Hyperbaric Oxygen Therapy Risks & Side-Effects
As with all medical treatments, there are risks and side-effects that are associated with hyperbaric oxygen therapy. Many are related to the unique aspects of HBO such as significant and relatively rapid changes in pressure inside the chamber and the high levels of oxygen used. Most are relatively mild and self-limited, but some can be severe and even life-threatening. In general, these issues can be divided into safety risks (primarily fire safety) and medical risks (complications and side-effects).
Fire Safety in Hyperbaric Oxygen Therapy
If a fire does occur, the chamber is equipped with extensive fire suppression systems. First of all, there is a fire hose inside the chamber that an attendant can use to manually extinguish any flames. Secondly, the chamber is equipped with a deluge system which can be activated by the inside attendant, the outside attendant, or by an automatic fire detection system. When activated, this deluge system releases large sprays of water that saturate every surface in the chamber and quickly extinguish any flame.
There has never been a fire-related fatality in a patient treatment chamber in North America, and the strict adherence to the precautions stated above will help to continue this excellent safety record.
The risk of fire in a hyperbaric environment is a major concern for several reasons.
First, in order for a fire to occur three conditions must be met. There must be adequate fuel, sufficient oxygen, and an ignition source. By definition, during treatments, the hyperbaric chamber is a high oxygen environment. In addition, there is always fuel present in the form of cloth, paper, etc. Thus, the potential for a fire to occur is always present during a treatment.
Second, due to the enclosed and pressurized nature of the chamber, it is impossible to quickly open the door at depth, so rapid evacuation is not always possible in the event of a fire.
Third, also due to the enclosed nature of the system, it is difficult to rapidly ventilate the smoke and noxious fumes that often accompany fires.
Thus, fire safety is of utmost concern and several procedures are in place to prevent fire and extinguish it quickly if it occurs.
To minimize the chance of fire, the three necessary element must be reduced.
Fuel: Highly flammable materials such as grease, oil and other petroleum products are not allowed in the chamber. Similarly, cosmetics and hair-sprays are prohibited. The amount of paper and cloth are minimized as much as possible. Fire retardant materials are used where possible.
Ignition sources: Any source of flame or spark is not allowed in the chamber. This includes lighters and smoking materials, hand warmers, and any non-approved electronic devices. All lighting is done through indirect methods. Patients and staff are required to wear 100% cotton garments since these minimize the chance of static spark (and also have the advantage of not releasing toxic fumes or melting into the skin if they do catch fire).
Oxygen concentration: The concentration of oxygen in the chamber is constantly monitored and steps are taken to keep it from getting too high. These steps include compressing the chamber with air rather than pure oxygen, having the patients breathe oxygen through an enclosed hood system that exhausts outside of the chamber, and continually venting the chamber to wash-out any oxygen that might be leaking from the patient breathing system.
Medical Risks of Hyperbaric Oxygen Therapy
Side Effects of Hyperbaric Oxygen Therapy
Hyperbaric oxygen is usually well tolerated with few side-effects. However, there are some side effects that patients may experience.
Visual Refractive Changes: Hyperbaric oxygen therapy treatments can temporarily change the shape of the lens in the eye. This usually results in worsening myopia (nearsightedness), but improvement in presbyopia (the inability to focus on objects near the eye due to age-related changes in the lens). This change usually reverts back to its pre-treatment status 6-8 weeks after treatments stop. Rarely, the change will not completely return to its baseline level.
Cataract Maturation: While HBO therapy has not been shown to cause cataracts, there is some thought that it may cause pre-existing cataracts to mature faster than normal.
Claustrophobia: Due to the confined and enclosed nature of the hyperbaric chamber, some patients can develop a feeling of claustrophobia, and those who are already claustrophobic can experience a worsening of their symptoms. Multi-place chamber (such as we operate) can help alleviate some of these feelings due to the size of the chamber. If claustrophobic symptoms become severe enough, pre-treatment sedation can be considered on a case-by-case basis.
Hypoglycemia: Some patients with diabetes experience a drop in blood sugar during hyperbaric treatments. In order to prevent this, patients are encouraged to eat before coming for treatments and blood glucose is monitored during the dive at appropriate intervals.
Complications of Hyperbaric Oxygen Therapy
While it's generally very safe, as with all medical treatments, Hyperbaric Oxygen Therapy carries with it the risk of complications that rarely can be life threatening and/or result in permanent or long-term disability.
Barotrauma of the Ear: Barotrauma is a term that refers to injury due to increased pressure. Barotrauma of the ear is the most frequent complication of HBO. The middle-ear is an air-filled cavity behind the ear drum that connects to the throat through a slit-like passage called the Eustachian Tube. During compression, if the air pressure in the middle-ear cannot be equalized with the external pressure, the ear drum will bow inward, leading to pain and possibly rupture, which can lead to hearing loss.
Round or Oval Window Rupture: Round and/or oval window rupture is a phenomenon that is related to ear barotruama. The round and oval windows are membranes that separate the air-filled middle ear from the fluid-filled inner ear. Rarely, over-vigorous attempts to equalize the pressure in the middle ear can lead to increased pressure in the inner-ear which can rupture these membranes. Deafness is the result. So, while rupture of these windows is not related to pressure change per-se, it is related to maneuverers used to prevent another complication.
Sinus Squeeze: Similarly to the middle-ear, the sinuses are air-filled spaces in the skull. Failure to equalize the pressure in the sinuses and the external environment leads to severe pain and possibly bleeding into the sinuses.
Tooth Squeeze: Recent dental work can leave air-filled voids in teeth. The inability to equalize the pressure in these pockets can lead to pain and even cracking of the teeth.
Pneumothorax or Pulmonary Barotrauma: Pulmonary barotruama is a term that refers to damage to the lung tissue as a result of pressure change that results in air leaking from the lungs into the chest cavity which causes a dropped lung, or pneumothroax. This generally occurs in patients with air trapping lesions in the lungs, such as can occur in emphysema or asthma. During decompression, these air-filled pockets will begin to expand, and if the pressure is not relieved by the airways in the lungs, these pockets can rupture. This released air can cause excess pressure in the chest cavity leading to difficulty breathing and decreased blood pressure that can result in death if untreated. Treatment consists of emergency evacuation the air from the chest cavity by inserting a needle through the chest wall, and, subsequently, placing a chest tube to re-expand the lung.
Oxygen Toxicity Seizures: The high level of oxygen in the blood that occurs during HBO treatments can be toxic to the central nervous system and can result in seizure activity. While this is rare during clinical hyperbaric treatments, it does occur and may be more likely in those with pre-existing seizure disorders or hypoglycemia (low blood sugar). Treatment consists of simply removing the supplemental oxygen from the patient, which will terminate the seizure.
Pulmonary Oxygen Toxicity: Similarly to the brain, elevated oxygen concentrations can be detrimental to the lungs. Prolonged exposure to high level of oxygen can eventually lead to chest pain, difficulty breathing, and eventually, respiratory failure. However, in the early stages of the condition, the lungs rapidly return to baseline once the oxygen concentration is decreased. Thus, due to the intermittent nature of HBO treatments, pulmonary oxygen toxicity is rarely seen in clinical practice. On the other hand, this can become a concern in critically-ill patients who must be maintained on supplemental oxygen between treatments or those patients who require unusually frequent or prolonged treatment courses.
Decompression Sickness: Decompression sickness, or the bends, is a result of the uptake of nitrogen into the blood when air (which is ~80% nitrogen) is breathed at increased ambient pressure. This is generally more of a concern for the inside attendants, who breathe air during a treatment, rather than patients, who are breathing 100% oxygen. However, this can become a concern if a patient must be removed from oxygen for prolonged periods of time during the dive. Decompression sickness can result in pain, neurological injury, cardiopulmonary collapse, and possibly death.