Frank Golden

Immersion deaths and deterioration in swimming performance in cold water

BACKGROUND General hypothermia (deep body temperature <35 degrees C) has been implicated in immersion-related deaths, but many deaths occur too quickly for it to be involved. We investigated changes in swimming capability in cold water to find out whether such changes could lead to swim failure and drowning. METHODS Ten volunteers undertook three self-paced breaststroke swims in a variable-speed swimming flume, in water at 25 degrees C, 18 degrees C, and 10 degrees C, for a maximum of 90 min. During each swim, we measured oxygen consumption, rectal temperature, swim speed and angle, and stroke rate and length. Swim failure was defined as being unable to keep feet off the bottom of the flume. FINDINGS All ten swimmers completed 90 min swims at 25 degrees C, eight completed swims at 18 degrees C, and five at 10 degrees C. In 10 degrees C water, one swimmer reached swim failure after 61 min and four were withdrawn before 90 min with rectal temperatures of 35 degrees C when they were close to swim failure. Swimming efficiency and length of stroke decreased more and rate of stroke and swim angle increased more in 10 degrees C water than in warmer water. These variables seemed to characterise impending swim failure. INTERPRETATION Impaired performance and initial cardiorespiratory responses to immersion probably represent the major dangers to immersion victims. Consequently, treatment should be aimed at symptoms resulting from near-drowning rather than severe hypothermia.

Habituation of the initial responses to cold water immersion in humans: a central or peripheral mechanism?

1 The initial respiratory and cardiac responses to cold water immersion are thought to be responsible for a significant number of open water deaths each year. Previous research has demonstrated that the magnitude of these responses can be reduced by repeated immersions in cold waterwhether the site of habituation is central or peripheral. 2 Two groups of subjects undertook two 3 min head‐out immersions in stirred water at 10 °C of the right‐hand side of the body (R). Between these two immersions (3 whole days) the control group (n= 7) were not exposed to cold water, but the habituation group (n= 8) undertook a further six 3 min head‐out immersions in stirred water at 10 °C of the left‐hand side of the body (L). 3 Repeated L immersions reduced (P < 0.01) the heart rate, respiratory frequency and volume responses. During the second R immersion a reduction (P < 0.05) in the magnitude of the responses evoked was seen in the habituation group but not in the control group, despite both groups having identical skin temperature profiles. 4 It is concluded that the mechanisms involved in producing habituation of the initial responses are located more centrally than the peripheral receptors.

Temperature dependence of habituation of the initial responses to cold-water immersion

Abstract The initial responses to cold-water immersion, evoked by stimulation of peripheral cold receptors, include tachycardia, a reflex inspiratory gasp and uncontrollable hyperventilation. When immersed naked, the maximum responses are initiated in water at 10°C, with smaller responses being observed following immersion in water at 15°C. Habituation of the initial responses can be achieved following repeated immersions, but the specificity of this response with regard to water temperature is not known. Thirteen healthy male volunteers were divided into a control (C) group (n = 5) and a habituation (H) group (n = 8). Each subject undertook two 3-min head-out immersions in water at 10°C wearing swimming trunks. These immersions took place at a corresponding 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 another six, 3-min, head-out immersions in water at 15°C. Respiratory rate (fR), inspiratory minute volume (V˙I) and heart rate (fH) were measured continuously throughout each immersion. Following repeated immersions in water at 15°C, the fR, V˙I and fH responses of the H group over the first 30 s of immersion were reduced (P < 0.01) from 33.3 breaths · min−1, 50.5 l · min−1 and 114 beats · min−1 respectively, to 19.8 breaths · min−1, 26.4 l · min−1 and 98 beats · min−1, respectively. In water at 10°C these responses were reduced (P < 0.01) from 47.3 breaths · min−1, 67.6 l · min−1 and 128 beats · min−1 to 24.0 breaths · min−1, 29.5 l · min−1 and 109 beats · min−1, respectively over a corresponding period of immersion. Similar reductions were observed during the last 2.5 min of immersions. The initial responses of the C group were unchanged. It is concluded that habituation of the cold shock response can be achieved by immersion in warmer water than that for which protection is required. This suggests that repeated submaximal stimulation of the cutaneous cold receptors is sufficient to attenuate the responses to more maximal stimulation.

Cold sensitivity test for individuals with non-freezing cold injury: the effect of prior exercise

BackgroundOne of the chronic symptoms of non-freezing cold injury (NFCI) is cold sensitivity. This study examined the effects of prior exercise on the response to a cold sensitivity test (CST) in NFCI patients with the aim of improving diagnostic accuracy.MethodsTwenty three participants, previously diagnosed with NFCI by a Cold Injuries Clinic, undertook two CSTs. Participants either rested (air temperature 31°C) for approximately 80 min (prior rest condition (REST)) or rested for 30 min before exercising gently for 12 min (prior exercise condition (EX)). Following REST and EX, the participants placed their injured foot, covered in a plastic bag, into 15°C water for 2 min; this was followed by spontaneous rewarming in 31°C air for 10 min.ResultsThe great toe skin temperature (Tsk) before immersion averaged 32.5 (3.4)°C in both conditions. Following immersion, the rate of rewarming of the great toe Tsk was faster in EX compared to REST and was higher 5 min (31.7 (3.4)°C vs. 29.8 (3.4)°C) and 10 min (33.8 (4.0)°C vs. 32.0 (4.0)°C) post-immersion. Over the first 5 min of rewarming, changes in the great toe Tsk correlated with the changes in skin blood flow (SkBF) in EX but not the REST condition. No relationship was observed between Tsk in either CST and the severity of NFCI as independently clinically assessed.ConclusionsExercise prior to the CST increased the rate of the toe Tsk rewarming, and this correlated with the changes in SkBF. However, the CST cannot be used in isolation in the diagnosis of NFCI, although the EX CST may prove useful in assessing the severity of post-injury cold sensitivity for prognostic and medico-legal purposes.

Swimming performance in surf: the influence of experience

This study tested the hypothesis (H1) that surf swimming involves a quantifiable experience component. Sixty-five beach lifeguards with (n = 35) and without surf experience (n = 30) completed: a best effort 200-m swim in a 25-m pool, a calm and a surf sea; an anthropometric survey; maximum effort 30-s swim bench test; 50-m pool swim (25 m underwater). In both groups, time to swim 200 m was slower in calm seas than in the pool and slower in surf than in either calm seas or the pool (p < 0.05). Calm sea swim times of the two groups did not differ significantly, but the no experience group was, on average (Sp-pooled variance), 49 s (62) slower on the 200-m swim in the surf conditions (p < 0.05). A stepwise regression identified surf experience as a predictor of surf swim time (R(2) = 0.32, p < 0.01). It is concluded that there is a significant and quantifiable (18 %) experience factor in surf swimming. This limits the usefulness of pool swim times and other land-based tests as predictors of surf swimming performance. The hypothesis (H1) is accepted.

Sublingual glyceryl trinitrate and the peripheral thermal responses in normal and cold-sensitive individuals

Non-freezing cold injury (NFCI) is a prevalent, but largely undiagnosed and poorly understood syndrome afflicting many who, as part of their work or leisure, expose their extremities to cold temperatures. The long term sequelae of NFCI are hyperhidrosis, cold-sensitivity and pain; these can last a lifetime. We tested the hypothesis that, in comparison with a placebo, sublingual glyceryl trinitrate (GTN) would increase the peripheral microcirculation during and after a mild cold challenge of individuals who had not been diagnosed with NFCI, but were cold-sensitive. Naive participants were categorised into two cohort groups: control (n=7) or cold-sensitive (n=6). All participants undertook a standardised two minute cold exposure of their right foot while toe skin temperature (Tsk; infra-red thermograms) and blood flow (toe pad laser Doppler) were measured. GTN increased the rate of rewarming and absolute Tsk of the coldest toe after the cold challenge in cold-sensitive individuals. GTN also increased the blood flow in the great toe during rewarming in some cold-sensitive individuals. We accept our hypothesis and suggest that the impairment in the vasodilatory response seen in individuals with cold-sensitivity can be overcome by the use of GTN, an endothelial-independent NO donor, and thereby improve the rewarming of cooled peripheral tissues.

Drowning: guidelines extant, evidence-based risk for rescuers?

In recent editions of Resuscitation there has been an interesting nd constructive debate on the topic of the rescue and resusciation of submerged victims. This was prompted by a paper we rote1 which itself was prompted by a request for clear guidance n the issue from the emergency services.2 Our guidance was clear, ualified and specific to those that are submerged; as evidenced y the title “A proposed decision-making guide for the search, rescue nd resuscitation of submersion (head under) victims based on expert pinion”. On the basis of the available literature we concluded that, f water temperature is warmer than 6 ◦C survival/resuscitation s extremely unlikely if submerged longer than 30 min. If water emperature is 6 ◦C or below, survival/resuscitation is extremely nlikely if submerged longer than 90 min.1 In a recent edition of Resuscitation, in an Editorial under the eading “Drowning: more hope for patients, less hope for guidelines”3 rofessor Deakin reviews our guidelines in the light of two papers ublished in the same edition.4,5 In contrast to Professor Deakin’s onclusion, we can find nothing in the papers that changes our view, ndeed just the opposite. It is important to understand how this osition can come about, lest the issue gets clouded by semantics nd confuses those still in search of clear, evidence-based guidance. In his editorial, Professor Deakin uses “immersion” and “subersion” interchangeably; the editorial also includes a somewhat mbiguous statement “.. it may be premature to abandon search and escue efforts as soon as 30 min after submersion in water above ◦C”. We must be clear about this; it is submersion (head under) hat we are interested in rather than immersion (head out), and our aper refers to those who remain submerged in water warmer than ◦C and have not been found despite 30 min of searching. Professor eakin’s statement could be misunderstood as meaning that if an ndividual has had a brief period of submersion at the start or end f an immersion, resuscitative efforts should not be undertaken if 0 min have elapsed – this is not our position. We are interested n when the risk to rescuers – which is likely to increase with time may outweigh the likelihood of finding a submerged individual ho can be resuscitated. It follows that this guidance is particularly ertinent in conditions that place rescuers at high risk. What do the papers reviewed by Professor Deakin actually add o the debate on the rescue and resuscitation of submerged vicims? The answer is that neither paper provides data associated ith prolonged submersion and subsequent survival that changes ur original conclusion. The data of Claesson et al4 are insufficient to ake conclusions concerning water temperature, however when eporting accidents where divers were required (submersions), hey state (page 4, under “3.3.3. Survival”) “The median submerion time was 15 min, no survivors were found after this time in the

The physiology of cooling in cold water

During immersion in cold water, there is a very clear chronology with regard to cooling of the tissues of the body. Firstly, during head-out immersion, the skin is cooled, followed by cooling of the superficial nerves and musculature and finally of the deep tissues. The stages of immersion in cold water associated with particular risk were first outlined by Golden and Hervey [1] and are directly related to the cooling of these tissues.

Peripheral thermal responses in normal and cold-sensitive individuals to sublingual Glyceryl Trinitrate (GTN)

Non-freezing cold injury (NFCI) is caused by prolonged exposure of the extremities to cold. The long-term sequelae of NFCI, include cold-sensitivity and pain[1]. The cold sensitivity is characterised by a reduction in basal skin blood flow and augmented vasoconstriction during cold exposure. We tested the hypothesis that sublingual GTN would increase blood flow in the peripheral microcirculation during and after a mild cold challenge in individuals who had not been diagnosed with NFCI, but were cold-sensitive.