MedicalResearch.com Interview with:
Tae-Min Rhee, M.D.
Chief of Undersea and Diving Medicine,
Underwater Medical Institute,
National Maritime Medical Center,
Republic of Korea Navy, Changwon
Republic of Korea
MedicalResearch.com: What is the background for this study?
Response: The sudden sensorineural hearing loss (SSNHL) has an incidence of 5 to 20 per 100,000 person-years in the general population and sometimes results in permanent deafness followed by considerable socio-economic costs. The causes of SSNHL are often unclear, and in these cases there are no treatment of choice that is proven to be effective. In addition, spontaneous recovery is not uncommon in SSNHL, making it difficult to predict the natural course of the disease, and thus a well-controlled clinical trial is rare in spite of its clinical significance.
Many treatment options (systemic or intratympanic steroids, antiviral agents, vasodilators, and hyperbaric oxygen therapy) have been suggested and tried to date, but only systemic steroid therapy has been the most effective among them. However, for the cases with contraindications to steroids, or steroid-refractory SSNHL, there is paucity of information on the second line treatment option.
Hyperbaric oxygen therapy (HBOT), i.e., high-pressurized oxygen therapy, is a method of treating patients within a chamber saturated with 100% oxygen maintained at a high pressure of 2.0 to 2.5 atm. Cochlea is an organ that relies more on the diffusion of oxygen than the direct vascular supply, and thus it is known to be vulnerable to ischemia. Since this is suggested as one of the main pathophysiology of SSNHL, we wanted to prove the hypothesis that, by providing high-pressure oxygen, the partial pressure of oxygen delivered to the inner ear is maximized, and the additional or complementary therapeutic effects can be observed. A number of reports have been published for 20 years, but there is no systematically organized evidence except a Cochrane Review in 2012. Therefore, our research team tried to integrate the evidence through a comprehensive meta-analysis and to provide important clues for further research.
MedicalResearch.com: What are the main findings?
- The pooled odds ratios for both complete and any hearing recovery were significantly higher in the HBOT+MT (hyperbaric oxygen therapy plus standard medical therapy based on steroids) group.
- The absolute hearing gain was also significantly larger in the HBOT+MT group than in the medical therapy alone group, showing similar trends at all individual frequencies.
- The hyperbaric oxygen therapy appeared to be more beneficial in patients with severe hearing loss at the baseline.
- The beneficial effect of HBOT was prominent in groups with salvage HBOT for refractory cases, and hyperbaric oxygen therapy with a prolonged duration of over 1,200 minutes.
MedicalResearch.com: What should readers take away from your report?
Response: The most important finding we can get from our work is that hyperbaric oxygen therapy can be especially useful as a salvage option in cases with severe SSNHL (≥ 70 dB at baseline) or refractory to steroids. I think this result can shed a light on the way to treat patients with refractory SSNHL or contraindications to steroids.
In addition, we also analyzed the effect of HBOT protocol on the clinical outcomes for the first time. It may be recommended to apply a 2-week protocol with a 90-minute session per day, or a 20-day protocol with a 60-minute session per day to achieve at least 1,200 minutes of total HBOT duration. However, since increasing maximal pressure above 2.5 atm did not provide any benefit for hearing recovery, it may be considered to keep the air pressure of 2.0 to 2.5 atm as currently recommended.
Hyperbaric oxygen therapy is basically a very safe and effective treatment with few side effects. Almost all patients can be applied without fear of adverse effects, except when there is a history of claustrophobia or pneumothorax. Even considering the cost-effectiveness, it may be worthy to try salvage HBOT treatment at least for refractory cases after the failure of medical treatment with steroids.
MedicalResearch.com: What recommendations do you have for future research as a result of this work?
Response: Through a subgroup analysis, we were able to obtain several clues for the future studies: First, the need for a universal HBOT protocol, and second, the need for a well-controlled clinical trial based on this protocol. Most reports to date used various indications, timing, dose, pressure, and duration of HBOT. Therefore, future trials should use the standardized HBOT regimen to reveal the efficacy of hyperbaric oxygen therapy as a salvage treatment for patients refractory to the steroids. Further, it should be clarified that how much time interval is appropriate between onset, assessment of initial treatment failure, and salvage HBOT treatment. We hope that future studies could complement this issue and gain more solid evidence.
MedicalResearch.com: Is there anything else you would like to add?
Response: This study was carried out at the Maritime Medical Research Center, a national medical research institute of the Ministry of National Defense of the Republic of Korea. This is a non-profit public medical institution dedicated to the treatment of decompression sickness of military and private divers. Recently, in addition to decompression sickness, various novel indications of high-pressure oxygen therapy have been further clarified. In accordance with this trend, this institute has carried out the present study to improve the utilization of the high-pressure oxygen chamber. Therefore, we disclose that we do not have any financial or industrial conflict of interests in any process of this study.
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