Assessment Of Core Temperature Research Articles

Relationships of infrared thermography temperature with core temperature in goat.

Rectal temperature is widely used as an indicator of animal health. However, rectal temperature is conventionally measured by an invasive method, which may reduce animal welfare. So, this study aimed to determine the relationships between the deep-body (core) temperature and body surface temperatures in goats and develop a linear regression equation to establish the core temperature based on body surface temperatures. Body surface temperatures (head, eye, muzzle, horn, back, scrotum and groin) of goats were measured by infrared thermography (IRT). Ambient temperatures were measured by digital thermometer. Core temperatures were measured by a digital vet thermometer. Pearson correlation analysis was used to analyze the relationship between body surface temperatures, ambient temperature, and core temperature. Simple linear regression analysis was used to develop core temperature assessment equations. Correlation analysis showed that groin temperature was highly correlated with core temperature, and low correlated with ambient temperature. The body surface temperature of other region was low correlated with core temperature, and highly correlated with ambient temperature. Regression analysis showed that the determination coefficient of core temperature assessment equation based on groin temperature was the highest (P < 0.0001, R2 = 0.55), and those based on surface temperature of other regions were low (P < 0.01, R2 ≤ 0.16). We concluded that body surface temperatures obtained by IRT could be used for the assessment of goat core temperature. The core temperature assessment equations developed by the temperature of the body surface, which is less affected by ambient temperature, was found to have a higher determination coefficient than the equations developed using body surface temperature that is more affected by ambient temperature.

Validity of heart rate derived core temperature estimation during simulated firefighting tasks

Rectal core temperature monitoring can help fire services mitigate heat injury but can be invasive and impractical. EQ02 + LifeMonitor provides a non-invasive estimation of core temperature. Therefore, the primary purpose of this study was to determine the validity of the EQ02 + LifeMonitor compared to the gold standard rectal thermometer core temperature assessment, as well as the potential influence of turnout gear on the estimated and physiological strain experienced during these activities. Thirteen participants completed simulated firefighting tasks with and without turnout gear, involving four rounds of a 5-min walk on a treadmill at 2.8 mph/2.5% grade and 20 deadlifts over 5 min in an environmental chamber set to 40.6 °C; 50% humidity. During each trial participants wore both an EQ02 + LifeMonitor and DataTherm II rectal thermometer. The results from the devices were statistically equivalent (p < 0.001), yet there was a statistically significant difference in the value (~ 0.1 °C; p < 0.001). There was a significant effect of devices [p < 0.001] and time [p < 0.001], but no interaction effect [p = 0.70] on core temperature drift. Estimated core temperature was marginally different from that measured via the DataTherm II. The EQ02 on average overestimated core temperature. Heart rate, rating of perceived exertion, and area under the curve of core temperature were significantly elevated due to turnout gear [ps < 0.025], but not core temperature skin temperature, or ventilatory rate [ps > 0.372]. These results suggest the EQ02 + LifeMonitor may be a viable, non-invasive alternative for assessing core temperature compared to rectal temperature monitoring, especially during rigorous, intermittent activities. Turnout gear does however increase heart rate, cumulative core temperature, and perceived exertion. Additionally, the validity of the estimated core temperature is not impacted by the use turnout gear. This is likely due to significant changes in heart rate, which allowed the heart-rate derived estimate of core temperature to remain consistent with changes in DataTherm II rectal temperatures.

Body Core Temperature Assessment in Emergency Care Departments

BackgroundThere is concern that the values provided by devices using infrared thermometry in emergency departments (EDs) do not reflect body core temperature accurately. ObjectivesEvaluation of three thermometers commonly used in the ED. MethodsTwo infrared ear thermometers and an infrared forehead thermometer were evaluated using 1) the Voltcraft IRS-350 calibration device, 2) comparing temperature values to a rectal end-exercise temperature (T-RECT) of 38.1°C in 12 participants, and 3) comparing temperature values to rectal temperature in 133 ED patients. ResultsCalibration across the human core temperature range revealed that the ear thermometers underestimated radiant temperature by 0.77 ± 0.39°C and 1.84 ± 0.26°C, respectively, whereas the forehead thermometer overestimated radiant temperature by 0.90 ± 0.51°C. After cycling exercise, all thermometers underestimated T-RECT (0.54 ± 0.27°C and 1.03 ± 0.48°C for the ear thermometers and 1.14 ± 0.38°C for the forehead thermometer). In the ED, the ear thermometers underestimated T-RECT by 0.31 ± 0.37°C and 0.46 ± 0.50°C, whereas the forehead thermometer exhibited a nonsignificant overestimation of 0.04 ± 0.46°C. If the threshold for fever in all systems had been set to 37.5°C instead of 38.0°C, the sensitivity and specificity of the systems for real fever (T-RECT ≥ 38°C) are, respectively, 71% and 96% (ear thermometer 1), 57% and 97% (ear thermometer 2), and 86% and 90% (forehead thermometer). ConclusionWe conclude that the investigated thermometers are not reliable as devices to measure radiant temperature, cannot be used to assess body core temperature during exercise, but may be used as a screening device, with 37.5°C as a threshold for fever in emergency care settings.

Concurrent validity of the CORE wearable sensor with BodyCap temperature pill to assess core body temperature during an elite women’s field hockey heat training camp

ABSTRACT Wearable temperature sensors offer the potential to overcome several limitations associated with current laboratory- and field-based methods for core temperature assessment; however, their ability to provide accurate data at elevated core temperatures (Tc) has been questioned. Therefore, this investigation aimed to determine the concurrent validity of a wearable temperature sensor (CORE) compared to a reference telemetric temperature pill (BodyCAP) during a team-sport heat training camp prior to the 2020 Olympic Games. Female field hockey players (n = 19) in the Australian national squad completed 4 sessions in hot conditions where their temperature was monitored via CORE and BodyCAP. Concurrent validity of the wearable CORE device was determined with reference to the ingested BodyCAP pill. Lin’s Concordance Correlation Coefficients determined there was “poor” agreement between devices during all sessions. Mean bias demonstrated that CORE underestimated Tc in all sessions (−0.06°C to −0.34°C), with wide mean 95% confidence intervals (±0.35°C to ±0.56°C). Locally estimated scatterplot smoothing regression lines illustrated a non-linearity of error, with greater underestimation of Tc by the CORE device, as Tc increased. The two devices disagreed more than ±0.3°C for 41-60% of all data samples in each session. Our findings do not support the use of the CORE device as a valid alternative to telemetric temperature pills for Tc assessment, particularly during exercise in hot conditions where elevated Tc are expected.

Zero-heat-flux thermometry over the carotid artery in assessment of core temperature in craniotomy patients

Zero-heat-flux core temperature measurements on the forehead (ZHF-forehead) show acceptable agreement with invasive core temperature measurements but are not always possible in general anesthesia. However, ZHF measurements over the carotid artery (ZHF-neck) have been shown reliable in cardiac surgery. We investigated these in non-cardiac surgery. In 99 craniotomy patients, we assessed agreement of ZHF-forehead and ZHF-neck (3M™ Bair Hugger™) with esophageal temperatures. We applied Bland-Altman analysis and calculated mean absolute differences (difference index) and proportion of differences within ± 0.5 °C (percentage index) during entire anesthesia and before and after esophageal temperature nadir. In Bland-Altman analysis [mean (limits of agreement)], agreement with esophageal temperature during entire anesthesia was 0.1 (−0.7 to +0.8) °C (ZHF-neck) and 0.0 (−0.8 to +0.8) °C (ZHF-forehead), and, after core temperature nadir, 0.1 (−0.5 to +0.7) °C and 0.1 (−0.6 to +0.8) °C, respectively. In difference index [median (interquartile range)], ZHF-neck and ZHF-forehead performed equally during entire anesthesia [ZHF-neck: 0.2 (0.1–0.3) °C vs ZHF-forehead: 0.2 (0.2–0.4) °C], and after core temperature nadir [0.2 (0.1–0.3) °C vs 0.2 (0.1–0.3) °C, respectively; all p > 0.017 after Bonferroni correction]. In percentage index [median (interquartile range)], both ZHF-neck [100 (92–100) %] and ZHF-forehead [100 (92–100) %] scored almost 100% after esophageal nadir. ZHF-neck measures core temperature as reliably as ZHF-forehead in non-cardiac surgery. ZHF-neck is an alternative to ZHF-forehead if the latter cannot be applied.

Heat flux systems for body core temperature assessment during exercise

Heat flux systems are increasingly used to assess core body temperature. However, validation of multiple systems is scarce. Therefore, an experiment was performed in which three commercially available heat flux systems (3 M, Medisim and Core) were compared to rectal temperature (Tre). Five females and four males performed exercise in a climate chamber set at 18 °C/50% relative humidity until exhaustion. Exercise duration was 36.3 ± 5.6 min (mean ± standard deviation). Tre in rest was 37.2 ± 0.3 °C. Medisim's-values were lower than Tre (36.9 ± 0.4 °C, p < 0.05); 3 M (37.2 ± 0.1 °C) and Core's (37.4 ± 0.3 °C) did not differ from Tre. Maximal temperatures after exercise were 38.4 ± 0.2 °C (Tre), 38.0 ± 0.4 °C (3 M), 38.8 ± 0.3 °C (Medisim) and 38.6 ± 0.3 °C (Core); Medisim was significantly higher than Tre (p < 0.05). The temperature profiles of the heat flux systems during exercise differed to varying degree from the rectal profiles; the Medisim system showed a faster increase during exercise than Tre (0.48 ± 0.25 °C in 20 min, p < 0.05), the Core system tended to show a systematic overestimation during the entire exercise period and the 3 M system showed large errors at the end of exercise, likely due to sweat entering the sensor. Therefore, the interpretation of heat flux sensor values as core body temperature estimates should be done with care; more research is required to elucidate the physiological significance of the generated temperature values.

Clinical evaluation of a cutaneous zero-heat-flux thermometer during cardiac surgery.

We evaluated the disposable non-invasive SpotOn™ thermometer relying on the zero-heat-flux technology. We tested the hypothesis that this technology may accurately estimate the core temperature. The primary objective was to compare cutaneous temperature measurements from this device with blood temperatures measured with the pulmonary artery catheter. Secondary objective was to compare measurements from the zero-heat-flux thermometer indirectly with other routinely used thermometers (nasopharyngeal, bladder, rectal). We included 40 patients electively scheduled for either off-pump coronary artery bypass surgery or pulmonary thromboendarterectomy. Temperatures were measured using zero-heat-flux (SpotOn™), pulmonary artery catheter, nasopharyngeal, rectal, and bladder thermometers. Agreement was assessed using the Bland and Altman random effects method for repeated measures data, and Lin's concordance correlation coefficient. Accuracy was estimated (defined as <0.5° difference with the gold standard), with a 95% confidence interval considering the multiple pairs of measurements per patient. 17 850 sets of temperature measurements were analyzed from 40 patients. The mean overall difference between zero-heat-flux and pulmonary artery catheter thermometer was -0.06°C (95% limits of agreement of ± 0.89°C). In addition, 14 968 sets of temperature measurements were analyzed from 34 patients with all thermometers in situ. Results from the zero-heat-flux thermometer showed better agreement with the pulmonary artery catheter than the other secondary core thermometers assessed. In conclusion,the SpotOn™ thermometer reliably assessed core temperature during cardiac surgery. It could be considered an alternative for other secondary thermometers in the assessment of core temperature during general anesthesia.

A Comparative Study of Two Ambulatory Core Temperature Assessment Methods

Background. Given the need to identify reliable non-invasive solutions for core temperature ambulatory monitoring, the purpose of this study was to evaluate the performance of zero-heat-flux (ZHF) temperature sensor on the forehead (TCOzhf) by comparing it with intestinal temperature (TCOpill) in different ambient and physiological conditions.Methods. Seven trained male subjects were followed during a 45-min rest period (STA) and a 25-min self-regulated cycling exercise performed in neutral (TMP, 22.8 °C) and hot (HOT, 38.5 °C) ambient temperature.Results.TCOzhf values differed from TCOpill of −0.23 ± 0.13 in STA, 0.15 ± 0.30 °C in TMP and 0.28±0.38 °C in HOT. The 95% limits of agreement showed an acceptable bias between TCOzhf and TCOpill in STA (±0.26 °C), but not in TMP and HOT (±0.60 and ±0.75 °C).Conclusion. The non-invasive ZHF sensor gave an accurate estimation of TCOpill in steady state but not during exercise. However, complementary results let suppose that ZHF performance is not affected by ambient conditions and could be a relevant alternative for deep body temperature measurement during whole-body heat stress.

Improving Thermoregulation for Trauma Patients in the Emergency Department: An Evidence-Based Practice Project.

Extensive evidence exists on the association between hypothermia and increased morbidity and mortality in trauma patients. Gaps in practice related to temperature assessment have been identified in literature, along with limited personnel knowledge regarding management of patients with accidental hypothermia. An interdisciplinary team identified gaps in practice in our institution regarding temperature assessment and documentation of rewarming and initiated an evidence-based practice project to change practice at our institution. The goals were to decrease time to temperature assessment, increase core temperature assessment, and increase implementation of appropriate rewarming methods. This project used the Iowa Model of Evidence-Based Practice to provide a framework for execution and evaluation. We conducted a literature review to address all aspects of hypothermia, including incidence, associated and contributing factors, prevention, recognition, and treatment. This evidence-based knowledge was then applied to clinical practice through staff education and training, equipment availability, and environmental adjustments. More patients with hypothermia and hyperthermia were identified in 2017, as compared with 2016. There was a significant increase in core temperature assessment from 4% in 2016 to 23% in 2017 (p < .001). Blanket use in normothermic patients increased in 2017 (p = .002). This project is an example of how nurses can utilize an evidence-based practice model to translate research into clinical practice. Best practice interventions regarding temperature assessment and rewarming measures for trauma patients can be successfully implemented with negligible cost. Further research should be dedicated to examine barriers to implementation and adherence to evidence-based practice interventions.

Heat-related illness in the African wilderness

Wilderness heat-related illnesses span a variety of conditions caused by excessive or prolonged heat exposure, and/or the inability to compensate adequately for increased endogenous production during strenuous outdoor activities. Despite management of well-known risk factors, such as lack of fitness or acclimatisation, dehydration, underlying illness and certain medications, even highly trained individuals may exceed their physiological capability to dissipate increased core temperature. Heat illnesses range from benign cramps to the more concerning heat syncope and exercise-associated collapse (with or without hyperthermia), and culminate in life-threatening heat stroke. The differential diagnosis in the wilderness is broad and should include exercise-associated hyponatraemia with or without encephalopathy. Clinical guidelines for wilderness and hospital management of these conditions are available. Field management and evacuation are based on severity, and include cooling, rehydration and assessment of core temperature and serum sodium, if possible. Hyponatraemia should be corrected with the use of oral or intravenous hypertonic saline, depending on whether the patient can safely take oral fluids. Hospital management may include aggressive and potentially invasive cooling, careful assessment for organ dysfunction, and intensive multi-organ support, if required. Paracetamol, non-steroidal anti-inflammatory drugs and dantrolene should not be used.

Neural mechanisms underlying stress resilience in Ahi1 knockout mice: relevance to neuropsychiatric disorders

The Abelson helper integration site 1 (AHI1) gene has a pivotal role in brain development. Studies by our group and others have demonstrated association of AHI1 with schizophrenia and autism. To elucidate the mechanism whereby alteration in AHI1 expression may be implicated in the pathogenesis of neuropsychiatric disorders, we studied Ahi1 heterozygous knockout (Ahi1(+/-)) mice. Although their performance was not different from wild-type mice on tests that model classical schizophrenia-related endophenotypes, Ahi1(+/-) mice displayed an anxiolytic-like phenotype across different converging modalities. Using behavioral paradigms that involve exposure to environmental and social stress, significantly decreased anxiety was evident in the open field, elevated plus maze and dark-light box, as well as during social interaction in pairs. Assessment of core temperature and corticosterone secretion revealed a significantly blunted response of the autonomic nervous system and the hypothalamic-pituitary-adrenal axis in Ahi1(+/-) mice exposed to environmental and visceral stress. However, response to centrally acting anxiogenic compounds was intact. On resting-state functional MRI, connectivity of the amygdala with other brain regions involved in processing of anxiogenic stimuli and inhibitory avoidance learning, such as the lateral entorhinal cortex, ventral hippocampus and ventral tegmental area, was significantly reduced in the mutant mice. Taken together, our data link Ahi1 under-expression with a defect in the process of threat detection. Alternatively, the results could be interpreted as representing an anxiety-related endophenotype, possibly granting the Ahi1(+/-) mouse relative resilience to various types of stress. The current knockout model highlights the contribution of translational approaches to understanding the genetic basis of emotional regulation and its associated neurocircuitry, with possible relevance to neuropsychiatric disorders.

Placement of an Esophageal Temperature Probe by Nurses

Background Current guidelines support therapeutic hypothermia after cardiac arrest. An esophageal temperature probe (ETP) provides a core temperature assessment; however, accurate placement is necessary. Objectives To demonstrate accurate placement of an ETP and evaluate the effectiveness of high-fidelity simulation with anatomic imaging. Methods Registered nurses (RNs) were educated using 3-dimensional, high-fidelity simulation with VH Dissector technology (Touch of Life Technologies, Aurora, Colorado) to demonstrate ETP placement. The RNs provided survey responses on the effectiveness of simulation before and after using the simulator. Results Thirty-two RNs participated and did not demonstrate difficulties with the skill; however, 53.1% required more than 1 attempt for accurate placement in the distal esophagus. Survey results found that participants had increased confidence and high satisfaction with simulation and 3-dimensional imaging (P &amp;lt; .001). Conclusions Literature is lacking to guide ETP placement. In this study, RNs overestimated the depth for ETP insertion. Accurate temperature readings are highly dependent on accurate anatomical location placement. Providing skill competency training that incorporated anatomical imaging technology enhanced RNs’ awareness for effective skill acquisition.

Placement of an Esophageal Temperature Probe by Nurses

Current guidelines support therapeutic hypothermia after cardiac arrest. An esophageal temperature probe (ETP) provides a core temperature assessment; however, accurate placement is necessary. To demonstrate accurate placement of an ETP and evaluate the effectiveness of high-fidelity simulation with anatomic imaging. Registered nurses (RNs) were educated using 3-dimensional, high-fidelity simulation with VH Dissector technology (Touch of Life Technologies, Aurora, Colorado) to demonstrate ETP placement. The RNs provided survey responses on the effectiveness of simulation before and after using the simulator. : Thirty-two RNs participated and did not demonstrate difficulties with the skill; however, 53.1% required more than 1 attempt for accurate placement in the distal esophagus. Survey results found that participants had increased confidence and high satisfaction with simulation and 3-dimensional imaging (P < .001). Literature is lacking to guide ETP placement. In this study, RNs overestimated the depth for ETP insertion. Accurate temperature readings are highly dependent on accurate anatomical location placement. Providing skill competency training that incorporated anatomical imaging technology enhanced RNs' awareness for effective skill acquisition.

Development of a perceptual hyperthermia index to evaluate heat strain during treadmill exercise

Fire suppression and rescue is a physiologically demanding occupation due to extreme external heat as well as the physical and thermal burden of the protective garments. These conditions challenge body temperature homeostasis and results in heat stress. Accurate field assessment of core temperature is complex and unreliable. The present investigation developed a perceptually based hyperthermia metric to measure physiologic exertional heat strain during treadmill exercise. Sixty-five (28.9 ± 6.8 years) female (n = 11) and male (n = 54) firefighters and non-firefighting volunteers participated in four related exertional heat stress investigations performing treadmill exercise in a heated room while wearing thermal protective clothing. Body core temperature, perceived exertion, and thermal sensation were assessed at baseline, 20-mins exercise, and at termination. Perceived exertion increased from baseline (0.24 ± 0.42) to termination (7.43 ± 1.86). Thermal sensation increased from baseline (1.78 ± 0.77) to termination (4.50 ± 0.68). Perceived exertion and thermal sensation were measured concurrently with body core temperature to develop a two-dimensional graphical representation of three exertional heat strain zones representative of a range of mean body core temperature responses such that low risk (green) incorporated 36.0-37.4°C, moderate risk (yellow) incorporated 37.5-37.9°C, and high risk (red) incorporated 38.0 to greater than 40.5°C. The perceptual hyperthermia index (PHI) may provide a quick and easy momentary assessment of the level of risk for exertional heat stress for firefighters engaged in fire suppression that may be beneficial in high-risk environments that threaten the lives of firefighters.

Limitations of temperature measurement in the aural canal with an ear mould integrated sensor

Aural canal temperature measurement using an ear mould integrated sensor (Tac) might be a method suited for continuous non-invasive core temperature estimation in operational settings. We studied the effect of ambient temperature, wind and high intensity exercise on Tac and its ability to predict esophageal (Tes) and rectal temperatures (Tre). Seven subjects performed a protocol of rest at 21, 10 and 30 °C, followed by exercise and recovery at 30 °C. The subjects performed the protocol twice: with and without face-wind from halfway through the 30 °C rest period. Extra auricle insulation was applied at one side. Ambient temperature changes affected Tac significantly, while Tes and Tre remained stable. Insulating the auricle reduced but did not abolish this effect. Wind had an immediate cooling effect on Tac independent of auricle insulation. During exercise and recovery in 30 °C, Tac provided acceptable group predictions of Tre in trials without wind (bias: −0.66 ± 0.21 °C covered, −1.20 ± 0.15 °C uncovered). Bias was considerably higher with wind, but variability was similar (−1.73 ± 0.11 °C covered, −2.49 ± 0.04 °C uncovered). Individual predictions of Tes and Tre showed more variation, especially with wind. We conclude that Tac may be used for core temperature assessment of groups in warm and stable conditions.

Telemetry Pill and Oesophageal Assessment of Core Temperature during Moderate Duration, High Intensity Exercise

Telemetric monitoring systems using an ingestible pill provide a practical means of assessing core temperature compared with more invasive measurement sites such as the oesophagus. Telemetric pills provide valid measurements of core temperature during prolonged steady-state exercise or in clinical situations requiring ambulatory monitoring. A comparison of such core temperature measurements during self-paced, moderate duration, high intensity exercise has yet to be reported. PURPOSE: To compare telemetry pill and oesophageal temperature responses to a simulated 4-km cycling time trial performed at different environmental temperatures. METHODS: Nine competitive cyclists (mean ± SD age = 34 ± 4.5 y, maximal oxygen uptake = 61.7 ± 8.6 ml·kg−1min−1) completed a 4-km cycling time trial in laboratory dry bulb temperatures of 35°C and 13°C (relative humidity = 60%, air velocity 5.6 m.s−1). A temperature pill was ingested 4 hrs prior to exercise, during which time participants remained in a fasted state. An oesophageal probe was inserted through the nasal passage at a distance equal to one-quarter of the participants standing height. Oesophageal (Tes) and telemetric pill (Tpill) responses were analysed using a three-factor (condition x site x time) general linear model with repeated measures. RESULTS: Pooled mean Tes (37.41 ± 0.93 °C) and Tpill (37.40 ± 0.82 °C) during the 4 km time trials were not significantly different (p=0.957). Nevertheless, there was a significant interaction between body temperature methods and time trial distance (p=0.01), with the largest difference occurring at the end of the time trial in the hotter environment (Tes = 38.19 ±1.31 °C; Tm = 37.62 ± 0.45 °C). The rate of increase in Tes during the time trial was significantly higher than that in Tpill, irrespective of environmental temperature (0.17 °C.min−1 vs. 0.06 °C.min−1; p CONCLUSION: These data indicate that an ingestible pill is less sensitive to exercise-induced increases in body temperature compared to oesophageal temperature. This blunted response may lead to underestimations of core body temperature during the latter stages of moderate duration high intensity exercise. Such differences may be scientifically and clinically important.

Infrared tympanic temperature and ear canal morphology

Several publications indicate that the infrared tympanic temperature (IRTT) underestimates the core temperature of the body when the ear canal is long, curvy and narrow. In order to quantify these observations, a study was performed in 10 subjects. The IRTT was determined and compared to the oesophageal temperature (Tes), taken as the reference for core temperature. Also, the oral and rectal temperatures were monitored. A three-dimensional print of the ear canal was made to determine the ear canal morphology. The core temperature of the subjects was increased by at least 1°C during the experiment in order to investigate the dynamics of the core temperature assessment. Two devices were used to determine the IRTT: the Braun Thermoscan® PRO 1 and the predecessor of the Braun IRT3020 (code name IRT3000P). Both IRTT-devices underestimated the core temperature, as measured by Tes, by 0.38°C on average. The difference ΔT between IRTT and Tes was related to ear canal morphology. The circumference of the ear canal at the distal bend in the ear canal and the visibility of the tympanum were the most important parameters. About 22% of the variance in ΔT was explained by ear canal morphology for the steady state resting period. Wide ear canals and good visibility of the tympanic membrane were related to a smaller ΔT. A good visibility of the tympanic membrane was generally found in the absence of cerumen. The IRT3000P showed better results than the PRO 1 (ΔT: −0.31 ± 0.27°C and −0.44 ± 0.30°C respectively). Also, the IRT3000P was less dependent on ear canal morphology. The dynamic response of the measured core temperatures was determined by the decrease or rise in core temperature after the heating period was ended. The oesophageal temperature dropped by 0.22°C. The IRTT and oral temperature showed an identical increase of 0.19°C. The slow reacting rectal temperature had an after rise of 0.49°C.

Splanchnic vasoconstriction in hyperthermic man--role of falling blood pressure.

Results of a study in which six supine resting subjects, wearing water-perfused suits, had body skin temperature controlled at 35 C for 30 min (control period), then rapidly increased to 40.5 C for 43 to 50 min (heating period) in a two-part experiment. In the first part of the experiment arterial mean pressure (MP) in three men was increased back to, or above control levels at the 30 to 35th min of heating by total occlusion of both legs for 8 to 10 min. Splanchnic blood flow (SBF), which had fallen from 1.4 to 0.9 L/min at occlusion, rose only 0.05 L/min during occlusion. Splanchnic vascular resistance (SVR) rose throughout heating and occlusion. In the second part of the experiment (three men) SBF fell despite a spontaneous rise in MP and aortic pulse pressure prior to leg occlusion. Cardiac output (CO) was measured just before, during and after occlusion. Occlusion raised MP 10 to 15 mm Hg and reduced CO only slightly. It is concluded that falling MP or aortic pulse pressure are not major causes of the splanchnic vasoconstriction in response to heating man.