Non-freezing Cold Research Articles

Thermoregulatory and Metabolic Demands of Naval Special Warfare Divers During a 6-h Cold-Water Training Dive.

Introduction: Extreme environmental conditions induce changes in metabolic rate and substrate use due to thermoregulation. Cold-water full-body submersion for extended periods of time is inevitable for training and missions carried out by Naval Special Warfare divers. Anthropometric, physiologic, and metabolic data have been reported from partial immersion in cold water in non-thermally protected men; data is limited in thermally protected divers in extremely cold water. Thermoregulatory and metabolic demands during prolonged cold-water submersion in Naval Special Warfare divers are unknown.Objective: Assess thermoregulatory and metabolic demands of Naval Special Warfare divers surrounding prolonged cold-water submersion.Materials and Methods: Sixteen active-duty U.S. Navy Sea Air and Land (SEAL) operators tasked with cold-water dive training participated. Divers donned standard military special operations diving equipment and fully submerged to a depth of ∼ 6 m in a pool chilled to 5°C for a 6-h live training exercise. Metabolic measurements were obtained via indirect calorimetry for 10-min pre-dive and 5-min post dive. Heart rate, skin temperature, and core temperature were measured throughout the dive.Results: Core temperature was maintained at the end of the 6-h dive, 36.8 ± 0.4°C and was not correlated to body composition (body fat percentage, lean body mass) or metabolic rate. SEALs were not at risk for non-freezing cold injuries as mean skin temperature was 28.5 ± 1.6°C at end of the 6-h dive. Metabolic rate (kcal/min) was different pre- to post-dive, increasing from 1.9 ± 0.2 kcal/min to 2.8 ± 0.2 kcal/min, p < 0.001, 95% CI [0.8, 1.3], Cohen’s d effect size 2.3. Post-dive substrate utilization was 57.5% carbohydrate, 0.40 ± 0.16 g/min, and 42.5% fat, 0.13 ± 0.04 g/min.Conclusion: Wetsuits supported effective thermoprotection in conjunction with increase in thermogenesis during a 6-h full submersion dive in 5°C. Core temperature was preserved with an expected decrease in skin temperature. Sustained cold-water diving resulted in a 53% increase in energy expenditure. While all participants increased thermogenesis, there was high inter-individual variability in metabolic rate and substrate utilization. Variability in metabolic demands may be attributable to individual physiologic adjustments due to prior cold exposure patterns of divers. This suggests that variations in metabolic adjustments and habituation to the cold were likely. More work is needed to fully understand inter-individual metabolic variability to prolonged cold-water submersion.

Capsaicin 8% Patch Treatment in Non-Freezing Cold Injury: Evidence for Pain Relief and Nerve Regeneration.

Introduction: Neuropathic pain associated with Non-freezing Cold Injury (NFCI) is a major burden to military service personnel. A key feature of NFCI is reduction of the intra-epidermal nerve fibre density in skin biopsies, in keeping with painful neuropathy. Current oral treatments are generally ineffective and have undesirable side effects. Capsaicin 8% patch (Qutenza) has been shown to be well-tolerated and effective for reducing neuropathic pain, for up to 3 months after a single 30-minute application.Methods: In this single-centre open label study, 16 military participants with NFCI (mean duration 49 months) received 30-minute Capsaicin 8% patch treatment to the feet and distal calf. Pain symptoms were assessed using a pain diary (with the 11-point Numerical Pain Rating Scale, NPRS) and questionnaires, the investigations included skin biopsies, performed before and three months after treatment.Results: Participants showed significant decrease in spontaneous pain (mean NPRS: −1.1, 95% CI: 0.37 to 1.90; p = 0.006), and cold-evoked pain (−1.2, 95% CI: 0.40 to 2.04; p = 0.006). The time-course of pain relief over 3 months was similar to other painful neuropathies. Patient Global Impression of Change showed improvement (p = 0.0001).Skin punch biopsies performed 3 months after the patch application showed significant increase of nerve fibres with structural marker PGP9.5 (intra-epidermal nerve fibres [IENFs], p < 0.0001; sub-epidermal nerve fibres [SENFs]; p =< 0.0001), and of regenerating nerve fibres with their selective marker GAP43 (p = 0.0001). The increase of IENFs correlated with reduction of spontaneous (p = 0.027) and cold-evoked pain (p = 0.019).Conclusions: Capsaicin 8% patch provides an exciting new prospect for treatment of NFCI, with regeneration and restoration of nerve fibres, for the first time, in addition to pain relief.

Successful Recovery of Peripheral Polyneuropathy from Non-Freezing Cold Injury: A Case Report

Successful Recovery of Peripheral Polyneuropathy from Non-Freezing Cold Injury: A Case Report

Interventions for non-freezing cold injuries

Interventions for non-freezing cold injuries

Nonfreezing Cold Injury in a Pediatric Hiker

AbstractNonfreezing cold injury has been primarily described in military populations as a result of prolonged exposure to wet environments and cold, but not freezing, temperatures. This type of injury occurs less commonly in the civilian population and in children, but poses a risk for short-term debilitating extremity pain, tissue damage, and infection and for long-term chronic neuropathic pain and temperature intolerance. We describe a case of nonfreezing cold injury in a pediatric hiker.

Previous recreational cold exposure does not alter endothelial function or sensory thermal thresholds in the hands or feet.

What is the central question of this study? Does recreational cold exposure result in cold sensitivity and is this associated with endothelial dysfunction and impaired sensory thermal thresholds? What is the main finding and its importance? Previous cold exposure was correlated with cold sensitivity of the foot, which might indicate the development of a subclinical non-freezing cold injury. Endothelial function and thermal detection were not impaired in cold-sensitive individuals; therefore, further research is required to understand the pathophysiology of subclinical and clinical forms of non-freezing cold injury. In this study, we investigated whether cold-sensitive (CS) individuals, who rewarm more slowly after a mild cold challenge, have impaired endothelial function and sensory thermal thresholds (STTs) and whether this is related to reported cold exposure. Twenty-seven participants with varying previous cold exposure undertook three tests: an STT test, i.e. determination of warm and cold STTs of the fingers and dorsal foot; an endothelial function test, i.e. measurement of cutaneous vascular conductance (CVC) during iontophoresis of ACh on the forearm, finger and foot; and a CS test, involving immersion of a foot for 2min in water at 15°C followed by 10min of rewarming in air at 30°C. Toe skin temperature (Tsk ) measured during the CS test was used to form a CS group (<32°C before and 5min after immersion) and an otherwise closely matched control group [Tsk >32°C; n=9 (four women) for both groups]. A moderate relationship was found between cold exposure ranking and Tsk rewarming (r=0.408, P=0.035, n=27) but not STT or endothelial function. The Tsk and blood flow were lower in CS compared with control subjects before and after foot immersion [Tsk , mean (SD): 30.3(0.9) versus 34.8(0.8) and 27.9(0.8) versus 34.3(0.8)°C, P<0.001; and CVC: 1.08(0.79) versus 3.82(1.21) and 0.79(0.52) versus 3.45(1.07)fluxmmHg-1 , n=9, P<0.001, respectively]. However, no physiologically significant differences were observed between groups for endothelial function or STT. A moderate correlation between previous cold exposure and toe Tsk rewarming after foot immersion was observed; however, CS was not associated with impaired endothelial function or reduced thermal detection.

Nonfreezing Cold Injuries Among Long-Distance Polar Rowers

Nonfreezing cold injury (NFCI) is a peripheral cold injury that occurs when the extremities are exposed to cold temperatures, at or near the freezing point, for sustained periods of time (48-96 h at temperatures of usually around 0 to 6°C with associated wind chill). Although NFCI often goes unreported and may be underdiagnosed, it is a cause of significant morbidity in those working in cold conditions, particularly those in the military. Thus, further research into the prevention, recognition, and treatment of NFCI is warranted. The height, body weight, and body composition of 6 rowers taking part in 1 or 2 legs of the 2017 Polar Row expedition were measured. The weather conditions of the 2 legs of the journey were recorded, and symptoms relating to NFCI were documented. All incidences of NFCI occurred during Leg 2 of the expedition, which was colder and wetter. Of the Leg 2 rowers, those who developed NFCI had a trend toward higher pre-row body weight and body mass index and a trends toward losing more weight and body water relative to those who did not. The main factor contributing to the incidence of NFCI appeared to be weather; NFCI only occurred during the colder and wetter leg of the expedition. We also tentatively suggest that nutrition and dehydration may be linked to the incidence of NFCI as predisposing factors. More work, with sample sizes greater than those reported here, is required to investigate these associations to further characterize risk factors.

My Feet Are Killing Me: A Hiker’s Journey

My Feet Are Killing Me: A Hiker’s Journey

Non-freezing cold event stresses can cause significant damage to mangrove seedlings: assessing the role of warming and nitrogen enrichment in a mesocosm study

Mangroves are expanding poleward along coastlines globally as a response to rising temperatures and reduced incidence of freezing under climate change. Yet, knowledge of mangrove responses to infrequent cold events in the context of climate warming and regional nitrogen (N)-enriched eutrophication is limited. We conducted a mesocosm experiment in which the seedlings of two mangrove species (A. marina and B. gymnorrhiza) were grown either at ambient temperature or under warming with and without nitrogen (N) loading. During a short winter period, an unusually severe cold event occurred with the lowest temperature of 2 °C in the experimental region. We took this unique opportunity to assess possible response of these mangrove species to the cold stress under various environmental conditions. The cold event caused various degrees of damage to the seedlings of both mangrove species, with the warming treatment seemingly protecting leaves and branches from the cold damage. However, the warming treatment did not buffer mangroves to mortality from the low temperature stress in either species. The cold event resulted in significant decreases in seedling growth rates and net ecosystem CO2 uptake in the post-cold period relative to the pre-cold period, although the cold event did not alter the effects of warming treatment on these parameters of both mangrove species. The cold event differentially altered physiological responses of the two species growing under N loading, with the seedlings of A. marina growing in higher N concentrations having a reduced growth response after the cold event, whereas those of B. gymnorrhiza showed no change in post-cold period versus pre-cold period growth. Our results suggest that cold events may play a pivotal role in regulating mangrove survival and growth even under future warming scenarios. Two mangrove species exhibited differential survival and growth responses to the cold event at different N concentrations, which may have implications for how we can restore and conserve mangroves among the world’s eutrophied sub-tropical estuaries and with future warming.

Effects of chronic cold water exposure in fish harvesters on sensory and motor performance and cold tolerance

The purpose of this study was to compare how fish harvesters who have years of chronic cold water exposure, differ from controls, with no history of cold exposure, on tests of sensation, motor performance and cold tolerance. Twelve fish harvesters and eight controls performed the following tests in both room temperature and cold conditions: VonFrey touch, grooved pegboard, manual dexterity, maximum cold exposure, and a discomfort rating. During the room temperature test, fish harvesters had a statistically higher VonFrey touch score than controls indicating decrements to their sense of touch. Results showed no statistically significant findings between groups for either of the motor performance, maximum cold exposure or discomfort tests. Findings suggest that chronic cold water exposure does not appear to lead to an adaptation to working in the cold, but instead can lead to non-freezing cold exposure injury.

Erythromelalgia: skin redness and pain

Erythromelalgia is a rare disease that is associated with hemato-oncological diseases or after taking certain drugs and toxins, but it can also occur as an independent clinical picture, for example, due to mutations in the sodium channel NaV1.7. Clinically, there is a characteristic triad of attack-like burning pain and skin redness in the area of the distal extremities, which can be alleviated by excessive cooling. The attacks are triggered by heat, exertion, and stress. The diagnosis is primarily made clinically and can be confirmed by genetic testing if a sodium channel NaV1.7 mutation is present. Important differential diagnoses are complex regional pain syndrome, the non-freezing cold injury, and small fiber neuropathies. Therapy is multidisciplinary and has to be planned individually and include physical therapy and psychotherapy as well as drug therapy as integral components.

A review of trench foot: a disease of the past in the present.

From the French Invasion of Russia in 1812, to Glastonbury festival in 2007, trench foot has been reported, yet the exact nature of the condition remains unclear. This review explores the pathogenesis and treatment of trench foot. Trench foot is considered to be a nonfreezing cold injuryoften complicated by infection, in which exposure to cold temperatures just above freezing, combined with moisture, results in a peripheral vasoneuropathy. The presence of physical trauma, bacterial or fungal infections, malnutrition, venous hypertension and lymphoedema mean that some individuals are at greater risk of trench foot. Trench foot may be prevented by warming the feet, changing socks, staying active, rubbing the skin with oil and regularly inspecting the feet. Avoiding risk factors may help prevent the condition. The management of trench foot is less clear. Vasodilators such as iloprost and nicotinyl tartrate or sympathectomy may help. Trench foot may lead to necrosis, cellulitis, sepsis and amputation. It remains a poorly understood condition.

A 4-year follow-up of non-freezing cold injury with cold allodynia and neuropathy in 26 naval soldiers.

Background and aims Non-freezing cold injuries (NFCI), which typically may occur in military personnel, may result from exposure to cold, at temperatures around 0 °C or above, and worsened by wind and moisture. The injury is due to cooling but not freezing of tissue like in frostbite. NFCI may result in in chronic neuropathy and cold hypersensitivity. A recent retrospective study of small-and large fibres has suggested that NFCI results in neuropathic pain due to a sensory neuropathy and question a longitudinal study to verify a possible observation of improvement of NFCI over time. The present study is a 4-year follow-up investigation of large - and small-fibre function in 26 naval cadets and officers who were exposed to cold injury during the same military expedition. Methods The 26 soldiers were investigated clinically (with investigation of motor function, reflexes, sensibility), with nerve conduction studies (NCS) of major nerves in upper- and lower extremity, small fibre testing (QST, measurement of thermal thresholds), measurements of subcutaneous fat tissue and maximal O2 uptake. Investigations found place 2 months following the actual military expedition, with follow-up investigations of affected soldiers at 6-12 months and up to 3-4 years. In order to elucidate possible mechanisms (disinhibition of cold pain by myelinated nerve fibres) of cold allodynia, cold pain thresholds were measured following an ischemic block of conduction of large and small myelinated nerve fibres. Results Of 26 soldiers, 19 complained of numbness in feet and a large majority of 16 of cold hypersensitivity 2 months following injury. There were significant alterations of both large- and small-fibre function, indicating a general large- and small-fibre neuropathy. The most prominent finding was a pronounced cold allodynia, inversely correlated with the amount of subcutaneous fat. During the first year, results of NCS and thermal testing gradually normalized in most. Seven soldiers developed chronic symptoms in the form of cold hypersensitivity and with findings of cold allodynia, which was not further enhanced, but abolished following block of conduction of myelinated nerve fibres. Seven soldiers were free of symptoms from that start of the investigation, probably because they had been more eager to keep their legs moving during the exposure to cold. Conclusions Of a total of 26 soldiers, only seven developed chronic symptoms of cold hypersensitivity, corresponding to the finding of cold allodynia by thermal testing. The cold allodynia may not be explained by disinhibition of cold pain by myelinated fibres as in healthy subjects. A large majority recovered from an initial large-and small fibre neuropathy, demonstrating that recovery from NFCI may occur. Implications Although large-and small fibre neuropathy may be restored following cold injury, there is a risk of a permanent and disabling cold hypersensitivity, corresponding to the findings of cold allodynia. It is of uttermost importance to secure military personnel from the risk of cold injuries. It seems important to avoid immobilisation of extremities during exposure to cold.

Case series of non-freezing cold injury: the modern clinical syndrome

BackgroundNon-freezing cold injury (NFCI) occurs when peripheral tissue is damaged by cold exposure but not to the extent of freezing. Historically, the phenotype of NFCIs sustained was severe, whereas today...

20 Armoured Infantry Brigade downgrade study: epidemiology of principal conditions and plugging leaks in the rehabilitation pipeline

IntroductionIn April 2017, 22% of Army Full-time Trade Trained Strength was downgraded, reducing fully deployable strength to 60 546, against a target of 82 000. In June 2017, Commander 20...

Case series of non-freezing cold injury: epidemiology and risk factors

BackgroundNon-freezing cold injury (NFCI) occurs when the peripheral tissue is cooled sufficiently that damage occurs, but not to the point of tissue freezing. Historically, the phenotype of the injuries studied...

Distal limb pathologic conditions in horses treated with sleeve-style digital cryotherapy (285 cases)

Digital cryotherapy (DC) is frequently used as laminitis prophylaxis for horses. While DC with ice-water slurries is reported to be safe for up to 48 h, the safety of sleeve-style digital cryotherapy (SSDC) with ice in direct contact with the distal limb has not been evaluated. Our objective was to determine the incidence of distal limb pathologic conditions (DLPC) among horses treated with SSDC. A retrospective study of cases from 2011 to 2015 identified 285 horses treated with SSDC for a minimum of 12 h. Data collected from medical records included demographic, treatment, diagnostic, and SSDC treatment parameters. Bivariate statistics and a generalized linear regression model were created to evaluate risk factors associated with increased incidence of DLPC. Among horses treated with SSDC, 7% had tissue injury of the distal limb. Increasing duration of SSDC was associated with increased incidence of DLPC. Lesions observed included dermatitis, cellulitis, alopecia, coronitis, tissue necrosis, and distal limb edema. These lesions were similar to frostbite, non-freezing cold injury, and prolonged water immersion injuries seen in other species. While the incidence of DLPC was low, the authors recommend that horses undergoing SSDC with ice in direct contact with the skin should be monitored closely for injury when prolonged cryotherapy is clinically indicated. Further studies to improve safety, efficacy, and convenience of alternative methods of DC for horses are warranted.

Using a human thermoregulation model as a tool for design and refurbishment of industrial spaces for human occupancy

Requirements for industrial work conditions are determined by human occupancy, building construction and production processes and they should ensure the prevention and removal of heat and noxious substances from the working space. Till now costly and time-consuming experimental methods in existing buildings and fast but less reliable simulation methods at the design stage were used, which both treat the human factor as minor. In the present study we propose a user-centered methodology which combined the versatility of the thermo-physiological modeling and the reliability of in-situ measurements based on an example of a typical industrial hall.Based on the results we observed insufficient operative temperature for winter and summer months due to the missing HVAC system in the hall. As a consequence, sweat excretion, thermal sensation and skin wettedness exceeded their limits for physiological strain and thermal comfort during the summer months, and skin temperature decreased distinctly at the face and hands but was still above the limit for pain or non-freezing cold injury in the winter months.This methodology can be used for a wide range of thermal environments, activities and clothing. It eliminates the need for the exposure of human beings and provides information on physiological data, which are difficult or impractical to measure in a field study (e.g. sweat excretion, skin and core temperatures, thermal sensation). The methodology can be useful to reveal zones with distractive effect or are inappropriate for human exposition. Finally, this approach also allows using a single method and providing continuous output information for a variety of environments without needing to change approach and type of output data.

Field recognition and management of freezing and non-freezing cold injuries

AbstractPeripheral cold injuries have disabled entire armies in the past and, as recently as the Falklands conflict of 1982, jeopardised the success of an entire military operation. They can be divided into those that involve freezing of the peripheral tissue and those that do not, termed Freezing Cold Injury (FCI) and Non-Freezing Cold Injury (NFCI) respectively.This article focuses on the recognition and management of cold injuries in the field. It draws from the current literature, briefly outlining the pathophysiological basis of the two injuries, then focuses on the challenges of field recognition of cold injuries, especially NFCI, which is characterised by a lack of overt physical signs. A framework for field management of these injuries is then outlined, with an emphasis on the contrasting re-warming strategies for FCI and NFCI, and the pharmacological therapies used in each condition.The article is pertinent to those who may train or deploy to an area with temperatures lower than 20° Celsius, the generally accepted temperature below which peripheral cold injuries may occur. It is hoped that improved awareness of the risks coupled with better field recognition and management may reduce the incidence of cold injury, especially in light of recent observations that re-exposure to cold in those with NFCI can cause more significant morbidity, highlighting the importance of getting the diagnosis and management right in the field.

Field recognition and management of freezing and non-freezing cold injuries

Field recognition and management of freezing and non-freezing cold injuries