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pre-breathe

Please Do Not Walk and Pre-Breathe

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We’ve all seen our share of funny videos of people who are so captivated by their cell phones that they unknowingly walk into a glass door or fall into a public fountain. They are so engrossed in their technology that they do not even notice the world around them. They end up injured or sometimes dead. Divers that walk while pre-breathing their rebreather can be victims of similar dire outcomes with a slightly different motivation. Divers who walk while pre-breathing are often completely disconnected from their technology. They are watching their feet, instead of PO2.

But this is no joke. I have thrice attempted to revive these victims of inattention. One we could laugh about, one was a near miss and the third unrecoverable. Yes, he died. The first victim was waltzing to the entry deck while pre-breathing his unit, feeling satisfied that he looked quite cool. I saw him go down like a board, face first into the dirt. You know the faints you see in movies when somebody’s knees crumble beneath them in a swooning collapse? Apparently this guy didn’t see the movie. Straight as a soldier at attention he passed out. He had failed to open a cutoff valve and quickly went hypoxic while walking. He wasn’t looking at his displays. Fortunately, he was able to laugh about the situation afterwards and realized he had to change his procedures.

The second victim was not so lucky. The diver was standing in shallow water, awaiting his dive partner who was 100 yards away and behind a trailer. The victim was breathing his loop, standing in knee deep water while trying to put on his fins. At some point in the sequence, he passed out from hypoxia having failed to engage a switch that offered access to his onboard oxygen supply. I was inside the nearby trailer when my colleague Wes Skiles came bursting through the door yelling “911!” I leapt to action, helped drag the diver out of the water and offered CPR for over an hour until a Medivac helicopter arrived on the site. The diver died at the hospital.

The third victim was on a boat on the East Coast. It had only been a short week since my last attempted resuscitation. The mental wounds were quite fresh in my mind. I was working on my own rebreather while a nearby diver completed his pre-dive setup and walked to the back of the boat. He was pre-breathing the loop while putting on fins and leapt into the water to meet his instructor on the tag line behind the vessel. I resumed my own prep and a few minutes later heard “help.” I turned to see the instructor on the surface with a ghastly blue diver in his arms. I hardly recognized the man as the one I had seen on deck moments before. I jumped into the water and raced towards the victim. As I reached the pair I wasted a precious breath yelling, “I’ve done too much fucking CPR this week!” I grab the diver and quickly towed him to the transom, both adrenaline pumped and infuriated. I ripped off his mask and blew a full rescue breath into the lifeless man. Through miracle or sheer will of yelling at him, the diver sputtered to life, coughing up and fluttering his eyelids. About twenty minutes later, he was lucid on the boat and apologizing for his errors. It was a good day after all.

I guess I came away from those three situations with a renewed respect for the pre-breathe sequence. Though some recent research indicates that it may or may not offer a diver a chance to detect a CO2 issue such as a poorly packed canister, there are many other things that can be reviewed if you are paying attention. You can watch the PO2 change, listen to the solenoid valve, recheck gas supplies, depress manual add buttons, review gas mixtures, confirm set point, and check every other useful parameter including correct time and date. You can take a meditative moment to mentally prepare for the dive ahead and pre-visualize solutions to any potential problems that might lie ahead. So please, do us all a favor. Sit down, block your nose and spend five minutes assuring a safe and operational rebreather. Don’t jump in the water unless everything has passed your safety check. Then perhaps fewer of us will have to toss and turn at night with disturbing memories of divers who paid the ultimate price for a momentary lapse in judgement.

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Will Pre-Breathing Your Rebreather Save You?

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Pod Diver Radio interviews Simon Mitchell about his recent study into pre-breathing rebreathers. The results may surprise you! Listen to the the interview!

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Efficiently Pre-Breathing the Hollis Explorer

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Explorer Pre Breathe  7661When preparing the Explorer rebreather you will eventually reach the point where you are prompted to complete a pre-breathe. If you have difficulties getting through the five-minute sequence, try this tip. Begin by exhaling into the counterlungs until full, then start your pre-breathe in a safe seated position. By launching the sequence with “dirty air,” the unit will quickly jump into action to raise the PO2 and you will easily work through the pre-breathe without getting timed-out for inadequate ventilations. If you want to speed up your pre-dive check, add an optional CO2 sensor and watch the sequence shorten to one minute!

 

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