This study retrospectively reviewed 50 patients with sudden sensorineural hearing loss (SSNHL) who received hyperbaric oxygen therapy (HBOT) in addition to conventional treatment. The study found that HBOT significantly improved hearing outcomes in patients with SSNHL. Patients who received HBOT within 14 days of onset of SSNHL saw the greatest hearing gain. Those with more severe initial hearing loss (>70 dB) also experienced greater improvement with HBOT. Younger patients (<50 years old) generally had better hearing outcomes than older patients.

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2. Original Article
The role of hyperbaric oxygen therapy in Sudden
Sensorineural Hearing Loss: A retrospective review
of 50 patients
Tarun Sahni a,*
, Rachin Aggarwal b
, Anil Kumar Monga c
, Rajeev Puri d
,
Pavithra Shivkumar e
, Shweta Gupta f
, Sapna Verma f
a
Senior Consultant, Department of Internal and Hyperbaric Medicine, Indraprastha Apollo Hospital, Sarita Vihar,
Delhi-Mathura Road, New Delhi 110076, India
b
Department of Internal and Hyperbaric Medicine, Indraprastha Apollo Hospital, Sarita Vihar, Delhi-Mathura Road,
New Delhi 110076, India
c
Department of ENT, Sir Ganga Ram Hospital, New Delhi 110060, India
d
Prof., Department of ENT, Indraprastha Apollo Hospital, Sarita Vihar, Delhi-Mathura Road, New Delhi 110076,
India
e
Department of Genetics, Dr.ALM Post Graduate Institute of Basic Medical Sciences, University of Madras,
Chennai 600113, India
f
Research Associate, Department of Hyperbaric Medicine, Indraprastha Apollo Hospital, Sarita Vihar,
Delhi-Mathura Road, New Delhi 110076, India
a r t i c l e i n f o
Article history:
Received 11 July 2014
Accepted 19 July 2014
Available online xxx
Keywords:
Hearing loss
Hyperbaric oxygen
Sensorineural
Inner ear
a b s t r a c t
Background: Sudden Sensorineural Hearing Loss (SSNHL) is a hearing impairment of more
than 30 dB occurring within a period of upto 3 days in three consecutive pure tone fre-
quencies. Hyperbaric oxygen therapy (HBOT) in recent years has gained relevance for
treating SSNHL in combination with other agents. The aim of this study is to review the
outcomes in patients with SSNHL treated with HBOT at our centre.
Materials & methods: Records of 50 patients with SSNHL who received HBOT with conven-
tional management were retrospectively reviewed. They were treated in a multiplace hy-
perbaric chamber at 2.4 ATA, for 90 min once a day. Pre and post treatment audiograms at
500, 1000, 2000, 4000 and 6000 Hz were compared to assess improvement. Hearing gain in
relation to severity, age of patients, therapeutic delay and coexisting symptoms in prog-
nosis was evaluated.
Results: 94% patients had overall hearing improvement. 82% patients of severe hearing loss
presenting to us within 2 weeks of onset showed maximum gain. Those who received
treatment within 14 days showed highest gain from 76 ± 20.06 dB to 51.9 ± 17.1 dB as
compared to other patients. The hearing gain was greater at frequencies above 500 Hz.
Patients younger than 50 years showed greater gain of 25 ± 13.2 dB as compared to those
older than 50 years with gain of 19 ± 10.2 dB.
* Corresponding author. Tel.: þ91 9810038010; fax: þ91 (0)11 26823629.
E-mail addresses: aimhu@live.in, sshwetaa0186@gmail.com (T. Sahni).
Available online at www.sciencedirect.com
ScienceDirect
journal homepage: www.elsevier.com/locate/apme
a p o l l o m e d i c i n e x x x ( 2 0 1 4 ) 1 e5
Please cite this article in press as: Sahni T, et al., The role of hyperbaric oxygen therapy in Sudden Sensorineural Hearing Loss: A
retrospective review of 50 patients, Apollo Medicine (2014), http://dx.doi.org/10.1016/j.apme.2014.07.006
http://dx.doi.org/10.1016/j.apme.2014.07.006
0976-0016/Copyright © 2014, Indraprastha Medical Corporation Ltd. All rights reserved.

3. Conclusion: Addition of HBOT to standard treatment significantly improves outcome of
SSNHL in a subset of patients. We recommend additional multicentric, prospective studies
be carried out to define the role of HBOT in SSNHL.
Copyright © 2014, Indraprastha Medical Corporation Ltd. All rights reserved.
1. Introduction
Sudden Sensorineural Hearing Loss (SSNHL) is hearing
impairment of more than 30 dB of three consecutive pure tone
frequencies developing within 3 days or less.1e3
It is a clinical
manifestation with proposed diverse aetiologies such as viral
infection, vascular compromise, intra-cochlear membrane
rupture or inner ear disease among others.3e5
It is more
common in young and middle aged people with unilateral ear
involvement in more than 90% cases.1,5e8
Due to lack of definite cause of SSNHL, its treatment is
largely empirical and includes use of a wide variety of thera-
pies like systemic and intratympannic steroids, vasodilators,
osmotic drugs, antiviral and anticoagulants to counteract
possible inflammatory mechanism, modify hydrostatic pres-
sure and improving cochlear blood flow.8e12
The possible final
goal of any treatment modality of SSNHL has been the resto-
ration of oxygen tension in the cochlea to encourage healing
and return of hearing to normal levels.
Hyperbaric oxygen therapy (HBOT) is a treatment modality
involving the intermittent inhalation of 100% oxygen in
chambers pressurized above 1 atmosphere absolute (ATA).
HBOT has been used as an adjunctive therapy for SSNHL as it
raises the amount of oxygen in the inner ear by diffusion
which activates cell metabolism leading to restoration of ionic
balance and electrophysiological functions of cochlea.2,13e16
This study aims to analyse retrospective data of this
centre to evaluate the efficacy of addition of HBOT to con-
ventional treatment in patients with SSNHL and identify
specific groups of patients likely to benefit from the addition
of this therapy.
2. Materials and methods
In this retrospective study we reviewed records of 150 patients
with SSNHL who presented to our unit during the period
2006e2011. 50 Patients who met the following inclusion
criteria were taken for the study: unilateral onset of SSNHL of
30 dB or greater in atleast three contiguous frequencies, un-
known cause of hearing loss and no previous surgery in the
affected ear. These patients received HBOT in addition to
conventional treatment as prescribed by the referring ENT
Surgeon. The conventional treatment however was not stan-
dardized for patients in our study. HBOT was administered in
a multiplace chamber at 2.40 ATA for 90 min once daily for
atleast 10 days. The data collected included demographics,
initial symptoms of hearing loss, tinnitus, vertigo or any other
coexisting symptom, pure tone audiogram (PTA) and duration
of onset of hearing loss from starting of HBOT.
The patient's audiograms were reviewed before starting
treatment and after 10 sessions of HBOT. If the audiogram
showed improvement after 10 treatments, patients were
advised for additional 10 sessions of HBOT, this process was
repeated after further 10 sessions and a maximum of 30
sessions were given if they continuously showed improve-
ment. All patients were assessed with PTA at 500, 1000, 2000,
4000 and 6000 Hz and hearing gain at these frequencies was
calculated separately. The level of hearing loss at these 5
frequencies was evaluated in 3 groups: <40 dB (mild), be-
tween 41 and 70 dB (moderate), >70 dB (severe). The average
of mean hearing gain of patients according to age group and
therapeutic delay along with presence of associated com-
plaints as contributory factors to prognosis of SSNHL was
assessed.
Data of study was evaluated using descriptive statistical
methods i.e. mean and standard deviation.
3. Results
The clinical profile of the patients in our study is shown in
Table 1. The 50 subjects in our study were in the age range of
18e75 (28 males and 22 females). The co-morbid factors in
them were hypertension (8% cases), Diabetes Mellitus (16%
cases) and coronary artery disease (8%). There was history of
smoking in 22% of cases and 34% additionally complained of
tinnitus and vertigo.
Table 1 e Clinical profile of patients with sudden
sensorineural hearing loss.
Variables n ¼ 50 %
Gender Male 28 56
Female 22 44
Age 50 yrs 34 68
50 yrs 16 32
Affected ear Right 37 74
Left 13 26
Time lag 14 days 26 52
15e30 days 17 34
30 days 07 14
Severity Mild 06 12
Moderate 12 24
Severe 32 64
Presence of associated complaints Tinnitus 13 26
Vertigo 04 08
Coexisting illnesses Hypertension 05 10
Diabetes 08 16
CAD 04 08
Smoking 11 22
a p o l l o m e d i c i n e x x x ( 2 0 1 4 ) 1 e52
Please cite this article in press as: Sahni T, et al., The role of hyperbaric oxygen therapy in Sudden Sensorineural Hearing Loss: A
retrospective review of 50 patients, Apollo Medicine (2014), http://dx.doi.org/10.1016/j.apme.2014.07.006

4. The initial and final mean hearing levels at 500, 1000, 2000,
4000 and 6000 Hz of patients are presented in Table 2. The
mean hearing gain was highest at frequencies above 1000 Hz.
The mean hearing gain after treatment is shown in Table 3.
The average hearing gain at the five frequencies was signifi-
cantly higher in patients with initial level of 70 dB in com-
parison to patients with hearing levels of 70 dB.
Table 4 shows the mean hearing gain according to thera-
peutic delay of starting HBOT. Time of presentation ranged
between 1 and 60 days. The patients who received treatment
within 14 days had higher hearing gain
(76 ± 20.06 dBe51.9 ± 17.1 dB) as compared to patients with
therapeutic delay of 15e30 days
(77.85 ± 29.12 dBe59.85 ± 22.50 dB) and in patients who started
therapy after 30 days (77.8 ± 23.81 dBe64.5 ± 21.82 dB).
Table 5shows acorrelationbetweenthetime lagandseverity
on the improvement in mean hearing gain in patients. 82% pa-
tients presenting to us within 14 days showed maximum
improvement as compared to other subset of patients.
Average hearing gain of patients according to age group is
presented in Table 6 and was significantly high in patients
younger than 50 years.
No statistically significant difference was found among
patients with coexisting complaints of hypertension, diabetes,
smoking and presence of tinnitus or vertigo.
The hearing gain were 30 dB or more in 40%, between 20
and 30 dB in 20% and upto 20 dB in 34% of patients. There was
no response to HBOT in 6% patients (n ¼ 3).
The average number of hyperbaric sessions ranged from 10
to 25 with maximum number of patients showing improve-
ment after 10 exposures. Only one patient was given 25 ses-
sions of HBOT; however the patient did not show additional
improvement. In all patients the treatment was well tolerated
and no patient complained of any side effects. Hearing loss did
not worsen in any case.
4. Discussion
SSNHL is a loss of hearing greater than 30 dB in three contig-
uous frequencies occurring in less than 3 days.1e3
Most sud-
den hearing loss occurs within minutes to several hours. It is
considered as a clinical manifestation of possible several un-
derlying causes such as viral infection, vascular compromise,
intra-cochlear membrane rupture or inner ear disease.2e7
This
diversity demonstrates the prevailing uncertainty in aetiol-
ogies and an inability to predict the prognosis.
The high spontaneous recovery rate of SSNHL and its low
incidence make validation of empirical treatment modalities
difficult. Many treatment regimens have been proposed such
as antiviral agents, vasodilators, anti-inflammatory and oral
and intratympannic steroids. Hyperbaric oxygen therapy in
recent years has gained relevance for treating SSNHL in
combination with other agents.8e13
The Undersea Hyper-
baric Medicine Society (UHMS) has approved the use of HBOT
in SSNHL in October 2011.
HBOT increases oxygen tension (pO2) in blood by dissolving
in the plasma and diffuses into tissue fluids such as those
surrounding the sensory and neural elements of the coch-
lea.14e17
Gills showed oxygen induced osmosis as the mech-
anism for healing property of HBOT in such cases.11
Aslan et al and Bennett et al demonstrated that earlier the
treatment received, better is the prognosis.17
This was
confirmed in our study. The maximum recovery was in the 26
cases which received HBOT within 14 days after onset. They
showed significant mean hearing gain from 75.93 ± 20.06 dB to
51.90 ± 17.19 dB.
Topuz et al reported HBOT as more effective in severe
hearing loss.14
In our study, 64% cases had hearing loss of
70 dB and 81% of these patients showed improvement of
30 dB with mean hearing gain of 86 ± 11.9 dBe58.75 ± 13.0 dB.
We observed a significant correlation between patients with
severe hearing loss presenting to us within 2 weeks of onset.
82% of patients in this subset showed maximum
improvement.
Presence of tinnitus and vertigo has been reported to affect
reversibility of hearing loss in various studies.14,15
In our
study, 34% cases (n ¼ 17) with hearing loss had accompanied
tinnitus and vertigo but no significant difference was observed
between cases with and without these complaints.
Age has been found to be a prognostic factor for improve-
ment.18
In our study, patients in 50 year age group showed
better hearing gain as compared to patients with age of 50
years. Presence of diabetes, hypertension and other associ-
ated complaints in this age group might have been the
contributory factors to poor prognosis; however we were not
able to establish any correlations.
Table 2 e Mean hearing levels (MHL) at different
frequencies before and after treatment.
Frequency (Hz) Initial MHL Final MHL % Of patients
500 66.12 ± 22.0 49.16 ± 23.12 25
1000 64.68 ± 24.60 48.0 ± 20.46 40
2000 68.17 ± 21.90 52.83 ± 24.30 45
4000 74.0 ± 23.32 52.16 ± 21.00 65
6000 74.83 ± 19.76 54.83 ± 21.11 55
Table 3 e Change in mean hearing level before and after
treatment on basis of intensity.
Intensity
(db)
Pre MHL Post MHL % Of patients with
hearing
improvementa
40 35.5 ± 6.40 27.50 ± 3.53 16
41e70 60.55 ± 10.46 43.27 ± 11.6 33
70 86.50 ± 11.90 58.75 ± 13.0 81
a
Hearing improvement denotes 30 db gain in audiometry.
Table 4 e Change in mean hearing level before and after
treatment on basis of therapeutic delay.
Days of
onset
Pre MHL Post MHL % Of patients with
hearing improvement
14 75.93 ± 20.06 51.90 ± 17.19 56.25
14e30 77.85 ± 29.12 59.85 ± 22.50 42.10
30 77.8 ± 23.81 64.5 ± 21.82 25
a p o l l o m e d i c i n e x x x ( 2 0 1 4 ) 1 e5 3
Please cite this article in press as: Sahni T, et al., The role of hyperbaric oxygen therapy in Sudden Sensorineural Hearing Loss: A
retrospective review of 50 patients, Apollo Medicine (2014), http://dx.doi.org/10.1016/j.apme.2014.07.006

5. There is no consensus on the right number of treatments
with HBOT in the treatment of SSNHL. While some cases show
improvement within a few days other cases might need it
longer to achieve good results, however few studies report the
optimum number of sessions. In our study, maximum pa-
tients showed improvement after 10 exposures and
maximum improvement was seen on an average of 20 ses-
sions.19,20
We recommend that 20 sessions of HBOT may be
optimum for recovery in a majority of patients.
While the number of cases in this study is small, 94% of
patients in the study group showed statistically significant
improvement in hearing, when HBOT was administered along
with conventional therapy. While all patients were on oral
steroids the conventional treatment was not standardized in
our patients.
There appears to be a scientific rationale for use of HBOT in
SSNHL and our results are encouraging. We recommend
additional multicentric, prospective trials be carried out with
a standardized protocol to establish role of HBOT in SSNHL
patients.
5. Conclusion
This retrospective study reveals that the addition of HBOT to
conventional therapy significantly improves outcome inpatients
of SSNHL if started within 14 days. Improvement is best at fre-
quencies above 500 Hz and in hearing loss of above 70 dB. HBOT
was more effective in patients younger than 50 years of age.
Conflicts of interest
All authors have none to declare.
Acknowledgement
The Hyperbaric Oxygen Therapy Unit acknowledges the sup-
port given by the Department of ENT namely Dr Sindhu, Dr
Kishore, Dr Soni, Dr Raheja, Dr Nagpal, Dr Dhingra, Dr Prakash
Dr Ansari in this hospital and other clinicians from within
and outside Delhi.
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Table 5 e Correlation between hearing improvement on
basis of severity and time lag.
Time lag Severity (% of patients showing improvement)
Days Mild Moderate Severe
14 45 50 82
15e30 35 43 50
30 0 33 25
Table 6 e Comparison of mean hearing level according to
age group.
Age group (yr) Pre MHL Post MHL % Patients with
hearing
improvement
50 77.0 ± 19.30 52.0 ± 13.70 32
50 68.4 ± 17.22 49.4 ± 17.34 26
a p o l l o m e d i c i n e x x x ( 2 0 1 4 ) 1 e54
Please cite this article in press as: Sahni T, et al., The role of hyperbaric oxygen therapy in Sudden Sensorineural Hearing Loss: A
retrospective review of 50 patients, Apollo Medicine (2014), http://dx.doi.org/10.1016/j.apme.2014.07.006

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318.
a p o l l o m e d i c i n e x x x ( 2 0 1 4 ) 1 e5 5
Please cite this article in press as: Sahni T, et al., The role of hyperbaric oxygen therapy in Sudden Sensorineural Hearing Loss: A
retrospective review of 50 patients, Apollo Medicine (2014), http://dx.doi.org/10.1016/j.apme.2014.07.006

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