0 MINUTES, 3 SECONDS. Oh, shit! That's your only thought as your kayak wheels upside down through the air over the huge boulder that sits midstream in the river, creating an enormous hole. You manage to suck in one big breathfive liters of air before going under. Since air is made up of four-fifths nitrogen and one-fifth oxygen, this gives you one precious liter of oxygen trapped in your lungs. Plunging headfirst into the hole, you're instantly ripped out of the kayak. The cold water slapping your face triggers your mammalian "diving response": Your heart rate drops and your veins and arteries constrict to channel the oxygenated blood to your brain and organs instead of to your limbs.
0 MINUTES, 12 SECONDS, 825 MILLILITERS OF OXYGEN REMAINING.The
average human can hold his or her breath for about 90 seconds before blacking out. Already, you can feel the strain in your lungs. Sensors in your brain are "tasting" the buildup of carbon dioxide in your blood and signaling your lungs to exhale.
0 MINUTES, 37 SECONDS.Your blood, normally a rich, oxygenated red, is turning blue. Dimly, you feel your arms and legs burn from the buildup of lactic acid caused by oxygen deprivation. Your head breaks the surface of the water and you let out a great sigh of carbon dioxide. Just as you start to take a breath, the hole pulls you back under. You gag, your
larynx in spasms as it reflexively closes to keep water out of your lungs.
1 MINUTE, 23 SECONDS, 220 MILLILITERS OF OXYGEN REMAINING.You
lose consciousness. The water you inhaled has washed out the surfactanta protein coatingthat keeps your lungs' air sacs from collapsing. If rescued now, you could die a few hours later of
"secondary drowning" as your damaged lungs fill with fluid.
4 MINUTES, 21 SECONDS. Your feeble heartbeat pushes some residual oxygen to your brain. On dry land, brain damage begins roughly four minutes after breathing has stopped; after ten minutes there is almost zero chance of recovery. These times can decrease when the victim is underwater, particularly in cold water.
19 MINUTES, 36 SECONDS. Except for the faintest electrical impulses, your brain has stopped functioning. Your body normally would
sink, then rise to the surface as it filled with gases during
decomposition. With the life jacket still on, it gently spins into an eddy a half a mile downstream.