Drowning Deaths From Unsupervised Breath Holding: Separating Necessary Training From Unwarranted Risk.

In 2011, 2 healthy, young men died in a public pool in New York City while performing breath-holding exercises. This prompted the New York City Department of Health and Mental Hygiene to conduct an investigation into drowning events that involved potentially dangerous voluntary behaviors. They identified 16 cases that occurred in New York state from 1988 to 2011 and recently published a summary of what they termed dangerous underwater breath-holding behaviors in the Centers for Disease Control and Prevention’s (CDC) Morbidity and Mortality Weekly Report. Of the 16 cases, four were fatal. Of note three of the four fatalities, including the two that caused the initiation of the study, were associated with the military. On the morning of July 13, 2011 two young men conducted physical training at an outdoor pool operated by the City of New York. One was an Air Force recruit hoping to join Air Force Special Operations and the other had hopes of one day becoming a member of the Navy Sea, Air, and Land (SEAL) teams. They performed exercises both outside and in the pool and then conducted intentional hyperventilating with underwater breath holding. Despite the presence of two lifeguards and at least 20 other swimmers, they were both found underwater and died. The other military-related fatality in the CDC report was a 17-year-old lifeguard who died a week after being found beneath the surface of a 4-foot deep Young Men’s Christian Association pool in Long Island in February 2008. He was aspiring to become a Navy SEAL and was practicing hyperventilation and breath holding on his own. All three of these aspiring military recruits drowned after performing intentional hyperventilation and underwater breath holding. Hyperventilation is commonly performed before breath-holding exercises in an attempt to reduce the partial pressure of carbon dioxide in the blood. This is done to reduce chemoreceptor stimulation to delay the drive to breathe caused by hypercapnia. This potentially allows the diver to remain underwater longer without the feeling of distress caused by hypercapnia. However, intentional hyperventilation is considered a dangerous activity as it may delay the desire to surface without increasing the partial pressure of oxygen or the ability to remain underwater. Therefore, swimmers may not feel the need to surface until after they have reached dangerous oxygenation levels. This may result in shallow water blackout where the swimmer loses consciousness before surfacing or surface blackout where the swimmer losses consciousness shortly after surfacing but while still in the water. Although underwater breath holding is an activity that may at times seem like a low-risk childhood activity, its risks are becoming more apparent. The risk involved in this activity is of special importance to the military, as many military dive courses require breath holding as a portion of their curriculum. For instance the Army’s Combat Diver Qualification Course (CDQC) requires comfort with underwater activities such as ditching and donning of equipment, knot tying, drownproofing with lightly bound ankles and wrists, and 50 m underwater swims. These skills are similar to the Aquatic Adaptability Evolutions required of students at the Naval Diving and Salvage Training Center. Many of these courses expect quick progression of skills and have low pass rates. Therefore, many motivated students attempt to develop these skills prior to reporting, often without formal supervision. Breath holding exercises are not just a danger to trainees. This was unfortunately made evident when two fully trained Navy SEALs drowned as a result of breath-holding exercises at the Naval Special Warfare Group 2 Combat Swimmer Training Facility at Joint Expeditionary Base Little CreekFort Story, Virginia in April 2015. The two SEALs were performing breath-holding exercises despite rules prohibiting them during nonofficial workouts and despite having been verbally warned not to. They were discovered at the bottom of the pool and both died as a result. A review of the Navy Safety Center’s accident reports for Fiscal Years 2009 to 2015 identified four additional deaths while breath holding. In 2013, a Navy SEAL drowned while spearfishing on a training free dive in Hawaii, a sailor died when he became tangled in a rope spearfishing in San Diego, and a sailor drowned while breath holding on a training dive in Guam. In 2014, another sailor drowned while breath holding for spearfishing in Guam. It is suspected the hyperventilation was performed during some of these accidents. The military diving community is full of members who have volunteered for dangerous missions and who train hard in preparation. The qualifying courses to enter this community often require people to push their boundaries. It is expected that preparation for these courses will therefore be pushing boundaries as well. This is not unique to diving courses. It is expected that new military recruits will work Division of Anesthesiology, Department of Surgery, Walter Reed National Military Medical Center 8901 Rockville Pike, Bethesda, MD, 20889. doi: 10.7205/MILMED-D-16-00246