The Experts below are selected from a list of 205326 Experts worldwide ranked by ideXlab platform
Daniel I Sessler - One of the best experts on this subject based on the ideXlab platform.
-
effects of ambient Temperature and forced air warming on intraoperative Core Temperature a factorial randomized trial
Anesthesiology, 2018Co-Authors: Lijian Pei, Edward J Mascha, Yuguang Huang, Yongchang Zheng, Xinting Sang, Xiaoyun Zhou, Guangmei Mao, Daniel I SesslerAbstract:BACKGROUND The effect of ambient Temperature, with and without active warming, on intraoperative Core Temperature remains poorly characterized. The authors determined the effect of ambient Temperature on Core Temperature changes with and without forced-air warming. METHODS In this unblinded three-by-two factorial trial, 292 adults were randomized to ambient Temperatures 19°, 21°, or 23°C, and to passive insulation or forced-air warming. The primary outcome was Core Temperature change between 1 and 3 h after induction. Linear mixed-effects models assessed the effects of ambient Temperature, warming method, and their interaction. RESULTS A 1°C increase in ambient Temperature attenuated the negative slope of Core Temperature change 1 to 3 h after anesthesia induction by 0.03 (98.3% CI, 0.01 to 0.06) °CCore/(h°Cambient) (P < 0.001), for patients who received passive insulation, but not for those warmed with forced-air (-0.01 [98.3% CI, -0.03 to 0.01] °CCore/[h°Cambient]; P = 0.40). Final Core Temperature at the end of surgery increased 0.13°C (98.3% CI, 0.07 to 0.20; P < 0.01) per degree increase in ambient Temperature with passive insulation, but was unaffected by ambient Temperature during forced-air warming (0.02 [98.3% CI, -0.04 to 0.09] °CCore/°Cambient; P = 0.40). After an average of 3.4 h of surgery, Core Temperature was 36.3° ± 0.5°C in each of the forced-air groups, and ranged from 35.6° to 36.1°C in passively insulated patients. CONCLUSIONS Ambient intraoperative Temperature has a negligible effect on Core Temperature when patients are warmed with forced air. The effect is larger when patients are passively insulated, but the magnitude remains small. Ambient Temperature can thus be set to comfortable levels for staff in patients who are actively warmed.
-
axillary Temperature as recorded by the ithermonitor wt701 well represents Core Temperature in adults having noncardiac surgery
Anesthesia & Analgesia, 2017Co-Authors: Lijian Pei, Yuguang Huang, Guangmei Mao, Daniel I SesslerAbstract:Background Core Temperature can be accurately measured from the esophagus or nasopharynx during general anesthesia, but neither site is suitable for neuraxial anesthesia. We therefore determined the precision and accuracy of a novel wireless axillary thermometer, the iThermonitor, to determine its suitability for use during neuraxial anesthesia and in other patients who are not intubated. Methods We enrolled 80 adults having upper abdominal surgery with endotracheal intubation. Intraoperative Core Temperature was measured in distal esophagus and was estimated at the axilla with a wireless iThermonitor WT701 (Raiing Medical, Boston MA) at 5-minute intervals. Pairs of axillary and reference distal esophageal Temperatures were compared and summarized using linear regression and repeated-measured Bland-Altman methods. We a priori determined that the iThermonitor would have clinically acceptable accuracy if most estimates were within ±0.5°C of the esophageal reference, and suitable precision if the limits of agreement were within ±0.5°C. Results There were 3339 sets of paired Temperatures. Axillary and esophageal Temperatures were similar, with a mean difference (esophageal minus axillary) of only 0.14°C ± 0.26°C (standard deviation). The Bland-Altman 95% limits of agreement were reasonably narrow, with the estimated upper limit at 0.66°C and the lower limit at -0.38°C, thus ±0.52°C, indicating good agreement across the range of mean Temperatures from 34.9°C to 38.1°C. The absolute difference was within 0.5°C in 91% of the measurements (95% confidence interval, 88%-93%). Conclusions Axillary Temperature, as recorded by the iThermonitor WT701, well represents Core Temperature in adults having noncardiac surgery and thus appears suitable for clinical use.
-
estimation of mean body Temperature from mean skin and Core Temperature
Anesthesiology, 2006Co-Authors: Rainer Lenhardt, Daniel I SesslerAbstract:Background: Mean-body Temperature (MBT) is the mass-weighted average Temperature of body tissues. Core Temperature is easy to measure, but direct measurement of peripheral tissue Temperature is painful, risky, and requires complex calculations. Alternatively MBT can be estimated from Core and mean skin Temperatures with a formula proposed by Burton in 1935: MBT = 0.64. TCore + 0.36. TSkin. This formula remains widely used, but not been validated in the perioperative period and seems unlikely to remain accurate in dynamic perioperative conditions such as cardiopulmonary bypass. We thus tested the hypothesis that MBT, as estimated with Burton’s formula, poorly estimates measured MBT at a Temperature range between 18 and 36.5° C. Materials and Methods: We re-evaluated four of our previously published studies in which Core and mass-weighted mean peripheral tissue Temperatures were measured in patients undergoing substantial thermal perturbations. Peripheral compartment Temperatures were estimated using fourth-order regression and integration over volume from 18 intramuscular needle thermocouples, 9 skin Temperatures, and "deep" hand and foot Temperature. MBT was determined from mass-weighted average of Core and peripheral tissue Temperatures and estimated from Core Temperature and mean skin Temperature (15 area-weighted sites) using Burton’s formula. Results: 913 data pairs from 44 study subjects were included in the analysis. Measured MBT ranged from 18 to 36.5°C. There was a remarkably good relationship between measured and estimated MBT: MBTmeasured = 0.94 · MBTestimated + 2.15, r2 = 0.98. Differences between the estimated and measured values averaged -0.09 ± 0.42°C. Conclusions: We concluded that estimation of MBT from mean skin and Core Temperatures is generally accurate and precise.
-
influence of thermoregulatory vasomotion and ambient Temperature variation on the accuracy of Core Temperature estimates by cutaneous liquid crystal thermometers
Anesthesiology, 1997Co-Authors: Takehiko Ikeda, Daniel I Sessler, Danielle Marder, Junyu XiongAbstract:BACKGROUND Recently, liquid crystal skin-surface thermometers have become popular for intraoperative Temperature monitoring. Three situations during which cutaneous liquid-crystal thermometry may poorly estimate Core Temperature were monitored: (1) anesthetic induction with consequent Core-to-peripheral redistribution of body heat, (2) thermoregulatory vasomotion associated with sweating (precapillary dilation) and shivering (minimal capillary flow), and (3) ambient Temperature variation over the clinical range from 18-26 degrees C. METHODS The Core-to-forehead and Core-to-neck Temperature difference was measured using liquid-crystal thermometers having an approximately 2 degrees C offset. Differences exceeding 0.5 degree C (a 1 degree C) Temperature range) were a priori deemed potentially clinically important. Seven volunteers participated in each protocol. First, Core-to-peripheral redistribution of body heat was produced by inducing propofol/desflurane anesthesia; anesthesia was then maintained for 1 h with desflurane. Second, vasodilation was produced by warming unanesthetized volunteers sufficiently to produce sweating; intense vasoconstriction was similarly produced by cooling the volunteers sufficiently to produce shivering. Third, a canopy was positioned to enclose the head, neck, and upper chest of unanesthetized volunteers. Air within the canopy was randomly set to 18, 20, 22, 24, and 26 degrees C. RESULTS Redistribution of body heat accompanying induction of anesthesia had little effect on the Core-to-forehead skin Temperature difference. However, the Core-to-neck skin Temperature gradient decreased approximately 0.6 degree C in the hour after induction of anesthesia. Vasomotion associated with shivering and mild sweating altered the Core-to-skin Temperature difference only a few tenths of a degree centigrade. The absolute value of the Core-to-forehead Temperature difference exceeded 0.5 degree C during approximately 35% of the measurements, but the difference rarely exceeded 1 degree C. The Core-to-neck Temperature difference typically exceeded 0.5 degree C and frequently exceeded 1 degree C. Each 1 degree C increase in ambient Temperature decreased the Core-to-fore-head and Core-to-neck skin Temperature differences by less than 0.2 degree C. CONCLUSIONS Forehead skin Temperatures were better than neck skin Temperature at estimating Core Temperature. Core-to-neck Temperature differences frequently exceeded 1 degree C (a 2 degrees C range), whereas two thirds of the Core-to-forehead differences were within 0.5 degree C. The Core-to-skin Temperature differences were, however, only slightly altered by inducing anesthesia, vasomotor action, and typical intraoperative changes in ambient Temperature.
Osamu Fujiwara - One of the best experts on this subject based on the ideXlab platform.
-
estimation of Core Temperature elevation in humans and animals for whole body averaged sar
Progress in Electromagnetics Research-pier, 2009Co-Authors: Akimasa Hirata, Hironori Sugiyama, Osamu FujiwaraAbstract:Biological efiects due to whole-body radio-frequency exposure may be induced by Core Temperature elevation. According to the international safety guidelines/standards for human protection, the whole-body averaged speciflc absorption rate (WBA-SAR) is used as a metric. In order to understand the relationship between WBA-SAR and Core Temperature elevation, a theoretical solution or a closed formula for estimating Core Temperature elevation is essential. In the present study, we derived a formula for simply estimating Core Temperature elevation in humans and animals due to whole-body radio-frequency exposure. The Core Temperature elevation estimated with the formula is found to be in reasonable agreement with the computational results of flnite-difierence time- domain computation incorporated in anatomically-based models Based on the formula, the WBA-SAR is found to be a good metric for estimating Core Temperature elevation. The main factors in∞uencing the Core Temperature elevation are the perspiration rate and the body surface area-to-weight ratio.
-
fdtd analysis of body Core Temperature elevation in children and adults for whole body exposure
Physics in Medicine and Biology, 2008Co-Authors: Akimasa Hirata, Takayuki Asano, Osamu FujiwaraAbstract:The Temperature elevations in anatomically based human phantoms of an adult and a 3-year-old child were calculated for radio-frequency whole-body exposure. Thermoregulation in children, however, has not yet been clarified. In the present study, we developed a computational thermal model of a child that is reasonable for simulating body-Core Temperature elevation. Comparison of measured and simulated Temperatures revealed thermoregulation in children to be similar to that of adults. Based on this finding, we calculated the body-Core Temperature elevation in a 3-year-old child and an adult for plane-wave exposure at the basic restriction in the international guidelines. The body-Core Temperature elevation in the 3-year-old child phantom was 0.03 °C at a whole-body-averaged specific absorption rate of 0.08 W kg−1, which was 35% smaller than in the adult female. This difference is attributed to the child's higher body surface area-to-mass ratio.
-
fdtd analysis of human body Core Temperature elevation due to rf far field energy prescribed in the icnirp guidelines
Physics in Medicine and Biology, 2007Co-Authors: Akimasa Hirata, Takayuki Asano, Osamu FujiwaraAbstract:This study investigated the relationship between the specific absorption rate and Temperature elevation in an anatomically-based model named NORMAN for exposure to radio-frequency far fields in the ICNIRP guidelines (1998 Health Phys. 74 494-522). The finite-difference time-domain method is used for analyzing the electromagnetic absorption and Temperature elevation in NORMAN. In order to consider the variability of human thermoregulation, parameters for sweating are derived and incorporated into a conventional sweating formula. First, we investigated the effect of blood Temperature variation modeling on body-Core Temperature. The computational results show that the modeling of blood Temperature variation was the dominant factor influencing the body-Core Temperature. This is because the Temperature in the inner tissues is elevated via the circulation of blood whose Temperature was elevated due to EM absorption. Even at different frequencies, the body-Core Temperature elevation at an identical whole-body average specific absorption rate (SAR) was almost the same, suggesting the effectiveness of the whole-body average SAR as a measure in the ICNIRP guidelines. Next, we discussed the effect of sweating on the Temperature elevation and thermal time constant of blood. The variability of Temperature elevation caused by the sweating rate was found to be 30%. The blood Temperature elevation at the basic restriction in the ICNIRP guidelines of 0.4 W kg(-1) is 0.25 degrees C even for a low sweating rate. The thermal time constant of blood Temperature elevation was 23 min and 52 min for a man with a lower and a higher sweating rate, respectively, which is longer than the average time of the SAR in the ICNIRP guidelines. Thus, the whole-body average SAR required for blood Temperature elevation of 1 degrees C was 4.5 W kg(-1) in the model of a human with the lower sweating coefficients for 60 min exposure. From a comparison of this value with the basic restriction in the ICNIRP guidelines of 0.4 W kg(-1), the safety factor was 11.
Hiromi Tokura - One of the best experts on this subject based on the ideXlab platform.
-
Effects of pressure exerted on the skin by elastic cord on the Core Temperature, body weight loss and salivary secretion rate at 35°C
European journal of applied physiology, 2005Co-Authors: Sawako Tanaka, Tomoko Midorikawa, Hiromi TokuraAbstract:Effects of pressure exerted on the skin by elastic cord on the Core Temperature, body weight loss and salivary secretion rate were studied under conditions of ambient Temperature of 35°C and a relative humidity of 60%. Twelve healthy females, aged 18–23 years, served as subjects. The subjects entered a bioclimatic chamber and rested quietly in a chair for 80 min. Then, skin pressure was exerted by applying elastic cord (8.5 mm wide) to six different skin areas, such as axilla, under-bust, waist, inguines, thighs and ankles. The values of skin pressure by elastic cord ranged from 11.9 to 33.3 g/cm2. In the control experiment, wrapping with an elastic cord was loosely performed without any skin pressure. Rectal and skin Temperatures, body weight loss by sweating and salivary secretion rate were measured throughout the 160 min experimental period. Core Temperature increased more significantly under pressure exerted on the skin. Body weight loss by mainly sweating and salivary secretion rate were significantly suppressed under pressure exerted on the skin. We discussed the physiological mechanisms in terms of suppression of central nervous activity as to why significant increase of Core Temperatures, inhibition of body weight loss mainly by sweating and of salivary secretion rate occurred, and furthermore practical significance of these findings for impairment of digestion, swallowing, vocalizing, defense against disease bacteria and sport activity.
-
the effects of skin pressure by clothing on circadian rhythms of Core Temperature and salivary melatonin
Chronobiology International, 2000Co-Authors: Youngah Lee, Ki-ja Hyun, Hiromi TokuraAbstract:The present experiment investigated the effects of skin pressure by foundation garments (girdle and brassiere) on the circadian rhythms of Core Temperature and salivary melatonin. Ten healthy females (18-23 years) maintained regular sleep-wake cycles for a week prior to participation in the experiment. The experiments were performed from June to August 1999 using a bioclimatic chamber controlled at 26.5 degrees C +/- 0.2 degrees C and 62% +/- 3% RH. Ambient light intensity was controlled at 500 lux from 07:30 to 17:30, 100 lux from 17:30 to 19:30, 20 lux from 19:30 to 23:30; there was total darkness from 23:30 to 07:30. The experiment lasted for 58h over three nights. The participants arose at 07:30 on the first full day and retired at 23:30, adhering to a set schedule for 24h, but without wearing foundation garments. For the final 24h of the second full day, the subjects wore foundation garments. Rectal and leg skin Temperatures were measured continuously throughout the experiment. Saliva and urine were collected every 4h for the analysis of melatonin and catecholamines, respectively. Skin pressure applied by the foundation garments was in the range 11-17 gf/cm2 at the regions of the abdomen, hip, chest, and back. The main results were as follows: (1) Rectal Temperatures were significantly higher throughout the day and night when wearing foundation garments. (2) The nocturnal level of salivary melatonin measured at 03:30 was 115.2 +/- 40.4 pg/mL (mean +/- SEM, N = 10) without and 51.3 +/- 18.4 pg/mL (mean +/- SEM, N = 10) with foundation garments. (3) Mean urinary noradrenaline excretion was significantly lower throughout the day and night when wearing foundation garments (p < .05), but mean urinary adrenaline excretion was not different. The results suggest that skin pressure by clothing could markedly suppress the nocturnal elevation of salivary melatonin, resulting in an increase of rectal Temperature.
-
acclimatization effect on the evening fall in Core Temperature under the influence of two types of clothing
Cellular and Molecular Life Sciences, 1996Co-Authors: Hiromi TokuraAbstract:This paper reports the effect of acclimatization on the evening fall in Core Temperature under the influence of two different types of clothing. Two groups of subjects dressed in either knee-length skirts or full trousers during the daytime for the three months from April to June. To compare the circadian rhythm of Core Temperature, the experiments were carried out before and after the three month program of acclimatization. It was found that the subjects who had worn knee-length skirts showed lower rectal Temperatures during the nighttime and a bigger amplitude of circadian rhythm in July than in March.
Akimasa Hirata - One of the best experts on this subject based on the ideXlab platform.
-
estimation of Core Temperature elevation in humans and animals for whole body averaged sar
Progress in Electromagnetics Research-pier, 2009Co-Authors: Akimasa Hirata, Hironori Sugiyama, Osamu FujiwaraAbstract:Biological efiects due to whole-body radio-frequency exposure may be induced by Core Temperature elevation. According to the international safety guidelines/standards for human protection, the whole-body averaged speciflc absorption rate (WBA-SAR) is used as a metric. In order to understand the relationship between WBA-SAR and Core Temperature elevation, a theoretical solution or a closed formula for estimating Core Temperature elevation is essential. In the present study, we derived a formula for simply estimating Core Temperature elevation in humans and animals due to whole-body radio-frequency exposure. The Core Temperature elevation estimated with the formula is found to be in reasonable agreement with the computational results of flnite-difierence time- domain computation incorporated in anatomically-based models Based on the formula, the WBA-SAR is found to be a good metric for estimating Core Temperature elevation. The main factors in∞uencing the Core Temperature elevation are the perspiration rate and the body surface area-to-weight ratio.
-
fdtd analysis of body Core Temperature elevation in children and adults for whole body exposure
Physics in Medicine and Biology, 2008Co-Authors: Akimasa Hirata, Takayuki Asano, Osamu FujiwaraAbstract:The Temperature elevations in anatomically based human phantoms of an adult and a 3-year-old child were calculated for radio-frequency whole-body exposure. Thermoregulation in children, however, has not yet been clarified. In the present study, we developed a computational thermal model of a child that is reasonable for simulating body-Core Temperature elevation. Comparison of measured and simulated Temperatures revealed thermoregulation in children to be similar to that of adults. Based on this finding, we calculated the body-Core Temperature elevation in a 3-year-old child and an adult for plane-wave exposure at the basic restriction in the international guidelines. The body-Core Temperature elevation in the 3-year-old child phantom was 0.03 °C at a whole-body-averaged specific absorption rate of 0.08 W kg−1, which was 35% smaller than in the adult female. This difference is attributed to the child's higher body surface area-to-mass ratio.
-
fdtd analysis of human body Core Temperature elevation due to rf far field energy prescribed in the icnirp guidelines
Physics in Medicine and Biology, 2007Co-Authors: Akimasa Hirata, Takayuki Asano, Osamu FujiwaraAbstract:This study investigated the relationship between the specific absorption rate and Temperature elevation in an anatomically-based model named NORMAN for exposure to radio-frequency far fields in the ICNIRP guidelines (1998 Health Phys. 74 494-522). The finite-difference time-domain method is used for analyzing the electromagnetic absorption and Temperature elevation in NORMAN. In order to consider the variability of human thermoregulation, parameters for sweating are derived and incorporated into a conventional sweating formula. First, we investigated the effect of blood Temperature variation modeling on body-Core Temperature. The computational results show that the modeling of blood Temperature variation was the dominant factor influencing the body-Core Temperature. This is because the Temperature in the inner tissues is elevated via the circulation of blood whose Temperature was elevated due to EM absorption. Even at different frequencies, the body-Core Temperature elevation at an identical whole-body average specific absorption rate (SAR) was almost the same, suggesting the effectiveness of the whole-body average SAR as a measure in the ICNIRP guidelines. Next, we discussed the effect of sweating on the Temperature elevation and thermal time constant of blood. The variability of Temperature elevation caused by the sweating rate was found to be 30%. The blood Temperature elevation at the basic restriction in the ICNIRP guidelines of 0.4 W kg(-1) is 0.25 degrees C even for a low sweating rate. The thermal time constant of blood Temperature elevation was 23 min and 52 min for a man with a lower and a higher sweating rate, respectively, which is longer than the average time of the SAR in the ICNIRP guidelines. Thus, the whole-body average SAR required for blood Temperature elevation of 1 degrees C was 4.5 W kg(-1) in the model of a human with the lower sweating coefficients for 60 min exposure. From a comparison of this value with the basic restriction in the ICNIRP guidelines of 0.4 W kg(-1), the safety factor was 11.
Lijian Pei - One of the best experts on this subject based on the ideXlab platform.
-
effects of ambient Temperature and forced air warming on intraoperative Core Temperature a factorial randomized trial
Anesthesiology, 2018Co-Authors: Lijian Pei, Edward J Mascha, Yuguang Huang, Yongchang Zheng, Xinting Sang, Xiaoyun Zhou, Guangmei Mao, Daniel I SesslerAbstract:BACKGROUND The effect of ambient Temperature, with and without active warming, on intraoperative Core Temperature remains poorly characterized. The authors determined the effect of ambient Temperature on Core Temperature changes with and without forced-air warming. METHODS In this unblinded three-by-two factorial trial, 292 adults were randomized to ambient Temperatures 19°, 21°, or 23°C, and to passive insulation or forced-air warming. The primary outcome was Core Temperature change between 1 and 3 h after induction. Linear mixed-effects models assessed the effects of ambient Temperature, warming method, and their interaction. RESULTS A 1°C increase in ambient Temperature attenuated the negative slope of Core Temperature change 1 to 3 h after anesthesia induction by 0.03 (98.3% CI, 0.01 to 0.06) °CCore/(h°Cambient) (P < 0.001), for patients who received passive insulation, but not for those warmed with forced-air (-0.01 [98.3% CI, -0.03 to 0.01] °CCore/[h°Cambient]; P = 0.40). Final Core Temperature at the end of surgery increased 0.13°C (98.3% CI, 0.07 to 0.20; P < 0.01) per degree increase in ambient Temperature with passive insulation, but was unaffected by ambient Temperature during forced-air warming (0.02 [98.3% CI, -0.04 to 0.09] °CCore/°Cambient; P = 0.40). After an average of 3.4 h of surgery, Core Temperature was 36.3° ± 0.5°C in each of the forced-air groups, and ranged from 35.6° to 36.1°C in passively insulated patients. CONCLUSIONS Ambient intraoperative Temperature has a negligible effect on Core Temperature when patients are warmed with forced air. The effect is larger when patients are passively insulated, but the magnitude remains small. Ambient Temperature can thus be set to comfortable levels for staff in patients who are actively warmed.
-
axillary Temperature as recorded by the ithermonitor wt701 well represents Core Temperature in adults having noncardiac surgery
Anesthesia & Analgesia, 2017Co-Authors: Lijian Pei, Yuguang Huang, Guangmei Mao, Daniel I SesslerAbstract:Background Core Temperature can be accurately measured from the esophagus or nasopharynx during general anesthesia, but neither site is suitable for neuraxial anesthesia. We therefore determined the precision and accuracy of a novel wireless axillary thermometer, the iThermonitor, to determine its suitability for use during neuraxial anesthesia and in other patients who are not intubated. Methods We enrolled 80 adults having upper abdominal surgery with endotracheal intubation. Intraoperative Core Temperature was measured in distal esophagus and was estimated at the axilla with a wireless iThermonitor WT701 (Raiing Medical, Boston MA) at 5-minute intervals. Pairs of axillary and reference distal esophageal Temperatures were compared and summarized using linear regression and repeated-measured Bland-Altman methods. We a priori determined that the iThermonitor would have clinically acceptable accuracy if most estimates were within ±0.5°C of the esophageal reference, and suitable precision if the limits of agreement were within ±0.5°C. Results There were 3339 sets of paired Temperatures. Axillary and esophageal Temperatures were similar, with a mean difference (esophageal minus axillary) of only 0.14°C ± 0.26°C (standard deviation). The Bland-Altman 95% limits of agreement were reasonably narrow, with the estimated upper limit at 0.66°C and the lower limit at -0.38°C, thus ±0.52°C, indicating good agreement across the range of mean Temperatures from 34.9°C to 38.1°C. The absolute difference was within 0.5°C in 91% of the measurements (95% confidence interval, 88%-93%). Conclusions Axillary Temperature, as recorded by the iThermonitor WT701, well represents Core Temperature in adults having noncardiac surgery and thus appears suitable for clinical use.