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Mike Tipton - One of the best experts on this subject based on the ideXlab platform.
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Correction factors for assessing Immersion Suits under harsh conditions
Applied Ergonomics, 2016Co-Authors: Jonathan Power, Martin J. Barwood, Peter Tikuisis, Mike TiptonAbstract:Many Immersion Suit standards require testing of thermal protective properties in calm, circulating water while these Suits are typically used in harsher environments where they often underperform. Yet it can be expensive and logistically challenging to test Immersion Suits in realistic conditions. The goal of this work was to develop a set of correction factors that would allow Suits to be tested in calm water yet ensure they will offer sufficient protection in harsher conditions. Two Immersion studies, one dry and the other with 500 mL of water within the Suit, were conducted in wind and waves to measure the change in Suit insulation. In both studies, wind and waves resulted in a significantly lower immersed insulation value compared to calm water. The minimum required thermal insulation for maintaining heat balance can be calculated for a given mean skin temperature, metabolic heat production, and water temperature. Combining the physiological limits of sustainable cold water Immersion and actual Suit insulation, correction factors can be deduced for harsh conditions compared to calm. The minimum in-situ Suit insulation to maintain thermal balance is 1.553–0.0624·TW + 0.00018·TW2 for a dry calm condition. Multiplicative correction factors to the above equation are 1.37, 1.25, and 1.72 for wind + waves, 500 mL Suit wetness, and both combined, respectively. Calm water certification tests of Suit insulation should meet or exceed the minimum in-situ requirements to maintain thermal balance, and correction factors should be applied for a more realistic determination of minimum insulation for harsh conditions.
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Reduction in Predicted Survival Times in Cold Water Due to Wind and Waves
Applied ergonomics, 2015Co-Authors: Jonathan Power, Martin J. Barwood, Peter Tikuisis, Mike TiptonAbstract:Recent marine accidents have called into question the level of protection provided by Immersion Suits in real (harsh) life situations. Two Immersion Suit studies, one dry and the other with 500 mL of water underneath the Suit, were conducted in cold water with 10-12 males in each to test body heat loss under three environmental conditions: calm, as mandated for Immersion Suit certification, and two combinations of wind plus waves to simulate conditions typically found offshore. In both studies mean skin heat loss was higher in wind and waves vs. calm; deep body temperature and oxygen consumption were not different. Mean survival time predictions exceeded 36 h for all conditions in the first study but were markedly less in the second in both calm and wind and waves. Immersion Suit protection and consequential predicted survival times under realistic environmental conditions and with leakage are reduced relative to calm conditions.
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ECG during helicopter underwater escape training.
Aviation space and environmental medicine, 2010Co-Authors: Mike Tipton, Chris J. Brooks, Peter N. G. Gibbs, Tara J. ReillyAbstract:INTRODUCTION: Coincidental stimulation of the sympathetic and parasympathetic nervous system can cause "autonomic conflict" and consequent cardiac arrhythmias. The present study tested the hypotheses that: 1) cardiac arrhythmias would be seen in those undertaking helicopter underwater escape training (HUET); 2) the occurrence of arrhythmias in individuals could be predicted; and 3) the heart rate response to HUET would habituate with repeated runs. METHODS: There were 26 male volunteers who each undertook 5 HUET submersions into water at 29.5 degrees C, with each run separated by 10 min. Each submersion included a 3-min, 40-s pre-submersion period, a 10-s submersion, and 40-s post-submersion period. Participants wore a three-lead telemetric ECG system beneath an Immersion Suit and underclothing. Skin temperature was measured in one participant. Each participant undertook tests to establish their autonomic function, including heart rate variability, face Immersion, cold pressor test, and aerobic capacity assessment. RESULTS: The heart rate response to HUET was reduced by the fourth run when compared to the first run. Across all runs, 32 cardiac arrhythmias were identified (25%) in 22 different participants; all but 6 of the arrhythmias occurred just after submersion. Only aerobic fitness appeared inversely associated with the occurrence of arrhythmias. CONCLUSIONS: The heart rate response to HUET habituates. HUET produces cardiac arrhythmias; these are asymptomatic and probably of little clinical significance in young, fit individuals. It remains to be seen if this is the case with either an older, less fit cohort of people or in those undertaking longer breath holds in colder water.
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ASSESSMENT OF Immersion Suit PERFORMANCE: HUMAN COMPARED TO Immersion THERMAL MANIKIh' TESTS
1994Co-Authors: Mike Tipton, Prashant J. BalmiAbstract:INTRODUCTION Immersion thermal manikins have been widely used to assist in the evaluation of Immersion Suits and the determination of survival policies. The 200g leakage limit for uninsulated Immersion "dry" Suits included in many standards, specifications and guidelines is but one example of a pass criterion that has been primarily determined following tests with manikins (1, 2). The question remains: to what extent can the use of such techniques rather than manned tests prejudice the evaluation of an Immersion Suit, and how appropriate for humans are pass criteria, established and tested on manikins? In an attempt to address this question a series of experiments were undertaken in which the data obtained from humans were compared with those obtained from an iffilnersion thermal manikin.
Jonathan Power - One of the best experts on this subject based on the ideXlab platform.
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Correction factors for assessing Immersion Suits under harsh conditions
Applied Ergonomics, 2016Co-Authors: Jonathan Power, Martin J. Barwood, Peter Tikuisis, Mike TiptonAbstract:Many Immersion Suit standards require testing of thermal protective properties in calm, circulating water while these Suits are typically used in harsher environments where they often underperform. Yet it can be expensive and logistically challenging to test Immersion Suits in realistic conditions. The goal of this work was to develop a set of correction factors that would allow Suits to be tested in calm water yet ensure they will offer sufficient protection in harsher conditions. Two Immersion studies, one dry and the other with 500 mL of water within the Suit, were conducted in wind and waves to measure the change in Suit insulation. In both studies, wind and waves resulted in a significantly lower immersed insulation value compared to calm water. The minimum required thermal insulation for maintaining heat balance can be calculated for a given mean skin temperature, metabolic heat production, and water temperature. Combining the physiological limits of sustainable cold water Immersion and actual Suit insulation, correction factors can be deduced for harsh conditions compared to calm. The minimum in-situ Suit insulation to maintain thermal balance is 1.553–0.0624·TW + 0.00018·TW2 for a dry calm condition. Multiplicative correction factors to the above equation are 1.37, 1.25, and 1.72 for wind + waves, 500 mL Suit wetness, and both combined, respectively. Calm water certification tests of Suit insulation should meet or exceed the minimum in-situ requirements to maintain thermal balance, and correction factors should be applied for a more realistic determination of minimum insulation for harsh conditions.
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Comparison of thermal manikins to human thermoregulatory responses
Extreme physiology and medicine, 2015Co-Authors: Jonathan Power, Andrew BakerAbstract:Immersion Suits are lifesaving appliances (LSA) designed to protect the wearer if they become accidently immersed in cold water by reducing the cold shock response and delaying the onset of hypothermia. Immersion Suits are certified to both national and international standards; some of which require the thermal protective properties to be tested using humans or thermal manikins. The ethical nature of testing with humans has been questioned [1] due to the physically grueling nature of these tests, thus testing with manikins may be preferential. However, previous work has shown that discrepancies exist between thermal manikins and humans that could result in Immersion Suit selection that would benefit the former more than the latter who would ultimately use it [2]. This study investigated the thermoregulatory responses of humans and compared them to a thermal manikin while wearing Immersion ensembles with insulation distributed in various configurations hypothesized to be beneficial to humans and manikins.
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Reduction in Predicted Survival Times in Cold Water Due to Wind and Waves
Applied ergonomics, 2015Co-Authors: Jonathan Power, Martin J. Barwood, Peter Tikuisis, Mike TiptonAbstract:Recent marine accidents have called into question the level of protection provided by Immersion Suits in real (harsh) life situations. Two Immersion Suit studies, one dry and the other with 500 mL of water underneath the Suit, were conducted in cold water with 10-12 males in each to test body heat loss under three environmental conditions: calm, as mandated for Immersion Suit certification, and two combinations of wind plus waves to simulate conditions typically found offshore. In both studies mean skin heat loss was higher in wind and waves vs. calm; deep body temperature and oxygen consumption were not different. Mean survival time predictions exceeded 36 h for all conditions in the first study but were markedly less in the second in both calm and wind and waves. Immersion Suit protection and consequential predicted survival times under realistic environmental conditions and with leakage are reduced relative to calm conditions.
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Human temperature regulation in wind and waves
2012Co-Authors: Jonathan PowerAbstract:Many international and national standards exist for the testing and certification of Immersion Suits. Some require the thermal protective properties of Immersion Suits to be tested with human volunteers in calm, circulating 2°C water. The knowledge gap that currently exists between the benign testing conditions used in international standards and specifications, and the harsh environments that an immersed individual find themselves in following a marine accident, could result in unexpectedly poor levels of performance, with fatalities occurring sooner than expected following accidental Immersion. Study 1 determined the heat loss from the skin of volunteers in Immersion Suits and immersed in wind and waves. Twelve healthy participants (Age: 25.8 [5.9] years old; Mass: 81.7 [13.1]kg; Height: 176.2 [7.7]cm) performed four, one hour Immersions in the following conditions: Calm water; Wind-only; Waves-only; and Wind + Waves. Compared to Calm (67.21 [4.70]W·m-2), all the other Immersion conditions produced a significantly greater increase in mean skin heat flow (MSHF) (Wind: 79.60 [6.70]W·m-2; Waves: 78.8 [4.52]W·m-2; Wind + Waves: 92.00 [8.39]W·m-2). The Wind + Waves condition produced a significantly greater increase in MSHF compared to all other conditions. Study 2 built upon the findings of the first by investigating the extent to which human thermal responses were related to the severity of weather conditions. Twelve healthy males (Age: 23.9 [3.3] years old; Mass: 83.2 [4.9]kg; Height: 181.0 [4.9]cm) performed three, three hour Immersions in the following conditions: Calm water; Weather 1; and Weather 2. Compared to the calm water condition (62.96 [2.98]W·m-2], both weather conditions produced a significantly greater increase in MSHF (Weather 1: 76.75 [6.26]W·m-2; Weather 2: 79.53 [6.24]W·m-2). There were no significant differences in the change in gastro-intestinal temperature (TGI) across Immersion conditions (Calm: -0.10 [0.31]°C; Weather 1: -0.29 [0.30]°C; Weather 2: -0.20 [0.28]°C]. There were no significant differences in V · O2 across Immersion conditions (Calm: 0.325 [0.054]L·min-1; Weather 1: 0.332 [0.108]L·min-1; Weather 2: 0.365 [0.080]L·min-1). Study 3 investigated the effect of simulated water ingress under an Immersion Suit on human thermal responses during Immersions in varying weather conditions. Twelve healthy males (Age: 25.6 [5.6] years old; Mass: 82.7 [10.2]kg; Height: 181.0 [4.7]cm) performed three, three hour Immersions in the same conditions as Study 2, but with 500mL of water underneath the Immersion Suit. Compared to the calm water condition (79.45 [9.19]W·m-2), both weather conditions produced a significantly greater increase in MSHF (Weather 1: 102.06 [11.98]W·m-2; Weather 2: 107.48 [3.63]W·m-2). There were no significant differences in the change in TGI (Calm: -0.35 [0.14]°C; Weather 1: -0.38 [0.15]°C; Weather 2: 0.29 [0.25]°C) or V · O2 (Calm: 0.449 [0.054]L·min-1; Weather 1: 0.503 [0.051]L·min-1; Weather 2: 0.526 [0.120]L·min-1) across conditions. Survival times were calculated for the participants of Studies 2 and 3. There was no difference in the predicted survival times for the Study 2 participants for both the calm (> 36 hours) and wind and wave conditions (> 36 hours). The predicted survival times for the participants of Study 3 were significantly lower in the turbulent conditions (16 hours) compared to calm (27 hours). The predicted survival times of the participants in turbulent conditions were up to half those calculated for calm water Immersions. The results collected in Studies 2 and 3 were used to calculate the change in total insulation in varying conditions compared to being dry. Immersions in wind and waves will reduce Immersion Suit insulation by 27%; 500mL of water leakage will reduce it by 24%; wind, waves and 500mL of water combined will reduce it by 43%. The predicted amount of oxygen consumption (V · O2 P) to produce the amount of heat required to remain in thermal balance can be estimated by rearranging the equations used to calculate metabolic heat production and insulation. If heat loss exceeds the assumed maximum heat production of 206W·m-2, hypothermia will eventually develop. The point at which heat loss exceeds maximum heat production has been determined in a range of conditions. It is concluded that: Immersions in wind and waves causes a significant increase in heat flow from the body compared to calm conditions. Testing individuals and Immersion Suits in conditions not representative of the area where they are to be used may, or may not, result in an over-estimation of performance depending on the capacity of an individual’s thermoregulatory system.
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The effects of water temperature, gender and exercise on breath holding following sudden face Immersion
2004Co-Authors: Jonathan PowerAbstract:A potential risk that workers face when commuting to offshore oil platforms is the helicopter ditching or crashing in cold ocean water and inverting. This happens if the helicopter's flotation bags fail to deploy. In this scenario a person's chance of survival appears to depend ·on their ability to make a successful breath hold swim from the sunken fuselage to the surface. Since each passenger should be wearing full body Immersion Suit, only the face is exposed to the cold water during a breath hold swim. As such, the two studies in this thesis examined if water temperatures (between 0°C and 20°C), gender and exercise can affect a typical sized person's maximum breath hold time (BHTmax) following a sudden facial Immersion. In the studies the typical size males were significantly taller (p≤0.05) and heavier (p≤0.001) than the typical size females. The first study examined the effects of water temperature and gender on BHTmax for participants at rest with a sudden facial Immersion. The second study examined the same effects on BHTmax during moderate intensity upper body exercise. For resting participants, lower water temperatures resulted in significantly shorter BHTmax and females had shorter BHTmax than males. In study 2 during moderate intensity upper body exercise, BHTmax was not affected by water temperature but males continued to have significantly longer BHTmax than females. During the exercise condition the males had a BHTmax of ~25s across all breath hold conditions, and the females had a BHTmax of ~15s across all Immersion conditions. In conclusion, the effect of water temperature on breath holding is evident for resting but not in exercise conditions. Although in both studies males had significantly greater BHTmax than females, it remains to be established if this is an effect of gender or physical size.
Michel B. Ducharme - One of the best experts on this subject based on the ideXlab platform.
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Heat stress of helicopter aircrew wearing Immersion Suit.
Industrial health, 2006Co-Authors: Michel B. DucharmeAbstract:The objectives of the present study were to define the lowest ambient air and cabin temperatures at which aircrews wearing Immersion protection are starting to experience thermal discomfort and heat stress during flight operations, and to characterize during a flight simulation in laboratory, the severity of the heat stress during exposure to a typical northern summer ambient condition (25°C, 40% RH). Twenty male helicopter aircrews wearing Immersion Suits (insulation of 2.2 Clo in air) performed 26 flights within an 8-month period at ambient temperatures ranging between -15 and 25°C, and cabin temperatures ranging between 3 and 28°C. It was observed based on thermal comfort ratings that the aircrews were starting to experience thermal discomfort and heat stress at ambient and cabin air conditions above 18°C and at a WBGT index of 16°C. In a subsequent study, seven aircrews dressed with the same clothing were exposed for 140 min to 25°C and 40% RH in a climatic chamber. During the exposure, the aircrews simulated pilot flight maneuvers for 80 min followed with backender/flight engineer activities for 60 min. By the end of the 140 min exposure, the skin temperature, rectal temperature and heart rate had increased significantly to 35.7 ± 0.2°C, 38.4 ± 0.2°C and between 110 and 160 beats/min depending on the level of physical activity. The body sweat rate averaged 0.58 kg/h and the relative humidity inside the clothing was at saturation by the end of the exposure. It was concluded that aircrews wearing Immersion Suits during the summer months in northern climates might experience thermal discomfort and heat stress at ambient or cabin air temperature as low as 18°C.
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Testing a New Concept of Immersion Suit at Sea
2002Co-Authors: Michel B. DucharmeAbstract:Abstract : A new concept of Immersion Suit, the nearly dry Suit, was recently developed to overcome the main limitations of the wet and dry Suits. The main new feature of the Suit is the adjustable seals that can be closed before or upon entry in water. The purpose of the present study was to test the new Suit at sea against a standard dry Suit. Seven male subjects were immersed for over one hour in 3 deg water in the Atlantic ocean. Three conditions were tested during which the subjects were wearing a dry Suit (DRY), a nearly dry Suit with the seals closed (NEAR-DRY-C) or a nearly dry Suit with the seals opened upon entry in water (NEAR-DRY-O). The thermal resistance of the Suit, measured from the skin heat loss data and the temperature difference between the skin and the outside surface of the Suits, were 0.95 +/- 0.14, 0.69 +/- 0.13 and 0.58 +/- 0.09 Clo for DRY, NEAR-DRY-C and NEAR-DRY-O conditions, respectively, with the thermal resistance being significantly lower (p
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testing a new concept of Immersion Suit at sea
2002Co-Authors: Michel B. DucharmeAbstract:Abstract : A new concept of Immersion Suit, the nearly dry Suit, was recently developed to overcome the main limitations of the wet and dry Suits. The main new feature of the Suit is the adjustable seals that can be closed before or upon entry in water. The purpose of the present study was to test the new Suit at sea against a standard dry Suit. Seven male subjects were immersed for over one hour in 3 deg water in the Atlantic ocean. Three conditions were tested during which the subjects were wearing a dry Suit (DRY), a nearly dry Suit with the seals closed (NEAR-DRY-C) or a nearly dry Suit with the seals opened upon entry in water (NEAR-DRY-O). The thermal resistance of the Suit, measured from the skin heat loss data and the temperature difference between the skin and the outside surface of the Suits, were 0.95 +/- 0.14, 0.69 +/- 0.13 and 0.58 +/- 0.09 Clo for DRY, NEAR-DRY-C and NEAR-DRY-O conditions, respectively, with the thermal resistance being significantly lower (p <- 0.05) for the NEAR-DRY conditions. The decrease in insulation for the NEAR-DRY-O condition was attributed to a significantly larger water leakage through the seals (1.37 +/- 0.29 L) as compared to the other conditions (DRY: 0.41 +/- 0.20 L; NEAR-DRY-C: 0.35 +/- 0.28 L). It was concluded that the nearly dry Suit concept, while maintaining a greater comfort when the seals were opened before Immersion, successfully limited the water leakage into the Suit to a level observed with a dry Suit when the seals were closed upon entry in water. The thermal insulation provided by the nearly dry Suit when closed is not inferior to 0.75 Clo, the recommended insulation to obtain adequate thermal protection in cold water. During Immersion in the open mode, the nearly dry Suit can decrease the survival time by a factor a two.
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Water Entry Onto the MAC 200 Immersion Suit During Simulated Parachute Jump and Drag Trials
1998Co-Authors: Michel B. Ducharme, John A. ThompsonAbstract:Abstract : The MAC 200 Immersion Suit newly developed by Mustang Survival (Richmond, B.C.) has recently been considered a potential replacement Suit for the constant wear dry Immersion Suit currently used by Canadian Forces aircrew. The objective of the present evaluation trial was to evaluate the effectiveness of the new neck seal concept by measuring water leakage into the MAC 200 Suit during a simulated parachute jump into water followed by a 15 s drag. Four male aircrew members volunteered to participate in the study. On Day 1 they jumped from the back of a boat (about 30 cm above the water) moving at a speed of 5 km . h-1 and were dragged for 15 sec. On Day 2, the aircrew jumped from a platform 3 m above water to simulate the speed of parachute entry and were immediately attached to a line and dragged behind a boat for 15 sec at a speed of 5 km . h-1. Before and after the jump/drag procedure the aircrew were weighed to estimate the amount of water leakage into the Suit. The results showed that when the neck and wrist seals of the Suit were closed properly before the entry into the water, no leakage was observed following the jump/drag procedure on both testing days.
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The Effects of Wave Conditions on Dry Immersion Suit Insulation: A Comparison Between Humans and Manikin,
1996Co-Authors: Michel B. Ducharme, Christopher J. BrooksAbstract:Abstract : The objective of the present study was to investigate the effect of standard wave conditions (0 to 70 cm) on dry Immersion Suit insulation when tested on humans and a manikin simultaneously. Six human subjects and a thermal manikin dressed with the same dry Immersion Suit system (pile undergarment insulation, uninsulated Immersion Suit and neoprene gloves and hood) were immersed simultaneously for one hour in 16 deg C water rendered turbulent with an irregular wave pattein. One Immersion was performed for each randomly chosen wave condition, from 0 to 70 cm wave height, changing by steps of 10 cm. In addition to the physiological parameters measured on the human subjects (skin and rectal temperatures, skin heat loss and heart rate), and the ambient temperature of water and air, heat fluxes and surface temperatures were measured at 12 sites on the subjects and manikin for each compartment of the dry Suit system (skin, pile garment, Suit garment). This allowed the calculation of the thermal resistance of every Suit compartment in addition to the air and water boundary layer surrounding the Suit. The results showed that none of the physiological parameters were significantly affected by the wave conditions, except for the skin heat flux which increased with wave height from 72.0 +/- 1.9 W m(-2) at 0 cm to 85.5 +/- 2.9 W m(-2) at 70 cm. The thermal resistance data showed that wave height up to 70 cm decreased dry Suit system insulation by 14 and 17% when measured on human subjects and manikin, respectively; and that the only Suit component significantly affected by the wave motion was the insulation of the water and air boundary layers surrounding the body. The body sites that were the most affected by the effect of wave motion were the head, and the proximal limbs with a 58% and 63% decrement in Suit thermal resistance from 0 to 70 cm wave height for humans and mani
Peter Tikuisis - One of the best experts on this subject based on the ideXlab platform.
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Correction factors for assessing Immersion Suits under harsh conditions
Applied Ergonomics, 2016Co-Authors: Jonathan Power, Martin J. Barwood, Peter Tikuisis, Mike TiptonAbstract:Many Immersion Suit standards require testing of thermal protective properties in calm, circulating water while these Suits are typically used in harsher environments where they often underperform. Yet it can be expensive and logistically challenging to test Immersion Suits in realistic conditions. The goal of this work was to develop a set of correction factors that would allow Suits to be tested in calm water yet ensure they will offer sufficient protection in harsher conditions. Two Immersion studies, one dry and the other with 500 mL of water within the Suit, were conducted in wind and waves to measure the change in Suit insulation. In both studies, wind and waves resulted in a significantly lower immersed insulation value compared to calm water. The minimum required thermal insulation for maintaining heat balance can be calculated for a given mean skin temperature, metabolic heat production, and water temperature. Combining the physiological limits of sustainable cold water Immersion and actual Suit insulation, correction factors can be deduced for harsh conditions compared to calm. The minimum in-situ Suit insulation to maintain thermal balance is 1.553–0.0624·TW + 0.00018·TW2 for a dry calm condition. Multiplicative correction factors to the above equation are 1.37, 1.25, and 1.72 for wind + waves, 500 mL Suit wetness, and both combined, respectively. Calm water certification tests of Suit insulation should meet or exceed the minimum in-situ requirements to maintain thermal balance, and correction factors should be applied for a more realistic determination of minimum insulation for harsh conditions.
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Reduction in Predicted Survival Times in Cold Water Due to Wind and Waves
Applied ergonomics, 2015Co-Authors: Jonathan Power, Martin J. Barwood, Peter Tikuisis, Mike TiptonAbstract:Recent marine accidents have called into question the level of protection provided by Immersion Suits in real (harsh) life situations. Two Immersion Suit studies, one dry and the other with 500 mL of water underneath the Suit, were conducted in cold water with 10-12 males in each to test body heat loss under three environmental conditions: calm, as mandated for Immersion Suit certification, and two combinations of wind plus waves to simulate conditions typically found offshore. In both studies mean skin heat loss was higher in wind and waves vs. calm; deep body temperature and oxygen consumption were not different. Mean survival time predictions exceeded 36 h for all conditions in the first study but were markedly less in the second in both calm and wind and waves. Immersion Suit protection and consequential predicted survival times under realistic environmental conditions and with leakage are reduced relative to calm conditions.
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Prediction Of Cold Sea Survival Time
1996Co-Authors: Peter TikuisisAbstract:Abstract : Despite advances in personal protective equipment and locator technologies, circumstances can lead to life-threatening exposures at sea. Of particular concern is the survival time (ST) when a human is immersed in cold water. Estimations of ST is difficult since reliable controlled data are not available. However, studies on accidental Immersion are sufficient to begin the construction and calibration of a predictive ST model. The model is based on the cylindrical core-shell concept of heat conduction with internal heat production augmented by shivering. Variables include ambient temperature, clothing protection (with and without leakage), subject characteristics, sea state, and level of Immersion. If heat loss exceeds one's maximal rate of heat production, then ST is largely determined by the body's rate of cooling. Conversely, if a heat balance can be established, then ST is dependent on the depletion flme of one's energy capacity based on glycogen stores. ST is defined by the deep core temperature reaching 30 deg C. As an example, the predicted ST for a healthy normal sedentary individual immersed in a heavy sea condition at 5 deg C are 1.9, 2.3, 4.8, 12.6, and 24.2 h for nude, shirt + sweater, shirt + anti-exposure Suit, shirt + dry Immersion Suit, and 4 mm neoprene wet Suit conditions, respectively. While the model predictions must be considered speculative, it can potentially serve as a valuable resource and decision aid. At present, it would be prudent to apply the predictions in a relative vs absolute sense; i.e., for comparative purposes.
Martin J. Barwood - One of the best experts on this subject based on the ideXlab platform.
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Correction factors for assessing Immersion Suits under harsh conditions
Applied Ergonomics, 2016Co-Authors: Jonathan Power, Martin J. Barwood, Peter Tikuisis, Mike TiptonAbstract:Many Immersion Suit standards require testing of thermal protective properties in calm, circulating water while these Suits are typically used in harsher environments where they often underperform. Yet it can be expensive and logistically challenging to test Immersion Suits in realistic conditions. The goal of this work was to develop a set of correction factors that would allow Suits to be tested in calm water yet ensure they will offer sufficient protection in harsher conditions. Two Immersion studies, one dry and the other with 500 mL of water within the Suit, were conducted in wind and waves to measure the change in Suit insulation. In both studies, wind and waves resulted in a significantly lower immersed insulation value compared to calm water. The minimum required thermal insulation for maintaining heat balance can be calculated for a given mean skin temperature, metabolic heat production, and water temperature. Combining the physiological limits of sustainable cold water Immersion and actual Suit insulation, correction factors can be deduced for harsh conditions compared to calm. The minimum in-situ Suit insulation to maintain thermal balance is 1.553–0.0624·TW + 0.00018·TW2 for a dry calm condition. Multiplicative correction factors to the above equation are 1.37, 1.25, and 1.72 for wind + waves, 500 mL Suit wetness, and both combined, respectively. Calm water certification tests of Suit insulation should meet or exceed the minimum in-situ requirements to maintain thermal balance, and correction factors should be applied for a more realistic determination of minimum insulation for harsh conditions.
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Reduction in Predicted Survival Times in Cold Water Due to Wind and Waves
Applied ergonomics, 2015Co-Authors: Jonathan Power, Martin J. Barwood, Peter Tikuisis, Mike TiptonAbstract:Recent marine accidents have called into question the level of protection provided by Immersion Suits in real (harsh) life situations. Two Immersion Suit studies, one dry and the other with 500 mL of water underneath the Suit, were conducted in cold water with 10-12 males in each to test body heat loss under three environmental conditions: calm, as mandated for Immersion Suit certification, and two combinations of wind plus waves to simulate conditions typically found offshore. In both studies mean skin heat loss was higher in wind and waves vs. calm; deep body temperature and oxygen consumption were not different. Mean survival time predictions exceeded 36 h for all conditions in the first study but were markedly less in the second in both calm and wind and waves. Immersion Suit protection and consequential predicted survival times under realistic environmental conditions and with leakage are reduced relative to calm conditions.
