 |
|
Downsizing of Voice Prosthesis Diameter in Patients With Laryngectomy
An In Vitro Study
Simone E. J. Eerenstein, MD;
Wilko Grolman, MD, PhD;
Paul F. Schouwenburg, MD, PhD
Arch Otolaryngol Head Neck Surg. 2002;128:838-841.
ABSTRACT
| |
In patients with laryngectomy, voice prostheses inserted into a tracheoesophageal
fistula (TEF) are widely used for vocal rehabilitation. Gradual dilation of
the TEF may cause bothersome leakage around voice prostheses. Prosthesis-related
weight and mechanical trauma possibly exacerbate TEF dilation. If prosthesis
size were to be decreased, with a concomitant decrease in prosthesis weight
and diameter, dilation of the TEF would probably lessen. We performed in vitro
tests to study the effects on aerodynamic prosthesis function when the prosthesis
size—in particular, the inner diameter—was decreased. The effects
on airflow and pressure were specifically studied in the airflow range of
patients with laryngectomy. A 1-mm decrease of the regular inner prosthesis
diameter from 5 mm to 4 mm showed no significant aerodynamic consequences
at the average laryngectomized airflow point. Also, such a 1-mm decrease in
diameter involved a prosthesis weight reduction of 18%. In view of these findings,
downsizing the standard prosthetic diameter should be considered in future
voice prosthesis development.
INTRODUCTION
In patients with laryngectomy, the implantation of voice prostheses
is currently the vocal rehabilitation method of choice. Voice prostheses are
1-way valves inserted into a created tracheoesophageal fistula (TEF) allowing
for air shunting from the lungs and trachea into the esophagus where it generates
voice.1-2
Different types of voice prostheses have been developed and have come
into use. These indwelling devices vary in design, insertion methods, and
aerodynamics, but their diameters are compatible.1-9
Prosthesis size is defined by length and there are several lengths available.
In contrast to the variations in length, the prosthetic diameter of the regularly
used prosthesis types in Europe is a (relatively) constant 5 mm, and the weight
averages 1 g. Although the diameter does not vary between the different lengths,
it is a factor that should be taken into account when dealing with prosthesis-related
TEF problems.
Two diameters should be taken into account when dealing with these devices:
the inner and the outer. The inner diameter is important because it determines
the aerodynamic characteristics of the prosthesis by the amount of shunted
air allowed from the lungs into the pharyngoesophageal segment where it generates
voice. A decrease in inner diameter at a constant phonation pressure automatically
decreases the amount of shunted air, whereas the amount of shunted air can
be kept at the same level if the pressure is increased. Because phonation
is easier for a patient with laryngectomy when a lower pressure is needed,
it is important that phonation pressures be kept totally or largely unaltered
if prosthesis changes are to be made.
The outer diameter of the prosthesis is important to the TEF because
the TEF normally adapts to the outer prosthesis shape. A large outer diameter
will enlarge the TEF, whereas a smaller diameter will allow it to shrink.
When a constant thickness of the body of the prosthesis is maintained, changes
in outer diameter automatically involve changes in inner diameter, and vice
versa.
Gradual dilation or enlargement of the TEF (into which the voice prosthesis
is inserted) is one of the frequently encountered problems in prosthesis use.10-12 Due to the dilation
of the TEF, persistent and bothersome leakage of fluids from the esophagus
into the trachea occurs.10-12
The peripheral leakage is often treated using temporary surgical or conservative
means.10-12 These
solutions include measures such as temporary removal of the prosthesis, permitting
the TEF to shrink, or cauterization and injection of collagen into the dilated
tissue. Another option often considered in treating peripheral leakage is
an increase in prosthesis diameter. However, limitations of the local anatomy
at the TEF site, specifically the esophageal lumen, contradindicate a major
increase in prosthesis size.
All of the currently used treatments focus on eliminating peripheral
leakage, but none focus on the cause of the TEF dilation. The dilation is
attributed to several factors, including previous irradiation of the tissue
and mechanical fistula damage. Mechanical trauma can be caused by excessive
prosthesis size and weight and also by frequent prosthesis replacements, made
necessary in many cases by yeast-induced prosthesis dysfunction.10-12
Currently, methods for decreasing the frequency of prosthesis replacement
by diminishing yeast-related prosthetic problems are the topic of many ongoing
international research projects. In contrast, we opted for an analysis of
the possibility of decreasing prosthesis diameter. A smaller prosthesis diameter
with a concomitant lower weight would possibly have a positive effect on TEF
dilation. Changes in prosthesis diameter should also influence the aerodynamic
characteristics of the device, and we therefore performed in vitro tests.
The effects on airflow and pressure were specifically studied in the airflow
range of patients with laryngectomy.
MATERIALS AND METHODS
A total of 20 in vivo voice prostheses of the most commonly used lengths
were used for the aerodynamic tests: ten 6-mm and ten 8-mm VoiceMaster prostheses
(Entermed BV, Woerden, the Netherlands). All prostheses were taken directly
out of their boxes and placed into our specially constructed in vitro measuring
system. All prostheses were measured after removal of the prosthesis valve
to eliminate the effects of the specific aerodynamic characteristics of the
valve mechanisms.
The inner diameter of the VoiceMaster prosthesis measures 5.0 mm. Specifically
made prosthesis inserts in varying diameters (3.0, 3.5, 4.0, and 4.4 mm) were
inserted into the prostheses during the aerodynamic measurements. A 4.5-mm
insert could not be manufactured for technical reasons (Figure 1). The inner diameter could thus be decreased from the current
5 mm to 4.4, 4.0, 3.5, or 3.0 mm as desired.
|
|
|
|
Figure 1. Laryngectomy voice prostheses:
A, without valve and B, with valve. C, Prosthesis inserts of various sizes.
|
|
|
Aerodynamic pressure measurements were conducted by placing the prosthesis
in a specially built system made up of a pressure controller, mass flow meter,
pressure transducer, and a personal computer with data acquisition software.13 In this system, the pressure needed to maintain a
regulated airflow through the prosthesis could be measured.
The specific characteristics of the pressure-measuring system are as
follows. The pressure controller (Brooks Rosemount, Chanhassen, Minn) was
used for the regulation of airflow through the prosthesis to achieve conditions
similar to those in patients with laryngectomy. It regulated the airflow in
a semi-sawtooth pressure pattern in 1-minute intervals. The airflow used varied
from 0 to 0.35 L/s to ensure the full airflow range from 0 to the average
0.15 L/s present in patients with laryngectomy.14-18
The mass flow meter (Sierra Instruments, Monterey, Calif) measured flow
independently for temperature and pressure changes. The pressure transducer
(model 206; Setra Systems Inc, Acton, Mass), a differential pressure–measuring
device, was used to measure the pressure drop over the prosthesis. And the
personal computer ran on a Pentium 200 MHz chip with an analog-digital/digital-analog
converter (National Instruments, Austin, Tex).
Our data acquisition software (Lab View 4 for Windows 95; National Instruments)
was used to control the pressure controller, and thus regulate the airflow
through the devices, to acquire multichannel input from the sensors, and to
perform the data analyses. Each prosthesis was measured 5 times for each of
the 5 available diameters after an initial 5-minute period of testing before
recording the data from the sensors into the computer. Statistical analysis
of the accumulated data was performed using the 2-sample t test with a predetermined significance level ( ) of .01.
RESULTS
To allow for comparison of our in vitro data with the in vivo situation
in patients with laryngectomy, all measurements were performed in an in vitro
system with a wide airflow range that included the average laryngectomized
phonation airflow of 0.15 L/s. The results are calculated at the 0.15-L/s
airflow level.
A decrease in inner diameter of the prosthesis from 5.0 through 4.4
to 4.0 mm caused a gradual increase in pressure levels. Decreasing the inner
diameter even further caused a marked progressive increase in pressure. This
is visually demonstrated with a sharp change in the airflow-pressure curve
generated when the results are plotted (Table 1, Figure 2, and Figure 3). The 2-sample t test P values for the differences from 5.0-mm inner prosthesis
diameter were .12 for 4.4 mm; .04 for 4.0 mm; .002 for 3.5 mm; and .001 for
3.0 mm.
|
|
|
|
Table 1. Average Pressure per Prosthesis Diameter at Varying Amounts
of Airflow
|
|
|
|
|
|
|
Figure 2. Graph illustrating measured pressure
in relation to airflow for varying prosthesis diameters. The average airflow
during phonation in patients with laryngectomy is 0.15 L/s (arrow) .
|
|
|
|
|
|
|
Figure 3. Measured pressure at 0.15 L/s
airflow. The increase in pressure after decreasing the inner prosthesis diameter
from 4.0 to 3.5 mm is significant.
|
|
|
Statistical analysis of the results shows the visual marked change noted
in the plotted airflow-pressure curves to be significant. Whereas the decrease
in diameter from 5.0 to 4.4 mm did not cause a significant increase in pressure
(P = .12), and a decrease from 5.0 to 4.0 mm caused
only a slightly significant increase (P = .04) (with
predetermined significance level of P = .01), a decrease
from 5.0 to 3.5 mm and 5.0 to 3.0 mm resulted in substantially significant
pressure increases (P = .002 and P = .001, respectively). The aerodynamic results for both groups of
measured prostheses (the 6-mm and 8-mm length groups) were the same.
As our measurements for decreasing diameter were performed with the
aid of prosthesis inserts with decreasing diameters inserted into a regular
prosthesis, we could not measure the exact influence the changes would have
on the weight of the device. However, on the assumption that a standard thickness
(1 mm) of the prosthesis wall is maintained with decreasing inner diameter,
it is possible to calculate the percentage of weight loss with the use of
the formula  x  x (outer diameter)2 -
x x (inner diameter)2. With this formula
and a standard relative weight of any used material, the weight of any size
prosthesis and the percentage of weight loss in comparison with the standard
5-mm device can be calculated. These calculations, as provided in Table 2, show a 4.4-mm inner diameter prosthesis
to be 89% of the weight of the original 5.0-mm device. This represents a weight
loss of 11%, while a decrease to a 4.0-mm inner diameter leads to a weight
loss of 18%.
|
|
|
|
Table 2. Calculation of Percentage of Weight Loss With Decreasing Diameters
of the Prosthesis*
|
|
|
COMMENT
The results of the aerodynamic tests illustrate that a decrease in prosthesis
diameter would be a viable option if TEF dilation–inducing factors such
as prosthesis size and prosthesis-induced mechanical trauma were to be dealt
with. We focused on the influence of a smaller diameter on the prosthesis
aerodynamic characteristics. All valve mechanisms were removed from the prostheses
before the measurements; the results are thus not influenced by the specific
characteristics of the VoiceMaster type and are applicable to all types of
voice prostheses.
We found no difference between the 6-mm and 8-mm lengths. If aerodynamic
principles are taken into account, length should influence the aerodynamics.
However, given the short length of the tested prostheses (6 and 8 mm, respectively),
length did not affect the results.
As illustrated in the aerodynamic tests, the decrease in prosthesis
diameter influences the aerodynamic characteristics of the voice prosthesis.
If the in vitro results are extrapolated to the in vivo situation in patients
with laryngectomy, the altered aerodynamic prosthetic characteristics eventually
lead to a necessary increase in phonation pressure. As a large airflow range
was tested for all measurements, amply covering the average laryngectomized
airflow used for phonation, extrapolation of our results is possible. Currently,
in vivo aerodynamic measurements are being conducted in our clinic to assess
the influence of diameter decrease on phonation pressure.
Although our material (ie, standard-size prostheses with inserts of
decreasing diameter) does not allow for direct measurements of weight decrease,
our calculations of the effect on prosthesis weight show weight decrease percentages
that should not be dismissed. Given the in vitro aerodynamic results, decreasing
prosthesis diameter seems a feasible option, and one wonders if it could also
be technically achieved. Current technology within voice prosthesis production
allows for changes in dimension, rendering a decrease in prosthesis weight
and diameter a realistic possibility. Given the possible impact of a decreased
diameter on TEF dilation–induced peripheral leakage, we believe decreasing
initial prosthesis size should be further explored in prosthetic development.
In conclusion, TEF dilation causes bothersome leakage around voice prostheses.
It is suggested that the mechanical trauma of present-day voice prostheses
is a factor that contributes to this unwanted dilation. As a consequence,
smaller-diameter prostheses might cause less trauma owing to a lesser weight
and a smaller defect in the tracheoesophageal wall. Reduction of the outer
diameter of the prosthesis demands that the inner diameter also be reduced.
This in vitro study has shown that it is possible to reduce the effective
inner diameter of voice prostheses to 4.0 mm without significant aerodynamic
consequences within the average phonation airflow range for patients with
laryngectomy. Such a decrease in diameter would lessen prosthesis weight by
18%. These findings are of importance to prosthesis development should manufacturers
consider a decrease in prosthesis size.
AUTHOR INFORMATION
Accepted for publication November 19, 2001.
This study was presented at the Fifth International Conference on Head
and Neck Oncology, San Francisco, Calif, July 29-August 2, 2000.
Corresponding author: Simone E. J. Eerenstein, MD, Department of
Otolaryngology–Head and Neck Surgery, Academic Medical Center, University
of Amsterdam, PO Box 22700, 1100 DE Amsterdam, the Netherlands (e-mail: S.E.Eerenstein{at}AMC.UVA.NL).
From the Department of Otolaryngology–Head and Neck Surgery,
Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands.
REFERENCES
| |
1. Singer MI, Blom ED, Hamaker RC. Voice rehabilitation after total laryngectomy. J Otolaryngol. 1983;12:329-334.
ISI
| PUBMED
2. Singer MI, Blom ED. An endoscopic technique for restoration of voice after laryngectomy. Ann Otol Rhinol Laryngol. 1980;89:529-533.
ISI
| PUBMED
3. Panje WR. Prosthetic vocal rehabilitation following total laryngectomy: the voice
button. Ann Otol Rhinol Laryngol. 1981;90:116-120.
ISI
| PUBMED
4. Hilgers FJM, Schouwenburg PF. A new low-resistance, self-retaining prosthesis (Provox) for voice
rehabilitation after total laryngectomy. Laryngoscope. 1990;100:1202-1207.
ISI
| PUBMED
5. Schouwenburg PF, Eerenstein SEJ, Grolman W. The VoiceMaster voice prosthesis for the laryngectomized patient. Clin Otolaryngol. 1998;23:555-559.
FULL TEXT
|
ISI
| PUBMED
6. Leder SB, Erskine MC. Voice restoration after laryngectomy: experience with the Blom-Singer
extended-wear indwelling tracheoesophageal voice prosthesis. Head Neck. 1997;19:487-493.
FULL TEXT
|
ISI
| PUBMED
7. Nijdam HF, Annyas AA, Schutte HK, Leever A. A new voice prosthesis for voice rehabilitation following total laryngectomy. Arch Otolaryngol. 1982;237:27-33.
8. Manni JJ, van den Broek P, de Groot MAH, Berends E. Voice rehabilitation after laryngectomy with the Groningen prosthesis. J Otolaryngol. 1984;13:333-336.
ISI
| PUBMED
9. Hilgers FJ, Ackerstaff AH, Balm AJ, Tan IB, Aaronson NK, Persson JO. Development and clinical evaluation of a second-generation voice prosthesis
(Provox 2), designed for anterograde and retrograde insertion. Acta Otolaryngol. 1997;117:889-896.
PUBMED
10. Izdebski K, Reed CG, Ross JC, Hilsinger RL. Problems with tracheoesophageal fistula voice restoration in totally
laryngectomized patients: a review of 95 cases. Arch Otolaryngol Head Neck Surg. 1994;120:840-845.
ABSTRACT
11. Singer MI, Blom ED, Hamaker RC. Further experiences with voice restoration after total laryngectomy. Ann Otol Rhinol Laryngol. 1981;90:498-502.
ISI
| PUBMED
12. Garth RJ, McRae A, Rhys Evans PH. Tracheoesophageal puncture: a review of problems and complications. J Laryngol Otol. 1991;105:750-754.
ISI
| PUBMED
13. Grolman W. Physical Aspects of Voice Rehabilitation After Total
Laryngectomy [dissertation]. Amsterdam, the Netherlands: University of Amsterdam; 1998:97-109.
14. Moon JB, Sullivan J, Weinberg B. Evaluations of Blom-Singer tracheo-esophageal puncture prostheses performance. J Speech Hear Res. 1983;26:459-464.
15. Zijlstra RJ, Mahieu HF, van Lith Bijl JT, Schutte HK. Aerodynamic properties of the low-resistance Groningen button. Arch Otolaryngol Head Neck Surg. 1991;117:657-661.
ABSTRACT
16. Van den Hoogen FJ, Veenstra A, Verkerke GJ, Schutte HK, Manni JJ. In vivo aerodynamic characteristics of the Nijdam prosthesis. Acta Otolaryngol. 1997;117:897-902.
PUBMED
17. Wong Chung RP, Geskus J, Mahieu HF. The ultra-low resistance Groningen voice prosthesis: aerodynamic properties. Rev Laryngol Otol Rhinol (Bord). 1999;120:245-248.
18. Weinberg B, Moon JB. Airway resistances of Blom-Singer and Panje Low Pressure tracheoesophageal
puncture prostheses. J Speech Hear Disord. 1986;51:169-172.
FREE FULL TEXT
THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES
Some Comments on the Escalation of Tracheoesophageal Voice Prosthesis Dimensions
Blom
Arch Otolaryngol Head Neck Surg 2003;129:500-502.
FULL TEXT
|
