Main Menu
Join Undercurrent on Facebook

The Private, Exclusive Guide for Serious Divers Since 1975 | |
For Divers since 1975
The Private, Exclusive Guide for Serious Divers Since 1975
"Best of the Web: scuba tips no other
source dares to publish" -- Forbes
October 2006 Vol. 32, No. 10   RSS Feed for Undercurrent Issues
What's this?

Why Divers Die: Part I

embolism, the silent killer

from the October, 2006 issue of Undercurrent   Subscribe Now

For all the fear factors associated with the bends, it doesn’t kill divers. In DAN’s (Divers Alert Network) recently released 2006 report of U.S. and Canadian dive injuries and fatalities in 2004, DAN reported no fatalities due to DCS. Arterial gas embolisms (AGE) are the killer, occurring in 20 of the 88 fatalities studied.

As divers know, an AGE is caused when air pressure builds up excessively in the lungs, resulting in gas bubbles being carried to major organs, including the brain. With full lungs, a rise of just a few feet can cause an embolism. For example, 20 years ago, filmmaker Ron Church was filming in bluewater, holding his breath to steady his camera. He rose only a few feet, embolized and died.

You don’t have to dive deep to suffer an embolism. A 56-year-old who attempted to retrieve an anchor 17 feet deep surfaced in distress, called out for help, and quickly passed out (a classic sign of an embolism). Resuscitation efforts were unsuccessful. The diver was certified but had made only two dives in twelve months. The autopsy revealed a pulmonary barotrauma (gas forced through lung tissues, a prime cause of AGE).

One open-water student was practicing rescue procedures in a lake and ascended from 15 feet. While towing a fellow diver, the 50-year-old male began to struggle and then lost consciousness. Resuscitation efforts were unsuccessful. The autopsy found changes associated with drowning as well as intravascular gas.

Experienced Divers Can Err

Keep in mind that experienced divers can also make the mistake of rising while holding their breath. Eric Seibel, a popular dive instructor, was exploring the Lowrance, a wreck near Pompano Beach, Fl. Using trimix, the 50-year-old Seibel reached 192 fsw, then ascended to 80 fsw before heading back down to 150 fsw. His dive partner, an anesthesiologist, saw him “seizing . . . with the regulator hanging out of his mouth.’’ Seibel lost consciousness and seized the entire time he was assisted to the surface and brought aboard the Miss Conduct. Another diver said that he was bleeding from his ears, mouth and throat and was “white from head to toe.” Though six paramedics tried to revive him, he died. The autopsy, which noted his obesity, disclosed gas in the blood vessels of the brain, neck, and chest, indicative of an air embolism. However, DAN says that using trimix “would have had a low risk of causing a seizure but that is also a possibility.” Seibel founded the website,

Drowning is always the most cited cause of death — 64 percent of the fatalities 2004 — but DAN identified drowning as the disabling injury in only 29 percent. Many reported drownings were triggered by embolisms.

For example, a 48-year-old female who had received her open-water certification a month earlier died after making a shore-entry solo dive. She stayed in 15 fsw, but surfaced and called for help before losing consciousness. Her body was recovered from the bottom three hours later. The autopsy cited drowning as the cause of death, which DAN determined was probably triggered by an AGE.

Rapid ascents are the primary cause of AGE, and the primary cause of rapid ascents is running out of breathing gas. One would presume that divers with advanced certification would not normally run out of gas, but that’s what happened to a 58-year-old with an advanced certification and modest diving experience. He spent 34 minutes at 70 fsw and ran low on Nitrox. During ascent he separated from his buddy and later surfaced after dropping his weight belt. He had removed his mask and his tank was empty. In the boat he became unconscious and could not be resuscitated, a victim of an air embolism.

A 47-year-old male made a boat dive with a group of four, including a divemaster, and descended to 33 fsw. He used nearly his entire tank within 30 minutes, but declined the divemaster’s alternate air source. The divemaster surfaced with him and sent him back to the boat before going back down. The morbidly obese victim lost consciousness on the surface and died. The autopsy showed intravascular air in the blood vessels of the brain and heart as well as pulmonary barotrauma. His dive computer showed several rapid ascents.

You’re Never Out of Air

The irony, of course, is that a diver is never totally out of air at depth. One can always get a couple of extra breaths from an “empty” tank as one ascends and the ambient pressure decreases. Even a partially tank-inflated BCD can provide an emergency breathe or two. Training agencies don’t teach these techniques because they find them too complicated to master – especially in today’s truncated certification classes.

Yet if you must “blow and go,” the U.S. Navy recommends an ascent rate of 30ft per minute,” about half as fast as your bubbles rise. (Older divers were taught 60 ft. per minute.) Of course, you should breath normally while going up. Looking up while ascending extends your neck to help keep your airway open (and ensures you don’t slam into a boat hull). Some folks find that humming helps them remember to exhale. If your ascent is uncontrolled, spread your arms and arch your back until your body is almost parallel to the surface to create more drag and slow you down.

These are basic practices, which most of us have never reviewed, and panicky divers often forget such lessons. In their panicked state to survive, they can endanger others. A 57-year-old woman had trouble with her mask and regulator on a dive to 90 fsw. When she panicked, her buddy tried to render aid and ended up sustaining decompression sickness. The woman lost consciousness after an uncontrolled ascent and was pronounced dead at a local hospital, another drowning due an air embolism.

After plunging to 205 feet in a lake to examine a wreck, an instructor and technical diver panicked during the ascent and skipped her decompression stops. She refused assistance and lost consciousness at 30 feet. She was taken to the surface by her dive buddy, who omitted some decompression and was treated in a hyperbaric chamber. The 42-year-old woman died of an embolism


Symptoms of AGE include blurred vision, dizziness, sudden unconsciousness, loss of motor function, breathlessness, coughing, and bloody froth from the mouth. Fortunately, most cases are not fatal. Michael Strauss, MS, and Igor Aksenov, MD, in their book Diving Science: Essential Physiology and Medicine for Divers, write that “The first response intervention is the immediate breathing of 100% oxygen on the surface. This is so effective that 50 percent of people with AGE have complete remission of their symptoms. People who are unconscious should be placed flat on their backs. This position facilitates turning the head to the side to prevent inhalation of food or fluid into the lungs if vomiting occurs . . .One might think that positioning the patient in the head-down position would reduce the bubble load to the brain, but . . .this probably does not occur. In addition, the head-down position may increase swelling in the brain . . .If the person is alert, oral fluid administration is recommended to expand blood volume and increase blood flow with concomitant oxygen delivery. However, too much hydration can contribute to brain swelling.”

In the next two issues, we’ll continue discussing why divers die, hoping that presenting such cases will help us all dive more safely.

PS: Many of these divers were overweight, if not obese. We’ll look at how excess weight and poor conditioning can increase divers’ chances of problems while diving.

I want to get all the stories! Tell me how I can become an Undercurrent Online Member and get online access to all the articles of Undercurrent as well as thousands of first hand reports on dive operations world-wide

Find in  

| Home | Online Members Area | My Account | Login | Join |
| Travel Index | Dive Resort & Liveaboard Reviews | Featured Reports | Recent Issues | Back Issues |
| Dive Gear Index | Health/Safety Index | Environment & Misc. Index | Seasonal Planner | Blogs | Free Articles | Book Picks | News |
| Special Offers | RSS | FAQ | About Us | Contact Us | Links |

Copyright © 1996-2024 Undercurrent (
3020 Bridgeway, Ste 102, Sausalito, Ca 94965
All rights reserved.