Why do we feel discomfort in our ears during hyperbaric oxygen therapy?

Author: Liu Bo China Rehabilitation Research Center

Reviewer: Du Juan, deputy chief physician, China Rehabilitation Research Center

As the application of hyperbaric oxygen therapy becomes more and more widespread, many people have received hyperbaric oxygen therapy. During hyperbaric oxygen therapy, as the pressure in the cabin changes, most people in the cabin will feel ear discomfort, such as stuffy ears and hearing loss, just like flying or diving. Why is this? How to prevent it?

Let us first understand the structure and function of the ear.

Our ears are made up of three parts, including the outer ear, middle ear, and inner ear. The outer ear mainly includes the auricle and the external auditory canal, which are mainly responsible for collecting and conducting sound. The structure of the middle ear is a bit more complicated, including the eardrum, ossicles, and Eustachian tube, which are mainly responsible for amplifying sound signals and transmitting them to the inner ear. The inner ear has the cochlea, vestibule, and semicircular canals. Its main function is to convert sound signals into electrical signals and transmit them to the auditory center of the brain through the auditory nerve, so that we can hear the sound.

Figure 1 Copyright image, no permission to reprint

2. During hyperbaric oxygen therapy, we may feel discomfort in our ears in the cabin. Why is that?

The problem is mainly caused by the middle ear. The middle ear has a cavity called the tympanic cavity, which is covered by the eardrum. The front wall is connected to the nasopharynx through the Eustachian tube. The total length of the Eustachian tube in an adult is about 35mm. One end of the Eustachian tube is in the tympanic cavity and the other end is in the nasopharynx. The middle ear tympanic cavity has an opening in the nasopharynx, like a "valve". It is usually closed and only opens when we make some oral and maxillary movements. Air takes this opportunity to enter the middle ear tympanic cavity to balance the pressure inside and outside the eardrum.

If the Eustachian tube cannot be opened in time to allow gas to enter the tympanic cavity through the Eustachian tube during pressurization, the pressure in the tympanic cavity will be lower than the pressure of the external auditory canal outside the tympanic membrane, and the tympanic membrane will be pressed inward, causing the tympanic membrane to collapse, causing stuffy ears and ear pain. When the pressure in the hyperbaric oxygen chamber increases, the hollow organs in our body can adjust the pressure to the same as the external pressure through breathing movements, but the middle ear tympanic cavity cannot do this, and the Eustachian tube must be used to adjust the internal and external pressure balance. When the pressure difference between the inside and outside of the tympanic membrane is between 10 and 30 mmHg, the tympanic membrane will collapse, and people will feel stuffy ears and hearing loss. When the pressure difference reaches 60 mmHg, the mucous membrane of the tympanic membrane and tympanic cavity will become congested, and ear pain will be felt. When the pressure reaches 100 mmHg, the tympanic membrane will be widely congested, and there will be exudation in the tympanic cavity. People will feel blocked ears, tinnitus, and severe ear pain. When the pressure exceeds 120 mmHg, the tympanic membrane may rupture, which is the middle ear barotrauma.

3.How to adjust the pressure correctly during hyperbaric oxygen therapy?

Middle ear barotrauma is the most common side effect of hyperbaric oxygen therapy. So how to prevent it? The answer is to continuously adjust the pressure. When we enter the chamber for treatment, we should continuously perform the correct pressure adjustment action from the beginning of pressurization to ensure that the pressure difference between the two sides of the eardrum is not too large.

Pressure regulation actions include swallowing, opening the mouth wide, pinching the nose and blowing air during the process of increasing or decreasing pressure. By doing these actions, we can adjust the pressure on both sides of the eardrum, balance the pressure on both sides of the eardrum, and reduce the occurrence of middle ear barotrauma.

The details are as follows.

(1) Pinch the nose and blow air: The patient pinches both nostrils, closes his mouth, and blows his nose. He will hear a "chirping" sound, and the eardrum will feel as if the air is being pushed outwards. The stuffiness in the ear disappears. This indicates that the Eustachian tube is open and the air has entered the tympanic cavity through the Eustachian tube.

(2) Swallowing action: drinking water, swallowing saliva or swallowing food. We generally recommend drinking small sips of water or eating juicy fruits during the pressurization process and swallowing frequently to adjust the pressure.

(3) Yawning: When we yawn, our mouth opens wide, and the Eustachian tube opens, allowing air to enter the tympanic cavity and maintain pressure balance inside and outside the eardrum.

Figure 2 Copyright image, no permission to reprint

4. In addition to adjusting the pressure correctly, what other preparations should be made to prevent ear discomfort?

Although ear stuffiness and ear pain are the most common complications of hyperbaric oxygen therapy, most of the symptoms are mild and generally not a big deal as long as they are treated promptly and properly. Here are some ways to prevent ear pain.

(1) Fully understand your own condition before entering the cabin. If you have a history of otitis media, rhinitis, sinusitis, etc., especially during the acute attack period, or have recently developed cold symptoms such as nasal congestion and runny nose, you should inform the hyperbaric oxygen physician in advance. Generally, the physician will recommend that the patient go to the otolaryngology department for a specialist examination to evaluate the Eustachian tube function to determine whether hyperbaric oxygen treatment can be performed.

(2) Before entering the cabin, patients can learn and practice the action of pinching the nose and blowing air in advance. Some people may not be very good at blowing their noses, which may sound a little funny, but we often encounter this in our daily work. It should be noted that when pinching the nose and blowing air, you do not puff up your cheeks, but gently blow air into the tympanic cavity through the Eustachian tube. Therefore, try to practice before entering the cabin to feel the feeling of the eardrum being inflated.

(3) Prepare some water or peeled fruit before entering the cabin, cut into small pieces and set aside. When the pressurization starts, you can adjust the pressure in the middle ear tympanic cavity while tasting the fruit, killing two birds with one stone. It is recommended to prepare juicy fruits, such as apples and oranges, and peel them in advance to avoid wasting time on peeling or peeling and missing the opportunity to adjust the pressure.

Through the above recommended methods, we can avoid most earaches. However, if you feel stuffy ears and ear pain in the hyperbaric oxygen chamber because you do not adjust the pressure in time, you will be nervous and afraid. Our hyperbaric oxygen chamber staff will always protect you. You can inform the cabin staff through the intercom system. The cabin staff will stop pressurizing in time and guide you to adjust the pressure. Stop pressurizing until your ear stuffiness and ear pain symptoms are relieved and disappear. Then continue to adjust the pressure. If the symptoms have not been relieved, report to the staff and you can decompress and leave the cabin. During decompression, if your Eustachian tube function is normal, you generally do not need to adjust the pressure, because the pressure in the tympanic cavity is higher than the pressure outside the tympanic membrane. When the pressure difference is greater than 10mmHg, the gas will automatically discharge from the Eustachian tube. The patient can hear the bubbling sound of gas overflow and the "click" sound of the tympanic membrane reset. The hearing of both ears can gradually recover, and generally will not cause pain and other discomfort. If you still feel stuffy ears, ear pain and other discomfort after leaving the cabin, you can go to the ENT department for treatment. The doctor can make a clear diagnosis after examination. If it is confirmed to be middle ear barotrauma, there is no need to panic. Stop the hyperbaric oxygen therapy. It will get better after a period of time with regular treatment.

Nowadays, hyperbaric oxygen has been widely used in many fields such as first aid, rehabilitation, and health care. More and more people are benefiting from hyperbaric oxygen therapy. I hope everyone can learn more about oxygen chambers and use them reasonably to bring more benefits to our health.