Effect of hemodialysis on voice:
An acoustic and aerodynamic analysis
Eman S. Hassan, Ahlam A. El-Adawy*, Dalia G. Yasseen, Effat A. E.Tony**
Phoniatric Unit, Assiut University, South Valley University*, Internal Medicine Departement**, Assiut university
Abstract:
Objective:
This study was conducted with the purpose of analyzing the effects of hemodialysis on voice characteristics of patients with chronic renal failure.
Design:
A total of 66 patients were participated in the study, including 26 males and 40 females ranging in age from 19 to 68 years. Patients underwent evaluation of their voice directly before and after hemodialysis using computerized speech lab (CSL) (4300, Kay Elemetrics Corp.) and Aerophone II Model 6800 Kay Elemetrics Corp. The vocal acoustic parameters studied include average pitch, jitter, shimmer and noise-to-harmonic ratio. The aerodynamic parameters include vital capacity, maximum phonation time, phonation quotient, mean flow rate, sub glottic pressure and glottal efficiency. The data were analyzed using the paired t-test for the total sample, the male and female subgroups and also for the patient underwent ultrafiltration with hemodialysis.
Results:
In the total sample and in the female subgroup, there is a significant difference in phonation quotient after hemodialysis. The male subgroup showed no significant differences in all acoustic and aerodynamic parameters after hemodialysis. The group with positive ultrafiltration showed significant differences in both vital capacity and phonation quotient after hemodialysis.
Conclusion:
There was no effect of hemodialysis on acoustic characteristics of voice; however, there was a decrease in vital capacity and phonation quotient after hemodialysis especially with ultrafiltration.
Recommendation:
Further studies that include auditory perceptual assessment of voice and stroboscopic examination of the vocal folds may help in detecting subtle changes that may occur after hemodialysis.
Key words:
Hemodialysis, Acoustic and aerodynamic parameters of voice.
Introduction:
Vocal folds are covered by a thin layer of liquid (Fukuda et al., 1988). This liquid serves as a physical and biochemical barrier that protects the underlying tissue from damage from inhaled particulates and pathogens (Mogi et al., 1979). Presence of surface liquid is also important to maintain optimal biomechanical characteristics of vocal fold mucosa, increase efficiency of vocal fold oscillation, promote normal voice quality (Verdolini et al., 1994 and Leydon et al., 2010). This is consistent with the well accepted clinical practice of the importance of vocal fold hydration in maintaining optimal vocal fold physiology. However, the source of surface liquid and mechanisms for maintaining liquid homeostasis are not fully understood. The depth of airway surface liquid is maintained primarily by sodium ion (Na+) absorption and chloride ion (Cl) secretion by epithelia of the lungs, bronchi, trachea and nose (Tarran et al., 2006). Leydon et al., (2009) suggest that vocal fold epithelium may participate in regulating and maintaining vocal fold surface liquid homeostasis via ion transport and bidirectional water fluxes.
Systemic hydration refers to fluid within body and vocal fold tissue. Superficial hydration is the fluid lining the vocal fold surface and laryngeal lumen. Clinical interventions aim to increase both systemic and / or superficial hydration to facilitate optimal voice production (Sataloff, 1997). Adequate body and vocal fold hydration are believed to be critical to phonation. Verdolini et al., (1994) reported improvements in voice and in laryngeal appearance following hydration treatment. Based on previous theoretical work, hydration effects may be related to reductions in the viscosity of vocal fold tissue.
Optimal viscoelastic properties of vocal folds are necessary to maintain ease of phonation (Chan and Titze, 1999). Dehydration of vocal folds raised phonation threshold pressure (PTP) – a measure of efficiency of voice production- (Jiang et al., 1999), increased tissue stiffness and compromised voice quality and phonatory efficiency (Yiu and Chan 2003).
Drying of the vocal fold surface can occur due to environmental and behavioral challenges associated with mouth breathing, exercising and inhaling poorly conditioned air (Sivasankar and Fisher, 2003). Vocal fold dehydration can also occur secondary to reduced systemic hydration (Fisher et al., 2001 and Verdolini et al., 2002), emotional factors (Punt, 1974) and the normal aging process (Sato and Hirano, 1998).
Fisher and colleagues (2001) demonstrated an increase in phonation threshold pressure (PTP) and be associated with patient-perceived increases in phonatory effort and worsening voice quality temporarily following hemodialysis. Measure of phonatory effort returned to base line values in these patients following rehydration. Improved phonatory efficiency following interventions aimed to increase systemic hydration has also been reported (Yiu and Chan, 2003).
Ori et al., (2006) mentioned that patients on intermittent hemodialysis often experience transient hoarseness at the end of dialysis. The vocal folds may be affected by the hydration state. In their study, he stated that 60% of the patients had post dialysis hoarseness and in 72% of the patients, a decrease in the vocal folds' thickness was observed.
Human studies provide converging evidence that systemic and superficial dehydration are detrimental to vocal fold physiology. Dehydration increases the viscous properties of vocal fold tissue. Systemic, superficial and combined drying increases aerodynamic and acoustic measures of voice production in speakers. Emerging theoretical and clinical data suggest that increasing both systemic and superficial hydration levels may benefit voice production and help in prevention and management of voice disorders; however, robust evidence for positive outcomes of hydration treatments is lacking (Sivasankar and Leydon, 2010).
On the other hand, Prezant, (1990), stated that patients presenting for hemodialysis have been noticed to have generalized weakness, fatigue and shortness of breath, affecting their voice rendering it weak, perceptually. This muscle weakness can be caused by acid/base imbalance, electrolyte disorders, circulating ureic toxins, immune suppression, volume overload and anemia. Hemodialysis is known to affect many of these factors by improving muscle weakness and endurance by virtue of its negative fluid imbalance. This will improve the overall condition and hence the voices of these patients shortly after dialysis (Weiner et al., 1997) and Chen et al., (1998). This controversy has prompted us to study the effect of hemodialysis on voice.
Aim of the work:
This study was conducted with the purpose of analyzing the effects of hemodialysis on voice characteristics of patients with chronic renal failure.
Patients and methods:
Participants:
A total of 66 patients with chronic renal failure undergoing hemodialysis at Nephrology Unit in two hospitals (Assiut and Sohag University hospitals) were included in this study. Specifically 26 males and 40 females ranging in age from 19- 68 years and mean age 43.78 years participated. From those, 46 patients undergo hemodialysis with ultrafiltration (18 males and 28 females). The amount of body fluid removed via ultrafiltration ranged from .50 to 5.0 liter. Patients underwent an evaluation of their voices immediately before and after hemodialysis.
Methods:
Voice quality was assessed via acoustic and aerodynamic analysis.
Acoustic analysis:
With the patient seated in a quiet office, the patient's vocal signal was recorded during phonation of a sustained vowel /a:/ at a comfortable pitch and intensity levels using a microphone (Sure Prologue 14 Hz) at a constant 10 cm distance from the mouth and evaluated with computerized speech lab (CSL) (4300, Kay Elemetrics Corp.) Acoustic parameters included fundamental frequency, jitter, shimmer and noise-to-harmonic ratio.
Aerodynamic analysis:
Aerodynamic data were obtained from each subject and analyzed using a handheld transducer module Aerophone II Model 6800 Kay Elemetrics Corp.
Each subject was asked to:
1- Take a deep breath and then exhale as much as possible. Vital capacity was measured.
2- Take a deep breath and a sustain /a:/ phonation for as long as possible in his comfortable pitch and loudness. The duration of phonation was noted. Maximum phonation time, phonation quotient and mean flow rate were measured.
3- Repeat the vowel-consonant-vowel train 'ipipi' at comfortable pitch and intensity levels. Subglottal pressure and glottal efficiency were measured.
Statistical analysis:
The data were analyzed using the paired t-test for the total sample, the male, and the female subgroups and for the subgroup with positive ultrafiltration, using a commercially available software package (Version 17.0; SPSS). The data were expressed as mean ±SD. A p-value less than .05 was considered statistically significant.
Results:
Tables 1 and 2 showing descriptive statistics of the patients before and after hemodialysis:
Table1: Descriptive statistics of the patients before hemodialysis:
St. dev. / Mean / Maximum / Minimum13.033 / 43.787 / 68.00 / 19.00 / Age
Acoustic analysis:
41.694 / 185.027 / 269.871 / 95.556 / Pitch
.414 / .957 / 2.01 / .50 / Jitter
1.879 / 1.533 / 6.438 / .132 / Shimmer
3.780 / 9.022 / 16.623 / .728 / Noise to harmonic
Aerodynamic analysis:
1.023 / 2.986 / 5.299 / 1.425 / Vital cap.(in letter)
6.081 / 11.029 / 26.000 / 3.880 / Max. phonation time (in sec.)
.197 / .378 / .891 / .154 / Phonation Q.
.127 / .120 / .720 / .045 / Mean flow rate
2.404 / 4.726 / 8.910 / 1.073 / Sub. G. pressure
12.241 / 10.369 / 45.390 / .110 / Glottal eff.
Table 2: Descriptive statistics of the patients after hemodialysis:
St. dev. / Mean / Maximum / Minimum1.278 / 2.760 / 5.000 / .500 / Ultrafiltration
Acoustic analysis
47.686 / 185.306 / 284.656 / 90.790 / Pitch
.360 / 1.092 / 2.084 / .530 / Jitter
2.008 / 1.549 / 7.938 / .158 / Shimmer
3.074 / 7.875 / 13.094 / 2.739 / Noise to harmonic
Aerodynamic
1.293 / 2.593 / 5.290 / .492 / Vital cap.
5.486 / 11.339 / 25.000 / 3.884 / Max. phonation time
.166 / .290 / .780 / .051 / Phonation Q.
.130 / .119 / .560 / .042 / Mean flow rate
2.019 / 5.294 / 8.980 / 1.090 / Sub. G. pressure
8.450 / 7.436 / 39.470 / .630 / Glottal eff.
Table 3: Sex distribution in the group
Percent (%) / Frequency (No) / Sex39.4 / 26 / Male
60.6 / 40 / Female
100.0 / 66 / Total
Table 4: Distribution of cases of hemodialysis with ultrafiltration
Percent (%) / Frequency (No)30.3 / 20 / -ve ultrafiltration
69.7 / 46 / +ve ultrafiltration
100.0 / 66 / Total
Table 5: Comparison of the results of acoustic and aerodynamic analysis before and after hemodialysis (total group):
Significance / T- value / Post- dialysis (66) / Pre- dialysis(66)
St. D / Mean / St. D / mean
Acoustic analysis
.780 / .282 / 47.686 / 185.306 / 41.694 / 185.027 / Pitch
.086 / 1.773 / .360 / 1.092 / .414 / .957 / Jitter
.977 / .029 / 2.008 / 1.549 / 1.879 / 1.533 / Shimmer
.068 / 1.892 / 3.074 / 7.875 / 3.780 / 9.022 / Noise to Harmonic
Aerodynamic analysis
.057 / 1.977 / 1.293 / 2.593 / 1.023 / 2.986 / Vital capacity
.810 / .243 / 5.486 / 11.339 / 6.081 / 11.029 / Max. Phonation time
0.012* / 2.677 / .166 / .290 / .197 / .378 / Phonation Q.
.893 / .136 / .130 / .119 / .127 / .120 / Mean flow rate
.363 / .925 / 2.019 / 5.294 / 2.404 / 4.726 / Sub. Glottal pressure
.155 / 1.474 / 8.450 / 7.436 / 12.241 / 10.369 / Glottal efficiency
* P-value 0.05
There was a statistically significant decrease (P 0.05) in phonation quotient (PQ) (P 0.012) after hemodialysis. The rest of the parameters did not show any significant change after hemodialysis.
Table 6: Comparison of the results of acoustic and aerodynamic analysis before and after hemodialysis (female subgroup):
Significance / T- value / Post- dialysis (40) / Pre- dialysis(40)
St. D / Mean / St. D / mean
Acoustic analysis
.425 / .818 / 41.557 / 207.455 / 35.248 / 201.436 / Pitch
.077 / 1.886 / .280 / 1.231 / .420 / .998 / Jitter
.840 / .205 / 2.166 / 2.108 / 2.114 / 1.959 / Shimmer
.145 / 1.526 / 3.154 / 7.125 / 3.747 / 8.562 / Noise to Harmonic
Aerodynamic analysis
.068 / 1.949 / 1.119 / 2.279 / .922 / 2.801 / Vital capacity
.449 / .776 / 4.699 / 10.050 / 4.695 / 9.338 / Max. Phonation time (MPT)
.046* / 2.156 / .170 / .287 / .218 / .389 / Phonation Q.
.956 / .056 / .166 / .122 / .156 / .119 / Mean flow rate
.738 / .341 / 1.646 / 5.146 / 2.078 / 4.533 / Sub. Glottal pressure
.181 / 1.429 / 4.913 / 5.125 / 12.796 / 10.752 / Glottal efficiency
* P-value 0.05
There was a statistically significant decrease (P 0.05) in phonation quotient (PQ) (P 0.046) after hemodialysis. The rest of the parameters did not show any significant change after hemodialysis.
Table 7: Comparison of the results of acoustic and aerodynamic analysis before and after hemodialysis (male subgroup):
Significance / T- / Post- dialysis (26) / Pre- dialysis(26)
St. D / Mean / St. D / mean
Acoustic analysis
.138 / 1.587 / 38.517 / 154.638 / 39.108 / 159.784 / Pitch
.938 / .079 / .378 / .899 / .415 / .895 / Jitter
.840 / .206 / 1.521 / .774 / 1.255 / .876 / Shimmer
.266 / 1.166 / 2.742 / 8.914 / 3.870 / 9.729 / Noise to Harmonic
Aerodynamic analysis
.458 / .767 / 1.432 / 3.027 / 1.140 / 3.271 / Vital capacity
.650 / .466 / 6.164 / 13.126 / 7.185 / 13.630 / Max. Phonation time (MPT)
.136 / 1.600 / .168 / .295 / .188 / .353 / Phonation Q.
.274 / 1.152 / .064 / .115 / .069 / .121 / Mean flow rate
.301 / 1.080 / 2.461 / 5.476 / 2.883 / 5.008 / Sub. Glottal pressure
.674 / .435 / 10.824 / 9.956 / 11.945 / 9.826 / Glottal efficiency
* P-value 0.05