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Effects of laryngeal endoscopy on the vocal performanceof young adult females with normal voices
Journal of Voice Vol. 12, No. 1, pp. 68-77 © 1998 Singular Publishing Group, Inc.
Effects of Laryngeal Endoscopy on the Vocal Performance of Young Adult Females with Normal Voices *Valerie R C. Lim, *Jennifer M. Oates, tDebbie J. Phyland, and ~Matthew J. Campbell *School of Human Communication Sciences, La Trobe University; and "~Austin and Repatriation Medical Centre, Victoria, Australia
Summary: This study investigated changes in maximum phonation time and acoustic and perceptual measures of voice following topical anesthesia and laryngeal endoscopy with the flexible endoscope. Forty-four females, aged 18-33 years and with normal voices, performed four vocal tasks: (a) 3-second/i/prolongation, (b) maximum phonation time on/i/, (c) stepwise scale-singing, and (d) reading a standard passage. Subjects performed these tasks prior to anesthesia, after anesthesia, and again during laryngeal endoscopy. Voice samples were analyzed for jitter, shimmer, harmonic-to-noise ratio, speaking fundamental frequency, maximum phonational frequency range, maximum phonation time, harshness, and breathiness. Results demonstrated significant reductions in maximum phonational frequency range following anesthesia and, during laryngeal endoscopy, reductions in maximum phonation time and increases in speaking fundamental frequency, minimum fundamental frequency on scale-singing, and breathiness. Clinicians using laryngeal endoscopy for evaluation and management of vocal dysfunction should, therefore, consider the possible effects of these procedures on vocal functioning. Key Words" Laryngeal endoscopy-Topical anesthesia Normal voice.
Laryngeal endoscopy is a procedure whereby laryngeal structure and function are examined using a flexible fiberoptic endoscope inserted via one of the nasal passages or a rigid endoscope inserted through the mouth. The flexible endoscope has become a standard piece of equipment and has been routinely used as a
Accepted for publication March 25, 1997. This work was presented at the 26th Annual Symposium: Care of the Professional Voice, Philadelphia, Pennsylvania, June 1997. Address correspondence and reprint requests to Valerie E C. Lim, School of Human Communication Sciences, Faculty of Public Health Sciences, La Trobe University, Victoria 3083, Australia.
Journal of Voice, VoL 12, No. 1, 1998
diagnostic, therapeutic, and teaching tool (1--6) by many otolaryngologists, voice scientists, and speech pathologists around the globe. However, by its invasive nature, there is speculation that the endoscopic procedure may effect subtle changes in vocal behavior and hence, affect the interpretation of laryngeal observations. Although past research (5) has highlighted the potential for anesthetic and endoscopic effects on vocal function, this proposition has yet to be formally investigated. The present study therefore attempted to empirically determine the existence of such effects and, more importantly, the nature of such effects so that measures can be taken to increase the validity and reliability of laryngeal endoscopic examinations. 68
EFFECTS OF LARYNGEAL ENDOSCOPY ON, VOCAL PERFORMANCE OF YOUNG FEMALES
The success of laryngeal endoscopic techniques, the equipment used, and the effectiveness of the endoscope as a diagnostic and/or biofeedback tool with both children and adults is well documented (2,4,6-13). The advantage of the flexible fiberoptic endoscope over the rigid endoscope is that the former permits a view of the larynx and its adjacent structures during phonatory and nonphonatory manoeuvres (e.g., singing and connected speech). This visual assessment entails the observation of arytenoid symmetry and functioning, glottal closure, ventricular fold constriction and vibration, anterior-posterior constriction of the larynx, laryngeal movements during pitch change, and any evidence of laryngeal pathology. These variables are measured and documented using standard laryngeal endoscopy protocols (1,3,5,14). Not until recently has the endoscope been used to examine the anatomic and physiological characteristics of the normal human larynx. Previous studies of endoscopically derived data have shown the existence of extensive variability in normal laryngeal behavior. Certain behaviors, including anterior-posterior laryngeal constriction, structural asymmetries of the true vocal folds, and evidence of a posterior glottal chink, have not been found to meet with the accepted or reported expectation of "normal" laryngeal configurations (1,5,15). Although the studies differed with respect to the type of endoscope (i.e., flexible or rigid) and light used (i.e., stroboscopic or continuous), it is apparent that normal laryngeal variations exist regardless of the type of endoscopic procedure. Such variations in normal laryngeal behavior have implications for the accurate interpretation of endoscopic findings. Without overt signs of vocal pathology, it may be difficult, and at times impossible, to determine the integrity of normal and abnormal larynges based on endoscopic and/or stroboscopic data alone (1). Unfortunately, there is still a paucity of reliable information on endoscopic evaluations of normal laryngeal behavior. Without such normative data, there is a risk of measurement error and unreliable observer judgments during endoscopic laryngeal evaluation of patients with voice disorders. It is clear that additional data are required to ascertain whether endoscopic observations reflect normal laryngeal variation, mechanical interference associated with the presence of the endoscope or indeed, that of true vocal dysfunction.
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In addition, it is speculated that the use of topical anesthesia may confound endoscopic observations of vocal performance. Topical anesthesia (e.g., Xylocaine, Hurricaine or Co-Phenylcaine) is normally applied to the nasal or oropharyngeal passages to ensure minimal discomfort during endoscopic procedures. The pharmacologic action of the anesthesia reduces the sensitivity in the supraglottic region and, therefore, helps to eliminate excessive gagging. The need for topical anesthesia during laryngeal endoscopy is controversial. Boone and McFarlane (16) and McFarlane and Lavarato (10) argue the need for anesthesia to ensure greater patient comfort during the procedure. On the other hand, Selkin (11) and Yanagisawa (17) report that the use of anesthesia decreases laryngeal proprioception during phonation and, hence, alters vocal function. The effects of topical anesthesia on vocal performance have been empirically investigated in previous research (18-20). The results, however, have so far been equivocal. Peppard and Bless (19) used videostroboscopy with a rigid endoscope to compare different laryngeal variables (e.g., supraglottic activity, amplitude of glottal excursion, phase closure, secretions in the laryngeal area) before and after the application of Xylocaine (Lidocaine 10%) spray to the oropharynx. No significant differences were found between these conditions for any of the variables measured, indicating that the use of topical anesthesia in videostroboscopic examination did not affect vocal performance. On the other hand, Sorenson et al. (20) and Batchelor et al. (18) found significant anesthesia-related effects on vocal performance. Both studies involved the measurement of acoustic parameters. Sorenson et al. measured fundamental frequency perturbation (jitter) during sustained vowel phonations following anesthetization of the oropharynx and vocal folds. The data showed that the application of the topical anesthetic (2% tetracaine) resulted in an increase in jitter ratio values and that this was more prominent during high frequency phonations. The recent study by Batchelor et al. investigated changes in videostroboscopic and acoustic variables of vocal function during sustained vowel phonation and following the application of Hurricaine (Benzocaine 20%) to the oral cavity. Contrary to the results of Sorenson et al., these authors did not find any significant changes iia Joun~al of Voice, VoL 12, No. 1, 1998
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VALERIE P. C. LIM ET AL.
jitter (%) and amplitude variation before and after topical anesthesia. Significant changes, however, were noted for fundamental frequency level and shimmer (%). Although obvious methodological differences between these studies may account for such equivocal findings, the potential effects of topical anesthesia on vocal function cannot be overlooked. As highlighted, the accuracy of endoscopic observations of vocal function may be compromised by -several factors including normal laryngeal variation, topical anesthesia, and the use of the laryngeal endoscope. To ensure that endoscopic interpretations of normal and disordered larynges are as error-free as possible, the effects of the anesthesia and the procedure itself need to be investigated. As the investigation of endoscopic effects on vocal function is itself invasive, it is necessary to use noninvasive measurements of vocal performance (e.g., acoustic and perceptual measures). Such noninvasive parameters have been measured in previous studies on anesthesia, however, none have attempted to differentiate the effects resulting from the use of anesthesia or to the endoscopic procedure itself. The present study aimed to investigate whether or not the use of the flexible laryngeal endoscope and/or topical anesthesia were associated with changes in phonation time and acoustic and perceptual measures of voice quality and pitch in persons with normal voices. The purpose of the study was to delineate any vocal changes which resulted from the presence of the flexible fiberoptic endoscope and/or the routine use of topical anesthesia during the procedure. Two research hypotheses were investigated: (a) that vocal performance is altered during laryngeal endoscopy and (b) that the use of topical anesthesia alters vocal performance.
METHOD Participants Forty-four female undergraduate speech pathology students served as volunteer participants. The mean age of the subjects was 21 years, with a range of 18 to 33 years. All subjects passed standard audiometric screening at 20 dB Hearing Threshold Level (HTL) for all frequencies from 500 to 8000 Hz and were judged to have normal voice quality on the Buffalo Journal of Voice, VoL 12, No. 1, 1998
I11 Voice Screening Profile (21). Subjects who smoked more than three cigarettes a day, who suffered from an upper respiratory infection at the time of laryngeal endoscopy, and/or who had undergone ten or more formal and individual vocal training sessions were excluded from the study.
Experimental conditions Voice samples from each subject were collected in three consecutive experimental conditions: "Pre-Anesthetic," "Anesthetic Only," and, "Anesthetic + Endoscope." The duration of the entire procedure was approximately 30 minutes. The Pre-Anesthetic condition
The Pre-Anesthetic condition served as the control phase in the study. Subjects were seated in a dental chair (reclined to approximately 80 ° ) with their heads comfortably supported by a head rest. This head and seating position was maintained throughout each experimental condition. Voice samples were recorded following a brief orientation to the procedure and standardized instructions from the investigator. The Anesthetic Only condition
Upon inspection of the subject's nose, a total of 0.2 mg of Co-Phenylcaine (5% Lignocaine), in two 0.1 mg doses, was administered by a senior otolaryngology registrar into one of the subject's nares. A latency period of 5 minutes was allowed for the anesthetic to take effect. This was followed by a second recording of voice samples. The Anesthetic + Endoscope condition
A Pentax FNL-10S flexible fiberoptic endoscope (3.4 mm in diameter), with continuous, cold light supplied by a Bruel and Kjaer Larynx Stroboscope Type 4941, was used to visualize the vocal folds. A Panasonic color video camera system CD 1 (Model HF 35A-2), coupled to the endoscope, was used to video and record the full procedure on a Panasonic VHS videocassette recorder (Model No. NV-FS 100A). The endoscopic view of the procedure was simultaneously displayed on a JVC 14-inch color TV monitor (Model TM-1500 PS). Laryngeal endoscopy commenced immediately following the second audio-recording of voice samples.
EFFECTS OF LARYNGEAL ENDOSCOPY ON, VOCAL PERFORMANCE OF YOUNG FEMALES
The senior otolaryngology registrar inserted the endoscope via the inferior concha of the subject's anesthetized nose. To standardize the endoscope placement for all subjects, the endoscope was advanced such that the distal end of the scope was rostral to the tip of the epiglottis. The third audio-recording of voice samples commenced once the endoscope was in situ and the subject reported being in a comfortable state. Subjects were not given the opportunity to spend time adjusting their voicing to the presence of the endoscope so that the immediate effects of the endoscope could be investigated. The endoscope was routinely disinfected in a solution of Glutaraldehyde 10g/L before reusage.
Voice sampling In each of the experimental conditions, subjects performed four vocal tasks. Subjects were asked to (a) prolong the v o w e l / i / f o r as long as possible on one breath at comfortable pitch and loudness, (b) prolong the v o w e l / i / f o r 3 seconds at comfortable pitch and loudness, (c) sing/a:/in a stepwise manner at tone intervals in an ascending fashion and then in a descending fashion, and (d) read the first paragraph of "The Rainbow Passage" (22) at comfortable pitch and loudness. The SHURE Model SMI2A Professional HeadWorn Microphone was used to collect the acoustic signals. Microphone-to-mouth distance was standardized at 9 mm. The SHURE head-worn microphone is a low-impedance, unidirectional, dynamic microphone, designed for close-talk operation. The use of this microphone at a very close distance from the mouth in a quiet room ensured that extremely good signal-to-noise ratios were achieved. Voice signals were recorded on a SONY Digital Audio Tape (DAT)Corder (TCD-D10 PROII). The intensity of incoming signals on the VU-meter of the DAT-Corder was monitored and held constant across all conditions by the experimenter. The voice samples were recorded onto high quality 120 minute TDK (DA-R129EB) digital audio tapes. In the Pre-Anesthetic condition, vocal tasks were recorded in the following order: (1) 3-second prolongation of/i/, (2) maximum phonation duration of/i/, (3) scale-singing, and (4) "The Rainbow Passage," To prevent the potential occurrence of order effects, subjects performed the vocal tasks in random order
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during the Anesthetic Only and Anesthetic + Endoscope conditions. Practice sessions
Practice sessions were only conducted in the PreAnesthetic condition immediately prior to the recording of individual tasks. All practice sessions were conducted by the same experimenter using the same format and instructions for each subject. For the scale-singing, subjects first listened to a pre-recorded model of a trained singer with a wide frequency range performing this task. Subjects were allowed one practice of the 3-second prolongation o f / i / a n d scale-singing. Eight subjects, however, required two attempts for descending scales to achieve a range which they and the experimenter considered to be their maximum physiological range. These same eight subjects also required additional practice for descending scales in the Anesthetic only and Anesthetic + Endoscope condition. Three attempts at maximum sustained phonation were allowed, as this number of attempts is considered the minimum requirement for the elicitation of maximum performance criterion (23-24). Reading practice for "The Rainbow Passage" (22) immediately prior to audio-recording was not necessary, as each subject had been instructed to read the passage in the waiting room to familiarize themselves with its content.
Voice analyses Voice samples from the four vocal tasks described in the previous section were analyzed for maximum phonation time (MPT), seven acoustic parameters, and two perceptual parameters. Table 1 shows the vocal tasks and the corresponding acoustic and perceptual measures derived from each task. MPT was the only dependent variable measured on the day of laryngeal endoscopy. This was conducted "on line" by the investigator using a hand-held Micronta Model 63-9190 Digital Stopwatch. Measurements of MPT (in seconds) were then measured a second time via playback of recorded MPT samples to ensure reliability of measurements. The longest of the subjects' three attempts was recorded as the MPT measure. The acoustic analyses for all samples of vowel prolongations, scale-singing, and connected speech were performed using the SoundScope/16 Journal of Voice, Vol. 12, No. 1, 1998
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VALERIE P. C. LIM ET AL. T A B L E 1. Vocal tasks and dependent variables
Vocal Tasks
Dependent Variables
1. Prolongation of vowel/i/for as long as possible on one breath.
Maximum Phonation Time (MPT)
2. Prolong vowel/i/for 3 secs.
Acoustic Parameters 1. Jitter 2. Shimmer 3. Harmonic-to-noise (H/N) ratio
3. Sing/a:/in a step-wise manner at tone intervals up and down the scale.
4. Maximum Phonational Frequency Range (MPFR) 5. Maximum F o 6. Minimum Fo
4. Read "The Rainbow Passage."
7. Speaking Fo (SFF)
Perceptual Parameters 1. Harshness 2. Breathiness
(#GWI-SoS16) speech and sound analysis system (25) in concert with the Macintosh Quadra 800 computer. Voice samples were digitized through a 16-bit Digitizer at a 44.1 kHz sampling rate. For the purpose of acoustic analyses, the 1-Channel Analyzer (Instrument #2004) was used. The perceptual parameters, harshness, and breathiness, were analyzed on the first paragraph of "The Rainbow Passage" (22). Harshness and breathiness were rated on a 5-point equal-appearing, interval rating scale as follows: 1 = Normal, 2 = Slight, 3 = Slight-Mild, 4 = Mild, 5 = Moderate All 132 connected speech samples were transcribed onto separate tapes. Fifteen additional voice samples, randomly selected from the original samples, were duplicated for reliability assessment. Perceptual judgements were conducted in a sound-treated SoundMastering Studio on 2 days (1 week apart); each session lasted approximately 1 hour. Two speech pathologists with extensive experience in the evaluation and management of voice disorders listened to the speech samples in random order and analyzed the samples using the rating scale described above. Practice sessions were conducted immediately before the first rating session to familiarize listeners with the use of the rating scales. All speech samples were presented to listeners using the DAT-Corder (TCD-D10 PROI/) Journal of Voice, Vol. 12, No. 1, 1998
and via Pro-2 Dynamic Stereo Headphones (Model PH-550). Each connected speech sample was presented one time, unless an additional auditory presentation was requested by any one of the two listeners. The maximum number of presentations for each sample was two. ~S~TS M P T and acoustic parameters A one-way Analysis of Variance with repeated measures was used to separately analyze MPT and the acoustic parameters of jitter, shimmer, H/N ratio, Speaking Fundamental Frequency (SFF), Maximum Phonational Frequency Range (MPFR), and maximum and minimum fundamental frequency (Fo) for changes in vocal performance across experimental conditions. The results revealed significant main effects for MPT, F(2,43) = 5.642, p <.005; SFF, F(2,43) = 8.207, p <.001; and MPFR, F(2,42) = 26.484, p <.001. MPFR was reduced at both ends of the singing range: maximum F 0, F(2,43) = 23.136, p <.001; minimum F 0, F(2,43) = 15.777, p <.001. Due to the large number of separate ANOVAs conducted, Bonferroni-type adjustments (26) were undertaken to overcome the potential occurrence of "family-wise" Type 1 errors. The above results remained significant following these adjustments.
EFFECTS OF LARYNGEAL ENDOSCOPY ON,VOCAL PERFORMANCE OF YOUNG FEMALES
Table 2 summarizes the group means, standard deviations (SD), and ranges for MPT, SFF, and MFPR (maximum F 0 and minimum F0). Posthoc tests were then conducted to determine if the significant differences in group means for these variables were associated with the use of anesthesia and/or the use of the laryngeal endoscope. The results of the Tukey's Posteriori Test (27) revealed significant changes in the mean scores between the Pre-Anesthetic and Anesthetic Only conditions for MPFR. This finding indicated that the use of the topical anesthetic, CoPhenylcaine, was associated with a reduction in MPFR. This reduction in MPFR was found to be significant at both extreme limits of the singing range (i.e., affecting both maximum F o and minimum F0). That is, subjects were unable to reach the highest and lowest notes that they had produced before topical anesthesia. Although MPFR was the only parameter affected by the use of topical anesthesia, individual
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data indicated that, for a majority of subjects, the use of topical anesthesia was associated with negative change in one or more of the other vocal parameters measured. Posthoc test results also showed that the differences in mean scores between the Anesthetic Only condition and the Anesthetic + Endoscope conditions were significant for SFF, minimum F o, and MPT. More specifically, these results indicate that the use of the endoscope was associated with an increase in SFF, an increase in minimum F 0 (i.e., the lower end of the singing range was reduced), and a reduction in MPT. Although the difference in group means (Table 2) for MPT and SFF are small and may suggest overall minimal negative effects in vocal performance, inspection of individual data indicate otherwise. Reduced MPT scores were observed for 50% of the subjects following topical anesthesia and for 70% of subjects after insertion of the endoscope. While only
TABLE 2. Group means, standard deviations (SD) and rangesfor
MPT (sec), SFF (Hz), and MPFR (Hz) Conditions Variables
Pre-Anesthestic
Anesthetic Only
Anesthetic + Endoscope
21.520 7.908 7.10--43.69
21.251 7.719 10.56-41.65
19.389 7.319 5.81-43.34
201.228 13.039 175.53-225.182
203.127 13.924 168.570-229.163
205.228 15.365 173.041-248.549
743.368 251.227 199.640-1816.012
625.556 243.063 235.726-1554.808
596.670 218.938 188.719-1387.859
884.061 244.472 334.091-1917.391
775.007 242.682 370.588-1696.154
750.852 215.157 339.231-1520.690
141.372 22.424 93.830-190.086
148.778 18.921 111.364-189.270
154.574 16.523 111.646-195.133
MPT (seconds) Means SD Range
SFF (Hz) Means SD Range
MPFR (Hz) Means SD Range Maximum Fo (Hz) Means SD Range Minimum F0 (Hz) Means SD Range
Journal ofVoice, VoL 12, No. 1, 1998
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VALERIE P C. LIM ET AL.
four subjects (9%) experienced a reduction of more than 5 seconds after anesthesia, nine subjects (20%) were found to have MPT reductions of more than 5 seconds during endoscopy. Similarly, although no subject had an abnormally low MPT after anesthesia, twelve subjects (27%) had abnormal MPT values after insertion of the endoscope (i.e., <15.2 seconds) (3,23,28). For SFF, increased scores were observed for 28 subjects after anesthesia (64%) and for 31 sub-jects (70%) after insertion of the endoscope. Increases in SFF of greater than 10Hz were observed for two subjects (5%) after anesthesia and six subjects (14%) during endoscopy. These findings were not confined to performances in SFF and MPT, but were also observed in the individual scores for the other vocal parameters measured. Posthoc analysis and Bonferroni-type adjustments were not conducted for jitter, F(2,43) = .223, p >.8005; shimmer, F(2,43) = 2.346, p >.1019; or H/N ratio, F(2,43) = 1.268, p >2.866, as there were no significant main effects for these acoustic variables. That is, neither the use of topical anesthesia nor the flexible endoscope had a significant effect on jitter, shimmer, or H/N ratio. While group data was found to be nonsignificant, individual data again showed that the use of topical anesthesia and the laryngeal endoscope can produce negative effects in vocal quality for certain subjects. For example, normal jitter values (i.e.,
< 1%) were recorded for two subjects before the application of anesthesia; these values increased to levels outside the normal range (1.5-2.1%) after anesthesia and insertion of the laryngeal endoscope.
Perceptual Parameters Interrater and intrarater reliability for the perceptual voice parameters of harshness and breathiness were determined by examining percentage agreement on the 5-point rating scale. Identical ratings or ratings which differed by plus or minus I scale point were considered indicators of satisfactory reliability. The percentage agreement between raters was 94.69% for harshness and 95.45% for breathiness. Of the 5.3% harshness ratings and 4.5% breathiness ratings which exceeded this criterion for satisfactory reliability, none differed by more than 2 scale points between listeners. Based on the same criterion, listener one's intrarater reliability was 100% for harshness and 93.4% for breathiness. Listener two's intrarater reliability was 93.4% for harshness and 100% for breathiness. Again, the small percentage of ratings that did exceed the criterion for satisfactory reliability did not differ by more than 2 scale points for either listener. Table 3 summarizes the Friedman Rank Information for the variables harshness and breathiness. Harshness and breathiness ratings for the three experimental conditions were analyzed using the Friedman
TABLE 3. Summary of the Friedman rank information for harshness and breathiness on "The Rainbow Passage" Experimental Condition
Sum Rank
Mean Ranks
Harshness
Pre-Anesthetic Anesthetic only Anesthetic + Endoscope
84.0 84.5 89.5
1.953 1.965 2.081
Breathiness
Pre-Anesthetic Anesthetic only Anesthetic + Endoscope
84.0 80.5 93.5
1.953 1.872 2.174
Harshness
Pre-Anesthetic Anesthetic only Anesthetic + Endoscope
86.0 86.0 86.0
2.000 2.000 2.000
Breathiness
Pre-Anesthetic Anesthetic only Anesthetic + Endoscope
84.0 80.5 96.5
1.884 1.872 2.244
Listener 1
Listener 2
Journal ofVoice, VoL 12, No. 1, 1998
EFFECTS OF LARYNGEAL ENDOSCOPY ON, VOCAL PERFORMANCE OF YOUNG FEMALES
Analysis of Variance (by ranks). The results for the Friedman test (Chi-square corrected for ties) revealed nonsignificant results for listener one's ratings of harshness and breathiness. That is, overall, no perceptual changes in voice quality were observed by this listener. The Friedman test statistic was not obtained for listener two's rating of harshness because the rank scores were equal across experimental conditions. The results for the Friedman test, however, revealed a significant finding for listener two's rating of breathiness, Xr2 (2) = 9.324; p <.01. Closer examination of the Friedman Rank results indicated that the ratings of breathiness were higher in the Anesthetic + Endoscope condition than in the Pre-Anesthetic and Anesthetic Only condition as evidenced by the large difference in the sum of ranks between conditions. Although significant changes in voice quality were demonstrated only for listener two's rating of breathiness, there was an overall trend of greater degrees of harshness and breathiness in the "Anesthetic + Endoscope" condition when compared to the Pre-Anesthetic and Anesthetic-only conditions. That is, the presence of the endoscope in situ was associated with negative effects on vocal quality. DISCUSSION The results of the present study showed that for subjects with normal voice undergoing laryngeal endoscopy with the flexible endoscope, negative changes in voice were apparent following the application of topical anesthesia and the insertion of the endoscope. The results provide some empirical support for previous speculations of endoscopic effects on laryngeal behavior (5). In the present study, half of the eight vocal parameters measured, namely MPT, SFF, MPFR (both maximum and minimum F0), and perceived breathiness were affected negatively by the procedures. Only one of these parameters, MPFR, deteriorated after the application of Co-Phenlycaine nasal spray. This deterioration was observed at both extreme limits of the frequency range. There is evidence that local anesthetics, via their direct action on intact mucosa, affect coordination and proprioception (29). It may be then, that the application of topical anesthesia in the present study led to a diminution of the control of vocal function which compromised the
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subjects' pitch ranges. The anesthesia may have affected, for example, the laryngeal mucosal receptors hypothesized to be important in maintaining appropriate laryngeal tension, particularly for higher frequencies (30-32). The extent of the effects of CoPhenylcaine on specific physiological mechanisms required for pitch changing (e.g., vocal fold length, mass and tension, and laryngeal elevation), however, were not investigated in the present research. Although the application of Co-phenylcaine during endoscopy affected only one vocal parameter in this study, it must be remembered that the anesthesia was administered via the nasal passages and that the dosage and concentration of the anesthetic was minimal (i.e., 0.2 mg of Co-Phenylcaine, 5% Lignocaine). While it is unclear whether the effects of anesthesia on voice are related to the type, site of application, dosage, and concentration of the anesthetic, it may be that larger dosages applied to the oropharynx (as are often used for laryngeal examinations using the rigid endoscope) would have more extensive negative effects on vocal functioning than were demonstrated here. In contrast to the effects of topical anesthesia, a larger number of vocal parameters (i.e., four) were found to be significantly altered in a negative direction during endoscopy than after topical anesthesia. These parameters were MPT, SFF, minimum Fo, and breathiness. There are several possible explanations for these endoscopic effects on vocal performance. It may be that "scope trauma" (3,8) (i.e., discomfort resulting from mechanical stimulation of the laryngeal mucosa) and/or "scope-consciousness" (i.e., the increased awareness of the nasendoscope in the throat) were associated with the negative effects on vocal function. These possibilities were supported by subjective reports of throat discomfort and awareness of the endoscope by the majority of subjects in the study. The effects of "scope trauma" and "scope consciousness" may be either direct physiological effects on vocal functioning and/or effects which are mediated by anxiety. For example, increased laryngeal muscle tension leading to an increase in SFF and minimum F 0 may have arisen directly from laryngeal discomfort and/or from the anxiety associated with the endoscopic procedures reported by many of our subjects. The negative changes in voice demonstrated during endoscopy in this research were not confined to Journal of Voice, VoL 12, No. 1, 1998
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VALERIE P. C. LIM ET AL.
only one dimension of vocal function; rather the endoscopic procedure was associated with a range of effects on respiratory control for voicing, pitch, and voice quality. Although topical anesthesia and laryngeal endoscopy did not produce negative effects on all eight vocal parameters measured in this study, it was clear from posthoc testing that, when both effects were combined (i.e., anesthetic and endoscopic), significant results were found for all vocal parameters measured. Perhaps the most clinically important finding is that of individual responses to the procedures. Although several subjects appeared unaffected by either the anesthetic or the presence of the laryngeal endoscope, the data show that negative changes were greater and more apparent in the larger proportion of individual cases. Moreover, the data demonstrated that vocal performances can deteriorate to levels outside the accepted normal range. Clinically, these individual responses indicate that the effects of anesthesia and/or the presence of the laryngeal endoscope on vocal performance may be more prominent in some individuals than others. The results of the study therefore have some clinical implications for the interpretation of endoscopic data. Because the integrity of physiological parameters corresponding to the vocal parameters examined in this study are assessed during standard fiberoptic examinations for both clinical and research purposes, there is potential for misinterpretation of endoscopic images. For example, the increased breathiness and reduced MPTs shown in this study may be seen as incomplete vocal fold adduction during endoscopy. Similarly, it is well known (33) that changes in F0 as were observed in this study during endoscopy, influence parameters which are typically evaluated in fiberoptic examinations (e.g., mucosal wave, vibratory amplitude, and phase closure). Diagnosticians may then attribute features such incomplete glottal closure and reduced mucosal waves to chronic vocal dysfunction rather than to the possibility of short-term effects of the endoscopic procedure itself. The present study has highlighted the usefulness of acoustic and perceptual analyses as indicators of vocal change during procedures in which invasive observation of the larynx is required. Therefore, to avoid visual misinterpretations and the potential for inappropriate recommendations and intervention, percepJournal of Voice, Vol. 12, No. 1, 1998
tual (and possibly acoustic) changes in the client's voice prior to and during the procedure should be considered before interpreting endoscopic data. In the future, it may be beneficial to audio-tape voice samples or to document vocal changes on line using the many standard voice profiles that are presently available. At present, however, standard perceptual rating scales for the normal voice are not readily available. Further research is therefore required to develop voice profiles that will reliably and validly measure vocal performance in normal healthy adults. It would also be of interest to determine in further studies whether clients can be shown how to reduce or eliminate any effects of the endoscopic procedure on their habitual voices. In addition to the indirect measures of vocal physiology used in the present study, other noninvasive but direct measures of vocal physiology should be considered in future studies of endoscopic effects on voice. Although the eight vocal parameters investigated encompassed a broad range of vocal function, it is possible that other vocal measures (e.g., glottal resistance, electroglottography, long-term average spectra, and phonetograms) may also be sensitive to the effects of topical anesthesia and/or laryngeal endoscopy. Their inclusion in future research may provide additional objective data to support the findings demonstrated here. Further, in order to generalize the present findings to other groups of normal speaking adults, future studies should investigate the effects of anesthesia and endoscopy on the vocal performances of adult males, older adults, children, and professional voice users such as singers. CONCLUSION This research has represented an early attempt to increase the reliability and validity of endoscopic laryngeal observations for clinical and research purposes. The results of the present research support the hypotheses that the use of topical anesthesia via the nose and the flexible laryngeal endoscope are associated with negative changes in vocal performance, chiefly the dynamics of sustained phonation, pitch, and voice quality. This study also showed that the laryngeal endoscope had a negative impact on a wider range of vocal parameters than did the use of topical anesthesia. More importantly, the results highlighted
EFFECTS OF LARYNGEAL ENDOSCOPY 01~ VOCAL PERFORMANCE OF YOUNG FEMALES
the individuality of response to such effects. Diagnosticians using laryngeal endoscopy for evaluation, management, and research purposes need to take such factors into account, especially where changes are negative or outside the normal range. Further collaborative research is required to achieve a comprehensive understanding of endoscopic and anesthetic effects on the voice.
REFERENCES 11. Casper JK, Brewer DW, Colton RH. Variations in normal human laryngeal anatomy and physiology as viewed fiberscopicaily. J Voice 1987;1(2): 180-5. 12. Chait DH, Lotz WK. Successful pediatric examinations using nasendoscopy. Laryngoscope 1991; 101 : 1016-8. 13. Colton RH, Casper JK. Understanding voice problems---a physiological perspective for diagnosis and treatment. 2nd ed. Baltimore: Williams & Wilkins, 1996. 14. Lancer JM, Jones AS. Flexible fibreoptic rhinolaryngoscopy. Results of 338 consecutive examinations. J Laryngol Otol 1980;99:771-3. 15. Pemberton C, Russell A, Priestly J, Havas T, Hooper J, Clark P. Characteristics of normal larynges under flexible fiberscopic and stroboscopic examination: an Australian perspective. J Voice 1993;7(4):382-9. 16. Welch AR. The practical and economic value of flexible system laryngoscopy. J Laryngol Otol 1982;96:1125-9. 17. Bastian RW. Laryngeal image biofeedback for voice disorder patients. J Voice 1987;1(3):279-82. 18. Bolger WE, Kennedy DW. Nasal endoscopy in the outpatient clinic. Otol Clin N Am 1992;25(4):791-801. 19. Ibuki K, Karnell MP, Morris HL. Reliability of the nasopharyngeal fibrescope (NPF) for assessing velopharyngeal function. Cleft Palate J 1982;20(2):97-104. 10. McFarlane SC, Lavorato AS. The use of video endoscopy in the evaluation and treatment of dysphonia. Comm Dis 1984; 9(8),117-26. 11. Selkin SG. Other clinical applications of flexible fiberoptic endoscopy. Cleft Palate J 1984;21(1):29-32. 12. Williams GT, Farquharson IM, Anthony J. Fibreoptic laryngoscopy in the assessment of laryngeal disorders. J Laryngol Otol 1975;89:299-315. 13. Wilson FB, Kudryk WH, Sych JA. The development of flexible fiberoptic video nasendoscopy (FFVN). Clinical-teaching-research applications. Asha 1986;25-30. 14. Hirano M, Bless DM. VMeostroboscopic Examination of the Larynx. San Diego: Singular Publishing Group, Inc, 1993. 15. Gelfer PM, Bultemeyer DK. Evaluation of vocal fold vibratory patterns in normal voices. J Voice 1990;4(4):335--45. 16. Boone DR, McFarlane SC. The voice and voice therapy. 4th ed. Englewood Cliffs, NJ: Prentice-Hall, 1988.
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17. Yanagisawa E. Fiberscopic and telescopic videolaryngoscopy--a comparative study. In: Baer T, Sasaki C, Harris D, eds. Laryngeal function in phonation and respiration. Boston: College-Hill Press, 1987:475-84. 18. Batchelor BM, Oui WW, Nguyen HH, Stucker F. Effects of topical anesthesia on voice function in normal subjects. Poster session presented the 1994 ASHA Convention, New Orleans, LA, 1994. 19. Peppard RC, Bless DM. The use of topical anesthetic in videostroboscopic examination of the larynx. J Voice 1990; 5(1):57--63. 20. Sorensen D, Horii Y, Leonard R. Effects of laryngeal topical anesthesia on voice fundamental frequency perturbation. J Speech Hear Res 1980;23:274-83. 21. Wilson DK. Voice problems of children. 3rd ed. Baltimore: Williams & Wilkins, 1987. 22. Fairbanks G. Voice Articulation Drill Book. 2nd ed. New York, NY: Harper and Row, 1960. 23. Kent RD, Kent JF, Rosenbek JC. Maximum performance tests of speech production. J Speech Hear Dis 1987;52: 367-87. 24. Neiman GS, Edeson B. Procedural aspects of eliciting maximum phonation time. Folia Phoniatr 1981;33:285-93. 25. Crawford J, Karafiol P, Lawton S, Naidich Ed, Weinberg G. SoundScope(SuperScope H reference manual version 1.2. Sommerville, MA: GW Instruments Inc, 1993. 26. Tabachnick BG, Fidell LS. Using multivariate statistics. 2nd ed. New York, NY: Harper Collins Publishers, 1989. 27. Kirk RE. Experimental design: procedures for the behavioural sciences. 2nd ed. Monterey, CA: Brooks/Cole Publishing Company), 1982. 28. Hirano M. Clinical examination of voice. New York, NY: Springer-Verlag, 1981. 29. Martin FG. Drugs and vocal function. J Voice 1988;2(4): 338--44. 30. Wyke B. Recent advances in the neurology of phonation: phonatory reflex mechanisms in the larynx. An address given by invitation to the national Conference of the College of Speech Therapists. Brit J Dis Comm 1966;2:2-14. 31. Horii Y, Weinberg B. Sensory contributions to the control of phonation. In : Lawrence V, Weinberg B, eds. Transcripts of the Eighth Symposium: Care of the Professional Voice. Part II: Respiratory & phonatory control systems. New York, NY: The Voice Foundation, 1979:58-65. 32. Gould WJ. Interrelationship between voice and laryngeal mucosal reflexes. In : Lawrence V, Weinberg B, eds. Transcripts of the Eighth Symposium: Care of the Professional Voice. Part II: respiratory & phonatory control systems. New York, NY: The Voice Foundation, 1979:54-57. 33. Woo P. Quantification of videostrobolaryngoscopic findings--measurements of the normal glottal cycle. Laryngoscope 1996;106:1-19.
Journal of Voice, Vol. 12, No. 1, 1998
Effects of Laryngeal Endoscopy on the Vocal Performance of Young Adult Females with Normal Voices *Valerie R C. Lim, *Jennifer M. Oates, tDebbie J. Phyland, and ~Matthew J. Campbell *School of Human Communication Sciences, La Trobe University; and "~Austin and Repatriation Medical Centre, Victoria, Australia
Summary: This study investigated changes in maximum phonation time and acoustic and perceptual measures of voice following topical anesthesia and laryngeal endoscopy with the flexible endoscope. Forty-four females, aged 18-33 years and with normal voices, performed four vocal tasks: (a) 3-second/i/prolongation, (b) maximum phonation time on/i/, (c) stepwise scale-singing, and (d) reading a standard passage. Subjects performed these tasks prior to anesthesia, after anesthesia, and again during laryngeal endoscopy. Voice samples were analyzed for jitter, shimmer, harmonic-to-noise ratio, speaking fundamental frequency, maximum phonational frequency range, maximum phonation time, harshness, and breathiness. Results demonstrated significant reductions in maximum phonational frequency range following anesthesia and, during laryngeal endoscopy, reductions in maximum phonation time and increases in speaking fundamental frequency, minimum fundamental frequency on scale-singing, and breathiness. Clinicians using laryngeal endoscopy for evaluation and management of vocal dysfunction should, therefore, consider the possible effects of these procedures on vocal functioning. Key Words" Laryngeal endoscopy-Topical anesthesia Normal voice.
Laryngeal endoscopy is a procedure whereby laryngeal structure and function are examined using a flexible fiberoptic endoscope inserted via one of the nasal passages or a rigid endoscope inserted through the mouth. The flexible endoscope has become a standard piece of equipment and has been routinely used as a
Accepted for publication March 25, 1997. This work was presented at the 26th Annual Symposium: Care of the Professional Voice, Philadelphia, Pennsylvania, June 1997. Address correspondence and reprint requests to Valerie E C. Lim, School of Human Communication Sciences, Faculty of Public Health Sciences, La Trobe University, Victoria 3083, Australia.
Journal of Voice, VoL 12, No. 1, 1998
diagnostic, therapeutic, and teaching tool (1--6) by many otolaryngologists, voice scientists, and speech pathologists around the globe. However, by its invasive nature, there is speculation that the endoscopic procedure may effect subtle changes in vocal behavior and hence, affect the interpretation of laryngeal observations. Although past research (5) has highlighted the potential for anesthetic and endoscopic effects on vocal function, this proposition has yet to be formally investigated. The present study therefore attempted to empirically determine the existence of such effects and, more importantly, the nature of such effects so that measures can be taken to increase the validity and reliability of laryngeal endoscopic examinations. 68
EFFECTS OF LARYNGEAL ENDOSCOPY ON, VOCAL PERFORMANCE OF YOUNG FEMALES
The success of laryngeal endoscopic techniques, the equipment used, and the effectiveness of the endoscope as a diagnostic and/or biofeedback tool with both children and adults is well documented (2,4,6-13). The advantage of the flexible fiberoptic endoscope over the rigid endoscope is that the former permits a view of the larynx and its adjacent structures during phonatory and nonphonatory manoeuvres (e.g., singing and connected speech). This visual assessment entails the observation of arytenoid symmetry and functioning, glottal closure, ventricular fold constriction and vibration, anterior-posterior constriction of the larynx, laryngeal movements during pitch change, and any evidence of laryngeal pathology. These variables are measured and documented using standard laryngeal endoscopy protocols (1,3,5,14). Not until recently has the endoscope been used to examine the anatomic and physiological characteristics of the normal human larynx. Previous studies of endoscopically derived data have shown the existence of extensive variability in normal laryngeal behavior. Certain behaviors, including anterior-posterior laryngeal constriction, structural asymmetries of the true vocal folds, and evidence of a posterior glottal chink, have not been found to meet with the accepted or reported expectation of "normal" laryngeal configurations (1,5,15). Although the studies differed with respect to the type of endoscope (i.e., flexible or rigid) and light used (i.e., stroboscopic or continuous), it is apparent that normal laryngeal variations exist regardless of the type of endoscopic procedure. Such variations in normal laryngeal behavior have implications for the accurate interpretation of endoscopic findings. Without overt signs of vocal pathology, it may be difficult, and at times impossible, to determine the integrity of normal and abnormal larynges based on endoscopic and/or stroboscopic data alone (1). Unfortunately, there is still a paucity of reliable information on endoscopic evaluations of normal laryngeal behavior. Without such normative data, there is a risk of measurement error and unreliable observer judgments during endoscopic laryngeal evaluation of patients with voice disorders. It is clear that additional data are required to ascertain whether endoscopic observations reflect normal laryngeal variation, mechanical interference associated with the presence of the endoscope or indeed, that of true vocal dysfunction.
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In addition, it is speculated that the use of topical anesthesia may confound endoscopic observations of vocal performance. Topical anesthesia (e.g., Xylocaine, Hurricaine or Co-Phenylcaine) is normally applied to the nasal or oropharyngeal passages to ensure minimal discomfort during endoscopic procedures. The pharmacologic action of the anesthesia reduces the sensitivity in the supraglottic region and, therefore, helps to eliminate excessive gagging. The need for topical anesthesia during laryngeal endoscopy is controversial. Boone and McFarlane (16) and McFarlane and Lavarato (10) argue the need for anesthesia to ensure greater patient comfort during the procedure. On the other hand, Selkin (11) and Yanagisawa (17) report that the use of anesthesia decreases laryngeal proprioception during phonation and, hence, alters vocal function. The effects of topical anesthesia on vocal performance have been empirically investigated in previous research (18-20). The results, however, have so far been equivocal. Peppard and Bless (19) used videostroboscopy with a rigid endoscope to compare different laryngeal variables (e.g., supraglottic activity, amplitude of glottal excursion, phase closure, secretions in the laryngeal area) before and after the application of Xylocaine (Lidocaine 10%) spray to the oropharynx. No significant differences were found between these conditions for any of the variables measured, indicating that the use of topical anesthesia in videostroboscopic examination did not affect vocal performance. On the other hand, Sorenson et al. (20) and Batchelor et al. (18) found significant anesthesia-related effects on vocal performance. Both studies involved the measurement of acoustic parameters. Sorenson et al. measured fundamental frequency perturbation (jitter) during sustained vowel phonations following anesthetization of the oropharynx and vocal folds. The data showed that the application of the topical anesthetic (2% tetracaine) resulted in an increase in jitter ratio values and that this was more prominent during high frequency phonations. The recent study by Batchelor et al. investigated changes in videostroboscopic and acoustic variables of vocal function during sustained vowel phonation and following the application of Hurricaine (Benzocaine 20%) to the oral cavity. Contrary to the results of Sorenson et al., these authors did not find any significant changes iia Joun~al of Voice, VoL 12, No. 1, 1998
70
VALERIE P. C. LIM ET AL.
jitter (%) and amplitude variation before and after topical anesthesia. Significant changes, however, were noted for fundamental frequency level and shimmer (%). Although obvious methodological differences between these studies may account for such equivocal findings, the potential effects of topical anesthesia on vocal function cannot be overlooked. As highlighted, the accuracy of endoscopic observations of vocal function may be compromised by -several factors including normal laryngeal variation, topical anesthesia, and the use of the laryngeal endoscope. To ensure that endoscopic interpretations of normal and disordered larynges are as error-free as possible, the effects of the anesthesia and the procedure itself need to be investigated. As the investigation of endoscopic effects on vocal function is itself invasive, it is necessary to use noninvasive measurements of vocal performance (e.g., acoustic and perceptual measures). Such noninvasive parameters have been measured in previous studies on anesthesia, however, none have attempted to differentiate the effects resulting from the use of anesthesia or to the endoscopic procedure itself. The present study aimed to investigate whether or not the use of the flexible laryngeal endoscope and/or topical anesthesia were associated with changes in phonation time and acoustic and perceptual measures of voice quality and pitch in persons with normal voices. The purpose of the study was to delineate any vocal changes which resulted from the presence of the flexible fiberoptic endoscope and/or the routine use of topical anesthesia during the procedure. Two research hypotheses were investigated: (a) that vocal performance is altered during laryngeal endoscopy and (b) that the use of topical anesthesia alters vocal performance.
METHOD Participants Forty-four female undergraduate speech pathology students served as volunteer participants. The mean age of the subjects was 21 years, with a range of 18 to 33 years. All subjects passed standard audiometric screening at 20 dB Hearing Threshold Level (HTL) for all frequencies from 500 to 8000 Hz and were judged to have normal voice quality on the Buffalo Journal of Voice, VoL 12, No. 1, 1998
I11 Voice Screening Profile (21). Subjects who smoked more than three cigarettes a day, who suffered from an upper respiratory infection at the time of laryngeal endoscopy, and/or who had undergone ten or more formal and individual vocal training sessions were excluded from the study.
Experimental conditions Voice samples from each subject were collected in three consecutive experimental conditions: "Pre-Anesthetic," "Anesthetic Only," and, "Anesthetic + Endoscope." The duration of the entire procedure was approximately 30 minutes. The Pre-Anesthetic condition
The Pre-Anesthetic condition served as the control phase in the study. Subjects were seated in a dental chair (reclined to approximately 80 ° ) with their heads comfortably supported by a head rest. This head and seating position was maintained throughout each experimental condition. Voice samples were recorded following a brief orientation to the procedure and standardized instructions from the investigator. The Anesthetic Only condition
Upon inspection of the subject's nose, a total of 0.2 mg of Co-Phenylcaine (5% Lignocaine), in two 0.1 mg doses, was administered by a senior otolaryngology registrar into one of the subject's nares. A latency period of 5 minutes was allowed for the anesthetic to take effect. This was followed by a second recording of voice samples. The Anesthetic + Endoscope condition
A Pentax FNL-10S flexible fiberoptic endoscope (3.4 mm in diameter), with continuous, cold light supplied by a Bruel and Kjaer Larynx Stroboscope Type 4941, was used to visualize the vocal folds. A Panasonic color video camera system CD 1 (Model HF 35A-2), coupled to the endoscope, was used to video and record the full procedure on a Panasonic VHS videocassette recorder (Model No. NV-FS 100A). The endoscopic view of the procedure was simultaneously displayed on a JVC 14-inch color TV monitor (Model TM-1500 PS). Laryngeal endoscopy commenced immediately following the second audio-recording of voice samples.
EFFECTS OF LARYNGEAL ENDOSCOPY ON, VOCAL PERFORMANCE OF YOUNG FEMALES
The senior otolaryngology registrar inserted the endoscope via the inferior concha of the subject's anesthetized nose. To standardize the endoscope placement for all subjects, the endoscope was advanced such that the distal end of the scope was rostral to the tip of the epiglottis. The third audio-recording of voice samples commenced once the endoscope was in situ and the subject reported being in a comfortable state. Subjects were not given the opportunity to spend time adjusting their voicing to the presence of the endoscope so that the immediate effects of the endoscope could be investigated. The endoscope was routinely disinfected in a solution of Glutaraldehyde 10g/L before reusage.
Voice sampling In each of the experimental conditions, subjects performed four vocal tasks. Subjects were asked to (a) prolong the v o w e l / i / f o r as long as possible on one breath at comfortable pitch and loudness, (b) prolong the v o w e l / i / f o r 3 seconds at comfortable pitch and loudness, (c) sing/a:/in a stepwise manner at tone intervals in an ascending fashion and then in a descending fashion, and (d) read the first paragraph of "The Rainbow Passage" (22) at comfortable pitch and loudness. The SHURE Model SMI2A Professional HeadWorn Microphone was used to collect the acoustic signals. Microphone-to-mouth distance was standardized at 9 mm. The SHURE head-worn microphone is a low-impedance, unidirectional, dynamic microphone, designed for close-talk operation. The use of this microphone at a very close distance from the mouth in a quiet room ensured that extremely good signal-to-noise ratios were achieved. Voice signals were recorded on a SONY Digital Audio Tape (DAT)Corder (TCD-D10 PROII). The intensity of incoming signals on the VU-meter of the DAT-Corder was monitored and held constant across all conditions by the experimenter. The voice samples were recorded onto high quality 120 minute TDK (DA-R129EB) digital audio tapes. In the Pre-Anesthetic condition, vocal tasks were recorded in the following order: (1) 3-second prolongation of/i/, (2) maximum phonation duration of/i/, (3) scale-singing, and (4) "The Rainbow Passage," To prevent the potential occurrence of order effects, subjects performed the vocal tasks in random order
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during the Anesthetic Only and Anesthetic + Endoscope conditions. Practice sessions
Practice sessions were only conducted in the PreAnesthetic condition immediately prior to the recording of individual tasks. All practice sessions were conducted by the same experimenter using the same format and instructions for each subject. For the scale-singing, subjects first listened to a pre-recorded model of a trained singer with a wide frequency range performing this task. Subjects were allowed one practice of the 3-second prolongation o f / i / a n d scale-singing. Eight subjects, however, required two attempts for descending scales to achieve a range which they and the experimenter considered to be their maximum physiological range. These same eight subjects also required additional practice for descending scales in the Anesthetic only and Anesthetic + Endoscope condition. Three attempts at maximum sustained phonation were allowed, as this number of attempts is considered the minimum requirement for the elicitation of maximum performance criterion (23-24). Reading practice for "The Rainbow Passage" (22) immediately prior to audio-recording was not necessary, as each subject had been instructed to read the passage in the waiting room to familiarize themselves with its content.
Voice analyses Voice samples from the four vocal tasks described in the previous section were analyzed for maximum phonation time (MPT), seven acoustic parameters, and two perceptual parameters. Table 1 shows the vocal tasks and the corresponding acoustic and perceptual measures derived from each task. MPT was the only dependent variable measured on the day of laryngeal endoscopy. This was conducted "on line" by the investigator using a hand-held Micronta Model 63-9190 Digital Stopwatch. Measurements of MPT (in seconds) were then measured a second time via playback of recorded MPT samples to ensure reliability of measurements. The longest of the subjects' three attempts was recorded as the MPT measure. The acoustic analyses for all samples of vowel prolongations, scale-singing, and connected speech were performed using the SoundScope/16 Journal of Voice, Vol. 12, No. 1, 1998
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VALERIE P. C. LIM ET AL. T A B L E 1. Vocal tasks and dependent variables
Vocal Tasks
Dependent Variables
1. Prolongation of vowel/i/for as long as possible on one breath.
Maximum Phonation Time (MPT)
2. Prolong vowel/i/for 3 secs.
Acoustic Parameters 1. Jitter 2. Shimmer 3. Harmonic-to-noise (H/N) ratio
3. Sing/a:/in a step-wise manner at tone intervals up and down the scale.
4. Maximum Phonational Frequency Range (MPFR) 5. Maximum F o 6. Minimum Fo
4. Read "The Rainbow Passage."
7. Speaking Fo (SFF)
Perceptual Parameters 1. Harshness 2. Breathiness
(#GWI-SoS16) speech and sound analysis system (25) in concert with the Macintosh Quadra 800 computer. Voice samples were digitized through a 16-bit Digitizer at a 44.1 kHz sampling rate. For the purpose of acoustic analyses, the 1-Channel Analyzer (Instrument #2004) was used. The perceptual parameters, harshness, and breathiness, were analyzed on the first paragraph of "The Rainbow Passage" (22). Harshness and breathiness were rated on a 5-point equal-appearing, interval rating scale as follows: 1 = Normal, 2 = Slight, 3 = Slight-Mild, 4 = Mild, 5 = Moderate All 132 connected speech samples were transcribed onto separate tapes. Fifteen additional voice samples, randomly selected from the original samples, were duplicated for reliability assessment. Perceptual judgements were conducted in a sound-treated SoundMastering Studio on 2 days (1 week apart); each session lasted approximately 1 hour. Two speech pathologists with extensive experience in the evaluation and management of voice disorders listened to the speech samples in random order and analyzed the samples using the rating scale described above. Practice sessions were conducted immediately before the first rating session to familiarize listeners with the use of the rating scales. All speech samples were presented to listeners using the DAT-Corder (TCD-D10 PROI/) Journal of Voice, Vol. 12, No. 1, 1998
and via Pro-2 Dynamic Stereo Headphones (Model PH-550). Each connected speech sample was presented one time, unless an additional auditory presentation was requested by any one of the two listeners. The maximum number of presentations for each sample was two. ~S~TS M P T and acoustic parameters A one-way Analysis of Variance with repeated measures was used to separately analyze MPT and the acoustic parameters of jitter, shimmer, H/N ratio, Speaking Fundamental Frequency (SFF), Maximum Phonational Frequency Range (MPFR), and maximum and minimum fundamental frequency (Fo) for changes in vocal performance across experimental conditions. The results revealed significant main effects for MPT, F(2,43) = 5.642, p <.005; SFF, F(2,43) = 8.207, p <.001; and MPFR, F(2,42) = 26.484, p <.001. MPFR was reduced at both ends of the singing range: maximum F 0, F(2,43) = 23.136, p <.001; minimum F 0, F(2,43) = 15.777, p <.001. Due to the large number of separate ANOVAs conducted, Bonferroni-type adjustments (26) were undertaken to overcome the potential occurrence of "family-wise" Type 1 errors. The above results remained significant following these adjustments.
EFFECTS OF LARYNGEAL ENDOSCOPY ON,VOCAL PERFORMANCE OF YOUNG FEMALES
Table 2 summarizes the group means, standard deviations (SD), and ranges for MPT, SFF, and MFPR (maximum F 0 and minimum F0). Posthoc tests were then conducted to determine if the significant differences in group means for these variables were associated with the use of anesthesia and/or the use of the laryngeal endoscope. The results of the Tukey's Posteriori Test (27) revealed significant changes in the mean scores between the Pre-Anesthetic and Anesthetic Only conditions for MPFR. This finding indicated that the use of the topical anesthetic, CoPhenylcaine, was associated with a reduction in MPFR. This reduction in MPFR was found to be significant at both extreme limits of the singing range (i.e., affecting both maximum F o and minimum F0). That is, subjects were unable to reach the highest and lowest notes that they had produced before topical anesthesia. Although MPFR was the only parameter affected by the use of topical anesthesia, individual
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data indicated that, for a majority of subjects, the use of topical anesthesia was associated with negative change in one or more of the other vocal parameters measured. Posthoc test results also showed that the differences in mean scores between the Anesthetic Only condition and the Anesthetic + Endoscope conditions were significant for SFF, minimum F o, and MPT. More specifically, these results indicate that the use of the endoscope was associated with an increase in SFF, an increase in minimum F 0 (i.e., the lower end of the singing range was reduced), and a reduction in MPT. Although the difference in group means (Table 2) for MPT and SFF are small and may suggest overall minimal negative effects in vocal performance, inspection of individual data indicate otherwise. Reduced MPT scores were observed for 50% of the subjects following topical anesthesia and for 70% of subjects after insertion of the endoscope. While only
TABLE 2. Group means, standard deviations (SD) and rangesfor
MPT (sec), SFF (Hz), and MPFR (Hz) Conditions Variables
Pre-Anesthestic
Anesthetic Only
Anesthetic + Endoscope
21.520 7.908 7.10--43.69
21.251 7.719 10.56-41.65
19.389 7.319 5.81-43.34
201.228 13.039 175.53-225.182
203.127 13.924 168.570-229.163
205.228 15.365 173.041-248.549
743.368 251.227 199.640-1816.012
625.556 243.063 235.726-1554.808
596.670 218.938 188.719-1387.859
884.061 244.472 334.091-1917.391
775.007 242.682 370.588-1696.154
750.852 215.157 339.231-1520.690
141.372 22.424 93.830-190.086
148.778 18.921 111.364-189.270
154.574 16.523 111.646-195.133
MPT (seconds) Means SD Range
SFF (Hz) Means SD Range
MPFR (Hz) Means SD Range Maximum Fo (Hz) Means SD Range Minimum F0 (Hz) Means SD Range
Journal ofVoice, VoL 12, No. 1, 1998
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VALERIE P C. LIM ET AL.
four subjects (9%) experienced a reduction of more than 5 seconds after anesthesia, nine subjects (20%) were found to have MPT reductions of more than 5 seconds during endoscopy. Similarly, although no subject had an abnormally low MPT after anesthesia, twelve subjects (27%) had abnormal MPT values after insertion of the endoscope (i.e., <15.2 seconds) (3,23,28). For SFF, increased scores were observed for 28 subjects after anesthesia (64%) and for 31 sub-jects (70%) after insertion of the endoscope. Increases in SFF of greater than 10Hz were observed for two subjects (5%) after anesthesia and six subjects (14%) during endoscopy. These findings were not confined to performances in SFF and MPT, but were also observed in the individual scores for the other vocal parameters measured. Posthoc analysis and Bonferroni-type adjustments were not conducted for jitter, F(2,43) = .223, p >.8005; shimmer, F(2,43) = 2.346, p >.1019; or H/N ratio, F(2,43) = 1.268, p >2.866, as there were no significant main effects for these acoustic variables. That is, neither the use of topical anesthesia nor the flexible endoscope had a significant effect on jitter, shimmer, or H/N ratio. While group data was found to be nonsignificant, individual data again showed that the use of topical anesthesia and the laryngeal endoscope can produce negative effects in vocal quality for certain subjects. For example, normal jitter values (i.e.,
< 1%) were recorded for two subjects before the application of anesthesia; these values increased to levels outside the normal range (1.5-2.1%) after anesthesia and insertion of the laryngeal endoscope.
Perceptual Parameters Interrater and intrarater reliability for the perceptual voice parameters of harshness and breathiness were determined by examining percentage agreement on the 5-point rating scale. Identical ratings or ratings which differed by plus or minus I scale point were considered indicators of satisfactory reliability. The percentage agreement between raters was 94.69% for harshness and 95.45% for breathiness. Of the 5.3% harshness ratings and 4.5% breathiness ratings which exceeded this criterion for satisfactory reliability, none differed by more than 2 scale points between listeners. Based on the same criterion, listener one's intrarater reliability was 100% for harshness and 93.4% for breathiness. Listener two's intrarater reliability was 93.4% for harshness and 100% for breathiness. Again, the small percentage of ratings that did exceed the criterion for satisfactory reliability did not differ by more than 2 scale points for either listener. Table 3 summarizes the Friedman Rank Information for the variables harshness and breathiness. Harshness and breathiness ratings for the three experimental conditions were analyzed using the Friedman
TABLE 3. Summary of the Friedman rank information for harshness and breathiness on "The Rainbow Passage" Experimental Condition
Sum Rank
Mean Ranks
Harshness
Pre-Anesthetic Anesthetic only Anesthetic + Endoscope
84.0 84.5 89.5
1.953 1.965 2.081
Breathiness
Pre-Anesthetic Anesthetic only Anesthetic + Endoscope
84.0 80.5 93.5
1.953 1.872 2.174
Harshness
Pre-Anesthetic Anesthetic only Anesthetic + Endoscope
86.0 86.0 86.0
2.000 2.000 2.000
Breathiness
Pre-Anesthetic Anesthetic only Anesthetic + Endoscope
84.0 80.5 96.5
1.884 1.872 2.244
Listener 1
Listener 2
Journal ofVoice, VoL 12, No. 1, 1998
EFFECTS OF LARYNGEAL ENDOSCOPY ON, VOCAL PERFORMANCE OF YOUNG FEMALES
Analysis of Variance (by ranks). The results for the Friedman test (Chi-square corrected for ties) revealed nonsignificant results for listener one's ratings of harshness and breathiness. That is, overall, no perceptual changes in voice quality were observed by this listener. The Friedman test statistic was not obtained for listener two's rating of harshness because the rank scores were equal across experimental conditions. The results for the Friedman test, however, revealed a significant finding for listener two's rating of breathiness, Xr2 (2) = 9.324; p <.01. Closer examination of the Friedman Rank results indicated that the ratings of breathiness were higher in the Anesthetic + Endoscope condition than in the Pre-Anesthetic and Anesthetic Only condition as evidenced by the large difference in the sum of ranks between conditions. Although significant changes in voice quality were demonstrated only for listener two's rating of breathiness, there was an overall trend of greater degrees of harshness and breathiness in the "Anesthetic + Endoscope" condition when compared to the Pre-Anesthetic and Anesthetic-only conditions. That is, the presence of the endoscope in situ was associated with negative effects on vocal quality. DISCUSSION The results of the present study showed that for subjects with normal voice undergoing laryngeal endoscopy with the flexible endoscope, negative changes in voice were apparent following the application of topical anesthesia and the insertion of the endoscope. The results provide some empirical support for previous speculations of endoscopic effects on laryngeal behavior (5). In the present study, half of the eight vocal parameters measured, namely MPT, SFF, MPFR (both maximum and minimum F0), and perceived breathiness were affected negatively by the procedures. Only one of these parameters, MPFR, deteriorated after the application of Co-Phenlycaine nasal spray. This deterioration was observed at both extreme limits of the frequency range. There is evidence that local anesthetics, via their direct action on intact mucosa, affect coordination and proprioception (29). It may be then, that the application of topical anesthesia in the present study led to a diminution of the control of vocal function which compromised the
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subjects' pitch ranges. The anesthesia may have affected, for example, the laryngeal mucosal receptors hypothesized to be important in maintaining appropriate laryngeal tension, particularly for higher frequencies (30-32). The extent of the effects of CoPhenylcaine on specific physiological mechanisms required for pitch changing (e.g., vocal fold length, mass and tension, and laryngeal elevation), however, were not investigated in the present research. Although the application of Co-phenylcaine during endoscopy affected only one vocal parameter in this study, it must be remembered that the anesthesia was administered via the nasal passages and that the dosage and concentration of the anesthetic was minimal (i.e., 0.2 mg of Co-Phenylcaine, 5% Lignocaine). While it is unclear whether the effects of anesthesia on voice are related to the type, site of application, dosage, and concentration of the anesthetic, it may be that larger dosages applied to the oropharynx (as are often used for laryngeal examinations using the rigid endoscope) would have more extensive negative effects on vocal functioning than were demonstrated here. In contrast to the effects of topical anesthesia, a larger number of vocal parameters (i.e., four) were found to be significantly altered in a negative direction during endoscopy than after topical anesthesia. These parameters were MPT, SFF, minimum Fo, and breathiness. There are several possible explanations for these endoscopic effects on vocal performance. It may be that "scope trauma" (3,8) (i.e., discomfort resulting from mechanical stimulation of the laryngeal mucosa) and/or "scope-consciousness" (i.e., the increased awareness of the nasendoscope in the throat) were associated with the negative effects on vocal function. These possibilities were supported by subjective reports of throat discomfort and awareness of the endoscope by the majority of subjects in the study. The effects of "scope trauma" and "scope consciousness" may be either direct physiological effects on vocal functioning and/or effects which are mediated by anxiety. For example, increased laryngeal muscle tension leading to an increase in SFF and minimum F 0 may have arisen directly from laryngeal discomfort and/or from the anxiety associated with the endoscopic procedures reported by many of our subjects. The negative changes in voice demonstrated during endoscopy in this research were not confined to Journal of Voice, VoL 12, No. 1, 1998
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only one dimension of vocal function; rather the endoscopic procedure was associated with a range of effects on respiratory control for voicing, pitch, and voice quality. Although topical anesthesia and laryngeal endoscopy did not produce negative effects on all eight vocal parameters measured in this study, it was clear from posthoc testing that, when both effects were combined (i.e., anesthetic and endoscopic), significant results were found for all vocal parameters measured. Perhaps the most clinically important finding is that of individual responses to the procedures. Although several subjects appeared unaffected by either the anesthetic or the presence of the laryngeal endoscope, the data show that negative changes were greater and more apparent in the larger proportion of individual cases. Moreover, the data demonstrated that vocal performances can deteriorate to levels outside the accepted normal range. Clinically, these individual responses indicate that the effects of anesthesia and/or the presence of the laryngeal endoscope on vocal performance may be more prominent in some individuals than others. The results of the study therefore have some clinical implications for the interpretation of endoscopic data. Because the integrity of physiological parameters corresponding to the vocal parameters examined in this study are assessed during standard fiberoptic examinations for both clinical and research purposes, there is potential for misinterpretation of endoscopic images. For example, the increased breathiness and reduced MPTs shown in this study may be seen as incomplete vocal fold adduction during endoscopy. Similarly, it is well known (33) that changes in F0 as were observed in this study during endoscopy, influence parameters which are typically evaluated in fiberoptic examinations (e.g., mucosal wave, vibratory amplitude, and phase closure). Diagnosticians may then attribute features such incomplete glottal closure and reduced mucosal waves to chronic vocal dysfunction rather than to the possibility of short-term effects of the endoscopic procedure itself. The present study has highlighted the usefulness of acoustic and perceptual analyses as indicators of vocal change during procedures in which invasive observation of the larynx is required. Therefore, to avoid visual misinterpretations and the potential for inappropriate recommendations and intervention, percepJournal of Voice, Vol. 12, No. 1, 1998
tual (and possibly acoustic) changes in the client's voice prior to and during the procedure should be considered before interpreting endoscopic data. In the future, it may be beneficial to audio-tape voice samples or to document vocal changes on line using the many standard voice profiles that are presently available. At present, however, standard perceptual rating scales for the normal voice are not readily available. Further research is therefore required to develop voice profiles that will reliably and validly measure vocal performance in normal healthy adults. It would also be of interest to determine in further studies whether clients can be shown how to reduce or eliminate any effects of the endoscopic procedure on their habitual voices. In addition to the indirect measures of vocal physiology used in the present study, other noninvasive but direct measures of vocal physiology should be considered in future studies of endoscopic effects on voice. Although the eight vocal parameters investigated encompassed a broad range of vocal function, it is possible that other vocal measures (e.g., glottal resistance, electroglottography, long-term average spectra, and phonetograms) may also be sensitive to the effects of topical anesthesia and/or laryngeal endoscopy. Their inclusion in future research may provide additional objective data to support the findings demonstrated here. Further, in order to generalize the present findings to other groups of normal speaking adults, future studies should investigate the effects of anesthesia and endoscopy on the vocal performances of adult males, older adults, children, and professional voice users such as singers. CONCLUSION This research has represented an early attempt to increase the reliability and validity of endoscopic laryngeal observations for clinical and research purposes. The results of the present research support the hypotheses that the use of topical anesthesia via the nose and the flexible laryngeal endoscope are associated with negative changes in vocal performance, chiefly the dynamics of sustained phonation, pitch, and voice quality. This study also showed that the laryngeal endoscope had a negative impact on a wider range of vocal parameters than did the use of topical anesthesia. More importantly, the results highlighted
EFFECTS OF LARYNGEAL ENDOSCOPY 01~ VOCAL PERFORMANCE OF YOUNG FEMALES
the individuality of response to such effects. Diagnosticians using laryngeal endoscopy for evaluation, management, and research purposes need to take such factors into account, especially where changes are negative or outside the normal range. Further collaborative research is required to achieve a comprehensive understanding of endoscopic and anesthetic effects on the voice.
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