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

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?

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  1. 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

  2. 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)

  3. 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”

  4. 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)

  5. 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)

  6. 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)

  7. 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)

  8. In 2006… “If rescue is unlikely, it may be preferable to swim to safety” (CRCS, 2006)

  9. 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)

  10. 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)

  11. 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

  12. 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 ?

  13. 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

  14. 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?

  15. 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

  16. Km Average fatness, fit, expert Average fatness, fit, novice m Swimming distance in cold water Fat, fit, good swimmer Thin, unfit, bad swimmer

  17. The Defence Research and Development Branch provides Science andTechnology leadership in the advancement and maintenance of Canada’s defence and security capabilities.

  18. 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.

  19. 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

  20. 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

  21. 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)

  22. 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

  23. 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.

  24. 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

  25. 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

  26. Methods - Dressing Procedures EMG Dressed subject HR Rectal probe Belt TSk and HF

  27. 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.

  28. 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.

  29. 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)

  30. 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

  31. Results - Swimming Times Symbols: NS - no significant difference between NOV and EXP

  32. Results - Swimming Performance Symbols: * - NOV significantly different from EXP

  33. 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

  34. 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

  35. Results - Summary

  36. 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

  37. Energy expenditure (Kcal/min) Heat loss (Kcal/min) Swimming failure Swimming failure FS PC Time (min) Time (min) Results – Heat production and heat loss

  38. 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

  39. -176.0 Kcal = 417.0 Kcal – 33.4 Kcal – 559.6 Kcal 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

  40. Conclusions • 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

  41. Recommendations • 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

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