An Important Advance for Closed-Circuit Divers

With the advent of COVID and the news that people were being intubated in hospitals because their blood oxygen levels were too low, many folks bought inexpensive pulse oximeters to monitor their blood oxygen levels.

Now enterprising researchers at Duke University have found a way to monitor blood oxygen levels in divers while they are underwater, and this could save the lives of those using closed-circuit rebreathers. Rebreathers are an increasingly popular way to dive recreationally.

They discovered these pulse oximeters, adapted to be watertight and attached to the forehead and clipped to the nose, can provide rebreather divers with a 30-second warning that their oxygen levels are dipping dangerously low, and increasing their risk of blacking out.

Rebreather diving is said to be the second most lethal recreational activity in the world per hour, after BASE jumping. It's mainly because the CCR user's breathing is uninterrupted (unlike conventional scuba) because the diver continually rebreathes the same air, replenished with small amounts of oxygen as required. But the actual level of oxygen (PO2) in the gas being breathed may drop to less than life-sustaining levels, becoming hypoxic, resulting in sudden unconsciousness and drowning. It's the most common cause of rebreather fatalities.

A diveable pulse oximeter may give sufficient warning (about 30 seconds) to alert the diver to oncoming hypoxia, who will be able to take remedial action and bail out to an alternate open-circuit supply of breathing gas, which all CCR divers tend to carry now.

See Undercurrent February 2018 Rebreathers: What Every Scuba Diver Needs to Know.