'Shock response' holds key to drowning

University of Otago Associate Prof Chris Button is researching links between the shock of falling into cold water, and drowning. Photo by Peter McIntosh.
University of Otago Associate Prof Chris Button is researching links between the shock of falling into cold water, and drowning. Photo by Peter McIntosh.
Many drowning deaths can be prevented if people who fall into cold water keep calm and let the body's initial shock response wear off, ''dramatic'' new University of Otago research suggests.

Associate Prof Chris Button, of the Otago School of Physical Education, Sport and Exercise Sciences, and his colleagues have been testing the body's response to sudden cold water immersion, with support from Water Safety New Zealand.

And ''incredible'' results had been achieved, after study participants were plunged into 10degC water in the school's flume (pool), he said.

They recovered from the cold shock response in two to three minutes.

And researchers also found, that with repetition and basic mental training, the duration and intensity of this ''shock response'' could be halved.

After a week or so of repeated immersions, combined with mental skills training, and basic suggestions to improve treading water technique, the participants were ''much calmer in the cold water''.

This behaviour change ''blew me away'', he said.

The research findings could help ''dramatically reduce New Zealand's horrific drowning rates'', and also applied even when water was considerably colder.

Drowning is New Zealand's third highest cause of unintentional death, and there were 81 drowning-related deaths last year. Most drownings were thought to occur in the first few minutes after falling into the water. The body's ''shock response'' was to blame, he said.

An early ''gasp response'' was followed by rapid hyperventilation.

And often when people gasped, they also breathed water into their lungs and drowned, he said.

In the South, holidays were often spent beside icy lakes, rivers and the sea.

And people fell into rivers, from capsizing boats, or were swept off rocks while fishing.

It was ''absolutely critical'' that, instead of panicking, people who had fallen into the water should ''take a moment'', knowing that after two or three minutes they would be able to ''breathe more smoothly'', he advised.

After their bodies had adjusted to the cold, people should also avoid taking a ''bad decision'' and decide their best plan for survival.

Prof Button and Water Safety New Zealand have compiled a list of survival tips, which include remaining calm; holding the breath for the first five to seven seconds, if possible, after immersion, to avoid gasping; and floating initially, before deciding on the best survival plan.

Trying to swim while still affected by initial cold shock was ''probably the worst thing you could do'', Prof Button said.

Water Safety New Zealand chief executive Matt Claridge said the Otago findings were important and, combined with other efforts, could help cut the country's drowning toll.

- john.gibb@odt.co.nz