Breath-holding research could save lives

July 13, 2006, volume 36, no. 6
By Carol Thorbes

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Helicopters need to be equipped with breathing systems that passengers can don before their choppers crash into ice-cold, open waters, if federal regulators are to improve the abysmal survival rate in such accidents.

Simon Fraser University kinesiologist Matthew White's research team reached that conclusion after investigating further another group's study that found helicopter-crash survivors in warm water need 28 to 92 seconds to escape.

White is helping policymakers decide whether specially designed breathing systems for people such as peacekeepers and offshore oil rig workers, whose jobs take them over open water, are necessary.
Eighty percent of helicopter passengers survive an initial crash, but only 20 percent of them escape drowning.

In 2004, White's team found that in zero Celsius water, which approximates the temperature of northern open oceans, women could hold their breaths for only 15 seconds and men for only 25 seconds. Those breath-hold times were in resting, face-immersion experiments.

They dropped by 30 to 40 percent when the physical exertion of escaping from a submerged helicopter-crash simulator was factored in.

White's group's latest discovery is that average-sized women can't hold their breath as long as average-sized men — not for genetic or gender-based reasons — but because men usually have a height advantage.

Women and men of the same height can hold their breaths equally long. “This follows since there's a difference in lung capacity tied to height variation,” says White. “Taller individuals, irrespective of gender, generally have larger lung volumes and as a consequence this helps prolong breath-holding.”

White's latest research also indicates that helicopter-crash survivors in sub-zero temperature water (20 degrees C) have a potentially fatal gasp response from the moment their face hits cold water.

While an average-sized man's breath-hold time dropped a further 38 percent from what it was in zero or above zero water, an average-sized woman's dropped a further 66 percent.

The involuntary gasp was only evident in cold water. White's team believes this cold-induced drive to breathe was responsible for the severely shortened breath-hold times.

White says that there's no point in training helicopter passengers to hold their breaths longer underwater in the cold-water conditions of the North Atlantic and Pacific.

He adds: “They need to be wearing breathing systems before their faces even hit the water and during their escape swim to the surface.”

White is collaborating with researchers at Memorial and Dalhousie Universities in eastern Canada.

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