Evaluation of Online Information on the Cold Shock Response to Accidental Immersion in Cold Water

Accidental immersion in cold water is a risk factor for many occupations. Habituation to cold-water immersion (CWI) is one practical means of reducing the cold shock response (CSR) on immersion. We investigated whether repeated thermoneutral water immersion (TWI) induced a perceptual habituation (i.e., could lessen perceived threat and anxiety) and consequently reduce the CSR on subsequent CWI. There were 12 subjects who completed seven 7-min head-out immersions. Immersions one and seven were CWls [15.0 (0.1) degrees C], and immersions two to six were TWI [34.9 (0.10) degrees C]. Anxiety 120-cm visual analogue scale) and the cardiorespiratory responses [heart rate (f(C)), respiratory frequency (f(R)), tidal volume (V(T)), and minute ventilation (V(E))] to immersion were measured throughout. Data were compared within subject between conditions using ANOVA to an alpha level of 0.05. Acute anxiety was significantly reduced after repeated exposure to the immersion scenario (i.e., TWI): CWI-1: 6.3 (4.4) cm; and CWI-2: 4.5 (4.0) cm [condition mean (SD)]. These differences did not influence the peak in the CSR. The f(C), f(R), and V(E) responses were similar between CWI-1 and CWI-2. V(T) response was significantly lower in CWI-2; mean (SD) across the immersion: CWI-1 1.27 (0.17) vs. CWI-2 1.11 0.21 L. Repeated TWI lessened the anxiety associated with CWI (perceptual habituation). This had a negligible effect on the primary components of the CSR, but did lower VT, which may reduce the volume of any aspirated water in an emergency situation. Reducing the threat appraisal of an environmental stressor may be a useful biproduct of survival training, thereby minimizing psychophysiological strain.

Evaluation of Three Field Rewarming Techniques During Cold Weather Military Training

Sudden immersion in cold water initiates an inspiratory gasp response followed by uncontrollable hyperventilation and tachycardia. It is known that this response, termed the "cold shock" response, can be attenuated following repeated immersion. In the present investigation we examined how long this habituation lasts. Twelve healthy male volunteers participated in the experiment, they were divided into a control (C) group (n = 4), and a habituation (H) group (n = 8). In October, each subject undertook two 3-min head-out seated immersions into stirred water at 10 degrees C wearing swimming trunks. These immersions took place at the same time of day, with 4 days separating the two immersions. In the intervening period, the C group were not exposed to cold water, while the H group undertook six, 3-min head-out immersions in water at 15 degrees C. Two months (December), 4 months (February), 7 months (May) and 14 months (January) after their first immersion, all subjects undertook another 3-min head-out immersion in water at 10 degrees C. The H group showed a reduction in respiratory frequency (47 to 24 breaths x min(-1)), inspiratory minute volume (72.2 to 31.3 1 x min(-1)) and heart rate (128 to 109 beats x min(-1)) during the first 30 s of immersion on day 5 compared to day 1. Seven months later these responses were still significantly reduced compared to day 1. After 14 months, heart rate remained attenuated but respiratory frequency and inspiratory minute volume had returned towards pre-habituation levels. The responses of the C group during the first 30 s of immersion were not altered. Both groups showed an attenuation in the responses during the remaining 150 s of immersion following repeated immersions. It is concluded that repeated immersions in cold water result in a longlasting (7-14 months) reduction in the magnitude of the cold shock response. Less frequent immersions produced a decrease in the duration, but not the magnitude of the response.

Cold immersion evokes the life-threatening cold shock response (CSR). We hypothesised that anxiety may increase the magnitude of (Study 1), and diminish habituation to (Study 2), the CSR. Study 1: eleven participants completed two 7-min immersions in cold water (15 °C). On one occasion, to induce anxiety, participants were instructed that the water would be 5 °C colder (ANX); it was unchanged. The other immersion was a control (CON). Study 2: ten different participants completed seven, 7-min immersions. Immersions 1-5 induced habituation. Immersions 6 and 7 were counter-balanced to produce anxiety (ANX) or acted as a control (CON). Anxiety (20 cm scale) and cardiorespiratory responses (cardiac frequency [f(c)]), respiratory frequency [f(R)], tidal volume [V(T)], minute ventilation [V(E)]) were measured in both studies. Results of study 1: participants were more anxious in the ANX immersion (mean [SD]; CON 5.3 [3.6] and ANX 8.4 [5.0] cm). f(c) peaked at higher levels in ANX (136.4 [15.0]; CON: 124.0 [17.6] b min(-1)) and was higher pre-immersion and in minutes 3 and 5-7 by 7.2 [2.1] b min(-1). ANX [Formula: see text] was higher pre immersion and in minutes 5-6. Results of study 2: repeated immersion habituated the CSR. Anxiety was greater prior to ANX (CON 1.9 [2.3], ANX 6.6 [4.8] cm). f (c) in ANX was higher prior to immersion and in minutes 1-2, 4-6 cf CON; ANX f (c) was not different to the CSR seen in pre-habituation. f (R) was higher in minute 1 of immersion 1 (cf min 1 CON and ANX) following which it exceeded the CSR in CON. The magnitude and duration of CSR (f(c), V(E)) increased with anxiety. Anxiety diminishes CSR habituation.

The influence of body adiposity, arm skinfold thickness, aerobic capacity, and cooling rate were studied in a mock survival swimming situation conducted in water at around 14 degrees C. Seventeen adult participants wore personal floatation devices on top of seasonal clothing and were asked to swim as far as they could, as if attempting to reach shore following an accidental immersion in cold water. Triceps and patellar skinfold thickness showed a significant correlation with distance covered (r = 0.70 and 0.56, respectively), while abdominal skinfold and percent body fat showed no significant correlation. Maximum oxygen consumption (VO2max) was not significantly related to distance covered. There was a negative correlation between body cooling rate during the swimming period and distance covered. A multiple stepwise regression analysis, however, indicated that the only significant contributor to variance in the distance covered was the triceps skinfold thickness (r2 = 0.49). It was concluded that for a healthy subject accidentally immersed in cold water, triceps skinfold thickness is a stronger predictor of the swimming distance covered than body adiposity, VO2max, or the drop in core temperature.

Introduction: Drowning is a leading cause of accidental death. In cold-water, sudden skin cooling triggers the life-threatening cold shock response (CSR). The CSR comprises tachycardia, peripheral vasoconstriction, hypertension, inspiratory gasp, and hyperventilation with the hyperventilatory component inducing hypocapnia and increasing risk of aspirating water to the lungs. Some CSR components can be reduced by habituation (i.e., reduced response to stimulus of same magnitude) induced by 3–5 short cold-water immersions (CWI). However, high levels of acute anxiety, a plausible emotion on CWI: magnifies the CSR in unhabituated participants, reverses habituated components of the CSR and prevents/delays habituation when high levels of anxiety are experienced concurrent to immersions suggesting anxiety is integral to the CSR.Purpose: To examine the predictive relationship that prior ratings of acute anxiety have with the CSR. Secondly, to examine whether anxiety ratings correlated with components of the CSR during immersion before and after induction of habituation.Methods: Forty-eight unhabituated participants completed one (CON1) 7-min immersion in to cold water (15°C). Of that cohort, twenty-five completed four further CWIs that would ordinarily induce CSR habituation. They then completed two counter-balanced immersions where anxiety levels were increased (CWI-ANX) or were not manipulated (CON2). Acute anxiety and the cardiorespiratory responses (cardiac frequency [fc], respiratory frequency [fR], tidal volume [VT], minute ventilation [E]) were measured. Multiple regression was used to identify components of the CSR from the most life-threatening period of immersion (1st minute) predicted by the anxiety rating prior to immersion. Relationships between anxiety rating and CSR components during immersion were assessed by correlation.Results: Anxiety rating predicted the fc component of the CSR in unhabituated participants (CON1; p < 0.05, r = 0.536, r2= 0.190). After habituation immersions (i.e., cohort 2), anxiety rating predicted the fR component of the CSR when anxiety levels were lowered (CON2; p < 0.05, r = 0.566, r2= 0.320) but predicted the fc component of the CSR (p < 0.05, r = 0.518, r2= 0.197) when anxiety was increased suggesting different drivers of the CSR when anxiety levels were manipulated; correlation data supported these relationships.Discussion: Acute anxiety is integral to the CSR before and after habituation. We offer a new integrated model including neuroanatomical, perceptual and attentional components of the CSR to explain these data.

According to the 2006 Canadian Red Cross Drowning Report, 2007 persons died of cold-water immersion in Canada between 1991 and 2000. These statistics indicate that prevention of cold-water immersion fatalities is a significant public health issue for Canadians. What should a person do after accidental immersion in cold water? For a long time, aquatic safety organizations and government agencies stated that swimming should not be attempted, even when a personal flotation device (PFD) is worn. The objective of the present paper is to present the recent scientific evidence making swimming a viable option for self-rescue during accidental cold-water immersion. Early studies in the 1960s and 1970s led to a general conclusion that "people are better off if they float still in lifejackets or hang on to wreckage and do not swim about to try to keep warm". Recent evidence from the literature shows that the initial factors identified as being responsible for swimming failure can be either easily overcome or are not likely the primary contributors to swimming failure. Studies over the last decade reported that swimming failure might primarily be related not to general hypothermia, but rather to muscle fatigue of the arms as a consequence of arm cooling. This is based on the general observation that swimming failure developed earlier than did systemic hypothermia, and can be related to low temperature of the arm muscles following swimming in cold water. All of the above studies conducted in water between 10 and 14 degrees C indicate that people can swim in cold water for a distance ranging between about 800 and 1500 m before being incapacitated by the cold. The average swimming duration for the studies was about 47 min before incapacitation, regardless of the swimming ability of the subjects. Recent evidence shows that people have a very accurate idea about how long it will take them to achieve a given swimming goal despite a 3-fold overestimation of the absolute distance to swim. The subjects were quite astute at deciding their swimming strategy early in the immersion with 86% success, but after about 30 min of swimming or passive cooling, their decision-making ability became impaired. It would therefore seem wise to make one's accidental immersion survival plan early during the immersion, directly after cessation of the cold shock responses. Additional recommendations for self-rescue are provided based on recent scientific evidence.

Expired air volumes were measured from a random population of adult male and female human volunteers before and during short-term immersion in either cold (13.53 +/- 0.13 degrees C) or warm (33.18 +/- 0.11 degrees C) water. A statistically significant difference was found in the pulmonary ventilation over the first 4 min of immersion between males and females when immersed in cold water. The swim suits worn could not account for the differences observed. No statistically significant difference in pulmonary ventilation was found between males and females during warm water immersion. A numerically smaller group of volunteers was preheated in a sauna before immersion in cold or warm water and this resulted in an attenuated ventilatory response. In this instance there is no statistically significant difference in ventilation between males and females. Also, in another small group of volunteers, surface and deep skin temperatures were continuously measured before and during immersion in cold water. The rates of change of deep skin temperature between males and females were found to be similar.

Purpose Indigenous diving populations and recreational breath-hold divers often develop hypoxia while diving in cold water. Hypoxia may delay the onset and reduce magnitude of shivering during cold exposure. It is unclear if these hypoxia-induced alterations in the control of shivering reduce total energy expenditure, a function of both shivering and non-shivering thermogenesis, and/or modify the ability to maintain core temperature during cold water immersion. Therefore, this study tested the hypothesis that normobaric hypoxia decreases total energy expenditure and results in a greater decrease in core temperature during one hour of head out cold water immersion. Methods In a randomized crossover design, 6 healthy adults (27 ± 2 y, 1 woman) completed one hour of head out cold (22°C) water immersion breathing either normobaric normoxia (FiO2 = 0.21) or normobaric hypoxia (FiO2 = 0.13). Data were collected for 10 minutes prior to water immersion (baseline) and during water immersion. Energy expenditure was estimated from oxygen consumption (V̇O2) and respiratory exchange ratio (RER) measured via indirect calorimetry. Arterial oxyhemoglobin saturation (SpO2) was estimated using pulse oximetry on the forehead. Rectal temperature was used to estimate core temperature. Brown adipose tissue activation was estimated by measuring bilateral supraclavicular skin temperature. In a subset of subjects (n = 2) skin temperature was measured bilaterally on the back over the trapezius muscle, to confirm the unique profile of changes in supraclavicular skin temperature. Data during cold water immersion were compared relative to the last two-minutes of baseline and integrated throughout water immersion (60 minutes). Data are presented as mean ± SD. Results During water immersion, SpO2 was lower in hypoxia (90 ± 3%) compared to normoxia (98 ± 2%, P < 0.01). Baseline rectal temperature was not different between hypoxia (37.3 ± 0.2°C) and normoxia (37.4 ± 0.2°C, P = 0.52). At the end of water immersion, rectal temperature in hypoxia (36.6 ± 0.4°C) was lower than in normoxia (36.9 ± 0.3°C, P < 0.01). No differences in the total increase above baseline during water immersion were observed in V̇O2 (Hypoxia: 28.3 ± 7.2L; Normoxia: 29.5 ± 6.8 L, P = 0.74) or energy expenditure (Hypoxia: 191 ± 69 KJ·min; Normoxia: 143 ± 81 KJ·min, P = 0.32) between trials. Supraclavicular skin temperature increased with water immersion (P < 0.01), while back skin temperature decreased (P = 0.02). No differences were observed in the total increase from baseline in supraclavicular skin temperature (Hypoxia: 66.6 ± 30.3°C·min; Normoxia: 66.1 ± 35.3°C·min, P = 0.54) or total decrease from baseline in back skin temperature (Hypoxia: -42.3 ± 30.8°C·min; Normoxia: -56.6 ± 7.9 °C·min, P = 0.14). Conclusions These preliminary findings support that, compared to normoxia, normobaric hypoxia promotes a greater reduction in core temperature during one hour of head out cold water immersion. The mechanism(s) underlying this observation remains unclear as no differences in energy expenditure and brown adipose tissue activation were observed, but alterations in cutaneous blood flow cannot be excluded.

A primary hazard of working in cold maritime environments is the potential for a substantial man overboard situation in freezing waters. Sudden cold-water immersion (CWI) triggers the cold shock response (CSR), which consists of cardiorespiratory responses that increase the chance of drowning. If cold shock response severity can be mitigated, life-saving actions must be taken within the first 10 min, as after this time frame drowning occurs due to cold incapacitation. To date, research shows that executive functioning is generally impaired by intense, acute stress, which implies the ability to think through potential actions to maximize survival would also be impaired by the cold shock response. To examine whether the severity of cold shock response impairs higher-level thinking in a group, 29 active duty service members completed a group format Divergent Association Task (DAT; 4-5 per group) prior to and during a 13-min cold-water immersion (water temperature: 1.3°C, air temperature: -2.7°C). Results showed no relationship between cold shock response magnitude, indexed by peak heart rate, and DAT performance. However, results indicated that those with lower skin temperatures performed worse on the DAT. Results suggest that the ability to engage in divergent thinking is relatively preserved in the critical ~10-min window although skin cooling may bias attention toward the cold stress impacting task performance. Furthermore, subjective reports of the severity of the initial gasp tracked with peak heart rate demonstrating potential utility of subjective responses in the absence of respiratory measurements.

The effect of cold immersion on hands with different types of hand protection

The Workers' Compensation Board of British Columbia requested a retrospective analysis of all fishermen's deaths from immersion in water in British Columbia. To identify the underlying cause of drowning and make recommendations to improve safety in the fishing industry. Eighty-nine inshore and offshore fishing accidents were analysed. Where possible, deaths were classified into the four stages of cold-water immersion: cold shock, swimming failure, hypothermia and post-rescue collapse. Other factors that led up to the drowning were also identified. One hundred and thirty fishermen died from immersion between 1976 and 2002. One hundred and twenty-eight drownings were certified by the coroner as drowning or drowning/hypothermia and two were certified as cardiac event after immersion. The underlying causes of drownings were reclassified as: cold shock (5.4%), swimming failure (5.4%), hypothermia (5.4%), post-rescue collapse (0.8%), cardiac event (0.8%) and drowning/other (10%). In the remaining 72.2% of deaths, there was insufficient information to determine an underlying cause. All deaths occurred in water below 17.5 degrees C but 95% were in water less than 15 degrees C. Immersion in water below 15 degrees C is dangerous and this should be emphasized on marine survival courses. Accident investigators, coroners and pathologists need a common checklist to record vital data. A recommended format is included as Supplementary data available at Occupational Medicine Online. Fishermen should be educated about the dangers of sudden, unexpected immersion in cold water. Consideration should be given to making marine survival courses mandatory for fishermen.

Accidental cold water immersion or unprepared exposure to extreme cold temperatures can negatively impact warfighter performance and mission outcomes by hindering hands and feet use due to numbness. Skin or extremity temperature has been identified as a relevant variable that predicts impairment in manual dexterity and tactile sensitivity, yet no data have been presented showing performance of medically-specific tasks, such as intravenous (IV) insertion following a cold water immersion. PURPOSE: To determine the influence of cold water immersion and rewarming on IV insertion performance among military medical providers. METHODS: Thirty-eight military personnel (mean ± SD age: 25.8 ± 5.4 yrs, height: 179.5 ± 9.9 cm, weight: 83.2 ± 10.9 kg), trained in the technique of IV insertion, participated in a Cold Weather Medicine course. During the training exercise, students completed six stations: baseline in a classroom (5 min, 23° C), pre-immersion (pre) outdoors (5 min, -4.6° C), immersion in cold water (10 min, 0.2° C), post-immersion (post) (5 min, wet clothing, -4.6° C), transition (5 min, change into dry clothing), and rewarming (60 min, using various techniques). An IV insertion task was performed upon arrival at baseline, pre- and post-immersion, and after rewarming. The IV insertion task required students to insert an IV using a manikin arm. Students were assessed for time to insert IV and success of administering fluid. RESULTS: Assessment revealed a significant increase in IV insertion time (p<0.001) and a decrease in IV insertion success rate following cold water immersion. IV insertion times (seconds) for each station were: baseline 82 ± 17, pre 70 ± 12, post 168 ± 45, and rewarm 73 ± 14. IV insertion success rates were similar among baseline (76%), pre (71%), and rewarm (84%) stations; however, post-immersion, IV success trended downward (47%). CONCLUSION: Results were consistent with the expected loss of manual dexterity following cold water immersion. When given one hour of rewarming, performance returned to baseline. It is essential that military personnel are educated and trained on the effects of accidental cold exposure, the impact it may have on their performance as medical providers, and appropriate extremity rewarming techniques.

BackgroundAn increasing volume of anecdotal and scientific evidence suggests that mood may be enhanced following swimming in cold water. The exact mechanisms responsible are largely unknown, but may include the effects of exercise from swimming and the effects of cold. This study examined the effect on mood following immersion in cold water, where swimming was not the primary activity.MethodsThe Profile of Mood States (POMS) questionnaire was completed by 64 undergraduate students. The following week, 42 participants completed up to 20‐min immersion (18ʹ36ʺ ± 1ʹ48ʺ) in cold sea water (13.6°C). Twenty‐two participants acted as controls. The POMS was completed immediately following the cold‐water immersion by both groups.ResultsThe cold‐water immersion group showed a significant decrease, with a large effect size, of 15 points from 51 to 36, compared to 2 points in the control group, 42 to 40. Positive sub‐scales increased significantly in the cold‐water immersion group (Vigour by 1.1, and Esteem‐Related Affect by 2.2 points) and negative sub‐scales showed significant reductions (Tension by 2.5, Anger 1.25, Depression 2.1, Fatigue 2.2, and Confusion 2.8 points). The control showed no significant change except for depression, which was significantly higher after the period by 1.6 points.ConclusionCold‐water immersion is a well‐tolerated therapy that is capable of significantly improving mood in young, fit, and healthy individuals. A key aim of this study was to control for the effects of swimming as a mechanism responsible for the improvement in mood which has been shown in previous studies. Thus, the change in mood evidenced in this study was not due to physical activity per se. Consequently, the hypothesis that cold in and of itself can improve mood is supported.

Swimming is a popular activity in the United Kingdom (UK); however, cold water immersion often found in open waters in the UK is not without increased risk. Drowning is among the leading cause of accidental death in 1–14-year-olds in most countries. We examined whether children and adults exhibit similar cold shock responses; rates of cooling while swimming; and subjective recognition of cooling. Nineteen children aged 10–11 years voluntarily undertook a 5 min static immersion in 15 °C (59 °F) water. Ten of them completed a swim of up to 40 min. Resting heart rate, respiratory frequency, and inspiratory volume increased in all participants on initial immersion. The mean (± SD) cooling rate while swimming was 2.5 °C hr-1 (± 3.1°). No significant correlation was found between cooling rate and thermal sensation or comfort, implying a lack of subjective awareness in children. On comparing data from unacclimatized adults in 12 °C (53.6 °F) water, children showed a smaller cold shock response (p ≤ .05), and no difference was found in cooling rates during swimming.