Bubble Trouble: A Look at Hyperbaric Treatment

David is an experienced diver with hundreds of logged dives. He surfaces after his safety stop following a dive to 90fsw for 30 minutes. The dive was not overly strenuous, but he feels extremely fatigued. Within 20 minutes of surfacing, David notices an unusual pain in his shoulder. The pain does not subside and he has no history of injury. He feels lightheaded and weak, and he alerts his dive buddy that something is not right.

Hyperbaric treatment and the bends are terms well recognized by divers. But what exactly is involved in the process from “something is not right” to hyperbaric treatment?

Recognizing DCI

Decompression illness (DCI) actually encompasses two separate conditions: arterial gas embolism (AGE) and decompression sickness. Recognizing the symptoms is important, but differentiating between the two is not critical in the pre-hospital setting (or from the first responder perspective) as both conditions are treated with oxygen and ultimately with hyperbaric oxygen therapy.

AGE symptoms generally appear during or immediately after surfacing and commonly present with sudden unconsciousness or neurological symptoms. If survived, symptoms can include unsteady gait, disorientation, paralysis, weakness and personality changes. AGE may be associated with pulmonary barotrauma which may manifest with bloody froth seen in the mouth or nose.

Decompression sickness is typically characterized by a rash; pain that does not subside in arms, legs or torso; dizziness; numbness or tingling; paralysis; or extreme fatigue exceeding the exertion of the dive. Divers may also have trouble walking or may collapse. These symptoms typically appear within 15 minutes to 12 hours of surfacing. Symptom onset after 24 hours makes the diagnosis increasingly uncertain; however, delayed symptoms may occur if the diver flies after diving.

Responding to an Injured Diver

If you suspect that a diver has a dive-related injury, safely monitor the ABC’s: airway, breathing and circulation. If you are a trained oxygen provider, administer 100 percent oxygen to the diver. This is a vital step in helping to mitigate many dive injuries.

After you have assessed and stabilized the diver, contact local EMS for onsite assistance or transport to a medical facility. While maintaining oxygen therapy, doctors may also prescribe necessary fluids and medications and rule out any illnesses other than DCI.

After you have contacted EMS, call the DAN Emergency Hotline at +1-919-684-9111. While DAN cannot make a diagnosis over the phone, DAN can help recognize signs and symptoms, provide advice on first-responder care and coordinate transportation or evacuation to a higher level of care. DAN medics consider several factors to determine a diver’s risk of DCI, such as the dive profile, provocative nature of the dive, symptoms and timing of symptom onset following a dive.

If an injured diver is referred to a medical facility, the physician conducts a series of noninvasive neurological and cognitive assessments. The diver may be asked to perform simple tasks similar to those involved in a sobriety test, such as walking in a straight line heel to toe, crossing their arms, touching their finger to their nose or even drawing simple, familiar geometric shapes.

Next, if the physician concludes that the injured diver is bent, the diver may receive hyperbaric oxygen treatment. If the physician is not familiar with dive injuries, DAN can facilitate specialist consultation to help guide treatment.

The Chambers

Based on the description of the injury, DAN selects the hyperbaric chamber that best fits the injured diver’s needs. It is not advisable to take an injured diver to a chamber without contacting DAN first. Facilities may not be open, operating, staffed or properly equipped to meet the specific treatment needs of the diver. DAN maintains an up-to-date database and will ensure help awaits upon your arrival.

The two types of recompression chambers generally used to treat DCI are multiplace chambers and monoplace chambers. The major difference between the two is the number of patients they can accommodate. Let’s take a tour of both.

The most frequently used design in hyperbaric centers is the monoplace chamber. These chambers are comprised of a clear acrylic and can accommodate a single recumbent patient. The chamber is pressurized with pure oxygen. These chambers pressurize to a maximum of 3 atmospheres absolute (ATA), which equates to the approximate pressure experienced at 66fsw. Monoplace chambers may be equipped with communication intercoms and monitoring systems, and they are generally reserved for less severe cases of DCI.

A multiplace recompression chamber can accommodate several patients. A clinical staff member is present inside the chamber at all times to provide assistance and monitor therapy. There are communication features that enable direct verbal interaction between those within the chamber and the supervising physician or chamber operator who remain on the outside. Because treatments usually take place over several hours, the chambers are also outfitted with comfortable, often reclining seating.

The presence of pure oxygen does present a fire hazard. In the event that there is an ignition source and something to burn, a fire could ensue. In order to mitigate this risk, chamber operators are very careful about fabrics and items permitted in the chamber. Patients are given hospital scrubs to wear, and potentially flammable materials are prohibited from entering the chamber. Any objects that do enter the chamber must be rated for pressure and not pose a fire risk.

Taking a Dive: Hyperbaric Oxygen Therapy

As the patient “descends” to greater pressures in a hyperbaric chamber, he will need to equalize the pressure in his ears, just like he would during an aquatic dive. During compression, the air in the chamber warms up slightly and cools as it decompresses.

A recompression chamber is significantly safer than attempting recompression in the water for several reasons. The chamber is a dry, controlled environment where operators can monitor oxygen intake and temperature, as well as depth and ascent rates. And, in the event of an emergency, there is no drowning hazard.

The goal of recompression is to eliminate the excess nitrogen in the body over a short period of time. During treatment, patients breathe 100 percent oxygen at pressure higher than normal atmospheric pressure. This facilitates oxygenation of the blood, which helps to eliminate the excess nitrogen, reduce the size of the nitrogen bubbles and provides oxygen to compromised tissues.

The presence of bubbles can lead to systemic inflammation (involves the whole body). Hyperbaric oxygen treatment (HBOT) helps to reduce this inflammatory effect and speeds injury repair. Even at surface level, pure oxygen treatment helps to start the recovery process (which is why the administration of oxygen is recommended as a first-aid response to dive injuries).

Throughout hyperbaric oxygen treatment, patients breathe 100 percent oxygen and take scheduled air breaks in order to minimize the risk for oxygen toxicity. During these air breaks, the physician may have the patient perform the same simple tasks as during the initial evaulation to assess neurological and cognitive improvement. The only active aspects of hyperbaric oxygen therapy are the tests and equalizing during descent. Hyperbaric treatments for DCI typically start a pressure equivalent to 60fsw and subsequently move to a pressure equivalent to 30fsw.

There are many different oxygen treatment tables designating specific pure oxygen/normal air rotation requirements. The most frequently used table for recreational dive accidents is U.S. Navy Treatment Table 6.

Caption: Treatment Table 6, shown above, starts patients at 60 feet of pressure breathing pure oxygen for 20-minute increments with five-minute air breaks. The pressure is then reduced to that of 30 feet wherein the patient breathes pure oxygen for 60-minute increments with 15-minute air breaks. Then the pressure is reduced to normal atmospheric pressure. The table is based on four hours and 45 minutes of treatment, but can be lengthened to meet the needs of the patient.

Hyperbaric treatments may last from 5 to 12 hours; they may be longer for more severe injuries and repeated treatments may be necessary to resolve neurological effects of DCI. During treatments, patients are asked to sit back and relax in order to maximize the safety and effectiveness of the oxygen therapy. Boredom can be a challenge, so many chambers feature movies or other forms of entertainment during the treatment.

DAN Is Here For You

There is often an unnecessary stigma about DCI amongst divers; there is no reason to be ashamed or embarrassed if you have DCI. If any symptoms present after diving, call DAN.

Should you need hyperbaric treatment, DAN will be here for you from start to finish. Many insurance companies do not cover chamber treatments or medical evacuations for dive injuries. To avoid incurring high medical costs in the event of an emergency, make sure you have your DAN membership and dive accident insurance plan up-to-date prior to your dive.

If you have any questions about planning for an emergency, contact the DAN Medical Information Line at +1-919-684-2948 or via email. In the event of a medical emergency, call the DAN Emergency Hotline at +1-919-684-9111. To continue your dive training in preparation of a potential emergency enroll in one of DAN’s oxygen first aid training courses.

And most importantly, dive safely!