Take a Breather

 - October 8, 2007, 10:56 AM

On the day of AIN’s visit to Survival Systems, a group of paramedics was finishing up a two-day course on the use of emergency breathing systems–small air tanks that hold up to 30 breaths of air. Such systems are available from any dive shop for about $350. Ask for a diver’s “pony bottle” and a conventional two-stage regulator.  Submersible Systems of Huntington Beach, Calif., manufactures a line of mini-tanks known as Spare Air (www.spareair.com). They have a built-in breathing regulator–easier to pack but a bit less convenient to use, according to Survival Systems’ training manager Tom Lazzaro.

Products from Submersible Systems are standard equipment for military pilots, some emergency medical crews and some helicopter operations that serve offshore oil rigs. According to Survival Systems, an increasing number of private pilots are carrying some form of such tanks. Unfortunately for most corporate pilots, the tanks cannot be carried on pressurized aircraft because of the danger should there be a rapid cabin decompression.

At Survival Systems, Lazzaro, a veteran dive instructor, started the morning session with a simple admonishment. He said, “I’m going to spend the next 45 minutes explaining why you need to remember five simple words: ‘Do not hold your breath!’”

He followed with a diver’s-eye view of what happens to lungs that breathe in pressurized air from depths of as little as 15 ft and then rise to the surface without exhaling. Lazzaro explained that the lung, rather than being like one big balloon, is more like thousands of tiny balloons called alveoli that inflate and deflate as they absorb oxygen from the air we breathe in. At 33 ft underwater, air becomes compressed the equivalent of one “atmosphere.” So if you take a breath of air at 33 ft and don’t exhale on your way to the surface, each individual alveolus could expand and burst, releasing air into the chest cavity where it doesn’t belong. Because each alveolus is self contained, there is no feeling of the lungs expanding like a balloon should a diver ascend too fast while holding a lungful of air. It seems counterintuitive, therefore, that the diver who exhales all the way up does not feel as though the lungs are “emptying” as he or she blows bubbles all the way to the surface. But it’s true.

Part of the course involved a taped testimony by a Royal Air Force helicopter pilot who ditched unexpectedly, was temporarily trapped in the cockpit and used his emergency breather to buy time to get away. In common with many who have used the apparatus, the RAF pilot spoke of a heightened sense of calm the instant he took his first breath from the bottle. His panic eased, he was able to extricate himself from the cockpit window and survive, whereas he almost certainly would have drowned otherwise. According to Lazzaro, the deepest successful survivor recovery from a ditched aircraft came from 65 ft below the surface.