Self rescue during accidental cold water immersion is swimming an option
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Self-rescue during accidental cold water immersion: is swimming an option?. Michel B. Ducharme & David S. Lounsbury Human Protection and Performance, Defence R&D Canada – Toronto. Background. The problem of accidental cold water immersion…. drowning is the leading cause of accidental death

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Self rescue during accidental cold water immersion is swimming an option l.jpg

Self-rescue during accidental cold water immersion:is swimming an option?

Michel B. Ducharme & David S. Lounsbury

Human Protection and Performance,

Defence R&D Canada – Toronto


Background l.jpg
Background

The problem of accidental cold water immersion…

  • drowning is the leading cause of accidental death

  • for recreational activities in Canada (The National Drowning Report, 2003)

  • 35 % of drowning occur in cold water

  • (National Drowning Trends Report, 2006)

  • BC Fishing Industry: 95 % of drowning occur

  • in water with a temperature ≤15 ºC(Brooks et al, Occupational. Med, 2005)

  • 2007 persons died of cold immersion in Canada

  • during 1991-2000 (The National Drowning Report, 2006)


Slide3 l.jpg

What should a person do upon accidental

immersion in cold water?

Would you attempt a 300 m swim in 10C wearing

a PFD over seasonal clothing?

Result of survey:

70% of final year university graduates said “NO”


Background4 l.jpg
Background

  • public safety information agencies

  • attempting a swim of 100 m in cold water is too risky,

  • even for PFD-wearers(CRCS, 1995)

  • cold water swimming distance is only 1/10 of warm

  • water swimming distance(CRCS, 1983)

  • “Do not attempt swimming. It has been shown that a

  • strong swimmer has only a 50/50 chance of reaching

  • shore one-half mile away.”(RLSSC, 1997)

  • “If immersion is from a capsized craft: wait for rescue.

  • Don’t try to swim for safety unless you are sure you can

  • make it - you cool faster than you think.”(Ministry of the Environment)


Background5 l.jpg
Background

  • public safety information agencies

  • Cold water can paralyze your muscles instantly

  • (Transport Canada, 2006)

- If you end up in the water, do everything you can to

conserve energy and body heat…Do not swim to keep

warm. (Transport Canada, 2006)


Background6 l.jpg
Background

  • rationale for the recommendations

    • Subjects were only able to swim 7 to 12 min in 5°C water(Keatinge et al., 1969)

    • moderate intensity swimming (40 - 45 % VO2 MAX) in 10.5 °C water can cause a 35 %  in heat loss compared to holding steady (Hayward et al, 1975)

    • hypothermia was assumed to be the limiting factor to swimming in cold water(Pugh 1955, Hayward et al, 1975)

    • each °C  in TEs or TM induces a 5 - 6 %  in VO2 MAX (Bergh and Ekblom, 1979)


Background7 l.jpg
Background

“the traditional naval advice to cling to wreckage and not to waste energy by swimming is probable correct” (Pugh and Edholm, 1955)

“people are better off if they float still in lifejackets or hang on to wrekage and do not swim about to try to keep warm” (Keatinge, 1972)


In 2006 l.jpg
In 2006…

“If rescue is unlikely, it may be preferable to swim to safety”

(CRCS, 2006)


New evidence epidemiological studies l.jpg
New evidence (epidemiological studies)

1- More survivors of boating incidents swam for shore than

stayed with the boat (Sawyer and Barss, 1998)

2- 60% of survivors of cold water boating immersions swam

for shore as opposed to only 30% who stayed with the boat

(CRCS, 2006)


New evidence physiological studies l.jpg
New evidence (physiological studies)

1- Subjects not wearing PFD could swim on average 55 min

in 10°C water(Tipton et al., 1999)

2- Subjects wearing a PFD could swim on average 889 m

in 14°C water before incapacitation (Wallingford, Ducharme et al, 2000)

3- Subjects wearing a PFD could swim on average 792 m

in 10°C water before incapacitation, 3 times shorter than

the 2375 m in 24°C (Kenny, Ducharme et al., 2001; 2002)

4- Subjects wearing a PFD could swim on average 806 m

(novice swimmer) and 1439 m (expert swimmer) in 10°C

water before incapacitation (Lounsbury and Ducharme, 2005)


New evidence physiological studies11 l.jpg
New evidence (physiological studies)

A: Keatinge et al., 1969

B: Kenny et al., 2001

C1: Lounsbury & Ducharme, 2005

(novice swimmers)

C2: Lounsbury & Ducharme, 2005

(expert swimmers)

D: Wallingford et at., 2000

E: Kenny et al., 2001


New evidence physiological studies12 l.jpg
New evidence (physiological studies)

A: Keatinge et al., 1969

B: Kenny et al., 2001

C1: Lounsbury & Ducharme, 2005

(novice swimmers)

C2: Lounsbury & Ducharme, 2005

(expert swimmers)

D: Wallingford et at., 2000

E: Kenny et al., 2001

?


New evidence physiological studies13 l.jpg
New evidence (physiological studies)

The average swimming duration in all studies was about

45-50 min before incapacitation, irrelevant to the swimming ability

Swimming failure develops before incapacitating hypothermia

Swimming failure is likely primarily related to muscle fatigue

of the arms as a consequence of muscle cooling rather than

hypothermia


Slide14 l.jpg

Recommendations for self-rescue

1- Upon falling into water (cold shock):

- focus on keeping the head above water

- do not swim until regaining control of breathing

2- Ask yourself: “Am I likely to be rescued soon?”

- <10% body fat: 2-3 hours

- 15-20% body fat: 4-5 hours

- >30% body fat: several hours

- Yes: use HELP posture

3- No: swimming is an option

- look around for the nearest source of safety

- try to assess if you can swim the distance based on

your ability to swim and level of fitness

- can you swim the required distance within 45-50 min?


Slide15 l.jpg

Recommendations for self-rescue

4- Once you have made your decision, hold on to it, as your

judgment will become impaired with time

5- Try to swim with an even and sustained pace


Slide16 l.jpg

Km

Average fatness, fit, expert

Average fatness, fit, novice

m

Swimming distance in cold water

Fat, fit, good swimmer

Thin, unfit, bad swimmer


Slide17 l.jpg

The Defence Research

and Development Branch

provides Science andTechnology leadership

in the advancement and

maintenance of Canada’s

defence and security

capabilities.


Objective of the study l.jpg
Objective of the study

To compare two self-rescue strategies (e.g. swimming vs. preserving heat) for their thermal performance during immersion in cold water.


Hypothesis of the study l.jpg
Hypothesis of the study

- Swimming will induce a higher body heat loss as compared to HELP

- Swimming will not induce a higher change in body heat content as compared to HELP


Methods subjects l.jpg
Methods - Subjects

  • 15 subjects between 18 to 55 years of age

  • either gender

  • attempts made to recruit across a wide range of body sizes and somatotypes

  • classified by swimming skill into “novice” or “expert” categories


Methods subject characteristics l.jpg

Novice (n=7)

Age = 31.7 years

Height = 1.73 m

Mass = 69.8 kg

BMI = 23.0 kg/m2

BSA = 1.82 m2

BSA:mass = 0.027 m

%BF-SkF = 17.4

%BF-UWW = 13.7

VO2 MAX Trd = 42.1* mL/kg/min

VO2 MAX Arm = 20.4 mL/kg/min

Aqua Quest Level = 7*

Expert (n=8)

Age = 31.0 years

Height = 1.74 m

Mass = 74.4 kg

BMI = 24.5 kg/m2

BSA = 1.89 m2

BSA:mass = 0.026 m

%BF-SkF = 15.0

%BF-UWW = 13.3

VO2 MAX Trd = 52.1* mL/kg/min

VO2 MAX Arm = 24.6 mL/kg/min

Aqua Quest Level = 11*

Methods - Subject Characteristics

Total Subject Pool (n=15)

* - NOV vs. EXP (p<0.05)


Methods design l.jpg

HELP

Heat Escape

Lessing Position

Methods - Design

HELP

Nov.

Trial 1: Passive Cooling (PC)

Exp.

HELP

HELP

Free Swimming

Nov.

Trial 2: Free Swimming (FS)

Exp.

Cold

shock

0

3

45?

120

time (min)

TRec (°C)

37

34


Methods flume set up l.jpg
Methods: Flume set-up

  • - Twater: 10.0 ± 0.1 °C

  • - Speed: 0.2 to 0.8 m/s

  • Tair: ~20 °C

  • Clothing: cotton pants,

  • short-sleeved T-shirt,

  • sweat shirt, socks, shoes,

  • PFD.


Methods flume calibration l.jpg
Methods: Flume calibration

(Range: 0.1 to 1.0 m/s)

40 cm

lat. dev.

20 cm

lat. dev.

z

178 cm

length

flow

x

10 cm depth

30 cm depth

50 cm depth

y


Methods measurements l.jpg

Continuous

Swimming Performance

Speed (flume)

Technique (video)

Thermal

Rectal Temperature

Skin Temperature

Heat Flow

Heart Rate

Discrete

Oxygen Uptake

Electromyography

Grip Strength

Visuoperceptual

Decision Making

Psychophysical

Thermal Comfort

Rating of Perceived Exertion

Methods - Measurements


Methods dressing procedures l.jpg
Methods - Dressing Procedures

EMG

Dressed subject

HR

Rectal probe

Belt

TSk and HF


Results rectal temperature l.jpg
Results - Rectal Temperature

n=15

n=14

n=13

n=8

n=6

n=5

n=4

38.0

37.5

x

*

37.0

36.5

PC

Rectal Temperature (°C)

36.0

FS

35.5

35.0

34.5

34.0

0

10

20

30

40

50

60

70

80

Time (min)

Symbols: x - PC significantly different from FS, * - main effect of time first becomes significant.


Results skin temperature l.jpg
Results - Skin Temperature

n=15

n=14

n=13

n=8

n=6

n=5

n=4

35.0

30.0

*

x

25.0

PC

Skin Temperature (°C)

FS

20.0

15.0

10.0

0

10

20

30

40

50

60

70

80

Time (min)

Symbols: x - PC significantly different from FS, * - main effect of time first becomes significant.


Results core cooling and heat loss l.jpg

Core cooling rate (ºC/min)

PC

FS

Mean

0.037x

0.047

SEM

0.006

0.007

x - FS vs. PC (p<0.001)

Results - Core Cooling and Heat Loss

a - Swimming Phase vs. Passive Cooling Phase (p<0.001)


Results immersion time l.jpg
Results - Immersion Time

120

x

100

75.5

80

HELP

61.5

Time (min)

Swimming

60

20

40

41.5

20

0

PC

FS

Condition

Symbols: x - PC significantly different from FS


Results swimming times l.jpg
Results - Swimming Times

Symbols: NS - no significant difference

between NOV and EXP


Results swimming performance l.jpg
Results - Swimming Performance

Symbols: * - NOV significantly different

from EXP


Results grip and body comfort l.jpg
Results - Grip and Body Comfort

Symbols: * - PRE significantly different

from POST

Symbols: a - main effect of time first becomes significant, b - further main effects of time versus a


Results cardiovascular stress l.jpg
Results - Cardiovascular Stress

n=15

n=14

n=13

n=8

n=6

n=5

n=4

200

180

160

x

140

PC

Heart Rate (b/min)

FS

120

100

*

80

60

0

10

20

30

40

50

60

70

80

Time (min)

Symbols: x - PC significantly different from FS, * - main effect of time first becomes significant



Results change in body heat content l.jpg

Rate of change in body heat content (Rate of heat storage)

Work produced

Rate of heat loss

Metabolic heat production

Results – Change in Body Heat Content


Results heat production and heat loss l.jpg

Energy expenditure (Kcal/min)

Heat loss (Kcal/min)

Swimming failure

Swimming failure

FS

PC

Time (min)

Time (min)

Results – Heat production and heat loss


Results cumulative heat production and heat loss l.jpg

N=15 14 13 10 9 8 7 6 3 2 1

N=15 14 13 10 9 8 7 6 3 2 1

559.6 Kcal

Energy Expenditure (Kcal)

Heat loss (Kcal)

493.2 Kcal

417.0 Kcal

FS

233.8 Kcal

PC

Time (min)

Time (min)

Results – Cumulative heat production and heat loss


Results change in body heat content39 l.jpg

-176.0 Kcal = 417.0 Kcal – 33.4 Kcal – 559.6 Kcal 2 1

FS

Zamparo et al, Eur JAP, 2005

Results – Change in body heat content

Heat storage = Heat production – Work – Heat loss

PC

-259.4 Kcal = 233.8 Kcal – 0 Kcal – 493.2 Kcal


Conclusions l.jpg
Conclusions 2 1

  • swimming increases body heat loss and core cooling rate compared to HELP

  •  heat loss during swimming returned to HELP levels within 5 minutes of swimming cessation

  • NOV swam about 800 m before incapacitation

  • EXP swam about 1400 m before incapacitation

  • Body heat content is more reduced following HELP than swimming


Recommendations l.jpg
Recommendations 2 1

  • Upon accidental immersion into a cold lake, while equipped with a PFD and when land is in sight, one should:

    • Float for 3 minutes to overcome cold shock

    • Locate the nearest source of safety (e.g. land, capsized boat)

    • Assess whether distance is within swimming ability (45 min swim)

    • Choose survival strategy (stick to this decision)

    • Execute strategy. If "await rescue", DONE

    • If "swim for it", attempt to swim (head out) with an even pace, DONE