to record the signal which arises in the subglottal spaces and is transmitted through the soft tissue to the surface of the skin. Using the program Glottal Segmentation of Voice and Speech, jugular microphone recordings from two healthy subjects were compared with simultaneously recorded direct intratracheal measurements during the same phonation. A systematic error arising from the transmission properties of the microphone and the soft tissue leads to phase and amplitude deviations. These must be taken into account and require correction. This correction procedure leads to high correlations and a good agreement between the two signals. Even without this correction the jugular microphone measurements proved to be useful as a diagnostic and a therapeutic tool in cases where chest resonance specific processes appear affected. In addition, they offer material for research purposes. Although based on a small number of subjects, the new method shows a good validity; testing on a larger number of subjects will probably strengthen the validity.
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Affiliation(s)
- Katrin Neumann
- Clinic for Phoniatrics and Paedaudiology, Johann Wolfgang Goethe University, Frankfurt am Main, Germany.
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Jiang J, O'Mara T, Conley D, Hanson D. Phonation threshold pressure measurements during phonation by airflow interruption. Laryngoscope 1999; 109:425-32. [PMID: 10089970 DOI: 10.1097/00005537-199903000-00016] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE/HYPOTHESIS Most methods to measure phonation threshold pressure (PTP) are clinically impractical because they are invasive. This report concerns an airflow interruption system developed to allow noninvasive estimation of (PTP) at different levels of vocal intensity. An estimation of PTP was made for normal subjects with normal larynges and no voice complaints and for individuals who had dysphonia associated with vocal polyps to compare the estimated minimal pressure across the glottis that was required to sustain phonation in the two conditions. STUDY DESIGN This was a methodological study designed to measure an unanticipated PTP from a subject. METHODS Subjects sustained a constant tone and the airflow was directed into a section of pipe with an airtight mask over the mouth and nose. The airflow, intramask pressure, and intensity of the acoustic output were recorded. A PTP was predicted from a difference between an estimate of the subglottal pressure and the vocal tract pressure at the point that phonation ceased after interruption of airflow. Eleven control subjects and 13 patients with vocal fold polyps were studied. In each population there were eight men and five women. The individuals in the group with vocal fold polyps averaged 39 years of age, and the control subject group averaged 49 years of age. Normal subjects produced a steady vowel /a/ at 75, 80, and 85 dB. Patients with polyps were unable to sustain phonation at these levels but were able to produce phonation at 65, 70, and 75 dB. The validity of the system was tested using a laryngeal model and in a patient with a normal larynx and voice who had a tracheotomy (placed for sleep apnea syndrome) which allowed direct measurement of subglottal pressure. RESULTS The measured mean PTP levels (with standard deviation [SD]) for the control subjects were 2.38 (1.273), 2.67 (1.879), and 2.98 (2.23) cm H2O at 75, 80, and 85 dB, respectively. The measured mean PTP levels (with SD) for the patients with polyps were 4.79 (2.67), 5.85 (2.34), and 7.37 (3.26) cm H2O at 75, 80, and 85 dB, respectively. The differences in mean PTP between groups at 75, 80, and 85 dB were significant at P = .013, P = .017, and P = .010, respectively. CONCLUSIONS The estimations of PTP for patients with vocal fold polyps were significantly higher than for the control subjects at three phonation levels.
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Affiliation(s)
- J Jiang
- Department of Otolaryngology-Head and Neck Surgery, Northwestern University Medical School, Chicago, IL 60611, USA
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Abstract
A method of estimating subglottal pressure through intraoral pressure has been reported in the literature. In order to determine its clinical usefulness, however, the method should be tested against direct measurements made on subjects with pathologic larynges. The present study was designed to compare intraoral pressure versus subglottal pressure, as measured with a sensing tube inserted through a tracheal stoma. Results showed that intraoral pressure of /i:pi:/ was almost equivalent to subglottal pressure of /i:/ when the latter was smaller than about 25 cmH20. When subglottal pressure exceeded this value, however, the intraoral pressure was smaller than the subglottal pressure. We conclude that the magnitude of subglottal pressure is not invariably identical with intraoral pressure.
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Affiliation(s)
- K Kitajima
- Department of Otolaryngology, Shiga University of Medical Science, Otsu-shi, Japan
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Abstract
The author discusses the mechanisms of speech production, focusing on the measurement of its motor aspects. He examines the multiple representation levels at which physiological events that underlie speech production can be investigated, and examines measurement of neuromuscular activity, structure movement (e.g. kinematics and dynamics), aerodynamic phenomena, and/or the acoustic output. He describes two general approaches. Studies can focus on one system and obtain data at multiple levels; for example, simultaneous recording of EMG (electromyogram) and/or kinematic signals, as well as the acoustic signal; this permits comprehensive assessment of physiologic events within a particular system. Alternatively, studies can obtain recordings of the acoustic signal simultaneously with EMG and/or kinematic signals taken from several systems; this permits assessment of the organization of physiologic events within, as well as between, systems. The author illustrates these methods in a study of stuttering.
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Abstract
The variation of vocal efficiency for the mean values for normal subjects was investigated in patients with laryngeal disease. The relative contributions of mean flow rate and intrapulmonic pressure to the variation of efficiency were explored to explain aerodynamic aspects in voice disorders. Vocal efficiency was determined by use of expressions involving simultaneous values of sound pressure level, mean flow rate, and intrapulmonic pressure. The intrapulmonic pressure was noninvasively obtained by plethysmographic and pneumotachographic methods. Values of vocal efficiency were generally abnormally low for the types of larynges studied. An aerodynamic-biomechanical classification of laryngeal disease was inferred from the data: 1) large chink of glottis, associated with high flow rate; 2) mass on vocal fold, associated with high values of both flow rate and intrapulmonic pressure; and 3) high stiffness of vocal fold, associated with high values of intrapulmonic pressure.
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Abstract
In the past decade the number of voice laboratories has increased dramatically. Their primary mission is to enhance patient care by the application of knowledge gained from basic research. They also are dedicated to further improvement of diagnostic and therapeutic resources. The strength of the voice laboratory lies in collaboration between the clinician and the scientist.
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Dejonckere P, Lebacq J. [Phase relationship between dynamics of the subglottic pressure and oscillatory movement of the vocal folds. I. Sustained phonation]. ARCHIVES INTERNATIONALES DE PHYSIOLOGIE ET DE BIOCHIMIE 1980; 88:333-341. [PMID: 6163402 DOI: 10.3109/13813458009092903] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The phase relationship between subglottic pressure and vocal fold length has been studied during sustained phonation in five subjects with normal larynx. Pressure was measured by tracheal puncture and vocal fold length was deduced from simultaneous measurement of translaryngeal impedance in the horizontal plane and transglottal light flux in the vertical plane. The pressure sine wave shows a phase lead of slightly less than 90 degrees relative to the length sine wave. Thus during sustained phonation the vocal apparatus behaves like a harmonic oscillator; the frequency of oscillation is determined by the mechanical parameters of the vibrating system; the source of periodic energy supply is the subglottal pressure wave.
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Schultz-Coulon HJ. [Diagnosis of dysfunction of the voice (author's transl)]. ARCHIVES OF OTO-RHINO-LARYNGOLOGY 1980; 227:1-169. [PMID: 7469924 DOI: 10.1007/bf00456372] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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WARREN DONALDW. The Determination of Velopharyngeal Incompetence by Aerodynamic and Acoustical Techniques. Clin Plast Surg 1975. [DOI: 10.1016/s0094-1298(20)30074-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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