I reached the surface from my 83m/272-foot freedive and vaguely remember hearing the judge shout, “Grab her!” before everything went blank.
I was only out for about a second before I came back around, finished my surface protocol, told the judge “I’m okay,” then realized Robert, my safety diver, had ahold of my arm. “Ohh…I blacked out didn’t I?” I asked. The looks of you’ll-get-it-next-time and sympathetic pats on the back confirmed my worry.
The crazy thing about blackouts is that you don’t always know they happened until someone tells you. I often tell students in class that it’s hard to definitively tell a blackout is coming on, but that’s not the whole story.
The nature of a blackout is to shut down your conscious brain, thereby conserving oxygen for your more important bodily functions, like keeping your heart beating. A freediver awakening from a blackout will experience a number of things including disorientation, remembering strange dreams or simply a confusing time jump from the point of blackout to the return of consciousness.
It’s somewhat common after a blackout to experience a carbon dioxide-induced headache, particularly if the blackout occurred under a heavy workload. Following my 83m dive Dr. John Shedd, our on-site physician, brought me to the boat and put me on oxygen, which is always beneficial following a blackout. I experienced a migraine-like headache and just sat on the boat covering my eyes from the sunlight while the oxygen helped off-gas the CO2 from my system. Within about 10 minutes the headache subsided, but not without getting in a few punches first.
Extreme hypoxia puts a diver’s body under a high level of stress as it tries to maintain oxygen levels in critical areas of the body. Following a blackout its very common to feel extremely physically exhausted. The best thing to do is to give into it and sleep the whole mess off. After a good eight-hour night you’ll feel much better, though depending on the severity of the blackout you may find that it takes a couple of days to feel 100% again. Definitely don’t try to dive again after a blackout until you’ve had at least a day’s rest as it’s very likely you’ll blackout again.
Nope! Blacking out should not cause brain damage (ahem, unless it’s caused by something other than hypoxia!). A freediver undergoing hypoxia will blackout with a reasonable amount of oxygen in their system. Brain damage only occurs four to six minutes after the diver has reached anoxia, or a complete lack of oxygen in the system, which would happen several minutes following a blackout. With proper safety a diver should return to consciousness within seconds after a blackout. ***
So while blackouts are different for everyone, these are the most common reactions to extreme hypoxia that I’ve seen. If you’ve experienced or seen other reactions please feel free to add them in the comments section!
The important thing to remember though, is that all of these blackouts have occurred with proper safety. Blackouts don’t have to necessarily be traumatic events, but without safety there’s only one, pretty permanent result of blackout.
***I changed this section from “Blackouts do not cause brain damage” to “Blackouts SHOULD NOT cause brain damage” as research is still advancing in the sport and though much of what I’ve found (through outside research) over the years indicates to me that blackouts wouldn’t cause brain damage I realize now after some re-evaluation that saying they definitively don’t is too strong a statement.