Ted was stoked to begin his training as a rebreather diver. He had been working toward this goal for several years, building up his dive experience and researching the best unit for his needs. Now he was nearing the end of his first tec closed-circuit rebreather diving course.

He was a bit uncomfortable, struggling to catch his breath, but he chalked it up to nerves and getting used to the closed-circuit device.

The Diver

Ted was a 51-year-old male and an experienced, certified diver. He had reached a personal income level that allowed him to travel more. He wanted to up his dive game by learning to dive with a rebreather system. He looked forward to the extended bottom time the device provided, along with the ability to move silently through the water. As an avid underwater photographer, he hoped it would help him get closer to sea life so he could capture critters in their natural state.

A year earlier, he had consulted a local dive instructor about what he needed to do to get rebreather certified. Since then, he had been working toward the goal, logging hours underwater and practicing his diving skills.

The Dive

After reviewing the techniques unique to diving a rebreather system in a pool, Ted, his dive buddy and their instructor made their way to open water for a series of checkout dives. Conditions were good on the ocean as they entered the water from a local charter boat that was accustomed to working with technical divers. The boat and its crew didn’t have a problem with them making long, deep dives, and everyone on board was a tec diver.

Ted’s group planned the dive for 90 minutes at a max depth of 130 feet of seawater. They made their way gradually toward the final depth, descending along the reef structure.

The Accident

The divers had been in the water for 45 minutes, slowly making their way to their planned maximum depth. At 97 feet, Ted began struggling to breathe. He signaled that he was having trouble with his rebreather unit and indicated he needed to ascend to the surface.

One hard and fast rule of technical diving is that any diver can call any dive for any reason.

When Ted indicated he was having a problem, the instructor immediately agreed that they should end the dive.

All three divers began ascending toward the boat. On the way, Ted lost consciousness. The group had obligatory decompression time, but they ignored it and continued toward the boat to get Ted the help he needed.

The boat crew immediately began lifesaving procedures, but Ted could not be resuscitated.

Analysis

An after-accident analysis of Ted’s gear indicated his rebreather system was working normally. The equipment wasn’t to blame for this dive accident. Although the group omitted decompression on the way to the surface, that wasn’t the cause of this accident either. Ted’s problems began at depth.

Neither of the divers with Ted exhibited any symptoms of decompression sickness because of the omitted decompression, although they did not return to the water and were observed for the rest of the day to make sure no problems arose.

After performing an autopsy, the medical examiner determined that Ted had a cardiac event underwater. He had dilated cardiomyopathy, hypertensive heart disease (high blood pressure) and coronary atherosclerosis (hardening of the arteries). He was also obese and had a medical history of sleep apnea.

A dilated cardiomyopathy is a weakening of the heart’s primary pumping chamber, the left ventricle. This can be caused by a variety of conditions, including coronary artery blockages, long-standing high blood pressure, diabetes mellitus and viral infections. In fact, in a large percentage of cases, doctors are unable to determine the underlying cause of the condition. Regardless of the cause, this weakening of the heart muscle can result in a multitude of problems, such as fatigue, shortness of breath and life-threatening heart-rhythm abnormalities.

There is a special concern for divers with dilated cardiomyopathy. When humans are immersed in water (swimming or diving), there is a fluid shift of about 700 cubic centimeters (about 1.5 pints) from the periphery to the central circulation. In patients with dilated cardiomyopathy, this additional fluid load might not be tolerated by the heart, resulting in symptoms of severe shortness of breath from congestive heart failure. While we will never know for sure, this is probably what happened to Ted.

In preparation for learning to use the rebreather system, Ted spent a lot of time diving and working on his underwater skills. He also studied the physics of mixed gases. What he didn’t focus on was the physiology of diving and preparing his body.

What is important to remember is that diving, be it on open-circuit scuba or a rebreather, puts additional strain on the body. Water provides more resistance than air, so your body has to work harder to move. Your breathing is somewhat restricted, and you might need to exert yourself if, for instance, you are caught in a current and have to swim harder to get back to the boat.

Additionally, having a cardiac event underwater or on a dive boat makes it much more difficult to get to emergency medical care. At your local mall, you can expect to receive bystander care within moments. Emergency medical services will likely arrive with a full range of equipment and medicine to stabilize you before you get to the hospital, likely in less than 10 minutes.

On a dive boat, even with the best-trained crew available, there will be delays getting you out of the water and out of your gear before care can begin. And then there are longer delays getting you to advanced medical care.

We don’t know if Ted knew about his heart condition; it’s likely he did not. His doctor had diagnosed him with high blood pressure and sleep apnea, but Ted wasn’t controlling either condition well.

All of that reinforces the importance of being physically fit for diving. Ted was 51 years old, but his medical history indicates that he probably should have had a conversation with his doctor about diving and what those conditions meant to his overall health. During his year of preparation for technical diving, he should have spent more time training himself physically and managing his health complications.

There is a possibility that if Ted had been given a stress test, an echocardiogram and a complete physical, a diving physician would have told him he should consider giving up diving. While that choice might be unthinkable to some, the idea of dying on a dive boat, putting your dive buddy at risk in the process, is inarguably worse.

Douglas Ebersole, M.D., consulted on this column. He is an interventional cardiologist at the Watson Clinic in Lakeland, Florida, and the director of the Structural Heart Program at Lakeland Regional Health Medical Center. Additionally, he is a cardiology consultant to Divers Alert Network, as well as an accomplished diver and closed-circuit rebreather instructor.

Lessons for Life

• Stay fit for diving. Exercise regularly, and manage your weight.
• Taking medication does not necessarily prevent you from diving. Rather, the underlying condition the medication is intended to treat is the concern.
• Consult a physician familiar with diving to ensure you are fit to dive, especially if you have any medical conditions thought to be a contraindication.