In the Grip of Narcosis | Scuba Diving

In the Grip of Narcosis

March 2005

The valve shutdown drill had been easy for Brent in the pool, but here in the quarry at 140 feet, it had gone horribly wrong. Now he was narced out of his mind and desperate for his next breath. His alternate reg wasn't working, so he switched back to his primary second stage, only to find it was dead, too. Now in a full panic, he gripped the ascent line to pull his way to the surface. Suddenly his instructor was in the way, and for some odd reason, kept trying to grab Brent's mask. Furious that the man was blocking his access to the surface and its life-giving air, Brent pushed his instructor away and lunged toward the surface. His lungs ached, and all he could think about was getting air.

The Diver

Brent was in his early 40s, in good health, and he had been actively diving for about eight years when he was accepted into a Deep Air class. Looking forward to the adventure, Brent eagerly began acquiring the required gear, including twin tanks linked with an isolation manifold, and redundant high-performance regulators.

The Dive

Throughout the course, Brent did everything by the numbers, including a pool orientation with his new equipment and several hours of additional pool training on his own. He also completed two flawless tune-up dives in a local quarry to 120 feet.

On his third training dive--to a depth of 160 feet--Brent felt he was immune to nitrogen narcosis as he effortlessly recorded the detailed notes that his instructor required. He felt confident that he would ace the skill demonstrations yet to come.

Ascending to 140 feet, Brent and his instructor stopped near a log suspended in the water. The instructor signaled Brent to begin the valve shutdown drill. Brent had often practiced the procedure and knew the steps by rote: Close the isolator valve to preserve the gas in the non-leaking tank, then shut down the suspect regulator and evaluate the situation. If the problem isn't resolved, reopen the reg, switch back to it, and shut down the other. Piece of cake.

The Accident

Seeing the hand signal, Brent reached back, closing the isolator in what seemed to be record time. "I'm really getting the hang of this, he thought as he reached back and shut off his primary regulator, forgetting to switch to the alternate second stage. Brent was a little surprised when the primary reg stopped delivering air, but he recovered quickly.

Now breathing on the backup reg, Brent tried to regain his concentration. His instructor signaled that Brent still had a leaking system, so Brent immediately reached back to shut down his secondary regulator, omitting the crucial step of reopening the primary regulator. Brent's instructor saw the mistake and quickly signaled "no."

"What is he talking about? I've got to complete the shutdown," Brent thought, as he continued to turn the valve.

The instructor pulled his student's hand back. "Man, this guy is really screwing with me," Brent thought before jerking away and rushing to turn off the valve.

When the secondary reg went dead, Brent still didn't realize his mistake. Dropping the dead backup regulator, he picked up his primary reg and was surprised to find it did not work.

"My God, I must be out of air!" Brent thought in a sudden panic. The instructor's hand was in his face now. "Why won't he leave me alone? I've got to get air!" he thought, shoving the instructor away and pulling himself up the line.

The Rescue

When Brent shook off his attempts to help, the instructor moved in, placing the second stage directly in front of his student's face, but Brent forcibly pushed him away and surged upward.

The instructor quickly grabbed Brent's fin, pulling himself up the diver's body to quickly open both tank valves. Their computers were screaming as Brent climbed through 80 feet at four times the maximum safe ascent rate. Reaching around in front of Brent, the instructor grabbed one of his student's second stages, holding the purge open and shoving it against his student's closed mouth.

Later, Brent couldn't remember how it happened, but at 50 feet he got his first breath of air and began to calm down. The instructor immediately dragged him down the ascent line to around 100 feet, where they stopped for several minutes while Brent regained his composure. They then ascended slowly, completing their required decompression, and an extra 10 minutes on oxygen at 15 feet. Upon surfacing, Brent was monitored for signs of embolism or DCS. Fortunately, his only injuries were a rope burn on his hand and a bruised ego.


Brent was so focused on completing the drill that he failed to focus on the skill it was designed to teach--that of analyzing and adjusting his gas delivery system to ensure adequate air. This problem was compounded by a false sense of security brought on by severe nitrogen narcosis.

Lessons for Life

  • Narcosis affects every diver differently. Divers must be cognizant of their narcosis limitations and should terminate any dive when safety becomes a question.

  • Complex skills should be practiced first in shallow water and then moved gradually to greater depths. Although Brent had practiced the skills before, he had never attempted them below 100 feet.

  • Divers must understand how and why emergency skills work, not just how to do them. This knowledge is essential to responding effectively in real emergencies.