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ORIGINAL ARTICLE
Year : 2018  |  Volume : 24  |  Issue : 4  |  Page : 231-236

Efficacy of vestibular rehabilitation on quality of life of patients with unilateral vestibular dysfunction


1 Department of ENT - Audio-Vestibular Medicine, Faculty of Medicine, Zagazig University, El Sharkia, Egypt
2 Department of ENT, Faculty of Medicine, Minia University, Minia, Egypt; Department of Communication Science, College of Health and Rehabilitation Science, Princess Nourah bint Abdulrahman University, KSA

Date of Web Publication15-Mar-2019

Correspondence Address:
Dr. Reem Elbeltagy
Department of ENT – Audio-Vestibular Medicine, Faculty of Medicine, Zagazig University, El Sharkia
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/indianjotol.INDIANJOTOL_39_18

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  Abstract 


Objective: The aim of this study is to determine the efficacy of vestibular rehabilitation (VR) exercise of patients with uncompensated unilateral peripheral vestibular dysfunction. Materials and Methods: An intervention study was conducted on 20 patients their age ranging from 20 to 60 years. The main complaint of the participants was chronic dizziness (dizziness for >3 months). Dizzy patients were recruited from the Ear, Nose, and Throat department. The study was conducted in the audiovestibular unit. All participants in the study were subjected to basic audiological evaluation and vestibular evaluation (videonystagmography). The Dizziness handicap inventory questionnaire (DHI) was carried out twice (pre and post) rehabilitation program. The VR therapy was performed according to the protocol established by Cawthorne and Cooksey and Norre exercises. Results: All the DHI scores reduced significantly after VR. There were no differences among genders; adults and elderly patients. Conclusion: The result of this study proved the importance and the efficacy of VR. It considered a useful therapeutic approach for improvement in the quality of life of individuals with unilateral peripheral vestibular weakness. The improvement was not influenced by sex, age, or duration of disease. It considered a low-cost, short, and safe treatment technique which can be widely used in outpatients without the need for sophisticated tools.

Keywords: Dizziness handicap inventory questionnaire, rehabilitation, vestibular dysfunction


How to cite this article:
Elbeltagy R, Abd El-Hafeez M. Efficacy of vestibular rehabilitation on quality of life of patients with unilateral vestibular dysfunction. Indian J Otol 2018;24:231-6

How to cite this URL:
Elbeltagy R, Abd El-Hafeez M. Efficacy of vestibular rehabilitation on quality of life of patients with unilateral vestibular dysfunction. Indian J Otol [serial online] 2018 [cited 2019 Apr 23];24:231-6. Available from: http://www.indianjotol.org/text.asp?2018/24/4/231/254230




  Introduction Top


An individual perception of his situation in life in relation to the culture and value systems in his community can be defined as a quality of life, and it includes many domains including health status, economic resources, work position, relationships, and leisure activities. Health-related Quality of Life is a term used to represent that portion of the quality of life that is swayed and affected by the person's health.[1]

One of the common medical conditions that could be affecting the quality of life is dizziness. It is estimated that about 20%–30% of the worldwide population suffers from.[2] The prevalence of dizziness increases with age.[3] Furthermore, it is more common in female than male (2–3 higher in female than male). It is either a single symptom or associated with other signs and symptoms of auditory changes and neurovegetative disturbances.[2]

The functions of both sensory and motor mechanisms are affected in the case of peripheral vestibular abnormalities and the resulting symptoms of affection are either static or dynamic symptoms, the static symptoms that happen in the absence of head movements and are concomitant with a sudden unilateral loss of vestibular function including nausea, vomiting, vertigo, and imbalance while the dynamic symptoms which happen during head movements including loss of visual acuity, blurring of vision, and confusion in complex sensory situations while moving the head.[4] The most common type of peripheral vestibular abnormalities is the unilateral vestibular lesions which make unevenness in the vestibular pathways that simulate head movements.[5]

It is noted that family life, social, and professional activities are affected by a varieties of factors including intensity, duration, and prevalence of the clinical manifestations of vestibular disorders which as a result cause reduction in physical, economic and psychological activities, and also negatively affecting performance and concentration, so the quality of life is badly affected.[6],[7]

As a result of high degree of plasticity within the central vestibular pathways, the severity of the vestibular symptoms in many patients may be decreased or even improved even with persistence of vestibular loss. This improvement is due to what is called vestibular compensation.[8]

Vestibular rehabilitation (VR) is one of the treatment modalities of vertiginous patients that consist of certain physical activities and exercises offered to promote functional improvement in patients with vestibular disorders. It reduces body instability, and dizziness resulting in an improvement in the quality of life occurs due to improving competence and well-being in the performance of daily activities.[9],[10]

The most valuable method for promoting dynamic compensation is a physical exercise that is concentrated on eye-head coordination.[11] Those exercises help in increasing the vestibule-ocular reflex gain which is enhanced by the increased outflow of the neural activity originating from the velocity storage mechanism.[12]

The success of VR could be affected by some factors such as emotional state, medication use, patient's age, increased ability to practice physical exercises, and presence of disease affecting the central nervous system that may negatively affect the structures responsible of neuroplasticity of the vestibular system.[13]

A systematic review on VR in unilateral peripheral vestibular dysfunction was carried out by Hillier and Hollohan in 2007, concluded the safety and effectiveness of VR in the treatment of patients with unilateral peripheral vestibular dysfunction.[14]

Using quality life assessment tools, such as the dizziness handicap inventory questionnaire (DHI) before, during and after the treatment period is one of the efficient ways to measure the success of chronic disease interventions. The literature reported that the assessing of follow-up and reevaluate the success of the rehabilitation program using DHI is a good tool.[9]

The objective of this study was to determine the efficacy of VR exercises in patients with uncompensated unilateral peripheral vestibular dysfunction.


  Materials and Methods Top


Study design and subjects

An intervention study was conducted on 20 patients their age ranging from 20 to 60 years with a mean age of 41.25 years (±6.47 years). The main complaint of the participants was chronic dizziness (dizziness for >3 months). Dizzy patients were recruited from the Ear, Nose, and Throat department. The study was conducted in the audiovestibular unit.

  • The inclusion criteria included patients with clinical history of dizziness for >3 months. All patients were diagnosed with an uncompensated unilateral peripheral vestibular weakness as diagnosed by basic audiological assessment and videonystagmography (VNG) (all oculomotor tests were normal and unilateral caloric hyporesponsiveness or unresponsiveness of the horizontal canal of the affected ear. Vestibular paresis was defined as >25% asymmetry between the right-side and the left-side responses[15]
  • The exclusion criteria included patients using vestibular suppressant for a long period that prevent central compensation, bilateral peripheral vestibular weakness, and central vestibular weakness, mixed vestibular weakness, or acute vestibular weakness.


Audiological evaluation

All participants in the current study were subjected to the following:

  1. Full history taking including:


    • Personal history (age, name, sex, and occupation)
    • Patient history of dizziness, unsteadiness, and vertigo
    • History of hearing loss, tinnitus, discharge, earache, headache, and vertigo)
    • History of systemic disease, physical trauma, ototoxic drug, and operations.


  2. Otological examination: preauricular region, ear pinna, postauricular region, external acoustic canal, and tympanic membrane.
  3. Cranial nerve examination
  4. Basic audiological evaluation: using:


    • pure-tone audiometry using orbiter 922 (GM Otomtrix, Denmark): This included air conduction (air conduction hearing thresholds were determined by frequency range 0.250 and 8K Hz) and bone-conduction (bone conduction hearing thresholds were determined by frequency range 0.500 and 4K Hz. Hearing values >25 dB were considered as HL
    • Speech audiometry (speech reception threshold and the speech discrimination scores)
    • Immittancemetry using Amplaid 724 (Amplifon, Italy): including tympanometry and acoustic reflex threshold measurement.


Vestibular evaluation

VNG – was performed using VNG ICS Chart 200. The following tests were performed:

Oculomotor tests

Smooth pursuit testing

The patients were instructed to watch a target that moves horizontally in a sinusoidal fashion at a low frequency (0.2–0.7 Hz) with position amplitude of 200 in each direction. The computer then calculated the gain of smooth pursuit. A gain of <70% indicated impairment.

Saccade testing

The patients were instructed to fixate with eye movements while keeping the head stationary series of randomly displayed dots or lights at eccentricities of 5–300, both to the right and left. Observe for saccades: latency, velocity, accuracy, conjugacy, and asymmetry. A latency of >280°ms, an accuracy of <80%, and a peak velocity of <300° were considered abnormal. The patient with prolonged latency was diagnosed with having impaired saccadic movement if at least one of the accuracy or peak velocity scores was also outside the reference range.

Optokinetic nystagmus

It measures jerk nystagmus created by presenting a horizontally moving visual field to the subject, at velocities of 30, 40, or 600/s, for ~1 min, followed by a 1 min rest, after which the pattern is presented in the opposite direction.

Positional tests

The eye movements of each patient were recorded for 30 s without visual fixation. The patient had been placed in the sitting, supine, right ear down, left ear down position, right side, left side, and head hanging positions.

Positioning test (Dix-Hallpike test)

Each patient was seated upright on the examination table, and the head is turned 45 (such that the chin is toward the right shoulder). The patient is rapidly lowered with the head supported into right head hanging position 30 below the horizontal. The patient remains in this position for at least 30 s with careful observation for nystagmus or vertigo (Frenzel lenses will aid in the identification of nystagmus). The patient is returned to the upright position, and the maneuver is repeated with the head turned 45 toward the left shoulder.

Water caloric tests

Bi-thermal caloric tests were performed; each ear was irrigated with water at temperatures of 30°C and 44°C for 40 s. The recordings of responses were conducted for 3 min. Canal paresis and directional preponderance were calculated according to Jongkees' formula.[15] Values >20% for canal paresis and 25% for directional preponderance were considered abnormal.

Dizziness handicap inventory (answered twice pre and postrehabilitation program)

Composed of 25 questions, comprising seven questions evaluating the physical aspect, nine the emotional aspect and seven the functional aspect. The patients were instructed to answer each question only with the following answers: “yes,” “no,” or “sometimes.” For each “yes” answer 4 points were added, for each “no” 0 points and for each “sometimes” answer, 2 points were added. Therefore, the higher the score values were, the higher were the “damages” in the life quality. The questionnaire was applied before and after treatment.[16]

Rehabilitation program

VR was made up of customized exercises according to the patient complaint, and clinical aspects. The exercises proposed initially could be modified according to the clinical evolution of the patient during treatment, considering the improvement, or not of vestibular symptoms.

The exercises used were primarily taken from protocols established by Cawthorne-Cooksey and Norre exercises[17] that aim enhancing stabilization in the static and dynamic posture to enhance vestibular adaptation and alternative strategies and strategies to enhance gaze stabilization. Gaze stabilization exercise is used to improve control of eye movements so vision can be clear during head movement.

The patients were asked to fixate on an object while they repeatedly move their heads back and forth or up and down for up to a couple of minutes.

The exercises were given once a week and the patients were educated to do the exercises at home, thrice a week, for 12 weeks. Nonetheless, depending on the patient's progress or on factors not directly associated with treatment, the patients occasionally had a higher or lower number of sessions.

Ethical consideration

In the present study, all the testing procedures were performed using noninvasive techniques and adhering to the conditions of the ethical approval committee of the institute. All participants were given their written consent form before participation in the study.

Statistical analysis

Data were collected, and analysis was performed using the computer program IBM SPSS (SPSS Inc., Chicago, Illinois, USA), statistics (version 20). Continuous variables were presented as the Mean ±SD or Median(Range). Categorical variables were presented by the count and percentage. Paired t-test was used for parametric data to compare quantitative variables. P > 0.05 was considered statistically insignificant. P < 0.05 was considered statistically significant. Value of P < 0.001 was considered highly significant.


  Results Top


Demographic data and duration

Age ranged between 20 and 60 years with a mean age of 41.25 years (±6.47 years). They were 8 males (40%) and 12 females (60%). About 65% of dizzy patients had disease duration 1 year or less and 35% for >1 year with a mean duration of 9.8 months (±3.7 months) [Table 1].
Table 1: Demographic data and disease duration

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The number of rehabilitation sessions

Rehabilitation sessions ranged from 24 to 36 sessions with mean 31.9. The mean of sessions in older patients were 34.3 sessions whereas in the younger group was 28.8 sessions [Table 2].
Table 2: Mean of number of rehabilitation sessions

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Basic audiological evaluation in dizzy patients

About 80% of dizzy patients had normal hearing sensitivity, 10% had a unilateral high-frequency Sensorineural hearing loss (SNHL), and 10% bilateral SNHL. All patients had type A tympanogram. [Table 3] shows the means of pure-tone thresholds in dB in dizzy patients.
Table 3: Mean of pure tone thresholds of dizzy patient

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As shown in [Table 4], there was a highly significant difference in DHI pre and post-VR (P < 0.000). There was a highly significant difference in DHI pre and post-VR (P < 0.000) in all study groups as shown in [Table 5] and [Table 6].
Table 4: Comparison between dizziness handicap inventory pre- and post-vestibular rehabilitation

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Table 5: Comparison between dizziness handicap inventory pre- and post-vestibular rehabilitation regarding demographic data (age-sex)

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Table 6: Comparison between dizziness handicap inventory pre- and post-vestibular rehabilitation as regarding disease duration

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  Discussion Top


VR reduces vestibular symptoms through achieving central compensation through the central mechanisms of neuroplasticity. It should be done as early as possible throughout the time window that happens simultaneously with vestibular nuclei plastic reorganizations.[18]

The average age in this study was 41.25 years (±6.47 years) with higher prevalence in age group (41–60 years). According to other studies, the prevalence of dizziness increases with age, this may be attributed to aging that affects the performance of both peripheral and central nervous system abilities. Furthermore, young individuals can withstand manifestation of compromised body balance than elderly individuals.[19]

In the current study, the percentage of female participants was 60%, whereas the male percentage was 40%. This result matched with the results recorded from the previous study that showed the female prevalence of dizziness ranges from 61.3% to 62.5%.[20] In addition, Ricci et al. found the prevalence of dizziness in female reached (82%).[19] This high prevalence could be attributed to frequent variations in female hormones and metabolic alterations that increase the incidence of balance disorder. Moreover, females may suffer from medical conditions such as menopause, osteoporosis, cardiovascular, and metabolic diseases which cause symptoms of dizziness.[21]

In this study, all patients that customized VR programs showed an improvement in DHI as regarded functional, emotional and physical aspects. These findings were in agreement with findings reported by previous studies, which proved that VR can improve vestibular symptoms in patients with chronic unilateral vestibular dysfunction.[7] This improvement due to reduce the challenge and improve the skills required for performing all daily activities.[9] In contrast, the study conducted by Zeigelboim et al. in which a sample of 6 patients aged 43–70 years showed no significant improvement of dizziness and tinnitus as regards the functional, emotional, and physical aspects after VR.[22]

At the beginning of this study, the greatest impact was noted on the physical aspect followed by an emotional aspect, which matched with the results of Soares et al.[23] that reported marked affection of physical aspect followed by emotional aspect in patients suffering from the vestibular disorder. In the current study, after VR the greatest influence was observed on the physical aspect despite the marked reduction of the values in the emotional followed by functional aspects as well. It was noted that after the improvement in emotional symptoms, individuals were able to continue their routine activities that were previously limited due to fear of dizziness symptoms and this improvement consequently improved functional aspect. Moreover, Guzmán et al. reported the affection of the social life and daily activities by patient's performance.[24]

As the benefits obtained with the VR measured by a reduction ≥18 points resulting from the difference among DHI scores pre and post-VR.[25] The recorded difference in this study was (29.05 points). This revealed that the reduction in total values of the DHI was significant, in other words, the individuals had an important improvement in their quality of life after VR. This result In agreement with the study conducted by Patatas et al. who evaluated 22 patients with (24.82 points) reduction in the DHI.[13]

The results obtained from this study proved that all the individuals whether male or female; adults or elderly; and with different disease duration significantly improved from VR regarding quality of life.

The gender in this investigation is not connected either reasonably or causally to the response to VR, which agrees with the study that conducted by Moreira et al.[26] This could be due to the execution of the questionnaire and VR exercise out of the attack period of individuals and also the data analysis is restricted to the individuals' practice of attacks on a daily basis, while during vertigo, the symptoms are intensified.[27]

These results agreed with studies conducted by Cohen et al.[21] and Mali et al.[9] that reported the improvement of the manifestations was not affected by age, and also there was no significant difference about gender. The current result was matched with the result reported by Bittar and Pedalini that elderly responded to treatment as young, but needed a more number of VR sessions to obtain the same result of young.[28] As confirmed in this study, the mean of the number of rehabilitation sessions in young was (28.8 session) whereas the mean of the number of rehabilitation sessions in the elderly was (34.4 session). This result proved to require the elderly more number of sessions to achieve improvement in the quality of life. This could be explained by the association of other confusing symptoms in elderly dizziness such as sensorineural symptoms, cardiovascular disorders, and depression symptoms. Furthermore, it may be concomitant with difficulty in walking and limitation in daily life activities.[29]


  Conclusion Top


The result of this study proved the importance and the efficacy of VR. It considered a useful therapeutic approach for improvement in the quality of life of individuals with unilateral peripheral vestibular weakness. The improvement was not influenced by sex, age, or duration of disease. It considered a low-cost, short, and safe treatment technique which can be widely used in outpatients without the need for sophisticated tools.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Szabo S. The World Health Organization Quality of Life (WHO-QOL) assessment instrument. In: Spilker B, editor. Quality of Life and Pharmacoeconomics in Clinical Trials. Philadelphia: Lippincot-Raven; 1996. p. 355-62.  Back to cited text no. 1
    
2.
Neuhauser HK. Epidemiology of vertigo. Curr Opin Neurol 2007;20:40-6.  Back to cited text no. 2
    
3.
Benecke H, Agus S, Kuessner D, Goodall G, Strupp M. The burden and impact of vertigo: Findings from the REVERT patient registry. Front Neurol 2013;4:136.  Back to cited text no. 3
    
4.
Halmagyi GM, Weber KP, Curthoys IS. Vestibular function after acute vestibular neuritis. Restor Neurol Neurosci 2010;28:37-46.  Back to cited text no. 4
    
5.
Brain K. Clinical neurophysiology of the vestibular symptom. In: Katz J, Medwestsky L, Bukhart R, Hood L, editors. Handbook of Clinical Audiology. 6th ed. Pheladelphia, PA: Lippincott Williams & Wilkins; 2009. p. 431-66.  Back to cited text no. 5
    
6.
Knobel KA, Pfeilsticker LN, Stoler G, Sanchez TG. Contribution of vestibular rehabilitation in tinnitus recovery: A surprising result. Rev Bras Otorrinolaringol 2003;69:779-84.  Back to cited text no. 6
    
7.
Segarra-Maegaki JA, Taguchi CK. Study about the benefits of vestibular rehabilitation in peripheral vestibular disorders. Pro Fono 2005;17:3-10.  Back to cited text no. 7
    
8.
Curthoys IS, Halmagyi GM. Vestibular compensation: A review of the oculomotor, neural, and clinical consequences of unilateral vestibular loss. J Vestib Res 1995;5:67-107.  Back to cited text no. 8
    
9.
Meli A, Zimatore G, Badaracco C, De Angelis E, Tufarelli D. Vestibular rehabilitation and 6-month follow-up using objective and subjective measures. Acta Otolaryngol 2006;126:259-66.  Back to cited text no. 9
    
10.
Cunha F, Settanni FA, Ganança FF. What is the effect of dizziness on the quality of life for patients with Meniere's disease? Rev Laryngol Otol Rhinol (Bord) 2005;126:155-8.  Back to cited text no. 10
    
11.
Herdman SJ. Vestibular rehabilitation. Curr Opin Neurol 2013;26:96-101.  Back to cited text no. 11
    
12.
Laurens J, Valko Y, Straumann D. Experimental parameter estimation of a visuo-vestibular interaction model in humans. J Vestib Res 2011;21:251-66.  Back to cited text no. 12
    
13.
Patatas OH, Ganança CF, Ganança FF. Quality of life of individuals submitted to vestibular rehabilitation. Braz J Otorhinolaryngol 2009;75:387-94.  Back to cited text no. 13
    
14.
Hillier SL, Hollohan V. Vestibular rehabilitation for unilateral peripheral vestibular dysfunction. Cochrane Database Syst Rev 2007; 17;(4):CD005397.  Back to cited text no. 14
    
15.
Jongkees LB. Value of the caloric test of the labyrinth. Arch Otolaryngol 1948;48:402-17.  Back to cited text no. 15
    
16.
Lei-Rivera L, Sutera J, Galatioto JA, Hujsak BD, Gurley JM. Special tools for the assessment of balance and dizziness in individuals with mild traumatic brain injury. NeuroRehabilitation 2013;32:463-72.  Back to cited text no. 16
    
17.
Herdman SJ, Borello-France DF, Whitney SL. Treatment of vestibular hypofunction. In: Herdman SJ, editor. Vestibular Rehabilitation. Philadelphia: FA Davis; 1994. p. 287-313.  Back to cited text no. 17
    
18.
Lacour M, Bernard-Demanze L. Interaction between vestibular compensation mechanisms and vestibular rehabilitation therapy: 10 recommendations for optimal functional recovery. Front Neurol 2014;5:285.  Back to cited text no. 18
    
19.
Ricci NA, Goncalves DF, Coimbra IB, Coimbra AM. Factors associated with the history of falls of elderly assisted by the Family health program. Saude Soc 2010;19:898-909.  Back to cited text no. 19
    
20.
Cusin FS, Silva SM, Ganança CF. Electronystagmographic findings in patients with benign paroxysmal positional vertigo submitted to the Epley's maneuver. Acta ORL 2006;24:69-74.  Back to cited text no. 20
    
21.
Cohen H, Kane-Wineland M, Miller LV, Hatfield CL. Occupation and visual/vestibular interaction in vestibular rehabilitation. Otolaryngol Head Neck Surg 1995;112:526-32.  Back to cited text no. 21
    
22.
Zeigelboim BS, Rosa MR, Klagenberg KF, Jurkiewicz AL. Vestibular rehabilitation in the treatment of dizziness and tinnitus. Soc Bras Fonoaudiol 2008;13:226-32.  Back to cited text no. 22
    
23.
Soares SN, Gonçalves MA, Teixeira CG, Romualdo PC, Santos JN. Influence of vestibular rehabilitation on the quality of life of individuals with labyrinth disease. Rev CEFAC 2014;16:732-8.  Back to cited text no. 23
    
24.
Guzmán PV, Zeigelboim BS, Hassan SE, Frazza MM, Diniz J Jr., Caovilla HH. The Brandt-Daroff maneuver modified in rehabilitation of postural vertigo. Acta Awho 2000;19:189-92.  Back to cited text no. 24
    
25.
Jacobson GP, Newman CW. The development of the dizziness handicap inventory. Arch Otolaryngol Head Neck Surg 1990;116:424-7.  Back to cited text no. 25
    
26.
Moreira DA, Bohlsen YA, Momensohn-Santos TM, Cherubini AA. Study of the handicap caused by dizziness in patients associated or not with tinnitus complaint. Arq Int Otorrinolaringol 2006;10:270-7.  Back to cited text no. 26
    
27.
Socher DD, Socher JA, Azzi VJ. Evaluation of quality of life pre- and post-vestibular rehabilitation in patients with benign paroxysmal positional vertigo associated with Meniere's disease. Int Arch Otorhinolaryngol 2012;16:430-6.  Back to cited text no. 27
    
28.
Bittar RS, Pedalini ME. Balance disturbances in the elderly. Pró Fono 2002;14:119-28.  Back to cited text no. 28
    
29.
Gazzola JM, Perracini MR, Ganança MM, Ganança FF. Functional balance associated factors in the elderly with chronic vestibular disorder. Braz J Otorhinolaryngol 2006;72:683-90.  Back to cited text no. 29
    



 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]



 

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