Escenario social
2.3. Liderazgo alquilado al silencio
per-ception of the treatment from a functional perspective.
Assessment of voice based on a patient’s perceived se-verity and the need to recover vocal function may be the most appropriate manner to assess severity of voice handicap.
—Thomas Murry and Clark A. Rosen
References
Adelstein, D. J., Sharon, V. M., Earle, A. S., et al. (1990).
Long-term results after chemoradiotherapy of locally con-fined squamous cell head and neck cancer. American Jour-nal of Clinical Oncology, 13, 440–447.
Benninger, M. S., Atiuja, A. S., Gardner, G., and Grywalski, C. (1998). Assessing outcomes for dysphonic patients.
Journal of Voice, 12, 540–550.
Dejonckere, P. H. (2000). Perceptual and laboratory assess-ment of dysphonia. Otolaryngology Clinics of North Amer-ica, 33, 33–34.
Glicklich, R. E., Glovsky, R. M., Montgomery, W. W. (1999).
Validation of a voice outcome survey for unilateral vocal fold paralysis. Otolaryngology–Head and Neck Surgery, 120, 152–158.
Hartl, D. M., Hans, S., Vaissiere, J., Riquet, M., et al. (2001).
Objective voice analysis after autologous fat injection for unilateral vocal fold paralysis. Annals of Otology, Rhinol-ogy, and LaryngolRhinol-ogy, 110, 229–235.
Hassan, S. J., and Weymuller, E. A. (1993). Assessment of quality of life in head and neck cancer patients. Head and Neck Surgery, 15, 485–494.
Hogikyan, N. D., and Sethuraman, G. (1999). Validation of an instrument to measure voice-related quality of life (V-RQOL). Journal of Voice, 13, 557–559.
Jacobson, B. H., Johnson, A., Grywalski, C., et al. (1998). The Voice Handicap Index (VHI): Development and validation.
Journal of Voice, 12, 540–550.
Jacobson, G. P., Ramadan, N. M., Aggarwal, S., and New-man, C. W. (1994). The development of the Henry Ford Hospital Headache Disability Inventory (HDI). Neurology, 44, 837–842.
List, M. A., Ritter-Sterr, C., and Lansky, S. B. (1998). A per-formance status scale for head and neck patients. Cancer, 66, 564–569.
Ma, E. P., and Yiu, E. M. (2001). Voice activity and partici-pation profile: Assessing the impact of voice disorders on
daily activities. Journal of Speech, Language, and Hearing Research, 44, 511–524.
McHorney, C. A., Ware, J. E., Jr., Lu, J. F., and Sherbourne, C. D. (1993). The MOS 36-item short form health survey (SF-36): II. Psychometric and clinical tests of validity in measuring physical and medical health constructs. Medical Care, 31, 247–263.
Murry, T., Madassu, R., Martin, A., and Robbins, K. T.
(1998). Acute and chronic changes in swallowing and qual-ity of life following intraarterial chemoradiation for organ preservation in patients with advanced head and neck can-cer. Head and Neck Surgery, 20, 31–37.
Murry, T., and Rosen, C. A. (2001). Occupational voice dis-orders and the voice handicap index. In P. Dejonckere (Ed.), Occupational voice disorders: Care and cure (pp. 113–
128). The Hague, the Netherlands: Kugler Publications.
Murry, T., and Rosen, C. A. (2000). Voice Handicap Index results in singers. Journal of Voice, 14, 370–377.
Newman, C., Weinstein, B., Jacobson, G., and Hug, G. (1990).
The hearing handicap inventory for adults: Psychometric adequacy and audiometric correlates. Ear and Hearing, 11, 430–433.
Picarillo, J. F. (1994). Outcome research and otolaryngology.
Otolaryngology–Head and Neck Surgery, 111, 764–769.
Rosen, C. A., and Murry, T. (in press). The VHI 10: An out-come measure following voice disorder treatment. Journal of Voice.
Rosen, C., Lombard, L. E., and Murry, T. (2000). Acoustic, aerodynamic and videostroboscopic features of bilateral vocal fold lesions. Annals of Otology Rhinology and Lar-ynology, 109, 823–828.
Smith, E., Lemke, J., Taylor, M., Kirchner, L., and Ho¤man, H. (1998). Frequency of voice problems among teachers and other occupations. Journal of Voice, 12, 480–488.
Wolfe, V., Fitch, J., and Martin, D. (1997). Acoustic measures of dysphonic severity across and within voice types. Folia Phoniatrica, 49, 292–299.
World Health Organization. (1980). International Classification of Impairments, Disabilities and Handicaps: A manual of classification relating to the consequences of disease (pp. 25–
43). Geneva: World Health Organization.
Electroglottographic Assessment of Voice
A number of instruments can be used to help character-ize the behavior of the glottis and vocal folds during phonation. The signals derived from these instruments are called glottographic waveforms or glottograms (Titze and Talkin, 1981). Among the more common glotto-grams are those that track change in glottal flow, via inverse filtering; glottal width, via kymography; glottal area, via photoglottography; and vocal fold movement, via ultrasonography (Baken and Orliko¤, 2000). Such signals can be used to obtain several di¤erent physio-logical measures, including the glottal open quotient and the maximum flow declination rate, both of which are highly valuable in the assessment of vocal function.
Unfortunately, the routine application of these tech-niques has been hampered by the cumbersome and time-consuming way in which these signals must be acquired, conditioned, and analyzed. One glottographic method, Electroglottographic Assessment of Voice 23
electroglottography (EGG), has emerged as the most commonly used technique, for several reasons: (1) it is noninvasive, requiring no probe placement within the vocal tract; (2) it is easy to acquire, alone or in conjunc-tion with other speech signals; and (3) it o¤ers unique information about the mucoundulatory behavior of the vocal folds, which contemporary theory suggests is a critical element in the assessment of voice production.
Electroglottography (known as electrolaryngography in the United Kingdom) is a plethysmographic technique that entails fixing a pair of surface electrodes to each side of the neck at the thyroid lamina, approximating the level of the vocal folds. An imperceptible low-amplitude, high-frequency current is then passed between these electrodes. Because of their electrolyte content, tissue and body fluids are relatively good conductors of elec-tricity, whereas air is a particularly poor conductor.
When the vocal folds separate, the current path is forced to circumvent the glottal air space, decreasing e¤ective voltage. Contact between the vocal folds a¤ords a con-duit through which current can take a more direct route across the neck. Electrical impedance is thus highest when the current path must completely bypass an open glottis and progressively decreases as greater contact be-tween the vocal folds is achieved. In this way, the voltage across the neck is modulated by the contact of the vocal folds, forming the basis of the EGG signal. The glottal region, however, is quite small compared with the total region through which the current is flowing. In fact, most of the changes in transcervical impedance are due to strap muscle activity, laryngeal height variation induced by respiration and articulation, and pulsatile blood vol-ume changes. Because increasing and decreasing vocal fold contact has a relatively small e¤ect on the overall impedance, the electroglottogram is both high-pass fil-tered to remove the far slower nonphonatory impedance changes and amplified to boost the laryngeal contribu-tion to the signal. The result is a waveform—sometimes designated Lx—that varies chiefly as a function of vocal fold contact area (Gilbert, Potter, and Hoodin, 1984).
First proposed by Fabre in 1957 as a means to assess laryngeal physiology, the clinical potential of EGG was recognized by the mid-1960s. Interest in EGG increased in the 1970s as the importance of mucosal wave dynam-ics for vocal fold vibration was confirmed, and accel-erated greatly in the 1980s with the advent of personal computers and commercially available EGGs that were technologically superior to previous instruments. Today, EGG has a worldwide reputation as a useful tool to supplement the evaluation and treatment of vocal pa-thology. The clinical challenge, however, is that a valid and reliable EGG assessment demands a firm under-standing of normal vocal fold vibratory behavior along with recognition of the specific capabilities and limita-tions of the technique.
Instead of a simple mediolateral oscillation, the vocal folds engage in a quite complex undulatory movement during phonation, such that their inferior margins ap-proximate before the more superior margins make con-tact. Because EGG tracks e¤ective medial contact area,
the pattern of vocal fold vibration can be characterized quite well (Fig. 1). The contact pattern will vary as a consequence of several factors, including bilateral vocal fold mass and tension, medial compression, and the anatomy and orientation of the medial surfaces. Con-siderable research has been devoted to establishing the important features of the EGG and how they relate to specific aspects of vocal fold status and behavior.
Despite these e¤orts, however, the contact area function is far from perfectly understood, especially in the face of pathology. Given the complexity of the ‘‘rolling and peeling’’ motion of the glottal margins and the myriad possibilities for abnormality of tissue structure or bio-mechanics, it is not surprising that e¤orts to formulate simple rules relating abnormal details to specific pathol-ogies have not met with notable success. In short, the clinical value of EGG rests in documenting the vibratory consequence of pathology rather than in diagnosing the pathology itself.
Figure 1.At the top is shown a schematic representation of a single cycle of vocal fold vibration viewed coronally (left) and superiorly (right) (after Hirano, 1981). Below it is a normal electroglottogram depicting relative vocal fold contact area.
The numbered points on the trace correspond approximately to the points of the cycle depicted above. The contact phases of the vibratory cycle are shown beneath the electroglottogram.
Using multiple glottographic techniques, Baer, Lo¨fqvist, and McGarr (1983) demonstrated that, for normal modal-register phonation, the ‘‘depth of closure’’
was very shallow just before glottal opening and quite deep soon after closure was initiated. Most important, they showed that the instant at which the glottis first appears occurs sometime before all contact is lost, and that the instant of glottal closure occurs sometime after the vocal folds first make contact. Thus, although the EGG is sensitive to the depth of contact, it cannot be used to determine the width, area, or shape of the glottis.
For this reason, EGG is not a valid technique for the measurement of glottal open time or, therefore, the open quotient. Likewise, since EGG does not specify which parts of the vocal folds are in contact, it cannot be used to measure glottal closed time, nor can it, without addi-tional evidence, be used to determine whether maximal vocal fold contact indeed represents complete oblitera-tion of the glottal space. Identifying the exact moment when (and if ) all medial contact is lost has also proved particularly problematic. Once the vocal folds do lose contact, however, it can no longer be assumed that the EGG signal conveys any information whatsoever about laryngeal behavior. During such intervals, the signal may vary solely as a function of the instrument’s auto-matic gain control and filtering (Rothenberg, 1981).
Although the EGG provides useful information only about those parts of the vibratory cycle during which there is some vocal fold contact, these characteristics may provide important clinical insight, especially when paired with videostroboscopy and other data traces.
EGG, with its ability to demonstrate contact change in both the horizontal and vertical planes, can quite e¤ec-tively document the normal voice registers (Fig. 2) as well as abnormal and unstable modes of vibration (Fig.
3). However, to qualitatively assess EGG wave charac-teristics and to derive useful indices of vocal fold contact behavior, it may be best to view the EGG in terms of a vibratory cycle composed of a contact phase and a minimal-contact phase (see Fig. 1). The contact phase includes intervals of increasing and decreasing contact, whereas the peak represents maximal vocal fold contact and, presumably, maximal glottal closure. The minimal-contact phase is that portion of the EGG wave during which the vocal folds are probably not in contact. Much clinical misinterpretation can be avoided if no attempt is made to equate the vibratory contact phase with the glottal closed phase or the minimal-contact phase with the glottal open phase.
For the typical modal-register EGG, the contact phase is asymmetrical; that is, the increase in contact takes less time than the interval of decreasing contact.
The degree of contact asymmetry is thought to vary not only as a consequence of vocal fold tension but also as a function of vertical mucosal convergence and dynamics (i.e., phasing; Titze, 1990). A dimensionless ratio, the contact index (CI), can be used to assess contact sym-metry (Orliko¤, 1991). Defined as the di¤erence between the increasing and decreasing contact durations divided by the duration of the contact phase, CI will vary
be-tween 1 for a contact phase maximally skewed to the left andþ1 for a contact phase maximally skewed to the right. For normal modal-register phonation, CI varies between 0.6 and 0.4 for both men and women, but, as can be seen in Figure 2, it is markedly di¤erent for other voice registers. Pulse-register EGGs typically have CIs in the vicinity of0.8, whereas in falsetto it would not be uncommon to have a CI that approximates zero, indicating a symmetrical or nearly symmetrical contact phase.
Another EGG measure that is gaining some currency in the clinical literature is the contact quotient (CQ).
Defined as the duration of the contact phase relative to the period of the entire vibratory cycle, there is evidence from both in vivo testing and mathematical modeling to suggest that CQ varies with the degree of medial com-pression of the vocal folds (see Fig. 3) along a hypo-adducted ‘‘loose’’ (or ‘‘breathy’’) to a hyperhypo-adducted
‘‘tight’’ (or ‘‘pressed’’) phonatory continuum (Rothen-berg and Mahshie, 1988; Titze, 1990). Under typical vocal circumstances, CQ is within the range of 40%–
60%, and despite the propensity for a posterior glottal
Figure 2. Typical electroglottograms obtained from a normal man prolonging phonation in the low-frequency pulse, moderate-frequency modal, and high-frequency falsetto voice registers.
Electroglottographic Assessment of Voice 25
chink in women, there does not seem to be a significant sex e¤ect. This is probably due to the fact that EGG (and thus the CQ) is insensitive to glottal gaps that are not time varying. Unlike men, however, women tend to show an increase in CQ with vocal F0. It has been conjectured that this may be the result of greater medial compression employed by women at higher F0s that serves to diminish the posterior glottal gap. Nonetheless, a strong relationship between CQ and vocal intensity has been documented in both men and women, consistent with the known relationship between vocal power and the adductory presetting of the vocal folds. Because vocal intensity is also related to the rate of vocal fold contact (Kakita, 1988), there have been some prelimi-nary attempts to derive useful EGG measures of the contact rise time.
Because EGG is relatively una¤ected by vocal tract resonance and turbulence noise (Orliko¤, 1995), it al-lows evaluation of vocal fold behavior under conditions not well-suited to other voice assessment techniques. For this reason, and because the EGG waveshape is a rela-tively simple one, the EGG has found some success both as a trigger signal for laryngeal videostroboscopy and as a means to define and describe phonatory onset, o¤set,
intonation, voicing, and fluency characteristics. In fact, EGG has, for many, become the preferred means by which to measure vocal fundamental frequency and jitter.
In summary, EGG provides an innocuous, straight-forward, and convenient way to assess vocal fold vibra-tion through its ability to track the relative area of contact. Although it does not supply valid information about the opening and closing of the glottis, the tech-nique a¤ords a utech-nique perspective on vocal fold be-havior. When conservatively interpreted, and when combined with other tools of laryngeal evaluation, EGG can substantially further the clinician’s understanding of the malfunctioning larynx and play an e¤ective role in therapeutics as well.
See also acoustic assessment of voice.
—Robert F. Orliko¤
References
Baer, T., Lo¨fqvist, A., and McGarr, N. S. (1983). Laryngeal vibrations: A comparison between high-speed filming and glottographic techniques. Journal of the Acoustical Society of America, 73, 1304–1308.
Baken, R. J., and Orliko¤, R. F. (2000). Laryngeal function. In Clinical measurement of speech and voice (2nd ed., pp. 394–
451). San Diego, CA: Singular Publishing Group.
Fabre, P. (1957). Un proce´de´ e´lectrique percutane´ d’inscription de l’accolement glottique au cours de la phonation: Glot-tographie de haute fre´quence. Premiers resultats. Bulletin de l’Acade´mie Nationale de Me´decine, 141, 66–69.
Gilbert, H. R., Potter, C. R., and Hoodin, R. (1984). Laryn-gograph as a measure of vocal fold contact area. Journal of Speech and Hearing Research, 27, 178–182.
Hirano, M. (1981). Clinical examination of voice. New York:
Springer-Verlag.
Kakita, Y. (1988). Simultaneous observation of the vibratory pattern, sound pressure, and airflow signals using a physical model of the vocal folds. In O. Fujimura (Ed.), Vocal physiology: Voice production, mechanisms, and functions (pp. 207–218). New York: Raven Press.
Orliko¤, R. F. (1991). Assessment of the dynamics of vocal fold contact from the electroglottogram: Data from normal male subjects. Journal of Speech and Hearing Research, 34, 1066–1072.
Orliko¤, R. F. (1995). Vocal stability and vocal tract configu-ration: An acoustic and electroglottographic investigation.
Journal of Voice, 9, 173–181.
Rothenberg, M. (1981). Some relations between glottal air flow and vocal fold contact area. ASHA Reports, 11, 88–96.
Rothenberg, M., and Mahshie, J. J. (1988). Monitoring vocal fold abduction through vocal fold contact area. Journal of Speech and Hearing Research, 31, 338–351.
Titze, I. R. (1990). Interpretation of the electroglottographic signal. Journal of Voice, 4, 1–9.
Titze, I. R., and Talkin, D. (1981). Simulation and interpreta-tion of glottographic waveforms. ASHA Reports, 11, 48–55.
Further Readings
Abberton, E., and Fourcin, A. J. (1972). Laryngographic analysis and intonation. British Journal of Disorders of Communication, 7, 24–29.
Baken, R. J. (1992). Electroglottography. Journal of Voice, 6, 98–110.
Figure 3. Electroglottograms representing di¤erent abnormal modes of vocal fold vibration.
Carlson, E. (1993). Accent method plus direct visual feedback of electroglottographic signals. In J. C. Stemple (Ed.), Voice therapy: Clinical studies (pp. 57–71). St. Louis: Mosby–
Year Book.
Carlson, E. (1995). Electrolaryngography in the assessment and treatment of incomplete mutation (puberphonia) in adults. European Journal of Disorders of Communication, 30, 140–148.
Childers, D. G., Hicks, D. M., Moore, G. P., and Alsaka, Y. A. (1986). A model of vocal fold vibratory motion, con-tact area, and the electroglottogram. Journal of the Acousti-cal Society of America, 80, 1309–1320.
Childers, D. G., Hicks, D. M., Moore, G. P., Eskenazi, L., and Lalwani, A. L. (1990). Electroglottography and vocal fold physiology. Journal of Speech and Hearing Research, 33, 245–254.
Childers, D. G., and Krishnamurthy, A. K. (1985). A critical review of electroglottography. CRC Critical Review of Bio-medical Engineering, 12, 131–161.
Colton, R. H., and Conture, E. G. (1990). Problems and pit-falls of electroglottography. Journal of Voice, 4, 10–24.
Cranen, B. (1991). Simultaneous modelling of EGG, PGG, and glottal flow. In J. Gau‰n and B. Hammarberg (Eds.), Vocal fold physiology: Acoustic, perceptual, and physiologi-cal aspects of voice mechanisms (pp. 57–64). San Diego, CA: Singular Publishing Group.
Croatto, L., and Ferrero, F. E. (1979). L’esame elettro-glottografico appliato ad alcuni casi di disodia. Acta Pho-niatrica Latina, 2, 213–224.
Fourcin, A. J. (1981). Laryngographic assessment of phona-tory function. ASHA Reports, 11, 116–127.
Gleeson, M. J., and Fourcin, A. J. (1983). Clinical analysis of laryngeal trauma secondary to intubation. Journal of the Royal Society of Medicine, 76, 928–932.
Go´mez Gonza´les, J. L., and del Can˜izo Alvarez, C. (1988).
Nuevas tecnicas de exploracio´n funcional ları´ngea: La electroglotografı´a. Anales Oto-Rino-Otoları´ngologica Ibero-Americana, 15, 239–362.
Hacki, T. (1989). Klassifizierung von Glottisdysfunktionen mit Hilfe der Elecktroglottographie. Folia Phoniatrica, 41, 43–48.
Hertega˚rd, S., and Gau‰n, J. (1995). Glottal area and vibra-tory patterns studied with simultaneous stroboscopy, flow glottography, and electroglottography. Journal of Speech and Hearing Research, 38, 85–100.
Kitzing, P. (1990). Clinical applications of electroglottography.
Journal of Voice, 4, 238–249.
Kitzing, P. (2000). Electroglottography. In A. Ferlito (Ed.), Diseases of the larynx (pp. 127–138). New York: Oxford University Press.
Motta, G., Cesari, U., Iengo, M., and Motta, G., Jr. (1990).
Clinical application of electroglottography. Folia Phonia-trica, 42, 111–117.
Neil, W. F., Wechsler, E., and Robinson, J. M. (1977). Elec-trolaryngography in laryngeal disorders. Clinical Otolaryn-gology, 2, 33–40.
Nieto Altazarra, A., and Echarri San Martin, R. (1996). Elec-troglotografı´a. In R. Garcı´a-Tapia Urrutia and I. Cobeta Marco (Eds.), Diagno´stico y tratamiento de los transtornos de la voz (pp. 163–169). Madrid, Spain: Editorial Garsi.
Orliko¤, R. F. (1998). Scrambled EGG: The uses and abuses of electroglottography. Phonoscope, 1, 37–53.
Roubeau, C., Chevrie-Muller, C., and Arabia-Guidet, C.
(1987). Electroglottographic study of the changes of voice registers. Folia Phoniatrica, 39, 280–289.
Wechsler, E. (1977). A laryngographic study of voice disorders.
British Journal of Disorders of Communication, 12, 9–22.