I became scuba certified when I was 12, diving with my family in the warm clear shallow waters of Florida and the Caribbean. I was fascinated and terrified by my parents’ stories of black water diving for megalodon teeth in the Cooper River. After living on the coast in Charleston for medical school, I vowed to always live by the ocean, so I moved to San Diego for my EM residency and never left.
Wilderness medicine, particularly marine medicine and diving medicine, have become my focus area. I love to lecture on survival at sea and find myself drawn to the incredible stories of those who endured our earth’s greatest wilderness. Maybe this fascination is rooted in a Hobie catamaran incident when I was a child, or perhaps because I am continually amazed by the vast unknown of our beautiful yet hostile one-world ocean. With more than 40% of the U.S. population living in coastal regions, clinicians should be familiar with the essentials of caring for patients in the marine environment. That is why I helped lead the design of the Diploma in Diving and Marine Medicine offered through the Wilderness Medical Society.
The Titan submersible has brought international attention to several of the important areas of diving and marine medicine. This tragic event was ultimately due to a catastrophic and immediate implosion without time to realize what had occurred. However, the ultimate cause was not known for days as multiple countries with various assets joined together to try and locate and rescue the five person crew.
Let's look at the incident through the lens of the “Rules of 3” principle for survival to better understand how these rescue operations were approaching the situation and what the crew would have been prioritizing had the structural integrity of the vessel remained intact.
Rules of 3 of Survival:
- 3 minutes without breathable air
- 3 hours without shelter
- 3 days without water
- 3 weeks without food
- 3 months without companionship or hope
3 minutes without breathable air: This rule typically refers to how long one can hold their breath (drowning, icy water, space). There are some impressive breath-hold diving records (24 minutes and 37 seconds!), but most of us resort to scuba diving to survive underwater for longer periods of time. The Titan crew’s “3 minutes” was greatly extended by the reported 96 hour emergency air supply; however, that still felt limited as the rescue clock counted down. Symptoms of hypoxia vary from person to person, but all would have developed a certain degree of incapacitation in an increasingly hypoxic environment.
While the media focused on attempting rescue prior to severe hypoxia, the other component — hypercapnia — was rarely mentioned. Ventilatory management of acute respiratory failure in the ED or the ICU can be equally challenging when carbon dioxide levels are sky high. The development of hypoxia and hypercapnia would have been a more gradual process for the crew, all breathing out carbon dioxide that had no place to go without a working battery for proper ventilation or CO2 scrubbers. Worsening hypercarbia would have initially caused headache and fatigue and eventually led to confusion, seizure, and coma.
3 hours without shelter to survive a harsh environment (hypothermia, pressure): Hypothermia was another focus of rescue considerations. Water conducts heat 25 times faster than air, which is why we emphasize always getting as much of your body out of the water as you can in a survival situation. We all remember the scene in Titanic when Jack is submerged in the water (an estimated 28°F (-2°C) at the time of sinking) with Rose floating on debris — she could have scooted over! The average water temperature surrounding the Titanic shipwreck, located greater than 12,500 feet below the surface, is estimated to be 39°F (4°C). When discussing cold water immersion, it just takes water temperatures below 59°F (15°C) to provoke significant physiological responses that affect how well we can participate in our own self-rescue. As hypothermia progresses, meaningful movement is impaired, shivering is lost, and alertness wanes before losing consciousness and being so cold that one is at risk of spontaneous ventricular fibrillation or asystole. Equally important is handling severely hypothermic patients gently as you rewarm them to avoid provoking an already irritable cold heart.
The Titan’s 5-inch-thick carbon fiber internal hull plus the external glass fiber would have decreased conductive heat loss from the surrounding to a certain degree. There was a heater on board that was presumed nonfunctional due to battery failure. Regardless, increasing time at extreme depths in freezing water temperatures under pressure would certainly have accelerated the development of hypothermia, further complicating a rescue mission.
Ultimately, we learned that it was the loss of pressure that led to the demise of these individuals. Pressure increases by one atmosphere for every 33 feet in saltwater. The submersible was under 400 atmospheres of pressure. By comparison, most recreational scuba divers stick to profiles between two to three atmospheres, roughly the same as an inflated car tire. The world's deepest human dive on open circuit scuba was to 1,090 feet (33 atmospheres) in the Red Sea. Even the remarkable Cuvier’s beaked whale, the deepest diving marine mammal, has only been tracked down to 9,874 feet (roughly 300 atmospheres). Had the submersible been recovered, further considerations regarding need for decompression treatments would have been dictated on whether the vessel had maintained its internal surface-like atmospheric pressure. There was no time for the crew to feel the effects of common types of barotrauma, including ear, sinus, mask, and suit squeeze. Dental implosions have been described in diving medicine and result from air trapped under faulty fillings or implants that collapse while descending in the water column. If painful dental implosions can happen in recreational divers at relatively shallow depths, then one can imagine the force of this incident.
The remaining rules of three don’t apply to this case as their survival limit was dictated by the above.
I believe that through wilderness medicine we can bridge the gap between health care and the great outdoors, reconnecting us with the inherent healing power of nature. I hope that oceanographers, engineers, and medical professionals alike can learn from this tragedy so that we can continue to appreciate nature’s most challenging environment under safe conditions.
Dr. Coffey is an EM doctor at UC San Diego, where she runs their wilderness medicine program (with focus on marine and diving medicine). She is the prior chair of the Wilderness Medicine Society's (WMS) Diploma in Diving and Marine Medicine and is the conference chair for the annual Marine Medicine and Medicine at Sea courses through the WMS.
Image by Malte Mueller / Gettyimages