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Aerodynamic Findings in Esophageal Voice
Sergio Motta, MD;
Iacopo Galli, MD;
Lino Di Rienzo, MD
Arch Otolaryngol Head Neck Surg. 2001;127:700-704.
ABSTRACT
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Objective To define the perceptive and aerodynamic characteristics of esophageal
voice in relation to different rehabilitation modalities.
Design Cross-sectional study comparing perceptive and aerodynamic variables
in 3 subject groups.
Setting Referral center.
Subjects A total of 19 subjects who underwent total laryngectomy were divided
into groups A and B. Group A consisted of 13 subjects (who required speech
therapy)—8 good speakers (subset A1 who were >80% intelligible)
and 5 mediocre speakers (subset A2 who were <70% intelligible).
Group B consisted of 6 subjects with a tracheoesophageal prosthesis (who were
>90% intelligible).
Main Outcome Measures Perceptive variables included phonatory pauses and stomal noise. Aerodynamic
variables included maximum phonation time, phonatory flow, phonatory volume,
postphonatory volume, intensity, and articulatory pressure.
Results Phonatory pauses and stomal noise statistically differentiated group
A from group B and good speakers from mediocre speakers. Phonation time, phonatory
volume, and phonatory flow were statistically higher in group B subjects compared
with group A subjects. Postphonatory volume was significantly higher in group
A. Intraoral pressure and postphonatory volume were statistically higher in
subset A2 subjects compared with subset A1 subjects
while maximum phonation time was significantly higher in subset A1
subjects compared with subset A2 subjects.
Conclusions In subset A1 subjects a positive ratio between phonatory
volume and phonatory flow was maintained with an adequate phonation time.
In subset A2 subjects a reduced phonatory volume was associated
with a more rapid dispersion of phonatory flow, lower duration of phonation,
and frequent pauses; stomal noise and consonant hyperarticulation worsened
the voice performance in this group. In group B subjects the positive ratio
between phonatory volume and phonatory flow represented the prerequisite of
speech without frequent pauses.
INTRODUCTION
TOTAL LARYNGECTOMY represents an operation that drastically affects
respiratory dynamics and phonation mechanisms, suppressing the normal verbal
communication. The acquisition of a new voice by the laryngectomized subject
is possible with the use of an electrolarynx, conventional speech therapy,
and surgical prosthetic methods.1 Use of an
electrolarynx is exclusively reserved for patients who did not profit from
conventional speech therapy or in whom a tracheoesophageal prosthesis (TEP)
cannot be applied.2 Speech therapy allows the
acquisition of autonomously produced esophageal voice (EV) and, therefore,
it is the most commonly used treatment in voice rehabilitation of laryngectomized
patients.3
Surgical prosthetic methods, introduced in 1980 by Singer and Blom,4 tended to become rapidly widespread based on the excellent
outcomes that they achieved. However, TEP is still an underused rehabilitative
procedure5; in fact, motivational and socioeconomic
factors, as well as contraindications associated to pathologic manifestations
of involved organs, limit its application.6, 7, 8
Intelligibility of EV can vary according to several perceptive factors
on the precise definition for which there is no general agreement.9, 10 Furthermore, aerodynamic data in the
study of EV physiology and, in particular, correlations between those data
and the perceptive findings have not been defined as yet. The purpose of our
study was to identify: the perceptive factors that affect EV intelligibility;
EV aerodynamic characteristics, in relation to the different rehabilitation
methods used; and the possible correlations between the findings of the perceptive
study of EV and those of the aerodynamic study. Furthermore, our study intends
to contribute to the knowledge of the pathophysiological mechanisms underlying
the EV to improve the rehabilitation techniques used at present.
SUBJECTS AND METHODS
SUBJECTS
The study subjects came consecutively to the Institute of Otorhinolaryngology,
Ateneo "Federico II," University of Naples, Naples, Italy, between January
1, 1990, and December 31, 1997. Twenty-two Italian-speaking male patients
(mean age, 52 years) undergoing total laryngectomy were enrolled in this study;
16 received speech therapy for the acquisition of EV (group A) while 6 received
a TEP (group B). Excluded were subjects who at the intelligibility test achieved
word intelligibility percentages lower than 50% (group A, 1 subject); and
subjects shown to be unable to undergo one or more examinations of the study
protocol (group A, 2 subjects). Overall 19 subjects were examined of whom
13 were in group A and 6 were in group B. The application of TEP (Bivona-Colorado
Low-Resistance; Bivona Medical Technologies, Gary, Ind) was performed according
to the surgical procedure described by Motta.6
METHODS
At the end of rehabilitation (mean duration, 4 months for group A and
1 month for group B) each subject underwent the following: (1) an intelligibility
test, (2) an acoustic-perceptive study, and (3) an aerodynamic study.
In the intelligibility test a panel of 6 members participated, drawn
for each subject from a pool of 60 students enrolled in the university course
Logopedics. Each subject, placed 3 m from the observers, was invited to produce
20 phonetically balanced words, of which 10 were bisyllabic and 10 were trisyllabic.
During the test the observers turned their backs to the subject to rule out
a possible interference of labial reading on the results of the test and to
prevent the identification of subjects with a TEP. Based on the percentage
of word intelligibility, group A subjects were subdivided into the following
2 subsets: subset A1, composed of 8 subjects defined as good speakers,
for whom intelligibility was shown to be higher than 80% (mean intelligibility,
97%); subset A2, composed of 5 subjects, considered mediocre speakers
for whom intelligibility was between 50% and 70% (mean intelligibility, 64%).
For group B subjects the percentage of word intelligibility was shown to be
higher than 90% (mean intelligibility, 99%). The statistical analysis performed
using the Mann-Whitney test showed the following: intelligibility values were
statistically not different in the comparison between group A and group B
subjects (P = .15); statistically different values
in the comparison between subset A1 and subset A2 subjects
(P<.002); and statistically not different values
between subset A1 and group B subjects (P
= .85); and statistically different values between subset A2 and
group B subjects (P<.001).
For the acoustic-perceptive study, performed with the same modalities
used for the intelligibility test, each subject was required to produce a
series of progressive numbers from 1 to 10; the panel had to report the number
of pauses perceived and the evaluation of stomal noise, score based on a 3-grade
scale (grade 1, no stomal noise; grade 2, discontinuous stomal noise; and
grade 3, continuous stomal noise).
The aerodynamic study was carried out by a computerized system with
physical flow calibration and automatic calibration of air pressure and sound
intensity, equipped with a facial mask connected with 3 transductors (Aerophone
II; F. J. Electronics, Copenhagen, Denmark). This examination allowed the
following observations: (1) During vowel /e/ emission
the maximum phonation time was expressed in seconds and tenths of a second;
mean phonatory flow, expressed in milliliters per second, indicating the ratio
between phonatory volume and maximum phonation time; phonatory volume, reported
in milliliters, equal to the volume of air expelled to produce the voice;
residual postphonatory volume, expressed in milliliters, which represents
the volume of air expelled not being sonorized or expelled with sound intensity
levels not recordable by the instrumentation (<50-dB sound pressure level);
and sound intensity expressed in decibles of sound pressure level. (2) During
the production of the phoneme pi-pi repeated 3 times, using a small silicon
tube placed into the oral cavity for approximately 5 cm, the mean articulatory
pressure, expressed the level of intraoral pressure in cm H2O during
the articulation of the phoneme. (3) The aerodynamic study was carried out
by one of us (S.M.) who was unaware of the results of the intelligibility
test but not of the interpretation of the results. The statistical comparison
was performed using the Mann-Whitney test (SPSS 8.0; SPSS, Chicago, Ill). P<.05 was accepted as the minimal level of statistical
significance.
RESULTS
The results of this study are summarized in Table 1. In the comparison between group A and group B, in subjects
undergoing TEP rehabilitation (group B) there was a lower number of pauses
(P<.01); a more reduced stomal noise (P<.001); higher values of maximum phonation time (P<.001), phonatory flow (P<.02), and
phonatory volume (P<.02); and a lower residual
postphonation volume (P<.02). Statistically similar
values were observed for sound intensity (P = .89)
and intraoral articulatory pressure (P = .46). In
the comparison between subset A1 and subset A2, in subjects
with good conventional EV (subset A1), there was a lower number
of pauses (P<.0001), a more reduced stomal noise
(P<.01), a longer maximum phonation time (P<.01), lower values of articulatory pressure (P<.03), and residual postphonation volume (P<.01). Phonatory flow was higher in subset A2 subjects
but without statistical significance (P = .12); phonatory
volume was shown to be higher in subset A1 subjects but without
statistical significance (P = .17); sound intensity
was higher, but without statistical significance, in subset A1
subjects (P = .52). In the comparison between subset
A1 and group B subjects, in subjects with a TEP (group B), there
was more reduced stomal noise (P<.02); higher
values of maximum phonation time(P<.001), phonatory
flow (P<.02), and phonatory volume (P<.001). The number of pauses was shown to be similar in the 2 groups
(P = .29); residual postphonation volume was shown
to be higher, but without statistical significance in subset A1
subjects (P = .14); sound intensity (P = .66), and articulatory pressure (P = .95)
were similar in the 2 groups. In the comparison between subset A2
and group B, in subjects undergoing TEP rehabilitation (group B) there was
a lower number of pauses (P<.001), a reduced stomal
noise(P = <.001), a longer maximum phonation time
(P<.001), higer values of phonatory volume (P<.001), and lower values of residual postphonation
volume(P<.001). Phonatory flow was higher, but
without statistical significance, in group B (P =
.17); sound intensity (P = .79) was shown to be higher
but without statistical significance in group B subjects; articulatory pressure
was shown to be higher but without statistical significance in subset A2 subjects (P = .17).
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Perceptive and Aerodynamic Findings in 19 Study Subjects
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COMMENT
The sound emission produced by subjects with EV acquired by conventional
speech rehabilitation or the application of a TEP was previously studied by
perceptive and spectrographic analysis to assess the intellegibility of EV
and its acoustic characteristics.11, 12, 13, 14
However, studies on air phenomena underlying the EV and conditioning its efficacy
are lacking. Max et al10 suggested that the
EV factors they studied (frequency, intensity, and maximum duration of phonation)
were correlated with different modalities and ill-defined aerodynamic mechanisms.
Ill-defined aerodynamic mechanisms would vary according to the modality of
EV production (whether conventional or secondary to TEP). However, to our
knowledge, there are no reports in the literature to support this hypothesis
even if there are interesting observations by Nieboer and Schutte15; these authors studied the relation between the intratracheal
and esophageal pressure in patients with a TEP to define the resistance to
the air flow by the prosthesis, finding a mean (SD) phonatory flow higher
in patients with a TEP (140 [40] mL/s) compared with conventional subjects
with EV (70 [40] mL/s). The EV pathophysiology has been analyzed in-depth
based on perceptive and aerodynamic studies.
INTELLEGIBILITY OF EV AND PERCEPTIVE STUDY
Various factors drawn from the acoustic findings of some listeners have
been considered in the literature to evaluate the quality of EV:11, 12, 16, 17
First is the percentage of words correctly articulated by patients and, therefore,
recognized by listeners. Literature data documentation that EV can achieve
satisfactory intelligibility independent of the rehabilitation modality.3, 11 Our observations show that the conventional
EV can also afford satisfactory results with percentages of correctly identified
words comparable to those observed in subjects with a TEP.
Second, speech fluency can be studied based on the number of words articulated
per minute3, 12 or the number of
syllables emitted per each air emission3, 9, 18
or, as in our study, by the number of pauses perceived during a predefined
vocal test. We preferred the latter method because it directly shows the relationship
between the EV quality and fluency alterations. Kischk and Gross9
have studied comparatively the articulation velocity in laryngectomized patients
rehabilitated by conventional speech therapy, a TEP application, or with an
electrolarynx but did not find statistically significant differences between
the study groups.
Our findings confirm that the absence or the reduced number of pauses
leads to a good understanding of EV; this is documented by the outcomes in
laryngectomized subjects with conventional EV who were good speakers (subset
A1) and in those with a TEP (group B).
To our knowledge, there are no reports in the literature showing which
alterations in the study factor could occur in laryngectomized subjects with
mediocre or poor EV. In this regard our observations clearly showed that in
these cases (subset A2), the number of pauses was markedly higher
(Table 1) and, therefore, the
reduced intelligibility was also consequent to an inadequate speech fluency.
Third, the presence of parasite stomal noise (this phenomenon has a
different genesis). In patients with conventional EV the stomal noise, usually
higher in mediocre speakers, is caused by an incorrect coordination of phonorespiratory
mechanisms, indicating a partial rehabilitation failure. In subjects with
a TEP it is attributable to an imperfect adhesion of the prosthesis to the
stoma during the vocal emission or, when a tracheostomal valve is used, to
its unsatisfactory functioning—these are casual, mechanical, readily
identifiable and, therefore, eliminating factors.
AERODYNAMIC STUDIES AND PATHOPHYSIOLOGY OF EV
Our study showed that the aerodynamic procedures play a major role in
the definition of the factors involved in the genesis of EV as well as in
the identification of some important functional patterns able to interfere
with the vocal performance of patients and also to hypothesize possible "compensation"
phenomena which may deteriorate the speaking proficiency. We found similar
values of sound intensity in the different study groups, in agreement with
the observations by Kischk and Gross.9 This
finding shows that there are no differences in the performance of the pseudoglottis
as the source of vibration with reference to the esophageal or pulmonary air
supply, as confirmed by the study by Isman and O'Brien19
that ruled out significant differences in the structure of the pseudoglottis
examined by videofluoroscopy in subjects able to speak with both types of
voice. The aerodynamic tests have documented that fluency depends on the volume
of phonatory air, its flow during the vocal emission and on the ratio between
these 2 factors.
In subjects with EV produced by conventional rehabilitation, the air
supply was drastically conditioned by the reduced capacity of esophageal storage.
In subjects with a satisfactory EV, it was observed that the limited esophageal
air volume corresponds to a reduced flow and, therefore, a positive ratio
between the 2 factors and, in turn, a good maximum duration of phonation was
maintained. In subjects with mediocre intelligibility, there was a reduced
phonatory volume and a more rapid (relatively high values of phonatory flow),
less effective dispersion of phonatory air (presence of a proportionally high
residual postphonation volume) involving a negative phonatory volume–flow
ratio and, consequently, a lower duration of phonation with frequent interruptions.
The increased articulatory pressure, usually higher in mediocre speakers,
should be correlated with the need for these subjects to increase the intraoral
pressure during the production of explosive consonants, not sustained by an
adequate aerodynamic flow. This consonant hyperarticulation while it tended
to compensate for the reduced effectiveness of the esophageal air, further
impaired the quality of the voice.
In subjects with TEP the relevant amount of air provided by the pulmonary
bellows, its regular flow that followed the normal pneumophonic coordination,
and the positive relationship between phonatory volume and phonatory flow
represented the prerequisite of a satisfactory EV produced without the interference
of frequent pauses.
CONCLUSIONS
In this study we have examined laryngectomized subjects undergoing voice
rehabilitation with conventional speech therapy and the use of a TEP, able
to produce more or less satisfactory speech but, in any case, showing an adequate
function of pseudoglottic sphincter. In subjects with conventional rehabilitation
who are good speakers, despite the reduced phonatory volume, there was a positive
volume–flow ratio because the subjects seemed to be able to maintain
a reduced flow and, therefore, air dispersion could be better controlled.
In conventional rehabilitation subjects who are mediocre speakers, the
air volume used for phonation was lower while its flow was proportionally
high with a consequent negative volume–flow ratio, worsened by the presence
of a relatively high residual postphonation volume. As a consequence of the
reduced maximum phonation time, the number of pauses increased and the intelligibility
was severely impaired in this group. Furthermore, there could be uncorrected
articulatory compensation (with increased intraoral pressure) that, in turn,
contributed to the worsening of EV intelligibility.
In subjects with a TEP, all excellent speakers, both phonatory air volume
and phonatory airflow were relevant; the positive ratio between phonatory
volume and phonatory flow represented the prerequisite of a satisfactory EV
produced without the interference of frequent pauses.
AUTHOR INFORMATION
Accepted for publication February 6, 2001.
From the Institute of Otorhinolaryngology, Ateneo "Federico II," University
of Naples, Naples, Italy (Dr Motta); and the Institute of Otorhinolaryngology,
Catholic University of the Sacred Heart, Rome, Italy (Drs Galli and Di Rienzo).
Dr Motta is now with the Institute of Otorhinolaryngology, Catholic University
of the Sacred Heart, Rome.
Corresponding author and reprints: Sergio Motta, MD, Clinica Otorinolaringoiatrica,
Università Cattolica del Sacro Cuore, Largo A. Gemelli, 00168 Rome,
Italy (e-mail: sermotta{at}Yahoo.it).
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