Save your breath: it's cold in there: Personal air recycling is one aspect of research by the Navy into survival at sea. Keith Hindell reports

'THIRTY seconds,' the timekeeper warns the research team, before the start of the experiment. Then the volunteer is swung out in a chair above the cold water tank and, exactly on the minute, is lowered into it.

Chris Eastwood, a physiology student, is joining a long line of his peers from Sheffield University who have helped the Institute of Naval Medicine, Portsmouth, to investigate the body's response to cold water. Chris is wired up so that his vital signs are monitored throughout the 45-minute experiment. Every minute the changes in his skin temperature, rectal temperature, blood pressure, and so on, are recorded by students on three sides of the small pool.

Dr Michael Tipton, of the Robens Institute at Surrey University, is supervising the research, while Surgeon Commander Howard Oakley ensures that the experiment is conducted ethically and that the volunteers' health is never put at risk.

But suffer Chris does. The 15C water in the Royal Navy Immersion Facility, at Seafield Park, Hampshire, soon induces uncontrollable shivering. If Chris's core temperature should reach 35C, he will be pulled out of the water regardless of the needs of research. At 33C core temperature, only four degrees below normal, a human begins to lose consciousness, and at 28C risks cardiac arrest.

Chris's deep body temperature is monitored through probes attached to his ear and rectum; he has swallowed a radio pill, which transmits temperature readings as it passes through his body; his heart rate is recorded on an electrocardiogram and his breathing on a pneumotachograph.

The research team is also testing a hypothesis about movement. When a person is dumped into cold water from a boat or a plane, it is best that they keep still to conserve heat. But if they must move, to avoid danger or reach a raft, is it better to swim with arms and legs or legs alone? To test one theory, Chris simulates swimming with his arms by lifting a weight through a pulley. Other volunteers will simulate swimming with legs only, then with all four limbs.

The natural reaction is to swim flat out for about a minute until one becomes used to the temperature, as if indulging in a warming-up exercise. In fact, the swimmer will be cooling down very fast. Dr Tipton says that it is better to sit still and get used to the water; and in rough water, the 'warming-up' method would be foolhardy.

After thousands of hours of work, medical researchers have discovered that the body reacts to cold water by breathing very hard; this reflex gasping can soon develop into uncontrollable breathing, which in rough conditions means you cannot hold your breath and therefore swallow lots of water. This reaction, known as Cold Shock Response, has led Dr Tipton and his colleagues to conclude that the initial period in cold water is the most dangerous; thereafter, the main risk is hypothermia.

In a plane crash at sea or the ditching of a helicopter, the priority is to escape the sinking craft. A high proportion of flight crew and passengers in North Sea helicopter accidents fail to survive, not because of injury but because they cannot hold their breath long enough to escape the semi-submerged fuselage.

In the light of Cold Shock Response, Eric Bramham, managing director of the survival suit manufacturers Shark Sports, and Professor David Eliott, of the Robens Institute, designed an 'air pocket' with a breathing tube attached. The pocket has a 'passive internal distributor', which enables a survivor to breathe from it even when upside down in water.

When immersion is about to occur, you place the tube in your mouth and re-breathe your own breath. Experiments with not only champion swimmers but also ordinary people have shown that this simple system more than triples the time that people can remain submerged without fresh air, thus providing 40 to 50 extra seconds in which to escape or to adjust to the water temperature without breathing uncontrollably.

Medical scientists have known for 40 years that you can extend your time without fresh air by re-breathing exhaled breath, but it was Dr Tipton who made the link with his research on Cold Shock Response.

Back in the tank, after 37 minutes Chris Eastwood's core temperature drops to 35C and he is lifted out of the water and revived gently in a warm bath. Charts of all Chris's vital signs will go into the bank of cold water research, along with those of hundreds of others.

In extensive tests in Nova Scotia, survival instructors and students have made successful underwater escapes in cold water using the Shark Air Pocket. If it really does help to save lives in real accidents, Sheffield University students will be able to claim part of the credit.

(Photograph omitted)

peopleFrankie Boyle responds to referendum result in characteristically offensive style
Lewis Hamilton will start the Singapore Grand Prix from pole, with Nico Rosberg second and Daniel Ricciardo third
F1... for floodlit Singapore Grand Prix
Arts and Entertainment
'New Tricks' star Dennis Waterman is departing from the show after he completes filming on two more episodes
tvHe is only remaining member of original cast
Arts and Entertainment
tvHighs and lows of the cast's careers since 2004
Fans hold up a scarf at West Ham vs Liverpool
footballAfter Arsenal's clear victory, focus turns to West Ham vs Liverpool
New Articles
i100... she's just started school
ebooksAn unforgettable anthology of contemporary reportage
New Articles
Life and Style
Couples have been having sex less in 2014, according to a new survey
Arts and Entertainment
musicBiographer Hunter Davies has collected nearly a hundred original manuscripts
New Articles
i100... despite rising prices
Holly's review of Peterborough's Pizza Express quickly went viral on social media
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Cover Supervisor

£75 - £90 per day + negotiable: Randstad Education Group: Are you a cover supe...

Marketing Manager - Leicestershire - £35,000

£30000 - £35000 per annum: Ashdown Group: Marketing Manager (CIM, B2B, MS Offi...

Marketing Executive (B2B and B2C) - Rugby, Warwickshire

£22000 - £25000 per annum: Ashdown Group: A highly successful organisation wit...

SEN Coordinator + Teacher (SENCO)

£1 per day: Randstad Education Leeds: Job Purpose To work closely with the he...

Day In a Page

Scottish referendum: The Yes vote was the love that dared speak its name, but it was not to be

Despite the result, this is the end of the status quo

Boyd Tonkin on the fall-out from the Scottish referendum
Manolo Blahnik: The high priest of heels talks flats, Englishness, and why he loves Mary Beard

Manolo Blahnik: Flats, Englishness, and Mary Beard

The shoe designer who has been dubbed 'the patron saint of the stiletto'
The Beatles biographer reveals exclusive original manuscripts of some of the best pop songs ever written

Scrambled eggs and LSD

Behind The Beatles' lyrics - thanks to Hunter Davis's original manuscript copies
'Normcore' fashion: Blending in is the new standing out in latest catwalk non-trend

'Normcore': Blending in is the new standing out

Just when fashion was in grave danger of running out of trends, it only went and invented the non-trend. Rebecca Gonsalves investigates
Dance’s new leading ladies fight back: How female vocalists are now writing their own hits

New leading ladies of dance fight back

How female vocalists are now writing their own hits
Mystery of the Ground Zero wedding photo

A shot in the dark

Mystery of the wedding photo from Ground Zero
His life, the universe and everything

His life, the universe and everything

New biography sheds light on comic genius of Douglas Adams
Save us from small screen superheroes

Save us from small screen superheroes

Shows like Agents of S.H.I.E.L.D are little more than marketing tools
Reach for the skies

Reach for the skies

From pools to football pitches, rooftop living is looking up
These are the 12 best hotel spas in the UK

12 best hotel spas in the UK

Some hotels go all out on facilities; others stand out for the sheer quality of treatments
These Iranian-controlled Shia militias used to specialise in killing American soldiers. Now they are fighting Isis, backed up by US airstrikes

Widespread fear of Isis is producing strange bedfellows

Iranian-controlled Shia militias that used to kill American soldiers are now fighting Isis, helped by US airstrikes
Topshop goes part Athena poster, part last spring Prada

Topshop goes part Athena poster, part last spring Prada

Shoppers don't come to Topshop for the unique
How to make a Lego masterpiece

How to make a Lego masterpiece

Toy breaks out of the nursery and heads for the gallery
Meet the ‘Endies’ – city dwellers who are too poor to have fun

Meet the ‘Endies’ – city dwellers who are too poor to have fun

Urbanites are cursed with an acronym pointing to Employed but No Disposable Income or Savings
Paisley’s decision to make peace with IRA enemies might remind the Arabs of Sadat

Ian Paisley’s decision to make peace with his IRA enemies

His Save Ulster from Sodomy campaign would surely have been supported by many a Sunni imam