by Gerry Smith

Divers are at risk for a particular set of maladies that are generally caused by rapid changes in pressure. These include decompression sickness (DCS,) commonly known as “the bends”, and air (or gas) embolisms, which result in either gas bubbles in tissues where they don’t belong. The bubbles from DCS areis from gas that has been dissolved in the body’s tissues during the dive and has come out of solution due to too rapid an ascent. Air embolism bubbles come from the rupture of an over-expanding lung, which can result if a diver ascends holding their breath (generally due to panic). Collectively, these two ailments fall under the term decompression illness (DCI). Routinely, divers manage this risk by carefully controlling their depth, dive time and ascent rates so as not to permit dangerous gas build-ups and by remembering to breath normally and never hold their breath. But when things go wrong and DCI strikes, the most effective treatment is that provided in a hyperbaric chamber – an environment where pressure can be precisely controlled for lengthy periods to allow for controlled release of the problematic gasses.

The Catalina Hyperbaric Chamber, located at the isthmus of Catalina Island on the University of Southern California’s Catalina Campus, was initially built to support the development of Lockheed’s high altitude SR-71 program. Operating at the edge of space, at altitudes above 80,000 feet, the SR-71 Blackbird pilots were exposed to extreme changes in pressure, and the chamber was built to treat pilots who might suffer from altitude DCS as a result of those changes. When the SR-71 program development was complete, the chamber was donated to USC where it was pressed into service to treat divers’ DCI problems.

Most chambers in the U.S. are used primarily for hyperbaric oxygen treatment for wounds or diabetes and secondarily if at all for diving accidents. They are smaller one or two person chambers meant to pressurize only to the equivalent of a 66-foot depth (3 ATA) in order to improve oxygen saturation to damaged tissues. The Catalina Hyperbaric Chamber has bunks to treat two divers and has been pressed into service to treat as many as four with attendant doctors, EMT’s, and tenders. It can pressurize to 165 feet (6 ATA) in order to squeeze bubbles to their smallest diameter to treat embolisms. It is, therefore, ideally suited to treatment of diving injuries.

Catalina is one of the top diving destinations in the world, and more than a million dives are conducted each year in the clean cold waters around this island located only 30 miles south of Los Angeles. As such, it provides an ideal location for a hyperbaric treatment facility devoted to divers. Since minimizing time between the onset of the disease and treatment is critically important, having the treatment facility located within minutes of some of the more popular dive sites saves time and lives. While accidents by recreational or technical divers account for the vast majority of chamber treatments, the presence of an on-site hyperbaric chamber also contributes to the safety of USC Dornsife's Scientific Diving Program, which does the majority of it's training dives almost in the shadow of the chamber facility.

The chamber is staffed by one full-time director, a part-time technician, and a group of about seventy dedicated volunteers who are on call 24/7 to operate the chamber when needed. On weekdays, it is the University’s staff and faculty, as well as residents of the nearby Two Harbors community, who answer emergency calls. On weekends volunteers drawn from the dive community from across the country come out to the island to support divers in need.

USC provides the physical facility for the chamber and administers it. Funding is shared about equally between the Los Angeles County Medical Alert Center and the local diving community. Annual Chamber Day and Chamber Evening activities are always fully subscribed with the gross proceeds going to support the chamber’s work. Local dive operators donate the proceeds of a day’s diving, and local divers fill up the boats for a day of diving that includes a visit to the chamber.

A typical case might begin with an emergency call to the chamber from the US Coast Guard or perhaps from a boat diving at Catalina Island. The chamber staff immediately begins preparing the chamber for patient arrival, and alert the on-call hyperbaric physician at County-USC hospital. By the time the patient arrives at the chamber by boat or helicopter, the chamber is manned and prepped for treatment.

A chamber crew consists of a tender who will accompany the patient into the chamber and tend to their needs during the treatment, an operator who controls the pressure in the chamber and the attached airlock, a timekeeper who records the details of the treatment and keeps everything on-schedule, and a supervisor who manages the treatment.

On arrival, paramedics from Los Angeles County Baywatch assess the patient in consultation via telephone with the doctor to determine whether the problem is likely DCI. If the determination is negative, arrangements are made to transport the patient to the mainland for treatment. If the injury is determined to be pressure-related a doctor will be flown by helicopter to the chamber. Most often, treatment in the chamber is begun on the doctor’s orders even before he or she arrives on scene. The patient and tender enter the chamber, the doors are sealed, and the chamber is quickly pressurized to the target depth specified by the specific treatment protocol.

On arrival, the doctor uses the airlock on the chamber to enter and make a hands-on assessment of the patient. An interesting detail is that the doctor can make an examination, but won’t prescribe treatment while in the chamber with the patient. The reasoning behind this is that the doctor, along with everyone else in the chamber, is affected by nitrogen narcosis, Jacques Cousteau’s “rapture of the deep”, and could make bad decisions while under its influence.

Throughout treatment the patient breathes 100% oxygen for twenty minutes at a time followed by five-minute air breaks to avoid seizures from oxygen toxicity. Treatment is usually continued as long as the patient’s condition continues to show improvement; it is rarely shorter than about five hours but can last twelve hours or more. At the end of the treatment, the patient and tender are brought slowly up to surface pressure and can then exit the chamber.

To learn more about the Catalina Hyperbaric Chamber, go to

About the Author: Gerry Smith is the Dive Safety Officer at the USC Dornsife Wrigley Marine Science Center on Catalina Island. Prior to joining USC he was a senior IT officer for the Cal State University System. He served in the U.S. Army during the Viet Nam war.

Editor’s note: Scientific Research Diving at USC Dornsife is offered as part of an experiential summer program offered to undergraduate students of the USC Dana and David Dornsife College of Letters, Arts and Sciences. This course takes place on location at the USC Wrigley Marine Science Center on Catalina Island and throughout Micronesia. Students investigate important environmental issues such as ecologically sustainable development, fisheries management, protected-area planning and assessment, and human health issues. During the course of the program, the student team will dive and collect data to support conservation and management strategies to protect the fragile coral reefs of Guam and Palau in Micronesia.

Instructors for the course include Jim Haw, Director of the Environmental Studies Program in USC Dornsife, Environmental Studies Lecturer Dave Ginsburg, SCUBA instructor and volunteer in the USC Scientific Diving Program Tom Carr and USC Dive Safety Officer Gerry Smith of the USC Wrigley Institute for Environmental Studies

Previously in this series:

Catching Up with Scientific Diving at USC Dornsife: Surfgrass Monitoring at Catalina

Catching up with Scientific Diving at USC Dornsife: The Robot Submarine

Catching up with Scientific Diving at USC Dornsife: Diving into the Aquarium of the Pacific

USC Dornsife Scientific Diving: Moving Forward to Guam and Palau 2012

USC Dornsife Scientific Diving: Finding My Career Through This Course

USC Dornsife Scientific Diving: The Devaluation of Ecosystem Services

USC Dornsife Scientific Diving: Why USC Dornsife was the Right Decision For Me

USC Dornsife Scientific Diving: Why Experiential Learning is Vital to Academic Life

USC Dornsife Scientific Diving: My Walden South of Los Angeles

USC Dornsife Scientific Diving: Crown-of-Thorns Outbreaks and Anthropogenic Pollution

USC Dornsife Scientific Diving: The International Policy Rationale for the Military Buildup on Guam and Some Environmental Drivers

USC Dornsife Scientific Diving: Marine Ecology from Antarctica to Micronesia