Hyperbaric Oxygen therapy Regimen-Sudden deafness

Hyperbaric Oxygen Therapy Program – Sudden Hearing Loss

Sudden deafness (commonly known as ear stroke) is a disease in which hearing is suddenly reduced; patients experience symptoms such as hearing loss on one side, tinnitus, a feeling of fullness in the ear, and even dizziness after waking up.

Definition of sudden hearing loss

According to the American Academy of Otolaryngology, sudden hearing loss is defined as a sensorineural hearing loss exceeding 30 decibels at three consecutive sound frequencies within three days, which may be accompanied by symptoms such as tinnitus, ear fullness, headache, and dizziness. In the United States, there are 5 to 20 cases per 100,000 people annually, with a roughly equal male-to-female ratio, primarily affecting people aged 40-60. It usually occurs in only one ear, and it is rare for both ears to be affected simultaneously.

Causes of sudden deafness

There are many possible causes of sudden deafness. The cause of this disease is unknown. It can be a single disease. More than 100 causes of this disease have been recorded in the literature. Currently, the cause can be found in only about 5-10% of cases in clinical practice.

Since human inner ear tissue is unavailable, the pathophysiology of the inner ear in these patients is difficult to study. Currently, the main hypotheses for the possible causes of sudden deafness are as follows:

1. Viral infections: such as acute vestibular neuritis, diffuse labyrinthitis (inner otitis), influenza, enterovirus, mumps, measles, etc. In the past, some scholars speculated that sudden deafness might be related to mumps virus or varicella-zoster virus. Other literature reports a possible link to recent infections with influenza virus, Epstein-Barr virus (EBV), herpes simplex virus, cytomegalovirus, etc. Furthermore, the recent increase in the number of patients with sudden deafness following SARS-CoV-2 infection, with MRI scans showing inflammation of the inner ear, has also contributed to this.

2. Blood and vascular problems: These include vasospasm (inner ear blood vessels), stroke, thrombosis, and vasculitis. Since the human cochlea is supplied by a tiny terminal blood flow, microcirculatory disturbances in the inner ear (including atherosclerosis, thrombosis, and vasospasm) have been proposed as a possible cause of sudden deafness. One analysis report indicates that patients with sudden deafness have a relative risk of developing a stroke approximately 1.42 times higher, while there is no significant association with subsequent myocardial infarction.

3. Systemic and immune diseases: such as poorly controlled diabetes, thyroid dysfunction, systemic autoimmune diseases, and kidney disease. Some autoimmune diseases can also manifest as sensorineural hearing loss, such as rheumatoid arthritis, systemic lupus erythematosus, Wegener's granulomatosis, polyarteritis nodosa, and Bethel's disease.

4. Sudden and drastic changes in the body: such as after long-term strenuous work and significant mental stress, after undergoing major surgery, or after long-term travel.

5. Tumor formation: such as acoustic neuroma, skull base tumors compressing the internal auditory canal; neuroma or tumors between the cerebellum and pons, etc.

6. Perilymphatic fluid leakage and fistula: such as head or ear injuries, car accidents, flying, diving, etc.

Treatment for sudden hearing loss

Traditional treatment, in addition to oral and injectable prednisolone during hospitalization, may also include hyperbaric oxygen therapy.

The principle is:

Increasing the partial pressure of oxygen increases the amount of dissolved oxygen in the plasma and the oxygen diffusion rate. Therefore, it can rapidly correct tissue hypoxia. Furthermore, the greater the partial pressure difference of gases, the faster the diffusion rate. Therefore, the more hypoxic a site is, the more oxygen will diffuse to that site under hyperbaric oxygen pressure.

It can reduce hematocrit, blood viscosity and increase red blood cell elasticity, thereby improving microcirculation and also greatly helping to improve tissue blood perfusion and hypoxia.

Anti-inflammatory effects: Hyperbaric oxygen has immunomodulatory and anti-inflammatory effects, thereby reducing tissue damage caused by inflammation.

When oxygen partial pressure increases, heart rate slows down, cerebral blood vessels constrict, arterial blood pressure decreases, and cerebral blood flow can decrease by 21%. However, due to the increased blood oxygen content, tissue oxygenation still increases, while vasoconstriction can improve or prevent edema, exudation, and hemorrhage in the inner ear tissues.

What is hyperbaric oxygen therapy?

Hyperbaric oxygen therapy involves placing the patient in a completely sealed pressure chamber and inhaling pure oxygen at a pressure higher than normal (above 1.3 atmospheres absolute). The main purpose of hyperbaric oxygen therapy is to increase blood oxygen concentration, promote oxygen dissolution in the blood, and increase tissue oxygen content, thereby accelerating the body's self-repair and enhancing tissue oxygenation. It also utilizes physical principles to increase the oxygen dissolved in blood plasma.

As of July 2021, the FDA has approved 13 indications for the use of hyperbaric oxygen therapy, including the treatment of hearing loss (sudden onset of complete hearing loss without any known cause); and the Undersea and Hyperbaric Medical Society (UHMS) also included sudden sensorineural hearing loss in its approved indications in 2011.

There are numerous studies and discussions on the evidence-based medical evidencefor the use of hyperbaric oxygen therapy in the treatment of sudden hearing loss .

In Jain's textbook on hyperbaric oxygen therapy (4th ed., 2004), many comparisons between control groups and hyperbaric oxygen groups are listed. These studies all indicate that adding hyperbaric oxygen therapy as an adjunct to traditional treatment can increase the effectiveness of treatment for sudden deafness.

In the Cochrane Evidence-Based Medicine database, Bennet et al.'s analysis showed that adjunctive hyperbaric oxygen therapy helps improve hearing in patients with sudden deafness. A small, prospective, randomized clinical study by Topuz et al. (2004) found that the hearing recovery in the hyperbaric oxygen therapy group (hyperbaric oxygen + conventional treatment) was significantly better than that in the control group (conventional treatment only). Furthermore, hyperbaric oxygen therapy significantly improved hearing in patients with sudden moderate to severe hearing loss (mean pure-tone audiometry greater than 60 dB). Aslan et al. and Topuz et al. also found that patients under 50 years of age responded better to hyperbaric oxygen therapy than those over 50 years of age.

The American Academy of Head and Neck Medicine also recommends that patients with sensorineural hearing loss undergo hyperbaric oxygen therapy within three months.

Hyperbaric oxygen therapy

The rationale for using hyperbaric oxygen therapy in ISSHL is based on the understanding of the cochlea's high metabolic rate and sparse blood vessels. The cochlea and its internal structures require a large supply of oxygen. Direct vascular supply, especially to the organ of Corti, is very limited. Tissue oxygenation of the cochlear structures is achieved through the diffusion of oxygen from the cochlear capillary network to the perilymph and cortical lymph. The perilymph is the primary source of oxygen for these cochlear structures. Unfortunately, perilymph oxygen tension is significantly reduced in ISSHL patients. To achieve a sustained increase in perilymph oxygen content, the arterial-pericymph oxygen concentration difference must be very high, which can be restored through hyperbaric oxygen therapy.

Improve inner ear hypoxia

Hyperbaric oxygen therapy (HBOT) increases tissue oxygen concentration by increasing the partial pressure and dissolved oxygen content of plasma. Furthermore, HBOT can reduce hematocrit, decrease blood viscosity, and increase red blood cell elasticity, thereby improving microcirculation and significantly aiding in tissue perfusion and hypoxia. Studies show that HBOT can indeed increase the partial pressure of oxygen in the inner ear lymph. This effect should counteract the tissue damage caused by vascular factors in sudden deafness and may even increase the inner ear's tissue repair capacity.

Anti-inflammatory effects

Studies have shown that hyperbaric oxygen therapy has immunomodulatory effects, and recent research has further discovered that it can inhibit the function of adhesion molecules on leukocytes, reduce inflammatory responses, and thus reduce tissue damage caused by inflammation. Although no studies have yet explored the therapeutic effects of hyperbaric oxygen therapy on inner ear inflammation in sudden deafness, the potential anti-inflammatory effects of hyperbaric oxygen therapy may play a protective role in sudden deafness caused by viral infections.

Precautions for hyperbaric oxygen therapy

Hyperbaric oxygen therapy has many benefits for the body's repair process. However, if you need to undergo hyperbaric oxygen therapy, please note the following:

Treatment environment

Treatment should be performed in a professional hyperbaric oxygen chamber, and the equipment should be safety certified to ensure environmental safety and compliance with relevant standards.

Medical assessment

A comprehensive evaluation must be conducted before receiving hyperbaric oxygen therapy to understand the patient's medical history and current health status.

Follow medical guidance

Strictly follow the doctor's advice and plan for treatment, and avoid adjusting the course or frequency of treatment on your own.