Reproducibility of the cold-induced vasodilation response in the human finger

Changes in Fingertip Cold-Induced Vasodilatation (Hunting Reaction) on Acute Exposure to Altitude

Fossati, Alexandre, and Aleid C. J. Ruijs. Changes in fingertip cold-induced vasodilatation (hunting reaction) on acute exposure to altitude. High Alt Med Biol. 00:000-000, 2024. Objective: Cold-induced vasodilation (CIVD) of the extremities is an interesting part of human physiology. Although the physiology of the CIVD reaction remains unknown, there are indications that hypoxia influences our CIVD reaction. The objective of this study is to measure the influence of acute hypoxia on the CIVD reaction of the fingertips. Methods: The CIVD reaction was measured using immersion of one hand in a water bath of 0°C in 12 healthy volunteers at low (1,235 m) and high (3,800 m) altitude during 35 minutes. High altitude was reached by a 20-minute cable car ride. Testing was performed indoors (room temperature, 22-25°C) at both altitudes. Data analysis was performed measuring the parameters of the CIVD reaction. Differences were found using the paired Student's t-test. Results: There was no significant difference in baseline finger temperature, onset time, peak time, and frequency of the CIVD reaction. However, at high altitude, maximum temperature and amplitude were significantly higher, slope was steeper, and minimum temperature was lower. Conclusion: We did not find evidence for a diminished CIVD reaction at high altitude due to hypoxia.

Short-term cocoa bioflavanol supplementation does not improve cold-induced vasodilation in young healthy adults

PURPOSE

Cold-induced vasodilation (CIVD) is an oscillatory rise in blood flow to glabrous skin that occurs in cold-exposed extremities. Dietary flavanols increase bioavailable nitric oxide, a proposed mediator of CIVD through active vasodilation and/or withdrawal of sympathetic vascular smooth muscle tone. However, no studies have examined the effects of flavanol intake on extremity skin perfusion during cold exposure. We tested the hypothesis that acute and 8-day flavanol supplementation would augment CIVD during single-digit cold water immersion (CWI).

METHODS

Eleven healthy adults (24 ± 6 years; 10 M/1F) ingested cocoa flavanols (900 mg/day) or caffeine- and theobromine-matched placebo for 8 days in a double-blind, randomized, crossover design. On Days 1 and 8, CIVD was assessed 2 h post-treatment. Subjects immersed their 3rd finger in warm water (42 °C) for 15 min before CWI (4 °C) for 30 min, during which nail bed and finger pad skin temperature were measured.

RESULTS

Flavanol ingestion had no effect on CIVD frequency (Day 1, Flavanol: 3 ± 2 vs. Placebo: 3 ± 2; Day 8, Flavanol: 3 ± 2 vs. Placebo: 3 ± 1) or amplitude (Day 1, Flavanol: 4.3 ± 1.7 vs. Placebo: 4.9 ± 2.6 °C; Day 8, Flavanol: 3.9 ± 1.9 vs. Placebo: 3.9 ± 2.0 °C) in the finger pad following acute or 8-day supplementation (P > 0.05). Furthermore, average, nadir, and apex finger pad temperatures during CWI were not different between treatments on Days 1 or 8 of supplementation (P > 0.05). Similarly, no differences in CIVD parameters were observed in the nail bed following supplementation (P > 0.05).

CONCLUSION

These data suggest that cocoa flavanol ingestion does not alter finger CIVD. Clinical Trial Registration Clinicaltrials.gov Identifier: NCT04359082. April 24, 2020.

Cold-induced vasodilation during sequential immersions of the hand

A common practice for those operating in cold environments includes repetitive glove doffing and donning to perform specific tasks, which creates a repetitive cycle of hand cooling and rewarming. This study aimed to determine the influence of intraday repeated hand cooling on cold-induced vasodilation (CIVD), sympathetic activation, and finger/hand temperature recovery. Eight males and two females (mean ± SD age: 28 ± 5 year; height: 181 ± 9 cm; weight: 79.9 ± 10.4 kg) performed two 30-min hand immersions in cold (4.3 ± 0.92 °C) water in an indoor environment (18 °C). Both immersions (Imm1; Imm2) were performed on the same day and both allowed for a 10-min recovery. CIVD components were calculated for each finger (index, middle, ring) during each immersion. CIVD onset time (index, p = 0.546; middle, p = 0.727; ring, p = 0.873), minimum finger temperature (index, p = 0.634; middle, p = 0.493; ring, p = 0.575), and mean finger temperature (index, p = 0.986; middle, p = 0.953; ring, p = 0.637) were all similar between immersions. Recovery rates generally demonstrated similar responses as well. Findings suggest that two sequential CIVD tests analyzing the effect of prior cold exposure of the hand does not impair the CIVD response or recovery. Such findings appear promising for those venturing into cold environments where hands are likely to be repeatedly exposed to cold temperatures.

Hybrid Photoacoustic Ultrasound Imaging System for Cold-Induced Vasoconstriction and Vasodilation Monitoring

Lewis hunting reaction refers to the alternating cold-induced vasoconstriction and dilation in extremities, whose underlying mechanism is complex. While numerous studies reported this intriguing phenomenon by measuring cutaneous temperature fluctuation under cold exposure, few of them tracked peripheral vascular responses in real-time, lacking a non-invasive and quantitative imaging tool. To better monitor hunting reaction and diagnose relevant diseases, we developed a hybrid photoacoustic ultrasound (PAUS) tomography system to monitor finger vessels' dynamic response to cold, together with simultaneous temperature measurement. We also came out a standard workflow for image analysis with self-defined indices. In the small cohort observational study, vascular changes in the first cycle of hunting reaction were successfully captured by the image series and quantified. Time difference between vasodilation and temperature recovery was noticed and reported for the first time, thanks to the unique capability of the PAUS imaging system in real-time and continuous vascular monitoring. The developed imaging system and indices enabled more objective and quantitative monitoring of peripheral vascular activities, indicating its great potential in numerous clinical applications.

A century of exercise physiology: concepts that ignited the study of human thermoregulation. Part 3: Heat and cold tolerance during exercise

In this third installment of our four-part historical series, we evaluate contributions that shaped our understanding of heat and cold stress during occupational and athletic pursuits. Our first topic concerns how we tolerate, and sometimes fail to tolerate, exercise-heat stress. By 1900, physical activity with clothing- and climate-induced evaporative impediments led to an extraordinarily high incidence of heat stroke within the military. Fortunately, deep-body temperatures > 40 °C were not always fatal. Thirty years later, water immersion and patient treatments mimicking sweat evaporation were found to be effective, with the adage of cool first, transport later being adopted. We gradually acquired an understanding of thermoeffector function during heat storage, and learned about challenges to other regulatory mechanisms. In our second topic, we explore cold tolerance and intolerance. By the 1930s, hypothermia was known to reduce cutaneous circulation, particularly at the extremities, conserving body heat. Cold-induced vasodilatation hindered heat conservation, but it was protective. Increased metabolic heat production followed, driven by shivering and non-shivering thermogenesis, even during exercise and work. Physical endurance and shivering could both be compromised by hypoglycaemia. Later, treatments for hypothermia and cold injuries were refined, and the thermal after-drop was explained. In our final topic, we critique the numerous indices developed in attempts to numerically rate hot and cold stresses. The criteria for an effective thermal stress index were established by the 1930s. However, few indices satisfied those requirements, either then or now, and the surviving indices, including the unvalidated Wet-Bulb Globe-Thermometer index, do not fully predict thermal strain.

Cold-induced vasodilation response in a Japanese cohort: insights from cold-water immersion and genome-wide association studies

BACKGROUND

Cold-induced vasodilation (CIVD) occurs after blood vessels in the skin are constricted due to local cold exposure. Although many CIVD studies have been conducted, the underlying molecular mechanisms are yet to be clarified. Therefore, we explored genetic variants associated with CIVD response using the largest-scale dataset reported to date in a CIVD study involving wavelet analysis; thus, the findings improve our understanding of the molecular mechanisms that regulate the CIVD response.

METHODS

We performed wavelet analysis of three skin blood flow signals [endothelial nitric oxide (eNO)-independent, eNO-dependent, and neurogenic activities] during finger cold-water immersion at 5 °C in 94 Japanese young adults. Additionally, we conducted genome-wide association studies of CIVD using saliva samples collected from the participants.

RESULTS

We found that the mean wavelet amplitudes of eNO-independent and neurogenic activities significantly increased and decreased prior to CIVD, respectively. Our results also implied that as many as ~ 10% of the Japanese subjects did not show an apparent CIVD response. Our genome-wide association studies of CIVD using ~ 4,040,000 imputed data found no apparent CIVD-related genetic variants; however, we identified 10 genetic variants, including 2 functional genes (COL4A2 and PRLR) that are associated with notable blunted eNO-independent and neurogenic activity responses in individuals without CIVD response during local cold exposure.

CONCLUSIONS

Our findings indicate that individuals without CIVD response differentiated by genotypes with COL4A2 and PRLR genetic variants exhibited notable blunted eNO-independent and neurogenic activity responses during local cold exposure.

Partial cooling of the upper body with a water-cooled vest in an environment exceeding body temperature

OBJECTIVES

To evaluate the efficacy of water-cooled clothing that continuously cools restricted body areas to suppress body temperature increase as an anti-heatstroke measure for workers in hot environments that exceed body temperature.

METHODS

Ten healthy men were placed in Room A (air temperature: 25°C, relative humidity: 50%) for 15 min. They were then transferred to Room B (air temperature: 40°C, relative humidity: 50%), where they rested for 10 min, then put on cooling clothing, and again rested for 15 min (the control group rested for 25 min). They then performed intense ergometer exercise for 40 min at 40% maximal oxygen consumption after which they rested for 10 min. The three trial conditions were CON (long-sleeved summer work clothes), VEST (cooling vest), and P-VEST (partial cooling vest). In VEST and P-VEST, water-cooled clothing continuously recirculated with 10°C water was used to cool the upper body. In P-VEST, only the neck, axillae, and heart areas were in contact with the cooled clothing. The measured indices were the rectal, esophageal, and external auditory canal temperatures; heart rate; estimated sweat volume; and subjective evaluations.

RESULTS

Compared with the CON condition, the rectal, esophageal, and external auditory canal temperatures and the heart rate were significantly lower and the subjective indices were decreased in the VEST and P-VEST conditions.

CONCLUSIONS

Partial cooling showed a body cooling effect similar to that of whole upper body cooling. Partial body cooling promoted the heat dissipation, suggesting that partial cooling is efficient for maintaining body cooling in hot environments.

The impact of winter warming and more frequent icing events on reindeer herder occupational safety, health, and wellbeing

BACKGROUND

Northern Finland, like the rest of the Arctic, has experienced increases in mean annual temperature, the number of winter rains, the number of thaw-freeze days, the number of extremely warm weather events, and a shortened snow season. These changes have produced numerous problems for reindeer herders whose livelihoods rely on a healthy ecosystem with predictable weather patterns.

METHODS

We performed a scoping literature review to assess how climate change induced extreme weather has negatively impacted reindeer herding as well as the health and wellbeing of reindeer herders.

RESULTS

Late snow cover negatively impacts reindeer herding through a more widely dispersed herd that increases the work to gather reindeer, leads to reduced calf weight, and results in less meat for sale. This increased labor, especially in extreme cold conditions, can also negatively impact reindeer herder health. Icing due to thaw-freeze and rain-on-snow events makes it impossible for reindeer to dig through the snow to access lichens, increasing the need for reindeer herders to keep the herd in winter enclosures and provide supplemental feed.

CONCLUSION

Climate change induced weather events such as late snow cover and icing increase reindeer herder efforts and expenses, put their livelihood at risk, and put their health at risk.

Acral skin vasoreactivity and thermosensitivity to hand cooling following 5 days of intermittent whole-body cold exposure

We sought to examine whether short-term whole-body cold acclimation would modulate finger vasoreactivity and thermosensitivity to localized cooling. Fourteen men were equally assigned to either the experimental (CA) or the control (CON) group. The CA group was immersed to the chest in 14°C water for ≤120 min daily over a 5-day period, while the skin temperature of the right-hand fingers was clamped at ~35.5°C. The CON group was instructed to avoid any cold exposure during this period. Before and after the intervention, both groups performed, on two different consecutive days, a local cold provocation trial consisting of a 30-min hand immersion in 8°C water, while immersed to the chest once in 21°C (mild-hypothermic trial; 0.5°C fall in rectal temperature from individual pre-immersion values) and on the other occasion in 35.5°C (normothermic trial). In the CA group, the cold-induced reduction in finger temperature was less (mild-hypothermic trial: P = 0.05; normothermic trial: P = 0.02), and the incidence of the cold-induced vasodilation episodes was greater (in normothermic trials: P = 0.04) in the post than in the pre-acclimation trials. The right-hand thermal discomfort was also attenuated (mild-hypothermic trial: P = 0.04; normothermic trial: P = 0.01). The finger temperature responses of the CON group did not vary between testing periods. Our findings suggest that repetitive whole-body exposure to severe cold within a week, may attenuate finger vasoreactivity and thermosensitivity to localized cooling. These regional thermo-adaptions were ascribed to central neural habituation produced by the iterative, generalized cold stimulation.

Reproducibility of Skin Temperature Response after Cold Stress Test Using the Game Ready System: Preliminary Study

The objective of this preliminary study was to determine the reproducibility of lower limbs skin temperature after cold stress test using the Game Ready system. Skin temperature of fourteen participants was measured before and after cold stress test using the Game Ready system and it was repeated the protocol in four times: at 9:00, at 11:00, at 19:00, and at 9:00 h of the posterior day. To assess skin temperature recovery after cold stress test, a logarithmic equation for each region was calculated, and constant (β₀) and slope (β₁) coefficients were obtained. Intraclass correlation coefficient (ICC), standard error (SE), and within-subject coefficient of variation (CV) were determined. No differences were observed between measurement times in any of the regions for the logarithmic coefficients (p > 0.38). Anterior thigh (β₀ ICC 0.33–0.47; β₁ ICC 0.31–0.43) and posterior knee (β₀ ICC 0.42–0.58; β₁ ICC 0.28–0.57) were the regions with the lower ICCs, and the other regions presented values with a fair and good reproducibility (ICC > 0.41). Posterior leg was the region with the better reproducibility (β₀ ICC 0.68–0.78; β₁ ICC 0.59–0.74; SE 3–4%; within-subject CV 7–12%). In conclusion, cold stress test using Game Ready system showed a fair and good reproducibility, especially when the posterior leg was the region assessed.

Comprehensive Treatment of Single Finger Frostbite: A Case Study

Third- and fourth-degree frostbites usually result in loss of skin and tissue requiring amputation, and scarring. The 3- to 6-week waiting period is often necessary to determine the severity of the lesion. This period is also a critical time for the rescue of frostbitten tissue. This patient was a 30-year-old man who developed frostbite of his right index finger. He presented to our hospital 4 hours after injury with loss of sensation on the whole index finger and early signs of necrosis. The patient received a series of comprehensive treatments, including fasciotomy, injection of papaverine hydrochloride, baking lamp irradiation, and negative pressure treatment. At the time of discharge, he had re-epithelialization of the index finger by 21 days after injury. The conclusion of this paper is that the comprehensive treatments combined with negative pressure wound treatment has certain clinical application value for the rescue of deep frostbite tissues.

Cold-induced vasodilation responses before and after exercise in normobaric normoxia and hypoxia

PURPOSE

Cold-induced vasodilation (CIVD) is known to protect humans against local cold injuries and improve manual dexterity. The current study examined the effects of metabolic heat production on cold-induced vasodilation responses in normobaric hypoxia and normoxia.

METHODS

Ten participants immersed their non-dominant hand into 5 °C water for 15 min. Minimum finger temperature (T_min), maximum finger temperature (T_max), onset time, amplitude, and peak time were measured before and after exercise under normoxia (21% O₂) and two levels of normobaric hypoxia (17% O₂ and 13% O₂).

RESULTS

Neither T_min nor amplitude was affected by hypoxia. However, T_max was significantly decreased by hypoxia while reduction in onset time and peak time trended towards significance. T_min, T_max, and amplitude were significantly higher during post-exercise CIVD than pre-exercise CIVD.

CONCLUSION

The CIVD response may be negatively affected by the introduction of hypoxia whereas metabolic heat production via exercise may counteract adverse effects of hypoxia and improve CIVD responses.

Wearable Sensors Reveal Menses-Driven Changes in Physiology and Enable Prediction of the Fertile Window: Observational Study

Background

Previous research examining physiological changes across the menstrual cycle has considered biological responses to shifting hormones in isolation. Clinical studies, for example, have shown that women’s nightly basal body temperature increases from 0.28 to 0.56 ˚C following postovulation progesterone production. Women’s resting pulse rate, respiratory rate, and heart rate variability (HRV) are similarly elevated in the luteal phase, whereas skin perfusion decreases significantly following the fertile window’s closing. Past research probed only 1 or 2 of these physiological features in a given study, requiring participants to come to a laboratory or hospital clinic multiple times throughout their cycle. Although initially designed for recreational purposes, wearable technology could enable more ambulatory studies of physiological changes across the menstrual cycle. Early research suggests that wearables can detect phase-based shifts in pulse rate and wrist skin temperature (WST). To date, previous work has studied these features separately, with the ability of wearables to accurately pinpoint the fertile window using multiple physiological parameters simultaneously yet unknown.

Objective

In this study, we probed what phase-based differences a wearable bracelet could detect in users’ WST, heart rate, HRV, respiratory rate, and skin perfusion. Drawing on insight from artificial intelligence and machine learning, we then sought to develop an algorithm that could identify the fertile window in real time.

Methods

We conducted a prospective longitudinal study, recruiting 237 conception-seeking Swiss women. Participants wore the Ava bracelet (Ava AG) nightly while sleeping for up to a year or until they became pregnant. In addition to syncing the device to the corresponding smartphone app daily, women also completed an electronic diary about their activities in the past 24 hours. Finally, women took a urinary luteinizing hormone test at several points in a given cycle to determine the close of the fertile window. We assessed phase-based changes in physiological parameters using cross-classified mixed-effects models with random intercepts and random slopes. We then trained a machine learning algorithm to recognize the fertile window.

Results

We have demonstrated that wearable technology can detect significant, concurrent phase-based shifts in WST, heart rate, and respiratory rate (all P<.001). HRV and skin perfusion similarly varied across the menstrual cycle (all P<.05), although these effects only trended toward significance following a Bonferroni correction to maintain a family-wise alpha level. Our findings were robust to daily, individual, and cycle-level covariates. Furthermore, we developed a machine learning algorithm that can detect the fertile window with 90% accuracy (95% CI 0.89 to 0.92).

Conclusions

Our contributions highlight the impact of artificial intelligence and machine learning’s integration into health care. By monitoring numerous physiological parameters simultaneously, wearable technology uniquely improves upon retrospective methods for fertility awareness and enables the first real-time predictive model of ovulation.

Ski-Everest (8848 m) Expedition: Digit Skin Temperature Responses to Cold Immersion May Reflect Susceptibility to Cold Injury

INTRODUCTION

We tested the hypothesis that individual susceptibility to freezing cold injury might be reflected in an attenuated cold-induced vasodilatation (CIVD) response by comparing the CIVD responses of an elite alpinist with a history of freezing cold injury in the feet (case alpinist) with those of an age- and ability- matched noninjured alpinists control group (controls). According to this hypothesis, the vasomotor responses to a CIVD test of the case alpinist would represent a pathophysiological response when compared with the normal physiological response of a noninjured cohort.

METHODS

The case alpinist and the controls in the cohort group conducted a cold water immersion test comprising sequential immersion of a hand and foot for 5 min in 35°C water, followed by a 30-min immersion in 8°C water and a 10-min recovery period in room air. During this test we monitored the finger and toe skin temperatures.

RESULTS

The case alpinist had a significantly attenuated CIVD response and a lower skin temperature in all injured and noninjured digits during immersion (∼2°C lower than in the control group) and an attenuated recovery of finger skin temperatures (∼6°C lower than in the control group).

CONCLUSIONS

The attenuated CIVD response of the case alpinist may reflect a previously unrecognized enhanced susceptibility to frostbite. In addition to the poor vasomotor response observed in the injured toes, he also exhibited a poor vasomotor response in his noninjured fingers. The results of the present study indicate that a test of vasomotor activity during thermal stress may identify individuals predisposed to cold injury.

Modern fertility awareness methods: wrist wearables capture the changes in temperature associated with the menstrual cycle

Core and peripheral body temperatures are affected by changes in reproductive hormones during the menstrual cycle. Women worldwide use the basal body temperature (BBT) method to aid and prevent conception. However, prior research suggests that taking one's daily temperature can prove inconvenient and subject to environmental factors. We investigate whether a more automatic, non-invasive temperature measurement system can detect changes in temperature across the menstrual cycle. We examined how wrist skin temperature (WST), measured with wearable sensors, correlates with urinary tests of ovulation and may serve as a new method of fertility tracking. One hundred and thirty-six eumenorrheic, non-pregnant women participated in an observational study. Participants wore WST biosensors during sleep and reported their daily activities. An at-home luteinizing hormone (LH) test was used to confirm ovulation. WST was recorded across 437 cycles (mean cycles/participant = 3.21, S.D. = 2.25). We tested the relationship between the fertile window and WST temperature shifts, using the BBT three-over-six rule. A sustained 3-day temperature shift was observed in 357/437 cycles (82%), with the lowest cycle temperature occurring in the fertile window 41% of the time. Most temporal shifts (307/357, 86%) occurred on ovulation day (OV) or later. The average early-luteal phase temperature was 0.33°C higher than in the fertile window. Menstrual cycle changes in WST were impervious to lifestyle factors, like having sex, alcohol, or eating prior to bed, that, in prior work, have been shown to obfuscate BBT readings. Although currently costlier than BBT, the present study suggests that WST could be a promising, convenient parameter for future multiparameter fertility awareness methods.

Koroška 8000 Himalayan expedition: digit responses to cold stress following ascent to Broadpeak (Pakistan, 8051 m)

PURPOSE

Cold-induced vasodilatation (CIVD) is a peripheral blood flow response, observed in both the hands and feet. Exercise has been shown to enhance the response, specifically by increasing mean skin temperatures (T_sk), in part due to the increased number of CIVD waves. In contrast, hypobaric hypoxia has been suggested to impair digit skin temperature responses, particularly during subsequent hand rewarming following the cold stimulus. This study examined the combined effect of exercise and hypobaric hypoxia on the CIVD response. We compared the CIVD responses in the digits of both the hands and feet of a team of alpinists (N = 5) before and after a 35-day Himalayan expedition to Broadpeak, Pakistan (8051 m).

METHODS

Five elite alpinists participated in hand and foot cold water immersion tests 20 days before and immediately upon return from their expedition.

RESULTS

The alpinists summited successfully without supplemental oxygen. Post-expedition, all alpinists demonstrated higher minimum T_sk in their hands (pre: 9.9 ± 1.1, post: 10.1 ± 0.7 °C, p = 0.031). Four alpinists had either greater CIVD waves, and, consequently, higher mean T_sk in their hands, or higher recovery temperatures (pre: 26.0 ± 5.5 °C post: 31.0 ± 4.1 °C, p = 0.052), or faster rewarming rate (pre: 2.6 ± 0.5 °C min^-1 post: 3.1 ± 0.4 °C min^-1,p = 0.052). In the feet, the responses varied: 1/5 had higher wave amplitudes and 1/5 had higher passive recovery temperatures, whereas 3/5 had lower mean toe temperatures during cold exposure.

CONCLUSIONS

The results of the cold stress test suggest after a 35-day Himalayan expedition, alpinists experienced a slight cold adaptation of the hands, but not the feet.

Cold Susceptibility of Digit Stumps Resulting from Amputation After Freezing Cold Injury in Elite Alpinists

Gorjanc, Jurij, Shawnda A. Morrison, Rok Blagus, and Igor B. Mekjavic. Cold susceptibility of digit stumps resulting from amputation after freezing cold injury in elite alpinists. High Alt Med Biol. 19:185-192, 2018.

AIM

The aim of the study was to assess whether previous freezing cold injury in fingers and/or toes might predispose alpinists to greater risk of further freezing cold injury, primarily due to a greater vasoconstrictor response to cold, resulting in a lower perfusion, reflected in lower skin temperature.

METHODS

Ten elite alpinists (N = 10; 8 male and 2 female) with amputations after freezing cold injury participated in a cold-water (8°C) immersion stress test of the hands and feet. Digit skin temperatures of amputated digits, their noninjured counterparts, noninjured digits of the affected side and noninjured digits of the corresponding side were measured. The skin temperatures were compared during three consecutive phases of the cold stress test: prewarming, cold water immersion, and passive heating.

RESULTS

Amputated toes cooled much faster compared to their uninjured counterparts (n = 26, p < 0.001), and attained lower skin temperatures during the cold exposure test (n = 26, p < 0.001). Higher cooling rate was observed in all the toes on the injured limb compared with the toes on the uninjured limb (n = 40, p < 0.001). In contrast to the toes, the fingers on the injured limb after freezing cold injury were warmer during cooling phase compared to uninjured fingers (n = 15, p < 0.001).

CONCLUSIONS

The lower digit temperatures observed in affected toe stumps during the cold stress test compared to the nonamputated toes may indicate a heightened risk of future freezing cold injury with subsequent cold exposures, as a consequence of less perfusion, reflected in the lower skin temperature. This relationship was not confirmed in the fingers.

No association between hand and foot temperature responses during local cold stress and rewarming

Purpose

The purpose was to examine whether associations exist between temperature responses in the fingers vs. toes and hand vs. foot during local cold-water immersion and rewarming phases.

Methods

Seventy healthy subjects (58 males, 12 females) immersed their right hand or right foot, respectively, in 8 °C water for 30 min (CWI phase), followed by a 15-min spontaneous rewarming (RW) in 25 °C air temperature.

Results

Temperature was lower in the toes than the fingers during the baseline phase (27.8 ± 3.0 vs. 33.9 ± 2.5 °C, p < 0.001), parts of the CWI phase (min 20–30: 8.8 ± 0.7 vs. 9.7 ± 1.4 °C, p < 0.001), and during the RW phase (peak temperature: 22.5 ± 5.1 vs. 32.7 ± 3.6 °C, p < 0.001). Cold-induced vasodilatation (CIVD) was more common in the fingers than in the toes (p < 0.001). Within the first 10 min of CWI, 61% of the subjects exhibited a CIVD response in the fingers, while only 6% of the subjects had a CIVD response in the toes. There was a large variability of temperature responses both within and between extremities, and there was a weak correlation between finger- and toe temperature both during the CWI (r = 0.21, p = 0.08) and the RW phases (r = 0.26, p = 0.03).

Conclusions

Results suggest that there is generally a lower temperature in the toes than the fingers after a short time of local cold exposure and that the thermal responses of the fingers/hands are not readily transferable to the toes/foot.

Relationships of self-identified cold tolerance and cold-induced vasodilatation in the finger

This study was conducted to investigate relationships of self-identified cold tolerance and cold-induced vasodilatation (CIVD) in the finger. Nine males and 34 females participated in the following 2 tests: a CIVD test and a self-reported survey. The CIVD test was conducted 30-min cold-water immersion (3.8 ± 0.3 °C) of the middle finger at an air temperature of 27.9 ± 0.1 °C. The self-reported questionnaire consisted of 28 questions about whole and local body cold and heat tolerances. By a cluster analysis on the survey results, the participants were divided into two groups: high self-identified cold tolerance (HSCT, n = 25) and low self-identified cold tolerance (LSCT, n = 18). LSCT had lower self-identified cold tolerance (P < 0.001), preferred hot thermal stimulation (P = 0.006), and wore heavier clothing during daily life (P < 0.001) than HSCT. LSCT had significantly lower maximal finger temperatures (T max) (P = 0.040), smaller amplitude (P = 0.029), and delayed onset time of CIVD (P = 0.080) when compared to HSCT. Some questions examining the self-identified cold or heat tolerance had relationships with cold tolerance index, T max, and amplitude (P < 0.1). These results indicate that self-identified cold tolerance classified through a standardized survey could be a good index to predict physiological cold tolerance.

Relation between blood flow and tissue blood oxygenation in human fingertip skin

BACKGROUND

Tissue blood flow (BF) is thought to be involved in the regulation of tissue blood oxygenation (StO2). The purpose of the present study was to show the relation between BF and StO2 by measuring them simultaneously under different conditions.

METHODS

Twenty-one healthy subjects (age 21-30years) participated in this study. We measured BF and StO2 in a small area of skin (fingertip, palm, forearm) simultaneously using a laser Doppler flowmeter and a tissue oxygenation monitor. Three measurements were made at rest while performing mental arithmetic and during constriction of the ipsilateral upper arm.

RESULTS

At rest, BF and StO2 were higher in the fingertip than in the palm or forearm (p<0.01). Performing mental arithmetic produced significant decreases in BF, oxygenated hemoglobin, and StO2 in the fingertip (p<0.05). Constriction of the ipsilateral upper arm produced significant decreases in BF and StO2 (p<0.05) and an increase in oxygenated hemoglobin (p<0.05). Both procedures produced significant increases in deoxygenated hemoglobin (p<0.05), which was in antiphase to the decrease in StO2.

CONCLUSIONS

BF decrease produced a significantly decreased StO2 in fingertip skin. The results show that simultaneous measurement of BF and StO2 is beneficial for showing the close relation between them.

Effects of Two Short-Term, Intermittent Hypoxic Training Protocols on the Finger Temperature Response to Local Cold Stress

The study examined the effects of two short-term, intermittent hypoxic training protocols, namely exercising in hypoxia and living in normoxia (LL-TH; n=8), and exercising in normoxia preceded by a series of brief intermittent hypoxic exposures at rest (IHE+NOR; n=8), on the finger temperature response during a sea-level local cold test. In addition, a normoxic group was assigned as a control group (NOR; n=8). All groups trained on a cycle-ergometer 1 h/day, 5 days/week for 4 weeks at 50% of peak power output. Pre, post, and 11 days after the last training session, subjects immersed their right hand for 30 min in 8°C water. In the NOR group, the average finger temperature was higher in the post (+2.1°C) and 11-day after (+2.6°C) tests than in the pre-test (p≤0.001). Conversely, the fingers were significantly colder immediately after both hypoxic protocols (LL-TH: -1.1°C, IHE+NOR: -1.8°C; p=0.01). The temperature responses returned to the pre-training level 11 days after the hypoxic interventions. Ergo, present findings suggest that short-term intermittent hypoxic training impairs sea-level local cold tolerance; yet, the hypoxic-induced adverse responses seem to be reversible within a period of 11 days.

Acute Hypobaric Hypoxia Effects on Finger Temperature During and After Local Cold Exposure

Mountain environments have combined stressors of lower ambient temperature and hypoxia. Cold alone can reduce finger temperature, resulting in discomfort, impaired dexterity, and increased risk of cold injury. Whether hypobaric hypoxia exacerbates these effects is unclear. To examine this, finger temperature responses to two cold water immersion tests were measured at sea level (SL, 99 kPa), 3000 m (70 kPa), and 4675 m (56 kPa) at the same air temperature (22°-23°C). Nine males sat quietly for 30 min, then completed the tests in balanced order. For the cold-induced vasodilation (CIVD) test, middle finger pad temperature was measured during immersion in 4°C water for 30 min. For the Rewarming test, finger temperature was measured for 30 min following a 5 min hand immersion in 16°C water. Average oxygen saturation was 98.6% during SL, 90.7% at 3000 m, and 75.8% at 4657 m. Mean finger temperature during the CIVD test (7.1°C) was similar among trials. There was no difference in CIVD parameters of nadir, apex, or mean finger temperatures; however both onset and apex times were earlier at 3000 m, compared to SL (0.6 min and 1.6 min, respectively). These differences did not persist at 4657 m. Rewarming after hand immersion was similar among trials, reaching 22.7°C after 30 min, compared to an initial finger temperature of 29.3°C. The results of this study provide no evidence that hypobaric hypoxia increases risk of cold injury. Previous findings of blunted finger temperatures at altitude are likely due to the lower ambient temperature that typically occurs at higher elevations.

Cold-induced vasodilation during single digit immersion in 0°C and 8°C water in men and women

The present study compared the thermal responses of the finger to 0 and 8°C water immersion, two commonly used temperatures for cold-induced vasodilation (CIVD) research. On two separate and counterbalanced occasions 15 male and 15 female participants immersed their index finger in 20°C water for 5 min followed by either 0 or 8°C water for 30 min. Skin temperature, cardiovascular and perceptual data were recorded. Secondary analyses were performed between sexes and comparing 0.5, 1 and 4°C CIVD amplitude thresholds. With a 0.5°C threshold, CIVD waves were more prevalent in 8°C (2 (1 – 3) than in 0°C (1.5 (0 – 3)), but the amplitude was lower (4.0 ± 2.3 v 9.2 ± 4.0°C). Mean, minimum and maximum finger temperatures were lower in 0°C during the 30 min immersion, and CIVD onset and peak time occurred later in 0°C. Thermal sensation was lower and pain sensation was higher in 0°C. There were no differences between males and females in any of the physiological or CIVD data with the exception of SBP, which was higher in males. Females reported feeling higher thermal sensations in 8°C and lower pain sensations in 0°C and 8°C compared to males. Fewer CIVD responses were observed when using a 4°C (1 (0 – 3)) threshold to quantify a CIVD wave compared to using a 1°C (2 (0 – 3)) or 0.5°C (2 (0 – 3)) amplitude. In conclusion, both 0 and 8 °C can elicit CIVD but 8°C may be more suitable when looking to optimise the number of CIVD waves while minimising participant discomfort. The CIVD response to water immersion does not appear to be influenced by sex. Researchers should consider the amplitude threshold that was used to determine a CIVD wave when interpreting previous data.

Finger and Toe Temperature Responses to Cold After Freezing Cold Injury in Elite Alpinists

OBJECTIVE

To assess whether previous freezing cold injuries (FCI) would affect digit skin temperatures and rewarming rates during a follow-up cold stress test protocol.

DESIGN

Nonrandomized control trial.

METHODS

Twenty elite alpinists participated; alpinists with previous FCI requiring digit amputations (injured, INJ: n = 10 total, n = 8 male) were compared with ability-matched, uninjured alpinists (control, CON: n = 10, all male). Digit skin temperature was measured using infrared thermography as an index of peripheral digit perfusion after a cold stress test, which consisted of 30 minutes of immersion in 8°C water.

RESULTS

The INJ alpinists' injured toes were warmer (approximately 6%) than their uninjured toes immediately after cold immersion (95% CI, 0.01°C to 1.00°C; P = .05); there were no differences between the rates of rewarming of injured and uninjured toes (INJ, 0.5° ± 0.1°C/min; CON, 0.7° ± 0.3°C/min; P = .16). Although the INJ alpinists had colder injured fingers immediately after the 35°C warm bath compared with their own uninjured fingers (32.2° ± 2.0°C vs 34.5° ± 0.5°C; P = .02), there were no differences observed between the rates of rewarming of injured and uninjured fingers after cold exposure (INJ, 1.1° ± 0.2°C/min; CON, 1.3° ± 0.5°C/min; P = .22).

CONCLUSIONS

Even after FCI that requires digit amputation, there is no evidence of different tissue rates of rewarming between the injured and uninjured fingers or toes of elite alpinists.

Thermoregulatory modeling for cold stress

Modeling for cold stress has generated a rich history of innovation, has exerted a catalytic influence on cold physiology research, and continues to impact human activity in cold environments. This overview begins with a brief summation of cold thermoregulatory model development followed by key principles that will continue to guide current and future model development. Different representations of the human body are discussed relative to the level of detail and prediction accuracy required. In addition to predictions of shivering and vasomotor responses to cold exposure, algorithms are presented for thermoregulatory mechanisms. Various avenues of heat exchange between the human body and a cold environment are reviewed. Applications of cold thermoregulatory modeling range from investigative interpretation of physiological observations to forecasting skin freezing times and hypothermia survival times. While these advances have been remarkable, the future of cold stress modeling is still faced with significant challenges that are summarized at the end of this overview.

Responses of the hands and feet to cold exposure

An initial response to whole-body or local exposure of the extremities to cold is a strong vasoconstriction, leading to a rapid decrease in hand and foot temperature. This impairs tactile sensitivity, manual dexterity, and muscle contractile characteristics while increasing pain and sympathetic drive, decreasing gross motor function, occupational performance, and survival. A paradoxical and cyclical vasodilatation often occurs in the fingers, toes, and face, and this has been termed the hunting response or cold-induced vasodilatation (CIVD). Despite being described almost a century ago, the mechanisms of CIVD are still disputed; research in this area has remained largely descriptive in nature. Recent research into CIVD has brought increased standardization of methodology along with new knowledge about the impact of mediating factors such as hypoxia and physical fitness. Increasing mechanistic analysis of CIVD has also emerged along with improved modeling and prediction of CIVD responses. The present review will survey work conducted during this century on CIVD, its potential mechanisms and modeling, and also the broader context of manual function in cold conditions.

Hands and feet: physiological insulators, radiators and evaporators

The purpose of this review is to describe the unique anatomical and physiological features of the hands and feet that support heat conservation and dissipation, and in so doing, highlight the importance of these appendages in human thermoregulation. For instance, the surface area to mass ratio of each hand is 4-5 times greater than that of the body, whilst for each foot, it is ~3 times larger. This characteristic is supported by vascular responses that permit a theoretical maximal mass flow of thermal energy of 6.0 W (136 W m(2)) to each hand for a 1 °C thermal gradient. For each foot, this is 8.5 W (119 W m(2)). In an air temperature of 27 °C, the hands and feet of resting individuals can each dissipate 150-220 W m(2) (male-female) of heat through radiation and convection. During hypothermia, the extremities are physiologically isolated, restricting heat flow to <0.1 W. When the core temperature increases ~0.5 °C above thermoneutral (rest), each hand and foot can sweat at 22-33 mL h(-1), with complete evaporation dissipating 15-22 W (respectively). During heated exercise, sweat flows increase (one hand: 99 mL h(-1); one foot: 68 mL h(-1)), with evaporative heat losses of 67-46 W (respectively). It is concluded that these attributes allow the hands and feet to behave as excellent radiators, insulators and evaporators.

Effect of caffeine intake on finger cold-induced vasodilation

OBJECTIVE

The purpose of the study was to investigate the effect of caffeine intake on finger cold-induced vasodilation (CIVD).

METHODS

Ten healthy men underwent 6 experimental trials characterized by control (NCAFF) or caffeine intake (CAFF) via chewing gum (300 mg of caffeine) while resting on a chair or performing submaximal (70% maximal oxygen consumption) or maximal (100% maximal oxygen consumption) treadmill exercise (Bruce protocol) followed by immersion of the middle finger in a water bath (5°C) for 20 minutes. Finger temperature (Tf ) and time parameters of the first CIVD cycle and post-test norepinephrine were measured.

RESULTS

Exercise duration for submaximal and maximal exercise was 8.9 ± 0.9 and 12.4 ± 0.8 minutes, respectively. CAFF had no effect on Tf, but exercise increased minimal Tf in NCAFF (9.08 ± 1.27°C, 13.02 ± 2.13°C, and 13.25 ± 1.63°C in rest, submaximal, and maximal exercise, respectively) and CAFF (8.76 ± 1.39°C, 12.50 ± 1.91°C, and 12.79 ± 1.20°C). Maximal Tf was significantly higher in NCAFF (15.98 ± 1.04°C, 16.18 ± 1.56°C, and 15.14 ± 1.52°C) than in CAFF (13.56 ± 1.19°C, 15.52 ± 1.31°C, and 14.39 ± 1.43°C), resulting in a significant difference between minimal and maximal Tf in rest (NCAFF, 6.89 ± 1.56°C and CAFF, 4.79 ± 1.23°C), but not in exercise conditions. CAFF had no effect on CIVD time responses, but exercise significantly shortened CIVD onset and peak time compared with rest in both NCAFF and CAFF. Norepinephrine concentration was significantly greater in CAFF (290.6 ± 113.0 pg/mL, 278.1 ± 91.4 pg/mL, and 399.8 ± 125.5 pg/mL) than NCAFF (105.6 ± 29.5 pg/mL, 199.6 ± 89.6 pg/mL, and 361.5 ± 171.3 pg/mL).

CONCLUSIONS

Caffeine intake before finger immersion in cold water does not result in a thermogenic effect and adversely affects CIVD responses, whereas exercise modifies CIVD temperature and time responses.

Qigong Effects on Heart Rate Variability and Peripheral Vasomotor Responses

Population aging is occurring worldwide, and preventing cardiovascular event in older people is a unique challenge. The aim of this study was to examine the effects of a 12-week qigong (eight-form moving meditation) training program on the heart rate variability and peripheral vasomotor response of middle-aged and elderly people in the community. This was a quasi-experimental study that included the pre-test, post-test, and nonequivalent control group designs. Seventy-seven participants (experimental group = 47; control group = 30) were recruited. The experimental group performed 30 min of eight-form moving meditation 3 times per week for 12 weeks, and the control group continued their normal daily activities. After 12 weeks, the interaction effects indicated that compared with the control group, the experimental group exhibited significantly improved heart rate variability and peripheral vasomotor responses.

Acute effects of normobaric hypoxia on hand-temperature responses during and after local cold stress

The purpose was to investigate acute effects of normobaric hypoxia on hand-temperature responses during and after a cold-water hand immersion test. Fifteen males performed two right-hand immersion tests in 8°C water, during which they were inspiring either room air (Fio2: 0.21; AIR), or a hypoxic gas mixture (Fio2: 0.14; HYPO). The tests were conducted in a counterbalanced order and separated by a 1-hour interval. Throughout the 30-min cold-water immersion (CWI) and the 15-min spontaneous rewarming (RW) phases, finger-skin temperatures were measured continuously with thermocouple probes; infrared thermography was also employed during the RW phase to map all segments of the hand. During the CWI phase, the average skin temperature (Tavg) of the fingers did not differ between the conditions (AIR: 10.2 ± 0.5°C, HYPO: 10.0 ± 0.5°C; p = 0.67). However, Tavg was lower in the HYPO than the AIR RW phase (AIR: 24.5 ± 3.4°C; HYPO: 22.0 ± 3.8°C; p = 0.002); a response that was alike in all regions of the immersed hand. Accordingly, present findings suggest that acute exposure to normobaric hypoxia does not aggravate the cold-induced drop in hand temperature of normothermic males. Still, hypoxia markedly impairs the rewarming responses of the hand.

Frostbite in an adolescent football player: a case report

OBJECTIVE

To present the case of vascular compromise of a finger from a confluent circumferential blister due to an inappropriately applied commercial cold pack in a high school athlete and to describe the mechanism of iatrogenic injury, acute surgical management, rehabilitation, and pathophysiology of frostbite and constriction injuries.

BACKGROUND

A 17-year-old male football player presented with a frostbite and constriction injury to the index finger secondary to prolonged use of a cooling pack after a mild traumatic injury to the digit. He developed a prolonged sensory deficit from thermal injury, as well as acute vascular compromise requiring urgent operative intervention.

DIFFERENTIAL DIAGNOSIS

Frostbite and constriction injury to the index finger.

TREATMENT

Emergency surgical decompression and occupational therapy.

UNIQUENESS

Frostbite injuries can occur iatrogenically because of inappropriate use of cooling devices or gel packs. Fingers are commonly injured extremities that are particularly susceptible to frostbite and compression injuries. To our knowledge, no case of vascular compromise from the blister constriction of digits has been reported.

CONCLUSIONS

Patients and their caregivers must be educated about how to properly use cooling devices. Clinicians need to fully evaluate patients with iatrogenic frostbite injuries, giving particular attention to neurovascular status, and must recognize the need for surgical release of constriction syndrome to prevent substantial morbidity.

Cold-induced vasodilatation response in the fingers at 4 different water temperatures

We evaluated the cold-induced vasodilatation (CIVD) response at 4 different water temperatures. Nine healthy young male subjects immersed their right hands in 35 °C water for 5 min, and immediately thereafter for 30 min in a bath maintained at either 5, 8, 10, or 15 °C. The responses of finger skin temperatures, subjective ratings of thermal comfort and temperature sensation scores were compared between the 4 immersion trials. The number of subjects who exhibited a CIVD response was higher during immersion of the hand in 5 and 8 °C (100%) compared with 10 and 15 °C water (87.5% and 37.5%, respectively). The CIVD temperature amplitude was 4.2 ± 2.6, 3.4 ± 2.0, 2.1 ± 1.6, and 2.8 ± 2.0 °C at 5, 8, 10, and 15 °C trials, respectively; higher in 5 and 8 °C compared with 10 and 15 °C water (p = 0.003). No differences in CIVD were found between the 5 and 8 °C immersions. However, during immersion in 5 °C, subjects felt “uncomfortable” while in the other trials felt “slightly uncomfortable” (p = 0.005). The temperature sensation score was “cold” for 5 °C and “cool” for the other trials, but no statistical differences were observed. Immersion of the hand in 8 °C elicits a CIVD response of similar magnitude as immersion in 5 °C, but with less thermal discomfort.

Dynamic adaptation of the peripheral circulation to cold exposure

Humans residing or working in cold environments exhibit a stronger cold-induced vasodilation (CIVD) reaction in the peripheral microvasculature than those living in warm regions of the world, leading to a general assumption that thermal responses to local cold exposure can be systematically improved by natural acclimatization or specific acclimation. However, it remains unclear whether this improved tolerance is actually due to systematic acclimatization, or alternately due to the genetic pre-disposition or self-selection for such occupations. Longitudinal studies of repeated extremity exposure to cold demonstrate only ambiguous adaptive responses. In field studies, general cold acclimation may lead to increased sympathetic activity that results in reduced finger blood flow. Laboratory studies offer more control over confounding parameters, but in most studies, no consistent changes in peripheral blood flow occur even after repeated exposure for several weeks. Most studies are performed on a limited amount of subjects only, and the variability of the CIVD response demands more subjects to obtain significant results. This review systematically surveys the trainability of CIVD, concluding that repeated local cold exposure does not alter circulatory dynamics in the peripheries, and that humans remain at risk of cold injuries even after extended stays in cold environments.

Trainability of cold induced vasodilatation in fingers and toes

Subjects that repeatedly have to expose the extremities to cold may benefit from a high peripheral temperature to maintain dexterity and tissue integrity. Therefore, we investigated if repeated immersions of a hand and a foot in cold water resulted in increased skin temperatures. Nine male and seven female subjects (mean 20.4; SD 2.2 years) immersed their right (trained) hand and foot simultaneously in 8°C water, 30 min daily for 15 days. During the pre and post-test (days 1 and 15, respectively) the left (untrained) hand and foot were immersed as well. Pain, tactile sensitivity and skin temperatures were measured every day. Mean (SD) toe temperature of the trained foot increased from 9.49°C (0.89) to 10.03°C (1.38) (p < 0.05). The trained hand, however, showed a drop in mean finger temperature from 9.28°C (0.54) to 8.91°C (0.44) (p < 0.001) and the number of cold induced vasodilation (CIVD) reactions decreased from 52% during the first test to 24% during the last test. No significant differences occurred in the untrained extremities. Pain diminished over time and tactile sensitivity decreased with skin temperature. The combination of less CIVD responses in the fingers after training, reduced finger skin temperatures in subjects that did show CIVD and the reduced pain and tactile sensitivity over time may lead to an increased risk for finger cold injuries. It is concluded that repeated cold exposure of the fingers does not lead to favorable adaptations, but may instead increase the injury risk.

Methods of evaluating protective clothing relative to heat and cold stress: thermal manikin, biomedical modeling, and human testing

Personal protective equipment (PPE) refers to clothing and equipment designed to protect individuals from chemical, biological, radiological, nuclear, and explosive hazards. The materials used to provide this protection may exacerbate thermal strain by limiting heat and water vapor transfer. Any new PPE must therefore be evaluated to ensure that it poses no greater thermal strain than the current standard for the same level of hazard protection. This review describes how such evaluations are typically conducted. Comprehensive evaluation of PPE begins with a biophysical assessment of materials using a guarded hot plate to determine the thermal characteristics (thermal resistance and water vapor permeability). These characteristics are then evaluated on a thermal manikin wearing the PPE, since thermal properties may change once the materials have been constructed into a garment. These data may be used in biomedical models to predict thermal strain under a variety of environmental and work conditions. When the biophysical data indicate that the evaporative resistance (ratio of permeability to insulation) is significantly better than the current standard, the PPE is evaluated through human testing in controlled laboratory conditions appropriate for the conditions under which the PPE would be used if fielded. Data from each phase of PPE evaluation are used in predictive models to determine user guidelines, such as maximal work time, work/rest cycles, and fluid intake requirements. By considering thermal stress early in the development process, health hazards related to temperature extremes can be mitigated while maintaining or improving the effectiveness of the PPE for protection from external hazards.

Effects of cold exposure and shear stress on endothelial nitric oxide synthase activation

Endothelial nitric oxide synthase (eNOS) is the primary enzyme that produces nitric oxide (NO), which plays an important role in blood vessel relaxation. eNOS activation is stimulated by various mechanical forces, such as shear stress. Several studies have shown that local cooling of the human finger causes strong vasoconstriction, followed after several minutes by cold-induced vasodilation (CIVD). However, the role played by endothelial cells (ECs) in blood vessel regulation in respond to cold temperatures is not fully understood. In this study, we found that low temperature alone does not significantly increase or decrease eNOS activation in ECs. We further found that the combination of shear stress with temperature change leads to a significant increase in eNOS activation at 37°C and 28°C, and a decrease at 4°C. These results show that ECs play an important role in blood vessel regulation under shear stress and low temperature.

Cold-induced vasodilatation following traumatic median or ulnar nerve injury

PURPOSE

Peripheral nerve injury of the upper extremity frequently causes changes in the thermoregulatory system of the hands and fingers and leads to reports of cold intolerance. In this study, we aimed to measure the influence of median or ulnar nerve injury on cold-induced vasodilatation (CIVD) during prolonged cooling at low temperatures.

METHODS

We tested 12 patients with a median (n = 6) or ulnar (n = 6) injury 4 to 76 months after nerve repair. The palmar sides of both hands were cooled continuously using a cold plate at 5°C. We measured the skin temperature of the fingers using videothermography and plotted graphs of the temperature changes of the nailbed. The presence of a CIVD reaction was defined as a minimum increase in temperature of 2.5°C starting at the distal phalanx. Furthermore, we measured self-reported symptoms of cold intolerance using the Cold Intolerance Severity Scale questionnaire.

RESULTS

A CIVD reaction was absent in the affected digits of 4 patients (follow-up, 6-37 mo), whereas the CIVD reaction in the uninjured hand was present. The CIVD was present in 6 patients after 50 months' follow-up (range, 24-76 mo). Two patients had no CIVD reaction in the injured or uninjured fingers. All patients with a CIVD response had at least diminished protective sensation. Presence of the CIVD reaction did not exclude self-reported symptoms of cold intolerance.

CONCLUSIONS

After peripheral nerve injury, it is possible to recover the CIVD reaction. This might be an indication of nerve recovery. However, a positive CIVD reaction does not exclude subjective symptoms of posttraumatic cold intolerance.

TYPE OF STUDY/LEVEL OF EVIDENCE

Diagnostic III.

National Athletic Trainers' Association position statement: environmental cold injuries

OBJECTIVE

To present recommendations for the prevention, recognition, and treatment of environmental cold injuries.

BACKGROUND

Individuals engaged in sport-related or work-related physical activity in cold, wet, or windy conditions are at risk for environmental cold injuries. An understanding of the physiology and pathophysiology, risk management, recognition, and immediate care of environmental cold injuries is an essential skill for certified athletic trainers and other health care providers working with individuals at risk.

RECOMMENDATIONS

These recommendations are intended to provide certified athletic trainers and others participating in athletic health care with the specific knowledge and problem-solving skills needed to address environmental cold injuries. Each recommendation has been graded (A, B, or C) according to the Strength of Recommendation Taxonomy criterion scale.

Infrared thermography based on artificial intelligence for carpal tunnel syndrome diagnosis

Thermography for the measurement of surface temperatures is well known in industry, although is not established in medicine despite its safety, lack of pain and invasiveness, easy reproducibility, and low running costs. Promising results have been achieved in nerve entrapment syndromes, although thermography has never represented a real alternative to electromyography. Here an attempt is described to improve the diagnosis of carpal tunnel syndrome with thermography using a computer-based system employing artificial neural networks to analyse the images. Method reliability was tested on 112 images (depicting the dorsal and palmar sides of 26 healthy and 30 pathological hands), with the hand divided into 12 segments and compared relative to a reference. Palmar segments appeared to have no beneficial influence on classification outcome, whereas dorsal segments gave improved outcome with classification success rates near to or over 80%, and finger segments influenced by the median nerve appeared to be of greatest importance. These are preliminary results from a limited number of images and further research will be undertaken as our image database grows.

Application of infrared thermography for the analysis of rewarming in patients with cold intolerance

Cold intolerance is a serious long-term problem after injury to the ulnar and median nerves, and its pathophysiology is unclear. We investigated the use of infrared thermography for the analysis of thermoregulation after injury to peripheral nerves. Four patients with injuries to the ulnar nerve and four with injuries to the median nerve (4-12 years after injury) immersed their hands in water at 15 degrees C for 5 minutes, after which infrared pictures were taken at intervals of 2-4 minutes. The areas supplied by the injured nerves could be identified easily in the patients with symptoms of cold intolerance. At baseline temperature distribution of the hand was symmetrical, but after testing the injured side warmed up much slower. We concluded that the infrared profile of the temperature of the hand after immersion in cold water is helpful to assess thermoregulation after injury to peripheral nerves.