Head and neck cooling decreases tympanic and skin temperature, but significantly increases blood pressure

Reduced Concussion Symptom Burden in Early Adolescent Athletes Using a Head-Neck Cooling Device

OBJECTIVE

To determine whether an investigational head-neck cooling device, Pro2cool, can better reduce symptom severity compared with standard postconcussion care in early adolescent athletes after a sports-related concussion.

DESIGN

Prospective, longitudinal, randomized trial design conducted over a 28-day period.

SETTING

Six pediatric medical centers in Ohio and Michigan.

PARTICIPANTS

The study enrolled 167 male and female 12- to 19-year-old athletes who experienced a sports-related concussion within 8 days of study enrollment and registering a Sports Concussion Assessment Tool 5 (SCAT5) composite score >7.

INTERVENTIONS

Pro2cool, an investigational head-neck cooling therapy device, was applied at 2 postinjury time points compared with postconcussion standard of care only.

MAIN OUTCOME MEASURES

Baseline SCAT5 composite symptom severity scores were determined for all subjects. Sports Concussion Assessment Tool 5 scores for concussed athletes receiving cooling treatment were analyzed across 6 independent postenrollment time points compared with subjects who did not receive cooling therapy and only standard care. Adverse reactions and participate demographics were also compared.

RESULTS

Athletes who received Pro2cool cooling therapy (n = 79) experienced a 14.4% greater reduction in SCAT5 symptom severity scores at the initial visit posttreatment, a 25.5% greater reduction at the 72-hour visit posttreatment, and a 3.4% greater reduction at the 10-day visit compared with subjects receiving only standard care (n = 88). Overall, 36 adverse events (increased blood pressure, decreased pulse, and dizziness) were reported, with 13 events associated with the device, of which 3 were classified as moderate in severity.

CONCLUSIONS

This study demonstrates the efficacy and safety of head and neck cooling for the management of concussion symptoms in adolescent athletes of an age group for which little to no prior data are available.

Head cooling wrap could suppress the elevation of core temperature after cardiac surgery during forced-air warming in a pediatric intensive care unit: a randomized clinical trial

PURPOSE

The main aim of the current trial was to explore our hypothesis that cooling head wraps lower the core temperature more effectively than ice packs on the head during forced-air warming after pediatric cardiac surgeries.

METHODS

This study was a single-center Randomized Controlled Trial. Participants were children with a weight ≤ 10 kg and hyperthermia during forced-air warming after cardiac surgeries. When the core temperature reached 37.5 °C, ice packs on the head (group C) or a cooling head wrap (group H) were used as cooling devices to decrease the core temperature. The primary outcome was the core temperature. The secondary outcomes were the foot surface temperature and heart rate. We measured all outcomes every 30 min for 240 min after the patient developed hyperthermia. We conducted two-way ANOVA as a pre-planned analysis and also the Bonferroni test as a post hoc analysis.

RESULTS

Twenty patients were randomly assigned to groups C and H. The series of core temperatures in group H were significantly lower than those in group C (p < 0.0001), and post hoc analysis showed that there was no significant difference in core temperatures at T0 between the two groups and statistically significant differences in all core temperatures at T30-240 between the two groups. There was no difference between the two groups' surface temperatures and heart rates.

CONCLUSIONS

Compared to ice packs on the head, head cooling wraps more effectively suppress core temperature elevation during forced-air warming after pediatric cardiac surgery.

Effects of cutaneous administration of an over-the-counter menthol cream during temperate-water immersion for exercise-induced hyperthermia in men

Introduction: Hyperthermia impairs various physiological functions and physical performance. We examined the effects of cutaneous administration with an over-the-counter (OTC) analgesic cream containing 20% methyl salicylate and 6% L-menthol during temperate-water immersion (TWI) for exercise-induced hyperthermia. Methods: In a randomized crossover design, twelve healthy males participated in both of two experiments. Firstly, participants underwent a 15-min TWI at 20°C with (CREAM) or without (CON) cutaneous application of an analgesic cream. Cutaneous vascular conductance (CVC) was measured using laser doppler flowmetry during TWI. In a subsequent experiment, same participants performed a 30-min strenuous interval exercise in a heated (35°C) environment to induce hyperthermia (~39°C), which was followed by 15 min of TWI. Results: Core body temperature, as measured by an ingestible telemetry sensor, and mean arterial pressure (MAP) were measured. CVC and %CVC (% baseline) were higher during TWI in CREAM than in CON (Condition effect: p = 0.0053 and p = 0.0010). An additional experiment revealed that core body heat loss during TWI was greater in CREAM than in CON (Cooling rate: CON 0.070 ± 0.020 vs. CREAM 0.084°C ± 0.026°C/min, p = 0.0039). A more attenuated MAP response was observed during TWI in CREAM than in CON (Condition effect: p = 0.0007). Conclusion: An OTC analgesic cream containing L-menthol and MS augmented cooling effects when cutaneously applied during TWI in exercise-induced hyperthermia. This was, at least in part, due to the counteractive vasodilatory effect of the analgesic cream. The cutaneous application of OTC analgesic cream may therefore provide a safe, accessible, and affordable means of enhancing the cooling effects of TWI.

Relationship between anxiety and monotonous task performance in response to local cooling: an experimental study in healthy young men

There are limited studies on monotonous task performance and its relationship with anxiety and stress traits. This study aimed to determine if local cooling exerts physiological effects and positively affects task performance. Ten male participants performed monotonous work for 24 min under control and local cooling conditions. We measured physiological arousal and anxiety using electroencephalography and the State-Trait Anxiety Inventory, respectively. The participants rated their drowsiness, the thermal sensation of the seat and whole-body thermal sensation. Despite the lack of significant differences in physiological arousal, the state anxiety score, which reflects the current stressful situation, was significantly lower in the local cooling condition. Therefore, cooling might help relieve stress during monotonous tasks, without impairing task performance. In addition, individuals with higher state anxiety scores tended to experience a faster increase in their arousal level. Thus, individual anxiety traits may modulate attentional resources during monotonous task performance.Practitioner summary: The study on topic related to monotonous task performance and its relationship with anxiety and stress traits is novel. Minimising negative emotions is key to monotonous task execution under stress. Individual anxiety might modulate resource allocation for monotonous task execution.

Topical Analgesic Containing Methyl Salicylate and L-Menthol Accelerates Heat Loss During Skin Cooling for Exercise-Induced Hyperthermia

Hyperthermia impairs physical performance and, when prolonged, results in heat stroke or other illnesses. While extensive research has investigated the effectiveness of various cooling strategies, including cold water immersion and ice-suit, there has been little work focused on overcoming the cutaneous vasoconstriction response to external cold stimulation, which can reduce the effectiveness of these treatments. Over-the-counter (OTC) topical analgesics have been utilized for the treatment of muscle pain for decades; however, to date no research has examined the possibility of taking advantage of their vasodilatory functions in the context of skin cooling. We tested whether an OTC analgesic cream containing 20% methyl salicylate and 6% L-menthol, known cutaneous vasodilators, applied to the skin during skin cooling accelerates heat loss in exercise-induced hyperthermia. Firstly, we found that cutaneous application of OTC topical analgesic cream can attenuate cold-induced vasoconstriction and enhance heat loss during local skin cooling. We also revealed that core body heat loss, as measured by an ingestible telemetry sensor, could be accelerated by cutaneous application of analgesic cream during ice-suit cooling in exercise-induced hyperthermia. A blunted blood pressure response was observed during cooling with the analgesic cream application. Given the safety profile and affordability of topical cutaneous analgesics containing vasodilatory agents, our results suggest that they can be an effective and practical tool for enhancing the cooling effects of skin cooling for hyperthermia.

The Otoprotective Effect of Ear Cryotherapy: Systematic Review and Future Perspectives

This systematic review investigates ear cooling and cryotherapy in the prevention and treatment of inner ear damage and disease, within the context of animal models and clinical studies. A literature search was carried out in the databases Pubmed and Cochrane Library. Ten studies were identified concerning the otoprotective properties of cryotherapy. Nine of these were rodent in vivo studies (mice, rats, gerbils, guinea pigs). One study involved human subjects and investigated cryotherapy in idiopathic sensorineural hearing loss. The studies were heterogeneous in their goals, methods, and the models used. Disorder models included ischemia and noise damage, ototoxicity (cisplatin and aminoglycoside), and CI-electrode insertion. All ten studies demonstrated significant cryotherapeutic otoprotection for their respective endpoints. No study revealed or expressly investigated otodestructive effects. While limited in number, all of the studies within the scope of the review demonstrated some degree of cryotherapeutic, otoprotective effect. These promising results support the conducting of further work to explore and refine the clinical applicability and impact of cryotherpeutics in otolaryngology.

Selective Brain Cooling: A New Horizon of Neuroprotection

Therapeutic hypothermia (TH), which prevents irreversible neuronal necrosis and ischemic brain damage, has been proven effective for preventing ischemia-reperfusion injury in post-cardiac arrest syndrome and neonatal encephalopathy in both animal studies and clinical trials. However, lowering the whole-body temperature below 34°C can lead to severe systemic complications such as cardiac, hematologic, immunologic, and metabolic side effects. Although the brain accounts for only 2% of the total body weight, it consumes 20% of the body's total energy at rest and requires a continuous supply of glucose and oxygen to maintain function and structural integrity. As such, theoretically, temperature-controlled selective brain cooling (SBC) may be more beneficial for brain ischemia than systemic pan-ischemia. Various SBC methods have been introduced to selectively cool the brain while minimizing systemic TH-related complications. However, technical setbacks of conventional SBCs, such as insufficient cooling power and relatively expensive coolant and/or irritating effects on skin or mucosal interfaces, limit its application to various clinical settings. This review aimed to integrate current literature on SBC modalities with promising therapeutic potential. Further, future directions were discussed by exploring studies on interesting coping skills in response to environmental or stress-induced hyperthermia among wild animals, including mammals and birds.

Insight into the use of tympanic temperature during target temperature management in emergency and critical care: a scoping review

BACKGROUND

Target temperature management (TTM) is suggested to reduce brain damage in the presence of global or local ischemia. Prompt TTM application may help to improve outcomes, but it is often hindered by technical problems, mainly related to the portability of cooling devices and temperature monitoring systems. Tympanic temperature (T_Ty) measurement may represent a practical, non-invasive approach for core temperature monitoring in emergency settings, but its accuracy under different TTM protocols is poorly characterized. The present scoping review aimed to collect the available evidence about T_Ty monitoring in TTM to describe the technique diffusion in various TTM contexts and its accuracy in comparison with other body sites under different cooling protocols and clinical conditions.

METHODS

The scoping review was conducted following the guidelines of the Preferred Reporting Items for Systematic Review and Meta-Analysis extension for scoping reviews (PRISMA-ScR). PubMed, Scopus, and Web of Science electronic databases were systematically searched to identify studies conducted in the last 20 years, where T_Ty was measured in TTM context with specific focus on pre-hospital or in-hospital emergency settings.

RESULTS

The systematic search identified 35 studies, 12 performing T_Ty measurements during TTM in healthy subjects, 17 in patients with acute cardiovascular events, and 6 in patients with acute neurological diseases. The studies showed that T_Ty was able to track temperature changes induced by either local or whole-body cooling approaches in both pre-hospital and in-hospital settings. Direct comparisons to other core temperature measurements from other body sites were available in 22 studies, which showed a faster and larger change of T_Ty upon TTM compared to other core temperature measurements. Direct brain temperature measurements were available only in 3 studies and showed a good correlation between T_Ty and brain temperature, although T_Ty displayed a tendency to overestimate cooling effects compared to brain temperature.

CONCLUSIONS

T_Ty was capable to track temperature changes under a variety of TTM protocols and clinical conditions in both pre-hospital and in-hospital settings. Due to the heterogeneity and paucity of comparative temperature data, future studies are needed to fully elucidate the advantages of T_Ty in emergency settings and its capability to track brain temperature.

Neck cooling induces blood pressure increase and peripheral vasoconstriction in healthy persons

Introduction

Noninvasive temperature modulation by localized neck cooling might be desirable in the prehospital phase of acute hypoxic brain injuries. While combined head and neck cooling induces significant discomfort, peripheral vasoconstriction, and blood pressure increase, localized neck cooling more selectively targets blood vessels that supply the brain, spares thermal receptors of the face and skull, and might therefore cause less discomfort cardiovascular side effects compared to head- and neck cooling. The purpose of this study is to assess the effects of noninvasive selective neck cooling on cardiovascular parameters and cerebral blood flow velocity (CBFV).

Methods

Eleven healthy persons (6 women, mean age 42 ± 11 years) underwent 90 min of localized dorsal and frontal neck cooling (EMCOOLS Brain.Pad™) without sedation. Before and after cooling onset, and after every 10 min of cooling, we determined rectal, tympanic, and neck skin temperatures. Before and after cooling onset, after 60- and 90-min cooling, we monitored RR intervals (RRI), systolic, diastolic blood pressures (BPsys, BPdia), laser Doppler skin blood flow (SBF) at the index finger pulp, and CBFV at the proximal middle cerebral artery (MCA). We compared values before and during cooling by analysis of variance for repeated measurements with post hoc analysis (significance: p < 0.05).

Results

Neck skin temperature dropped significantly by 9.2 ± 4.5 °C (minimum after 40 min), while tympanic temperature decreased by only 0.8 ± 0.4 °C (minimum after 50 min), and rectal temperature by only 0.2 ± 0.3 °C (minimum after 60 min of cooling). Index finger SBF decreased (by 83.4 ± 126.0 PU), BPsys and BPdia increased (by 11.2 ± 13.1 mmHg and 8.0 ± 10.1 mmHg), and heart rate slowed significantly while MCA-CBFV remained unchanged during cooling.

Conclusions

While localized neck cooling prominently lowered neck skin temperature, it had little effect on tympanic temperature but significantly increased BP which may have detrimental effects in patients with acute brain injuries.

Inducing therapeutic hypothermia via selective brain cooling: a finite element modeling analysis

Therapeutic hypothermia is a treatment method to reduce brain injuries after stroke, especially for cerebral ischemia. This study investigates in the temperature distribution of the head within selective brain cooling (SBC). Anatomically accurate geometries based on CT images of head and neck regions are used to develop the 3D geometry and physical model for the finite element modeling. Two cooling methods, the direct head surface cooling strategy and the combination cooling strategy of both head and neck, are evaluated to analyze the inducing hypothermia. The results show that for direct head surface cooling, the scalp and skull temperatures decrease significantly as the blood perfusion rate is constrained, but it is hard to affect the brain core temperature. To achieve a lower cerebral temperature, combination cooling strategy of both head and neck is an effective method in improving deep brain cooling. In normal condition, the cerebral temperature is reduced by about 0.12 °C in 60 min of hypothermia, while the temperature drop is approximately 0.98 °C in ischemic condition. Graphical abstract In this study, the 3D geometry of the head and carotid artery model based on the computed tomography (CT) were derived separately and the corresponding investigations were conducted to validate the reliability of the model. Direct head surface cooling strategy and the combination cooling strategy of both the head and neck were numerically researched.

Cold Blooded: Evaluating Brain Temperature by MRI During Surface Cooling of Human Subjects

BACKGROUND

Targeted temperature management (TTM) confers neurological and survival benefits for post-cardiac arrest patients with return of spontaneous circulation (ROSC) who remain comatose. Specialized equipment for induction of hypothermia is not available in the prehospital setting, and there are no reliable methods for emergency medical services personnel to initiate TTM. We hypothesized that the application of surface cooling elements to the neck will decrease brain temperature and act as initiators of TTM.

METHODS

Magnetic resonance (MR) spectroscopy was used to evaluate the effect of a carotid surface cooling element on brain temperature in healthy adults.

RESULTS

Six individuals completed this study. We measured a temperature drop of 0.69 ± 0.38 °C (95% CI) in the cortex of the brain following the application of the cooling element. Application of a room temperature element also caused a measurable decrease in brain temperature of 0.66 ± 0.41 °C (95% CI) which may be attributable to baroreceptor activation.

CONCLUSION

The application of surface cooling elements to the neck decreased brain temperature and may serve as a method to initiate TTM in the prehospital setting.

An experimental study and finite element modeling of head and neck cooling for brain hypothermia

Reducing brain temperature by head and neck cooling is likely to be the protective treatment for humans when subjects to sudden cardiac arrest. This study develops the experimental validation model and finite element modeling (FEM) to study the head and neck cooling separately, which can induce therapeutic hypothermia focused on the brain. Anatomically accurate geometries based on CT images of the skull and carotid artery are utilized to find the 3D geometry for FEM to analyze the temperature distributions and 3D-printing to build the physical model for experiment. The results show that FEM predicted and experimentally measured temperatures have good agreement, which can be used to predict the temporal and spatial temperature distributions of the tissue and blood during the head and neck cooling process. Effects of boundary condition, perfusion, blood flow rate, and size of cooling area are studied. For head cooling, the cooling penetration depth is greatly depending on the blood perfusion in the brain. In the normal blood flow condition, the neck internal carotid artery temperature is decreased only by about 0.13°C after 60min of hypothermia. In an ischemic (low blood flow rate) condition, such temperature can be decreased by about 1.0°C. In conclusion, decreasing the blood perfusion and metabolic reduction factor could be more beneficial to cool the core zone. The results also suggest that more SBC researches should be explored, such as the optimization of simulation and experimental models, and to perform the experiment on human subjects.

Tympanic membrane temperature decreases during head up tilt: relation to frontal lobe oxygenation and middle cerebral artery mean blood flow velocity

INTRODUCTION

Changes in blood flow influence temperature of surrounding tissues. Since the internal carotid artery (ICA) and internal jugular vein (IJV) neighbor the tympanic membrane, changes in their blood flow most likely determine changes in tympanic membrane temperature (TMT). We sought to evaluate the relationship between changes during a head-up tilt (HUT) induced reduction in cerebral blood flow (CBF) and TMT.

METHODS

Ten male subjects (age 19-28 years) underwent 50° HUT until presyncope. A non-contact infrared sensor in the ear canal targeted the tympanic membrane. Changes in CBF were monitored by transcranial Doppler which determined the mean blood flow velocity in the middle cerebral artery (MCA V_mean) and by near infrared spectroscopy assessed frontal lobe oxygenation (S_cO₂), while skin blood flow (SkBF) was evaluated by laser Doppler flowmetry.

RESULTS

During HUT, TMT decreased by 0.6 °C (median; range 0.2 to 1.6 °C) related to a decrease in MCA V_mean (51.0 ± 6.7 to 34.3 ± 5.8 cm/sec (mean ± SD); r = 0.518, p = .002) and S_cO₂ (78.6 ± 5.4% to 69.0 ± 5.7%; r = 0.352, p = .043), but not to SkBF (120 ± 78 to 69 ± 37 PU; r = 0.245, p = .142).

CONCLUSION

During an orthostatic challenge TMT decreases and the decrease is related to a reduction in CBF as indicated by MCA V_mean and S_cO₂, but not to SkBF. We consider TMT holds potential for non-invasive assessment of changes in cerebral perfusion.

Effect of temperature on FAD and NADH-derived signals and neurometabolic coupling in the mouse auditory and motor cortex

Tight coupling of neuronal metabolism to synaptic activity is critical to ensure that the supply of metabolic substrates meets the demands of neuronal signaling. Given the impact of temperature on metabolism, and the wide fluctuations of brain temperature observed during clinical hypothermia, we examined the effect of temperature on neurometabolic coupling. Intrinsic fluorescence signals of the oxidized form of flavin adenine dinucleotide (FAD) and the reduced form of nicotinamide adenine dinucleotide (NADH), and their ratios, were measured to assess neural metabolic state and local field potentials were recorded to measure synaptic activity in the mouse brain. Brain slice preparations were used to remove the potential impacts of blood flow. Tight coupling between metabolic signals and local field potential amplitudes was observed at a range of temperatures below 29 °C. However, above 29 °C, the metabolic and synaptic signatures diverged such that FAD signals were diminished, but local field potentials retained their amplitude. It was also observed that the declines in the FAD signals seen at high temperatures (and hence the decoupling between synaptic and metabolic events) are driven by low FAD availability at high temperatures. These data suggest that neurometabolic coupling, thought to be critical for ensuring the metabolic health of the brain, may show temperature dependence, and is related to temperature-dependent changes in FAD supplies.

A Novel Cooling Device for Targeted Brain Temperature Control and Therapeutic Hypothermia: Feasibility Study in an Animal Model

Background

Therapeutic hypothermia (i.e., temperature management) is an effective option for improving survival and neurological outcome after cardiac arrest and is potentially useful for the care of the critically ill neurological patient. We analyzed the feasibility of a device to control the temperature of the brain by controlling the temperature of the blood flowing through the neck.

Methods

A lumped parameter dynamic model, with one-dimensional heat transfer, was used to predict cooling effects and to test experimental hypotheses. The cooling system consisted of a flexible collar and was tested on 4 adult sheep, in which brain and body temperatures were invasively monitored for the duration of the experiment.

Results

Model-based simulations predicted a lowering of the temperature of the brain and the body following the onset of cooling, with a rate of 0.4 °C/h for the brain and 0.2 °C/h for the body. The experimental findings showed comparable cooling rates in the two body compartments, with temperature reductions of 0.6 (0.2) °C/h for the brain and 0.6 (0.2) °C/h for the body. For a 70 kg adult human subject, we predict a temperature reduction of 0.64 °C/h for the brain and 0.43 °C/h for the body.

Conclusions

This work demonstrates the feasibility of using a non-invasive method to induce brain hypothermia using a portable collar. This device demonstrated an optimal safety profile and represents a potentially useful method for the administration of mild hypothermia and temperature control (i.e., treatment of hyperpyrexia) in cardiac arrest and critically ill neurologic patients.

Electronic supplementary material

The online version of this article (doi:10.1007/s12028-016-0257-7) contains supplementary material, which is available to authorized users.

The effect of selective head-neck cooling on physiological and cognitive functions in healthy volunteers

In general, brain temperatures are elevated during physical sporting activities; therefore, reducing brain temperature shortly after a sports-related concussion (SRC) could be a promising intervention technique. The main objective of this study was to examine the effects of head and neck cooling on physiological and cognitive function in normal healthy volunteers. Twelve healthy volunteers underwent two different sessions of combined head and neck cooling, one session with a cold pack and one session with a room temperature pack. Physiological measurements included: systolic/diastolic blood pressure, pulse oximetry, heart rate, and sublingual and tympanic temperature. Cognitive assessment included: processing speed, executive function, and working memory tasks. Physiological measurements were taken pre-, mid- and post-cooling, while cognitive assessments were done before and after cooling. The order of the sessions was randomized. There was a significant decrease in tympanic temperature across both sessions; however more cooling occurred when the cold pack was in the device. There was no significant decrease in sublingual temperature across either session. The observed heart rates, pulse oximetry, systolic and diastolic blood pressure during the sessions were all within range of a normal healthy adult. Cognitive assessment remained stable across each session for both pre- and post-cooling. We propose that optimizing brain temperature management after brain injury using head and neck cooling technology may represent a sensible, practical, and effective strategy to potentially enhance recovery and perhaps minimize the subsequent short and long term consequences from SRC.

A novel head-neck cooling device for concussion injury in contact sports

Emerging research on the long-term impact of concussions on athletes has allowed public recognition of the potentially devastating effects of these and other mild head injuries. Mild traumatic brain injury (mTBI) is a multifaceted disease for which management remains a clinical challenge. Recent pre-clinical and clinical data strongly suggest a destructive synergism between brain temperature elevation and mTBI; conversely, brain hypothermia, with its broader, pleiotropic effects, represents the most potent neuro-protectant in laboratory studies to date. Although well-established in selected clinical conditions, a systemic approach to accomplish regional hypothermia has failed to yield an effective treatment strategy in traumatic brain injury (TBI). Furthermore, although systemic hypothermia remains a potentially valid treatment strategy for moderate to severe TBIs, it is neither practical nor safe for mTBIs. Therefore, selective head-neck cooling may represent an ideal strategy to provide therapeutic benefits to the brain. Optimizing brain temperature management using a National Aeronautics and Space Administration (NASA) spacesuit spinoff head-neck cooling technology before and/or after mTBI in contact sports may represent a sensible, practical, and effective method to potentially enhance recover and minimize post-injury deficits. In this paper, we discuss and summarize the anatomical, physiological, preclinical, and clinical data concerning NASA spinoff head-neck cooling technology as a potential treatment for mTBIs, particularly in the context of contact sports.

Effect of wearing an N95 respirator on infrared tympanic membrane temperature measurements

To determine the impact of wearing an N95 filtering facepiece respirator (N95 FFR) on tympanic temperature measurements. TMT measurements, with and without wearing an N95 filtering facepiece respirator (N95 FFR) were obtained at the onset and termination of 1 h of treadmill exercise in 21 subjects, and at staggered time intervals (0, 20, 40, 60 min) during combined sedentary activity and exercise of another 46 subjects, to determine any effect on TMT. A total of 877 TMT measurements were obtained that demonstrated a mean TMT increase of 0.05 °C in the first study group (p = 0.04) and a 0.19 °C decrease in the second study group (p < 0.001) with the wearing of an N95 FFR, both of which were lower than controls. Wearing an N95 FFR for 1 h, at different levels of activity, results in significantly lower TMT values than not wearing an N95 FFR, but the magnitude of the changes would likely have minimal clinical significance.

Effect of head and face insulation on cooling rate during snow burial

OBJECTIVES

Avalanche victims are subjected to a number of physiological stressors during burial. We simulated avalanche burial to monitor physiological data and determine whether wearing head and face insulation slows cooling rate during snow burial. In addition, we sought to compare 3 different types of temperature measurement methods.

METHODS

Nine subjects underwent 2 burials each, 1 with head and face insulation and 1 without. Burials consisted of a 60-minute burial phase followed by a 60-minute rewarming phase. Temperature was measured via 3 methods: esophageal probe, ingestible capsule, and rectal probe.

RESULTS

Cooling and rewarming rates were not statistically different between the 2 testing conditions when measured by the 3 measurement methods. All temperature measurement methods correlated significantly.

CONCLUSIONS

Head and face insulation did not protect the simulated avalanche victim from faster cooling or rewarming. Because the 3 temperature measurement methods correlated, the ingestible capsule may provide an advantageous noninvasive method for snow burial and future hypothermia studies if interruptions in data transmission can be minimized.

Influence of intranasal and carotid cooling on cerebral temperature balance and oxygenation

The present study evaluated the influence of intranasal cooling with balloon catheters, increased nasal ventilation, or percutaneous cooling of the carotid arteries on cerebral temperature balance and oxygenation in six healthy male subjects. Aortic arch and internal jugular venous blood temperatures were measured to assess the cerebral heat balance and corresponding paired blood samples were obtained to evaluate cerebral metabolism and oxygenation at rest, following 60 min of intranasal cooling, 5 min of nasal ventilation, and 15 min with carotid cooling. Intranasal cooling induced a parallel drop in jugular venous and arterial blood temperatures by 0.30 ± 0.08°C (mean ± SD), whereas nasal ventilation and carotid cooling failed to lower the jugular venous blood temperature. The magnitude of the arterio-venous temperature difference across the brain remained unchanged at −0.33 ± 0.05°C following intranasal and carotid cooling, but increased to −0.44 ± 0.11°C (P < 0.05) following nasal ventilation. Calculated cerebral capillary oxygen tension was 43 ± 3 mmHg at rest and remained unchanged during intranasal and carotid cooling, but decreased to 38 ± 2 mmHg (P < 0.05) following increased nasal ventilation. In conclusion, percutaneous cooling of the carotid arteries and intranasal cooling with balloon catheters are insufficient to influence cerebral oxygenation in normothermic subjects as the cooling rate is only 0.3°C per hour and neither intranasal nor carotid cooling is capable of inducing selective brain cooling.

Anatomical locations of human brown adipose tissue: functional relevance and implications in obesity and type 2 diabetes

We will review information about and present hypotheses as to the anatomy of brown adipose tissue (BAT). Why is it located where it is in humans? Its anatomical distribution is likely to confer survival value by protecting critical organs from hypothermia by adaptive thermogenesis. Ultimately, the location and function will be important when considering therapeutic strategies for preventing and treating obesity and type 2 diabetes, in which case successful interventions will need to have a significant effect on BAT function in subjects living in a thermoneutral environment. In view of the diverse locations and potential differences in responsiveness between BAT depots, it is likely that BAT will be shown to have much more subtle and thus previously overlooked functions and regulatory control mechanisms.

Induction of cooling with a passive head and neck cooling device: effects on brain temperature after stroke

BACKGROUND AND PURPOSE

Therapeutic hypothermia improves clinical outcome after cardiac arrest and appears beneficial in other cerebrovascular diseases. We conducted this study to investigate the relationship between surface head/neck cooling and brain temperature.

METHODS

Prospective observational study enrolling consecutive patients with severe ischemic or hemorrhagic stroke undergoing intracranial pressure (ICP) and brain temperature monitoring. Arterial pressure, ICP, cerebral perfusion pressure, heart rate, brain, tympanic, and bladder temperature were continuously registered. Fifty-one applications of the Sovika cooling device were analyzed in 11 individual patients.

RESULTS

Sovika application led to a significant decrease of brain temperature compared with baseline with a maximum of -0.36°C (SD, 0.22) after 49 minutes (SD, 17). During cooling, dynamics of brain temperature differed significantly from bladder (-0.25°C [SD, 0.15] after 48 minutes [SD, 19]) and tympanic temperature (-1.79°C [SD, 1.19] after 37 minutes [SD, 16]). Treatment led to an increase in systolic arterial pressure by >20 mm Hg in 14 applications (n=7 patients) resulting in severe hypertension (>180 mm Hg) in 4 applications (n=3). ICP increased by >10 mm Hg in 7 applications (n=3), led to ICP crisis >20 mm Hg in 6 applications (n=3), and a drop of cerebral perfusion pressure <50 mm Hg in 1 application.

CONCLUSIONS

Although the decrease of brain temperature after Sovika cooling device application was statistically significant, we doubt clinical relevance of this rather limited effect (-0.36°C). Moreover, the transient increases of blood pressure and ICP warrant caution.