New standards for devices used for the measurement of human body temperature

Significant changes in recording of human body temperature have been taking place worldwide in recent years. The clinical thermometer introduced in the mid-19th century by Wunderlich has been replaced by digital thermometers or radiometer devices for recording tympanic membrane temperature. More recently the use of infrared thermal imaging for fever screening has become more widespread following the SARS infection, and particularly during the pandemic H1N1 outbreak. Important new standards that have now reached international acceptance will affect clinical and fever screening applications. This paper draws attention to these new standard documents. They are designed to improve the standardization of both performance and practical use of these key techniques in clinical medicine, especially necessary in a pandemic influenza situation.     

Effects of altering rostral brain stem temperature on temperature regulation in the Adelie penguin,Pygoscelis adeliae

Summary In 4 Adelie penguins, thermodes were implanted in the rostral brain stem. Two animals were additionally equipped with spinal canal thermodes. At thermoneutral (+ 8 to + 16°C) and cold (–18 to –22° C) ambient conditions, the effects of hypothalamic heating and cooling on the surface temperature of one flipper (skin blood flow), oxygen consumption (metabolic heat production) and esophageal (core) temperature were observed in the conscious animals.—Heating the rostral brain stem induced heat defence responses: Heat production was reduced in the cold and skin vasodilatation was evoked at thermoneutral ambient conditions. As a rule, core temperature fell during rostral brain stem heating.—Cooling the rostral brain stem did not induce clear-cut cold defence responses. On the contrary, strong cooling at thermoneutral ambient conditions induced vasodilatation in the skin. In the cold, even slight degrees of rostral brain stem cooling decreased metabolic heat production. As a rule, core temperature fell when the rostral brain stem was cooled.—It is concluded from the results that thermosensitive structures in the stimulated section of the rostral brain stem of the Adelie penguin contribute to the central temperature signal input in the range of normal to elevated core temperatures. These hypothalamic warm signals appear to be at least as effective as spinal warm signals in controlling skin blood flow and metabolic heat production. The inhibition of ongoing thermoregulatory effector activity by rostral brain stem cooling suggests positive temperature coefficients of the integrative and/or efferent neurons in the hypothalamic temperature regulation center of the Adelie penguin.A preliminary report was given at the 45th meeting (autumn meeting) of the Deutsche Physiologische Gesellschaft, Wien, Sept. 23–26, 1975. Pflügers Arch.359, R57 (1975).     

Theoretical analysis of the transient thermal clearance method for regional blood flow measurement

In the noninvasive transient thermal clearance method a metal plate at room temperature is attached to the investigated skin. The plate is thermally insulated from the environment, and so the tissue temperature, after an initial decrease, is increased at a rate which depends both on heat convection by blood and on tissue thermal conductivity. The corresponding bioheat conductivity equation is solved and the dependence of plate temperature on time and on blood flow discussed. It is shown that, for an appropriate choice of metal and plate thickness, regional blood flow can be derived from temperature/time curves.     

肿瘤热疗无损测温方法的研究进展

肿瘤热疗(hyperthermia)是利用肿瘤组织对温度敏感性高于正常组织的性质,即人体正常细胞在42. 5～43℃下不会受到损伤,但大部分肿瘤细胞在该温度下会被诱导进入凋亡过程。临床上应用超声、微波或红外等作为加热源,加热并杀死肿瘤组织而使得正常组织基本不受损伤。但是对于如何精确测量肿瘤热疗的温度从而控制热疗剂量仍然是一个难题。本文综述了目前肿瘤热疗过程中电阻抗断层成像(ectrical impedance tomograph,EIT)测温、红外热图引导技术、微波辐射测温法、超声无损测温、磁共振成像测温(magnetic resonance imaging,MRI)等无损测温方法及其研究现状,展望了如何有效精确测量肿瘤热疗时的温度,为控制肿瘤热疗的热剂量提供参考,以期在不伤害正常组织的前提下,使肿瘤组织产生不可逆的损伤。     

Thermal distribution of radio-frequency inductive hyperthermia using an inductive aperture-type applicator: evaluation of the effect of tumour size and depth

A new radio-frequency (RF) inductive hyperthermia device using an inductive aperture-type applicator (IATA) is proposed. This paper reports the evaluation of the heating characteristics of the IATA using a computer simulation and clinical thermal parameters obtained during treatment of superficial and subsurface-seated tumours. The configuration of the IATA is a one-turn square column-like coil whose bottom plate is set to face the heating target. The IATA has advantages over RF capacitive-type heating, such as: generating less heat in the subcutaneous fat layer; less convergency of electric line of force at the edge of the applicator; and no physical contact with the target lesion. The induced magnetic fields and electrical currents within the heating substance are simulated using computer-assisted design software for electro-magnetic analysis. A total of 40 superficial and subsurface tumours are treated with the IATA. Invasive thermometry is performed continuously for 110 sessions using multi-sensor probes of an optical thermometer. Thermal parameters (Tmax, Tmin, Tave) are assessed based on the tumour size and depth. The treated tumours are categorised into three groups according to tumour depth: group 1 (< 3 cm, n = 28), group 2 (3-5 cm, n = 35) and group 3 (> 5 cm, n = 47). The computer simulation shows that induced electrical currents run without convergency, parallel to the surface of the heating material. All thermal parameters of group 3 are significantly higher than those of group 1 and 2 (p < 0.05), indicating that the larger lesions tend to abtain a higher temperature distribution. In conclusion, RF inductive hyperthermia using the IATA results in effective temperature distributions in superficial and subsurface tumours, with large tumours being most effectively heated.     

Theoretical simulation of temperature distribution in the brain during mild hypothermia treatment for brain injury

Mild or moderate hypothermia (>30°C) has been proposed for clinical use as a therapeutic option for achieving protection from cerebral ischaemia in brain injury patients. In this research, a theoretical model was developed to examine the brain temperature gradients during selective cooling of the brain surface after head injury. The head was modelled as a hemisphere consisting of several layers, representing the scalp, skull and brain tissue, respectively. The dimensions, physical properties and physiological characteristics for each layer, as well as the arterial blood temperature, were used as the input to the Pennes bioheat transfer equation to simulate the steady-state temperature distribution within the brain. Depending on the head surface temperature, a temperature gradient of up to 13°C exists in the brain tissue. The results have shown that the volumetric-averaged brain tissue temperature T_{bt, avg} for adults and infants can be 1.7 and 4.3°C, respectively, lower than the temperature of the arterial blood supplied to the brain tissue. The location where the probe should be placed to measure T_{bt, avg} was also determined by the simulation. The calculation suggests that the temperature sensor should be placed 7.5mm and 5.9 mm beneath the brain tissue surface for adults and infants, respectively, to monitor T_{bt, avg} continuously.     

Apparatus for the rapid measurement of electrocardiographic body surface potentials

A method for the rapid and reproducible recording of 24 chest electrode potentials is described. Rigid electrodes are equally spaced around the thorax in three rows of eight. The electrodes move radially and are spring loaded so as to maintain contact with the skin regardless of the shape of the subject's torso. The inclusion of an impedance convertor in the electrode assembly removes the necessity for using electrode cream. Although equal spacing of the electrodes around the thorax is inefficient in terms of information content per electrode the attention to detail required for electrode placement using the described system is minimised as compared with other multiple lead systems. Furthermore, the principles adopted in the design and construction of the apparatus do not limit the number of chest electrodes to 24.     

局部阻抗测量方法用于肌肉拉伤监测与评价

目的 通过测量局部肌肉的阻抗和相位信息,建立一种评价局部肌肉拉伤及康复情况的新方法.方法 采用局部阻抗测量方法提取拉伤肌肉的阻抗和相位值,以左右对称部位为伤前参考值,对拉伤肌肉组织的伤情及随后的恢复情况进行监测与评价.结果 拉伤肌肉组织的阻抗值明显下降.在康复过程中,其阻抗和相位值随时间逐步上升,并在康复后期达到或接近于健康侧肌肉的参考值.结论 局部阻抗测量有望为拉伤肌肉组织的伤情判断和恢复监测提供一种新的,无创、简便的评价方法,显示了良好的临床应用前景.     

Simple, reliable and inexpensive telemetry system for continuous monitoring of small animal core temperature

A core temperature telemetry system is described which includes a transmitter and circuitry for signal reception, noise elimination and computer interfacing. The system is inexpensive (less than $50), easily constructed, reliable, portable, and has proven to be sensitive to rapid fluctuations in core temperature.     

Adaptation of Paramecium caudatum to variable conditions of temperature stress

The environment is rarely constant and organisms are exposed to spatial and temporal variation that will impact life-histories. It is important to understand how such variation affects the adaptation of organisms to their local environment. We compare the adaptation of populations of the ciliate Paramecium caudatum exposed to constant (23 °C or 35 °C) and temporally variable temperature environments (random daily fluctuations between 23 °C or 35 °C). Consistent with theory, our experiment shows the evolution of specialists when evolution proceeds in constant environments and generalists when the environment is temporally variable. In addition, we demonstrate costs for specialists of being locally adapted through reduced fitness in novel environments. Conversely, we do not find any costs for generalists, as all populations from variable environments had equal or superior performance to specialists in their own environment. The lack of a cost for generalists is emphasised by the presence of a super generalist that has the highest performance at both assay temperatures.     

Dynamics and topography of human temperature regulation in response to thermal and work load

Summary Climatic chamber experiments were carried out with male subjects who were submitted to various rapid temperature changes. All experiments were performed first with the subjects at rest and later at work on a bicycle ergometer. The aims of the study were 1) to obtain quantitative data enabling to determine effects of a) abrupt thermal load, b) abrupt work load, and c) combined load on the topography and the dynamics of temperatures and effectors, and 2) to answer the question whether the effects of combined load may be computed by a linear superposition of pure thermal plus pure work load.Skin temperatures generally respond more directly to abrupt changes of thermal than of work load. This is in contrast to the dynamic behaviour of central temperatures which moreover exhibit the interesting effect of a transient paradoxical respone both to the onset of work and of thermal load.Time constants of the dynamics of metabolic heat production are high in response to changes of thermal load as compared to the time constants at the onset and end of worl. Generally the time constants of skin temperatures are shorter at rest than at work. Temperature topography changes only to a small extent in exercising subjects.The central temperature increase to combined thermal and work load is not significantly different from the added amount of temperature increases due to pure thermal and to pure work load. This suggests a quasi-linear superposition of both thermal effects and confirms, in accordance with further evidence of this and former studies, the hypothesis that work load does not interfere non-linearly with the regulatory processes. However, an input from thermosensitive elements in the muscles should be assumed.Supported by the Deutsche Forschungsgemeinschaft, SFB 114     

Predicting the glass transition temperature of bioactive glasses from their molecular chemical composition

A recently published paper (M.D. O’Donnell, Acta Biomaterialia 7 (2011) 2264–2269) suggests that it is possible to correlate the glass transition temperature (T_g) of bioactive glasses with their molar composition, based on iterative least-squares fitting of published T_g data. However, we show that the glass structure is an important parameter in determining T_g. Phase separation, local structural effects and components (intermediate oxides) which can switch their structural role in the glass network need to be taken into consideration, as they are likely to influence the glass transition temperature of bioactive glasses. Although the model suggested by O’Donnell works reasonably well for glasses within the composition range presented, it is oversimplified and fails for glasses outside certain compositional boundaries.     

A biocompatible microdevice for core body temperature monitoring in the early diagnosis of infectious disease

The early diagnosis of microbial infection is critical to the clinical instigation of effective post-exposure prophylaxis or therapy. However, diagnosis of infection is often attempted only when there are overt clinical signs, and for some of the serious human pathogens, this may jeopardise the efficacy of therapy. We have used a miniaturised sealed, implantable transponder incorporating a calibrated temperature sensor with an external receiver system, to monitor core body temperature (Tc) remotely. We have observed early changes in the diurnal rhythm of Tc, after infection of mice with bacterial pathogens. Changes in Tc preceded overt clinical signs by 3–10 h following challenge with Yersinia pestis, which causes acute infection, In contrast, changes in Tc were detected 11 days before clinical signs in mice exposed to Burkholderia pseudomallei, which causes a chronic syndrome. Significantly, mice pre-vaccinated against Y.pestis infection showed only slight and transient disruption to the diurnal rhythm for Tc, in the absence of clinical signs, when challenged with 10⁶ median lethal doses of Y.pestis. This remote monitoring technology could be used to monitor changes in more than one physiological parameter and extrapolation of these data to the clinic would define the available therapeutic window in which diagnosis and post-exposure prophylaxis could be instigated, after a suspected exposure.     

Current practice and knowledge of nurses regarding patient temperature measurement

Background: The measurement of patient temperature by nursing staff is a common activity. In recent years this area of practice has been largely under-investigated despite the introduction of new technologies into clinical practice, such as infrared tympanic thermometry (IRTT).

Study aim: To investigate current practice in clinical temperature measurement in general, and the use of IRTT in particular by nursing staff.

Sample and methods: 139 nursing staff from a general hospital in the UK were surveyed via a self-administered questionnaire.

Main findings and conclusions: The group most involved in temperature measurement was characterized as nursing auxiliary grades with the fewest years of experience. IRTT was the most frequently-used method for measuring patient temperatures, with high perceived accuracy, reliability, ease of use and acceptability to patients. A poor level of understanding and training in the use of IRTT was revealed across all clinical grades. Recommendations for future investigations are made.     

Thermal method for continuous measurement of cerebral perfusion

A new thermal system using constant heating power for continuous measurement of cerebral perfusion is presented. It is designed and implemented for optimal perfusion sensitivity and dynamic response based on heat-transfer analysis of perfused brain tissue with thermistors on the cortical surface. Two matched thermistors are used, one to serve as a perfusion sensor and the other to compensate for the base-line temperature changes. To improve the signal-to-noise ratio of the measurement system, lock-in amplifiers are used to minimise long-term drift and low-frequency noise. Errors in the measurement caused by electrical and thermal fluctuations are tested and analysed. In vitro tests show that the measurement accuracy of temperature change is better than 10⁻³°C, and the temperature resolution is even greater. In vivo evaluation confirms that the system is responsive to cerebral perfusion changes associated with sudden changes in mean arterial blood pressure caused by bolus injection of norepinephrine, blood withdrawal and blood infusion. The dynamic response of the system is sufficient to detect the autoregulatory perfusion changes in response to arterial blood pressure alteration and the oscillations of cerebral blood flow.     

Ring electrode for radio-frequency heating of the cornea: Modelling and<Emphasis Type="Italic">in vitro</Emphasis> experiments

Radio-frequency thermokeratoplasty (RF-TKP) is a technique used to reshape the cornea curvature by means of thermal lesions using radio-frequency currents. This curvature change allows refractive disorders such as hyperopia to be corrected. A new electrode with ring geometry is proposed for RF-TKP. It was designed to create a single thermal lesion with a full-circle shape. Finite element models were developed, and the temperature distributions in the cornea were analysed for different ring electrode characteristics. The computer results indicated that the maximum temperature in the cornea was located in the vicinity of the ring electrode outer perimeter, and that the lesions had a semi-torus shape. The results also indicated that the electrode thickness, electrode radius and electrode thermal conductivity had a significant influence on the temperature distributions. In addition,in vitro experiments were performed on rabbit eyes. At 5 W power, the lesions were fully circular. Some lesions showed non-uniform characteristics along their circular path. Lesion depth depended on heating duration (60% of corneal thickness for 20s, and 30% for 10s). The results suggest that the critical shrinkage temperature (55–63°C) was reached at the central stroma and along the entire circular path in all the cases.     

Effect of temporal and spatial temperature gradients on the ampullae of Lorenzini

Summary Afferent single fiber impulses were recorded from isolated ampullae of Lorenzini of dogfishes (Scyliorhinus canicula). The ampullae were placed between two thermodes, each of which could be circulated separately with water at 12°, 18° and 24° C, thus allowing cooling and warming with various combinations of spatial temperature gradients. At constant temperature, there was a static discharge in the ampullary fibers. Cooling elicited a dynamic overshoot in frequency, followed by adaptation to a new steady state, whereas warming led to a transient inhibition. Within the limits of error the direction and slope of the spatial temperature gradient had no influence whatsoever on the static and dynamic responses of the ampullae, the only effective parameters being the temperature at the site of the receptor and the rate of temperature change with time.About 13% of the single fibers responded with bursts of impulses, interrupted by silent intervals, and 10% showed an inversed dynamic response, i.e. dynamic overshoot on warming and transient inhibition on cooling. It is possible that these patterns of activity are anomalous responses.This work was supported by the Deutsche Forschungsgemeinschaft.     

一种基于ZigBee无线网络的多参数医疗监护节点的设计

对患者进行长时间实时生理参数监控一直是医院慢性病治疗的重要工作之一,针对传统医疗监护设备体形大、成本高、位置固定、接线复杂的缺点,本文结合Zigbee无线技术,从小型化、无线化、网络化入手,设计了一种佩戴于手腕,集成了血压、血氧、体温多参数测量的医疗监护节点,并增加了液晶显示、自动报警等功能。实地实验结果显示,该节点能较准确地测量出患者的多项生理参数,并结合上位网关,搭建起适用于医院、养老院等机构的无线监护系统,极大地方便患者的监护治疗过程与医院的管理。