Changes In Core Temperature Research Articles

Retinal and cerebral hemodynamics redistribute to favor thermoregulation in response to passive environmental heating and heated exercise in humans

ABSTRACT Core temperature (TC) changes, alongside exercise, affect hemodynamic responses across different conduit and microvascular beds. This study investigated impacts of ecologically valid environmental heat and exercise exposures on cerebral, skin and retinal vascular responses by combining physiological assessments alongside computational fluid dynamics (CFD) modeling. Young, healthy participants (n = 12) were exposed to environmental passive heating (PH), and heated exercise (HE) (ergometer cycling), in climate-controlled conditions (50 mins, 40°C, 50% relative humidity) while maintaining upright posture. Blood flow responses in the common carotid (CCA), internal carotid (ICA) and central retinal (CRA) arteries were assessed using Duplex ultrasound, while forearm skin microvascular blood flow responses were measured using optical coherence tomography angiography. Three-dimensional retinal hemodynamics (flow and pressure) were calculated via CFD simulation, enabling assessment of wall shear stress (WSS). TC rose following PH (+0.2°C, p = 0.004) and HE (+1.4°C, p < 0.001). PH increased skin microvascular blood flow (p < 0.001), whereas microvascular CRA flow decreased (p = 0.038), despite unchanged ICA flow. HE exacerbated these differences, with increased CCA flow (p = 0.007), unchanging ICA flow and decreased CRA flow (p < 0.001), and interactions between vascular (CCA vs. ICA p = 0.018; CCA vs. CRA p = 0.004) and microvascular (skin vs. retinal arteriolar p < 0.001) territories. Simulations revealed patterns of WSS and lumen pressure that uniformly decreased following HE. Under ecologically valid thermal challenge, different responses occur in distinct conduit and microvascular territories, with blood flow distribution favoring systemic thermoregulation, while flow may redistribute within the brain.

Regulating the interaction between protein and starch in noodles through heat loss: Used to improve the edible quality of noodles

The impact of heat loss during water-cooling process on the edible quality of cooked noodles currently remains unclear. This study aimed to explore the effects of different water-cooling times (0, 20, 40, 60, 80, 100, and 120 s) on changes in gluten and starch structures and their impact on the sensory evaluation and texture of noodles. Results showed that the control group had a higher core temperature, while the core temperature of the noodles equilibrated with the water temperature after water-cooling for 100 s. Within the range of 20–100 s of water-cooling time, a sudden drop in the core temperature of the cooked noodles caused the gluten conformation to transition toward more compact β-sheets. Surface hydrophobicity decreased, while S-S and hydrogen bonds increased. The microstructure of the noodles became more compact, reducing gaps between protein and starch molecules. Small-angle X-ray scattering and atomic force microscopy analyses demonstrated that gluten chains aggregated after water-cooling, resulting in increased chain width and height. The wheat gluten protein structure transitioned from a disordered state to a random coil. Ultimately, the hardness, springiness, and chewiness of the noodles gradually increased. Water distribution results revealed that the free water content of the noodles increased after 120 s of water-cooling, enhancing the hydration between protein and water molecules but decreasing the noodle texture. According to X-ray diffraction and differential scanning calorimeter analyses, heat loss did not alter the gelatinized starch crystal structure of noodles. Therefore, changes in core temperature were the primary cause of gluten structural changes prior to 100 s of water-cooling. After 120 s of water-cooling, increased hydration between noodle surface gluten and water negatively affected the edible quality of noodles. This study provides theoretical data on noodle edible quality and is of significant practical importance.

Probiotic Influence On Changes In Core Temperature And The Resultant Changes In Circulating Cytokines Following Aerobic Exercise In A Heated Environment

Probiotic Influence On Changes In Core Temperature And The Resultant Changes In Circulating Cytokines Following Aerobic Exercise In A Heated Environment

Ice vests extend physiological work time while wearing explosive ordnance disposal protective clothing in hot and humid conditions

BackgroundExplosive ordnance disposal (EOD) technicians may be required to work in hot, humid environments while wearing heavy protective clothing. We investigated the ability of an ice vest to attenuate physiological strain and subsequently extend work tolerance. MethodsEight male participants (24.3 ± 4.1 yr, 51.9 ± 4.6 mL kg−1 min−1) walked (4.5 km h−1) in simulated hot and humid conditions (35 °C; 50% relative humidity). Participants wore either an EOD suit (CON) or EOD and ice vest (IV). Heart rate, core and skin temperature were recorded continuously. ResultsParticipants walked longer in IV compared to CON (8.1 ± 7.4 min, p < .05). Over 90% of trials were terminated based on participants reaching 90% of their maximum heart rate. IV resulted in cooled skin (p < .001) and a physiologically negligible change in core temperature (p < .001). A condition by time interaction was identified for heart rate (p < .001), with a lower rate of rise in the IV condition. ConclusionsThe cardiovascular inefficiency that limited performance was attenuated in the IV condition. The ice vest facilitated heat loss from the periphery; thus, the observed reduction in heart rate may reflect the preservation of central blood volume. The results identify the efficiency of a simple, inexpensive ice vest to assist EOD technicians working in the heat.

An exploratory investigation of heart rate and heart rate variability responses to daylong heat exposure in young and older adults.

Heart rate variability (HRV) has shown potential as a tool for monitoring thermal strain, but there is limited data to support its efficacy in older adults during prolonged heat exposures. We compared HRV between young (19-31 years, n=20) and older (61-78 years, n=39) adults during 9 hours of heat exposure (40°C, 9% RH). We also explored whether heart rate (HR) and/or HRV could be used to distinguish older adults who achieved elevated thermal strain, defined as either 1) an increase in core temperature >1.0°C (occurring in 39% [15/39]) or 2) a reduction in systolic blood pressure >10 mm Hg (occurring in 67% [26/39]). Percentage of age-predicted maximal HR and percentage of heart rate reserve (HRR) were higher, whereas standard deviation of normal RR intervals (SDNN), the square root of the mean of squared differences between successive RR intervals (RMSSD), high frequency power (HF), and cardiac vagal index (CVI) were lower in older compared to young adults (P≤0.004) during heat exposure. In older adults, increases in core temperature were correlated with percentage of age-predicted maximal HR, percentage of HRR, RMSSD, and CVI (P≤0.031), whereas changes in systolic blood pressure were not significantly associated with HR or HRV indices (P≤0.327). Receiver operating characteristic curve analysis indicated that HR and HRV indices had generally poor ability to identify older adults with elevated thermal strain (area under the curve ≤0.65). Age-related differences in HRV, consistent with vagal withdrawal among older adults, remained during daylong heat exposure, but marked heterogeneity of response likely contributed to HRV providing limited discriminatory value in identifying changes in core temperature or blood pressure in older adults.

Creatinine clearance is maintained in a range of wet-bulb globe temperatures and work-rest ratios during simulated occupational heat stress.

We tested the hypothesis that compliance with the National Institute for Occupational Safety and Health (NIOSH) heat stress recommendations will prevent reductions in glomerular filtration rate (GFR) across a range of wet-bulb globe temperatures (WBGTs) and work-rest ratios at a fixed work intensity. We also tested the hypothesis that noncompliance would result in a reduction in GFR compared with a work-rest matched compliant trial. Twelve healthy adults completed five trials (four NIOSH compliant and one noncompliant) that consisted of 4 h of exposure to a range of WBGTs. Subjects walked on a treadmill (heat production: approximately 430 W) and work-rest ratios (work/h: 60, 45, 30, and 15 min) were prescribed as a function of WBGT (24°C, 26.5°C, 28.5°C, 30°C, and 36°C), and subjects drank a sport drink ad libitum. Peak core temperature (TC) and percentage change in body weight (%ΔBW) were measured. Creatinine clearance measured pre- and postexposure provided a primary marker of GFR. Peak TC did not differ among NIOSH-compliant trials (P = 0.065) but differed between compliant versus noncompliant trials (P < 0.001). %ΔBW did not differ among NIOSH-compliant trials (P = 0.131) or between compliant versus noncompliant trials (P = 0.185). Creatinine clearance did not change or differ among compliant trials (P ≥ 0.079). Creatinine clearance did not change or differ between compliant versus noncompliant trials (P ≥ 0.661). Compliance with the NIOSH recommendations maintained GFR. Surprisingly, despite a greater heat strain in a noncompliant trial, GFR was maintained highlighting the potential relative importance of hydration.NEW & NOTEWORTHY We highlight that glomerular filtration rate (GFR) is maintained during simulated occupational heat stress across a range of total work, work-rest ratios, and wet-bulb globe temperatures with ad libitum consumption of an electrolyte and sugar-containing sports drink. Compared with a work-rest matched compliant trial, noncompliance resulted in augmented heat strain but did not induce a reduction in GFR likely due to an increased relative fluid intake and robust fluid conservatory responses.

The roles of ACE I/D and ACTN3 R577X gene variants in heat acclimation

Roles of genes in heat acclimation (HA, repeated exercise-heat exposures) had not been explored. ACE I/D and ACTN3 R577X genetic polymorphisms are closely associated with outstanding exercise performances. This study investigated whether the two polymorphisms influenced the response to HA. Fifty young Han nationality male subjects were selected and conducted HA for 2 weeks. Exercise indicators (5-km run, push-up and 100-m run) were tested and rest aural thermometry (RTau) was measured before and after HA. ACE gene was grouped by I homozygote and D carrier, and ACTN3 gene was grouped by R homozygote and X carrier. Results showed that there were no differences between groups in age, body mass index, exercise indicators and RTau before HA. After HA, RTau of ACE I homozygote was lower than that of D carrier [F(1, 48) = 9.12, p = 0.004, η = 0.40]. Compared with RTau before HA, that of I homozygote decreased after HA (Δ = −0.26 °C, 95 % CI -0.34–0.18, p < 0.001), while that of D carrier did not change. There was a ACE gene × HA interaction in RTau [F(1, 48) = 14.26, p < 0.001, η = 0.48]. No effect of ACTN3 gene on RTau was observed. For exercise indicators, there were no differences between groups after HA, and no gene × HA interactions were observed. There may be a strong interaction of ACE gene and HA in the change of rest core temperature. I homozygote may have an advantage on improving heat tolerance.

Thermoregulatory Responses to Very Hot and Dry Heat Exposure: Interactions Between Age and Sex

Extreme heat events can cause mass morbidity and mortality. Older adults are more susceptible to the adverse effects of heat. Additionally, sex is known to independently influence the physiological responses to heat stress. However, less is known regarding the interaction between age and sex on thermoregulation. Purpose: This study investigated differences in thermoregulatory responses between males and females in older and younger individuals exposed to a hot and dry environment with accompanying activities of daily living. Methods: Twenty older (70 ± 4 yrs) and twenty younger (29 ± 5 yrs) adults (10 males and 10 females per group) were exposed to 3-hours of ambient heating, replicating peak environmental conditions during the 2018 Los Angeles heat wave (47 °C, 15% relative humidity). Participants performed seven 5-minute periods of light exercise (≍3 METS; metabolic heat production: 2.99 ± 0.33 W/kg) dispersed throughout the heat exposure to simulate heat generation associated with activities of daily living. Participants ingested 3 mL/kg/hr of tap-temperature water throughout the trial. Core temperature, skin temperature, and heart rate changes were assessed from pre-post heat exposure. Whole-body sweat rate and forearm blood flow changes were indexed to changes in core temperature. Data were analyzed using a two-way ANOVA (Age x Sex) Results: Delta core temperature was greater in older individuals (males: 1.43 ± 0.47°C, females: 1.31 ± 0.39°C) than in younger (males: 0.83 ± 0.22°C, females: 0.53 ± 0.24°C, p&lt;0.001) but there was no difference between sex (p = 0.063) nor was there an interaction (p = 0.423). There was an interaction of age and sex on delta heart rate (p = 0.019). Older females (32 ± 9 bpm) had greater increases in heart rate than older males (18 ± 8 bpm), younger males (18 ± 6 bpm), and younger females (18 ± 12 bpm, p ≤ 0.009 for all comparisons). There was no effect of age (p = 0.529), sex (p = 0.670), or interaction (p = 0.422) on delta skin temperature. There was an interaction between age and sex for whole-body sweat loss (WBSL) indexed to changes in core temperature and body surface area (p = 0.009). Younger females (1688 ± 685 mL/m2/°C) had greater WBSL than older females (612 ± 211 mL/m2/°C, p &lt; 0.0001), older males (694 ± 327 mL/m2/°C, p &lt; 0.0001), and younger males (1038 ± 282 mL/m2/°C, p &lt; 0.0001). There was a main effect of sex (p = 0.003) and age (p &lt; 0.0001), but no interaction (p = 0.152) on delta forearm blood flow indexed to changes in core temperature (older males: 116 ± 67 mL/min/°C, older females: 194 ± 73 mL/min/°C, younger males: 263 ± 72 mL/min/°C, younger females: 468 ± 243 mL/min/°C). Conclusion: These data suggest that many thermoregulatory responses to heat stress are influenced by the interaction between age and sex. Supported by NIH R01AG069005 (CGC). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

THE EFFECT OF WATER DOUSING ON HEAT STRAIN AND PERFORMANCE DURING ENDURANCE RUNNING IN THE HEAT

INTRODUCTION Water dousing (pouring water on the body) is an easy-to-implement cooling method while running due to the availability of water at race aid stations, and may decrease the risk of heat illness and improve performance. However, dousing has not been investigated in extended duration running (i.e., ≥10 km), a typical distance in both elite and community level events. AIMS: Assess the effect of water dousing on heat strain and performance during self-paced and fixed-intensity exercise in the heat. DESIGN: Crossover, block randomised controlled trial. METHODS 13 trained runners completed a 10 km time trial (TT) and 60 min fixed pace run (60% velocity of VO2max) in a 30°C, 47% relative humidity environment using either water dousing (DOUSE) or no dousing (CON). RESULTS 10 km TT performance was faster in DOUSE compared to CON (44:11±6:14 vs. 44:38±6:03 min:s; p=0.033). Change in core temperature (Tc) was not different between groups during the TT (+0.02±0.33°C in DOUSE; p=0.853) or fixed pace run (+0.02±0.30°C; p=0.848). Change in mean skin temperature (Tsk) was lower in DOUSE during the TT (-1.80±0.63°C; p&amp;lt;0.001) and fixed pace run (-1.38±0.78°C; p&amp;lt;0.001). Heart rate (HR) was lower for DOUSE during the fixed pace run (-3.5±5.5 bpm; p=0.041) but not during the TT (-0.2±4.2 bpm; p=0.853). Thermal sensation was lower for DOUSE during the TT (-49.3±41.9 mm; p&amp;lt;0.001) and fixed pace run (-44.7±27.6 mm; p&amp;lt;0.001). Rating of perceived exertion (RPE) was not different between groups for the TT (-0.2±0.9; p=0.390) or fixed pace run (-0.2±1.0; p=0.480). CONCLUSION Water dousing improves 10 km TT performance in the heat but does not mitigate a rise in Tc. The positive change in thermal perception (via lower skin temperature) likely drives this ergogenic effect.

The Effect of Brief Warming during Induction of General Anesthesia and Warmed Intravenous Fluid on Intraoperative Hypothermia in Patients Undergoing Urologic Surgery.

Background and Objectives: Transurethral urologic surgeries frequently lead to hypothermia due to bladder irrigation. Prewarming in the preoperative holding area can reduce the risk of hypothermia but disrupts surgical workflow, preventing it from being of practical use. This study explored whether early intraoperative warming during induction of anesthesia, known as peri-induction warming, using a forced-air warming device combined with warmed intravenous fluid could prevent intraoperative hypothermia. Materials and Methods: Fifty patients scheduled for transurethral resection of the bladder (TURB) or prostate (TURP) were enrolled and were randomly allocated to either the peri-induction warming or control group. The peri-induction warming group underwent whole-body warming during anesthesia induction using a forced-air warming device and was administered warmed intravenous fluid during surgery. In contrast, the control group was covered with a cotton blanket during anesthesia induction and received room-temperature intravenous fluid during surgery. Core temperature was measured upon entrance to the operating room (T0), immediately after induction of anesthesia (T1), and in 10 min intervals until the end of the operation (Tend). The incidence of intraoperative hypothermia, change in core temperature (T0-Tend), core temperature drop rate (T0-Tend/[duration of anesthesia]), postoperative shivering, and postoperative thermal comfort were assessed. Results: The incidence of intraoperative hypothermia did not differ significantly between the two groups. However, the peri-induction warming group exhibited significantly less change in core temperature (0.61 ± 0.3 °C vs. 0.93 ± 0.4 °C, p = 0.002) and a slower core temperature drop rate (0.009 ± 0.005 °C/min vs. 0.013 ± 0.004 °C/min, p = 0.013) than the control group. The peri-induction warming group also reported higher thermal comfort scores (p = 0.041) and less need for postoperative warming (p = 0.034) compared to the control group. Conclusions: Brief peri-induction warming combined with warmed intravenous fluid was insufficient to prevent intraoperative hypothermia in patients undergoing urologic surgery. However, it improved patient thermal comfort and mitigated the absolute amount and rate of temperature drop.

Biological sex does not independently influence time-dependent changes in core temperature and sweating of children exercising in uncompensable heat stress.

To investigate the influence of biological sex, independent of differences in aerobic fitness and body fatness, on the change in gastro-intestinal temperature (∆Tgi) and whole-body sweat rate (WBSR) of children exercising under uncompensable heat stress. Seventeen boys (mean±SD; 13.7±1.3 years) and 18 girls (13.7±1.4) years) walked for 45 min at a fixed rate of metabolic heat production per kg body mass (8 W·kg-1) in 40°C and 30% relative humidity. Sex and V̇O2peak were entered into a Bayesian hierarchical general additive model (HGAM) for Tgi. Sex, V̇O2peak and the evaporative requirement for heat balance (Ereq) were entered into a Bayesian hierarchical linear regression for WBSR. For 26 (12 M, 14 F) of the 35 children with measured body composition, body fat percentage was entered in a separate HGAM and hierarchical linear regression for Tgi and WBSR respectively. Conditional on sex-specific mean V̇O2peak, ∆Tgi was 1.00°C [90% credible intervals: 0.84, 1.16] for boys and 1.17°C [1.01, 1.33] for girls, with a difference of 0.17°C [-0.39, 0.06]. When sex differences in V̇O2peak were accounted for, the difference in ∆Tgi between boys and girls was 0.01°C [-0.25, 0.22]. The difference in WBSR between boys and girls was 0.03 L·h-1 [-0.02, 0.07], when isolated from differences in Ereq. The difference in ∆Tgi between boys and girls was -0.10°C [-0.38, 0.17] when sex differences in body fat (%) were accounted for. Biological sex did not independently influence the ∆Tgi and WBSR of children exercising under uncompensable heat stress.

Mixed-Method Heat Acclimation Induces Heat Adaptations in International Triathletes Without Training Modification

PurposeHeat acclimation (HA) kinetics often necessitates that the intervention is conducted in the weeks immediately preceding athletic competitions, potentially interfering with a training taper. Therefore, we investigated the efficacy of a mixed-method HA protocol, superimposed over planned external training loads, during the 3-weeks prior to the 2022 U23 World Triathlon Championships.MethodsSix international triathletes completed 8 pre-competition HA sessions (5 active: running/cycling, 3 passive: hot water immersion [HWI]), across 2-weeks. Outdoor high-intensity training sessions were followed by 30–60 min HWI, whilst low-intensity cycling/running sessions were completed in a hot, humid environmental chamber. To assess heat adaptations, participants completed three 25 min heat stress tests (HST) involving iso-speed treadmill running (session 1 = HST1, session 5 = HST2, and session 8 = HST3). Physiological, haematological and wellbeing monitoring were conducted throughout HA.ResultsReduced heart rate (~ − 6 beats/min) was observed within HST3 (P = 0.01, ηp2 = 0.64), versus HST1 and HST2. No changes in core temperature were observed across HSTs (P = 0.055,ηp2 = 0.44). Sweat sodium concentration was lower by HST2 at the arm (− 23 ± 16 mmol/L, P = 0.02) and back (− 27 ± 17 mmol/L, P = 0.01). White blood cell count reduced from baseline to the end of HA (P = 0.02, ηp2 = 0.27), but no changes were found in any other haematological markers (all P > 0.05). Perceptual wellbeing measures did not change across HA (all P > 0.05).ConclusionBy HST3, seven prior mixed-method HA sessions improved markers of heat adaptation (exercising HR and sweat concentration) within international triathletes. Mixed-method HA may be implemented without modifying training load, with no apparent detrimental effects on athlete health or training stress markers.

878 Selective Brain Cooling is Possible via CSF Exchange With Double Lumen EVD- Proof of Concept in Porcine Model

INTRODUCTION: Hypothermia is seen as neuroprotective after brain insult (BI). In acute phase after BI it affects brain metabolism by decreasing oxygen and glucose consumption. Hypothermia affects apoptosis and inflammatory mediators. In the later stage of BI, enzyme activation stimulates protein and lipid breakdown, which can be slowed and decreased with hypothermia. In the latest stage of BI hypothermia has shown positive affect in angiogenesis, neurogenesis, synaptogenesis. Hypothermia also reduces vasogenic oedema and blood brain barrier dysfunction. Despite hypothermia´s neuroprotective effect randomized control trials have demonstrated its benefits only limited scenarios - mainly in global ischemia (post-cardiac infarction and ischemia of new-born). Majority of complications related to hypothermia has been due to systemic hypothermia and selective brain cooling has never been demonstrated in large mammals without changes in core temperature of subject. METHODS: We inserted double lumen external ventricular drainage (EVD) into the lateral ventricle of porcine. We added spinal drainage to accelerate CSF exchange to cooled NaCl solution. Brain parenchymal temperature was measured from the contralateral brain hemisphere and the ipsilateral brain hemisphere. RESULTS: Contralateral brain hemisphere temperature dropped by 3.1C from baseline while core temperature changed only by 0.5C. Ipsilateral temperature cooled by 7.5C from baseline to 30.8C, while core temperature was 37.7C. Total time needed to achieve selective cooling was 1.5h. Porcine started to have arrhythmias when brain temperature approached 30.8C. CONCLUSIONS: We are first to describe that selective brain cooling is possible via CSF exchange with double lumen EVD to achieve significant temperature difference between body core and brain. The timing and rate of selective cooling needs to be established as cause of arrhythmias before starting human trials.

Relationship Between Running Biomechanics and Core Temperature Across a Competitive Road Race.

Outdoor races introduce environmental stressors to runners, and core temperature changes may influence runners' movement patterns. This study assessed changes and determined relationships between sensor-derived running biomechanics and core temperature among runners across an 11.27-km road race. Core temperatures would increase significantly across the race, related to changes in spatiotemporal biomechanical measures. Cross-sectional cohort study. Level 3. Twenty runners (9 female, 11 male; age, 48 ± 12 years; height, 169.7 ± 9.1 cm; mass, 71.3 ± 13.4 kg) enrolled in the 2022 Falmouth Road Race were recruited. Participants used lightweight technologies (ingestible thermistors and wearable sensors) to monitor core temperature and running biomechanics throughout the race. Timestamps were used to align sensor-derived measures for 7 race segments. Observations were labeled as core temperatures generally within normal limits (<38°C) or at elevated core temperatures (≥38°C). Multivariate repeated measures analyses of variance were used to assess changes in sensor-derived measures across the race, with Bonferroni post hoc comparisons for significant findings. Pearson's r correlations were used to assess the relationship between running biomechanics and core temperature measures. Eighteen participants developed hyperthermic core temperatures (39.0°C ± 0.5°C); core temperatures increased significantly across the race (P < 0.01). Kinetic measures obtained from the accelerometers, including shock, impact, and braking g, all significantly increased across the race (P < 0.01); other sensor-derived biomechanical measures did not change significantly. Core temperatures were weakly associated with biomechanics (|r range|, 0.02-0.16). Core temperatures and kinetics increased significantly across a race, yet these outcomes were not strongly correlated. The observed kinetic changes may have been attributed to fatigue-related influences over the race. Clinicians may not expect changes in biomechanical movement patterns to signal thermal responses during outdoor running in a singular event.

Research on the Magnetic Properties of High-Saturation Magnetically Induced Alloy Motors under Magnetocaloric Coupling.

In the face of the rapid development of the motor industry, some motors with traditional soft magnetic materials can no longer meet the needs of the market. Using new high-saturation magnetic density materials has become a new breakthrough to improve the torque density of motors. Fe-Co alloys (1J22) have high-saturation magnetic induction strength, which can effectively improve the motor's magnetic field strength and increase its torque density. At the same time, the temperature rise of the motor is also an important factor to consider in the motor design process. In particular, the change in core temperature caused by loss makes the coupling of the internal temperature field and the electromagnetic field of the motor more common. Therefore, it is necessary to test the temperature and magnetic properties of 1J22 together. In this paper, a coupling measurement device for magnetic properties of soft magnetic materials is built, and a 1J22 temperature field-electromagnetic field coupling experiment is completed. It is found that the maximum loss of 1J22 decreases by 4.44% with the increase in temperature; the maximum loss is 6.41% less than that of traditional silicon steel. Finally, a finite element simulation model is built to simulate the actual working conditions of the motor, and it is verified that the magnetic properties of the material at high temperature will have a certain impact on the performance of the motor.

Hyperthermic pressurized intraperitoneal aerosol drug delivery system in a large animal model: a feasibility and safety study.

We developed a novel drug delivery system called hyperthermic pressurized intraperitoneal aerosol chemotherapy (HPIPAC) that hybridized Hyperthermic intraperitoneal chemotherapy (HIPEC) and pressurized intraperitoneal aerosol chemotherapy (PIPAC). The present study aims to assess the feasibility and safety of HPIPAC system in a large animal survival model. Eleven pigs (eight non-survival models and three survival models) were used in the experiment. The heat module in the HPIPAC controller circulates hyperthermic CO2 in a closed-loop circuit and creates gas-based dry intraperitoneal hyperthermia. Three 12mm trocars were placed on the abdomen. The afferent CO2 tube wound with heat generating coil was inserted into a trocar, and the efferent tube was inserted into another trocar. Heated CO2 was insufflated and circulated in a closed circuit until the intra-abdominal and peritoneal surface temperature reached 42°C. 100ml of 5% dextrose in water was nebulized for 5min and the closed-loop circulation was resumed for 60min at 42°C. Tissue biopsies were taken from several sites from the pigs in the survival model. The average change in core temperature of the pigs was 2.5 ± 0.08°C. All three pigs displayed no signs of distress, and their vital signs remained stable, with no changes in their diet. In autopsy, inflammatory and fibrotic responses at the biopsy sites were observed without serious pathologic findings. We successfully proved the feasibility and safety of our novel HPIPAC system in an in-vivo swine survival model.

Continuous rise in oxygen consumption during prolonged military loaded march in the heat with and without fluid replacement: a pilot study

IntroductionV̇O2 drift, the rise in oxygen consumption during continuous exercise, has not been adequately reported during prolonged military marches. The purpose of this study was to analyse V̇O2 and energy...

Accuracy of a zero-heat-flux thermometer in cardiac surgery, a prospective, multicentre, method comparison study

Accurate measurement of core temperature is of utmost importance during on-pump cardiac surgery, for detection of hypothermia before cardiopulmonary bypass (CPB), guidance of temperature management on CPB, active rewarming on CPB and guidance of warming therapy after CPB. Most temperature measurement methods are known to become inaccurate during rapid changes in core temperature and suffer from delayed detection of temperature changes. Zero-heat-flux temperature (ZHF) measurement from the lateral forehead may be an alternative, non-invasive method quantifying the core temperature. A prospective, observational, multicentre study was conducted in one hundred patients scheduled for on-pump coronary artery bypass grafting. Core temperatures were measured every minute by two zero-heat-flux thermometer (SpotOn™) and a bladder thermometer and a pulmonary artery catheter (PAC) in the period after induction of anesthesia until CPB. Accuracy and precision of both methods were compared against core temperature measured in the pulmonary artery using the method of Bland and Altman. A high accuracy (around 0.1 °C) and a very good precision (Limits of agreement (LoA) − 0.6; 0.4 °C) were found between zero-heat-flux thermometer and core temperature measured by PAC. Among the two ZHF thermometers the bias was negligible (− 0.003 °C) with narrow LoA of − 0.42 °C and 0.41 °C. In contrast, bias between bladder temperature and PAC temperature was large (0.51 °C) with corresponding LoA of − 0.06 °C and 1.1 °C. ZHF thermometers are in contrast to bladder temperature a reliable core temperature monitor in cardiac surgery during the period after induction of anestesia until CPB. The zero-heat-flux method can provide clinicians reliably with continuous and non-invasive measurements of core temperature in normothermic and mild hypothermic temperature ranges and therefore can be helpful to guide temperature management.

Effect of Prewarming on Skin Temperature Changes After Spinal Anesthesia in Transurethral Resection of the Bladder

PurposeMonitoring of peripheral skin temperature changes is an objective and rapid method to evaluate the success of neuraxial block after spinal anesthesia. The aim of this study is to investigate the effect of prewarming on peripheral temperature changes after the administration of spinal anesthesia. DesignRandomized, prospective, single-blind study. MethodsIn this study, patients scheduled for transurethral resection of the bladder surgery under spinal anesthesia were divided into two groups: those with active prewarming and those without active prewarming. The groups were compared in core and skin temperature changes after administration of spinal anesthesia, length of stay in the postanesthesia care unit, shivering score, and the thermal comfort scale. FindingsA statistically significant difference was found between the groups on time for a 1 °C increase in ankle and toe skin temperatures (P < .001). There was a statistically significant difference between the groups in core temperature measurements (P < .001). When thermal comfort was compared between the groups, a statistically significant difference was found (P < .001). Patients' shivering score (P = .704), and length of stay in the postanesthesia care unit (P = .059) between the groups were similar. ConclusionsSkin temperature changes in the prewarming group were lower, and this group had a lower rate of increase than the nonprewarming group. Therefore, skin temperature changes in the lower extremity can be used to determine the success of spinal anesthesia in patients who are prewarmed, with the awareness of these differences.

Quantifying Exercise Heat Acclimatisation in Athletes and Military Personnel: A Systematic Review and Meta-analysis.

Athletes and military personnel are often expected to compete and work in hot and/or humid environments, where decrements in performance and an increased risk of exertional heat illness are prevalent. A physiological strategy for reducing the adverse effects of heat stress is to acclimatise to the heat. The aim of this systematic review was to quantify the effects of relocating to a hotter climate to undergo heat acclimatisation in athletes and military personnel. Studies investigating the effects of heat acclimatisation in non-acclimatised athletes and military personnel via relocation to a hot climate for < 6weeks were included. MEDLINE, SPORTDiscus, CINAHL Plus with Full Text and Scopus were searched from inception to June 2022. A modified version of the McMaster critical review form was utilised independently by two authors to assess the risk of bias. A Bayesian multi-level meta-analysis was conducted on five outcome measures, including resting core temperature and heart rate, the change in core temperature and heart rate during a heat response test and sweat rate. Wet-bulb globe temperature (WBGT), daily training duration and protocol length were used as predictor variables. Along with posterior means and 90% credible intervals (CrI), the probability of direction (Pd) was calculated. Eighteen articles from twelve independent studies were included. Fourteen articles (nine studies) provided data for the meta-analyses. Whilst accounting for WBGT, daily training duration and protocol length, population estimates indicated a reduction in resting core temperature and heart rate of - 0.19°C [90% CrI: - 0.41 to 0.05, Pd = 91%] and - 6beats·min-1 [90% CrI: - 16 to 5, Pd = 83%], respectively. Furthermore, the rise in core temperature and heart rate during a heat response test were attenuated by - 0.24°C [90% CrI: - 0.67 to 0.20, Pd = 85%] and - 7beats·min-1 [90% CrI: - 18 to 4, Pd = 87%]. Changes in sweat rate were conflicting (0.01L·h-1 [90% CrI: - 0.38 to 0.40, Pd = 53%]), primarily due to two studies demonstrating a reduction in sweat rate following heat acclimatisation. Data from athletes and military personnel relocating to a hotter climate were consistent with a reduction in resting core temperature and heart rate, in addition to an attenuated rise in core temperature and heart rate during an exercise-based heat response test. An increase in sweat rate is also attainable, with the extent of these adaptations dependent on WBGT, daily training duration and protocol length. CRD42022337761.