Effect of head skin temperature on tympanic and oral temperature in man.

Five subjects were sequentially heated and cooled in a double-climate chamber while mean skin temperature (except the head) and head skin temperature were separately varied. The tympanic membrane temperatures of these subjects were disproportionately influenced by changes in head skin temperature. By heating and cooling localized regions of the head, changes in tympanic membrane temperature that followed changes in skin temperature on the ipsilateral side of the head could be produced. During heating of the head, oral and tympanic membrane temperatures were influenced to a similar degree, while esophageal temperature remained essentially unaffected. However, under conditions in which the legs and feet were heated in a water bath, esophageal temperature showed more rapid changes than either tympanic membrane or oral temperature. These findings suggest that tympanic membrane temperature and, to a lesser degree, oral temperature may be affected by thermal exchange occurring between arteries and veins in the cervical and cephalic regions. In addition, the ability to influence selectively esophageal and tympanic membrane temperatures brings into question the arbitrary use of these measurements under widely different experimental conditions as estimates of core temperature.     

Finger vasodilation correlates better with tympanic than esophageal temperature

The relationship of finger blood flow (FBF) measured by venous occlusion plethysmography to tympanic temperature (Tty) was compared with that of FBF to esophageal temperature (Tes) during exercise at 50% VO2max for 40 min at an ambient temperature of 25 degrees C. The relationship of FBF to Tes showed an inflexion as Tes increased during exercise. The slope of the regression line showing the relationship between FBF and Tes was initially moderate, and then suddenly became steeper at the inflexion point. The relationship of FBF to Tty, however, was linear, without an inflexion. The results suggest that finger vasodilation during moderate exercise correlates better with tympanic than esophageal temperature.     

Comparison of methods of temperature measurement in swine

The purpose of these experiments was to test the equivalence of pulmonary artery, urinary bladder, tympanic, rectal and femoral artery methods of temperature measurement in healthy and critically ill swine under clinical intensive care unit (ICU) conditions using a prospective, time series design. First, sensors were tested for error and sensitivity to change in temperature with a precision-controlled water bath and a laboratory-certified digital thermometer for temperatures 34-42 degrees C. There was virtually no systematic (bias) or random (precision) error (<0.2 degrees C). The bladder sensor had the slowest response time to change in temperature (105-120 s). Next, testing was done in an experimental porcine ICU in a non-profit research institution with four male, sedated, and mechanically ventilated domestic farm pigs. The in vivo experiments were conducted over periods of 41-168 h with temperatures measured every 1-5 s. The bladder, tympanic and rectal methods had unacceptable bias (>or=0.5 degrees C) and/or precision (>or=0.2 degrees C). Response time varied from 7 s with the femoral artery method to 280 s (4.7 min) with the tympanic method. We concluded that equivalence of the methods was insufficient for them to be used interchangeably in the porcine ICU. Intravascular monitoring of core body temperature produces optimal measurement of porcine temperature under varying conditions of physiological stability.     

Effect of esophageal contraction on esophageal wall blood perfusion

Myocardial blood flow occurs during the diastolic phase of the cardiac cycle, because myocardial contraction during the systolic phase impedes myocardial perfusion. Using laser Doppler perfusion technique, we studied the effect of esophageal contraction on the esophageal wall perfusion. Studies were conducted in rats. A laser Doppler probe was anchored to the esophageal wall, and wall perfusion was studied under various experimental conditions. Increase and decrease in the systemic blood pressure induced by different pharmacological agents was associated with the increase and decrease in the esophageal wall perfusion, respectively. Esophageal contractions induced by electrical stimulation of the vagus nerve and electrical stimulation of the muscle directly resulted in a reduction in the esophageal wall perfusion, in a dose-dependent fashion. Esophageal wall perfusion could be monitored by placing the Doppler probe on the esophageal mucosa or on the outside of the esophageal wall. Esophageal contraction impedes entry of blood into the esophageal wall. Future studies may investigate if ischemia of the esophageal wall induced by sustained esophageal contractions/esophageal spasm is the cause of esophageal pain symptoms in humans.     

Sex differences in postexercise esophageal and muscle tissue temperature response

Factors associated with blood pressure regulation during recovery from exercise dramatically influence core temperature regulation. However, it is unknown whether sex-related differences in postexercise hemodynamics affect core and muscle temperature response. Sixteen participants (8 males, 8 females) completed an incremental isotonic test on a Kin-Com isokinetic apparatus to determine their activity-specific peak oxygen consumption during bilateral knee extensions (Vo(2)(sp)). On a separate day, participants performed 15 min of isolated bilateral knee extensions at a moderate (60% Vo(2)(sp)) exercise intensity followed by a 90-min recovery. Esophageal temperature (T(es)), mean arterial pressure (MAP), muscle temperature at four depths in the active vastus medialis (T(VM)) and three depths in the inactive triceps brachii (T(TB)) were measured concurrently with sweat rate and cutaneous vascular conductance (CVC). Relative to the preexercise resting T(es) of 36.7 degrees C (SD 0.1), between 10 and 50-min of recovery T(es) was 0.19 degrees C (SD 0.02) higher for females than males (P = 0.037). All measurements of T(VM) (0.036 > P > 0.014) and T(TB) (0.048 > P > 0.008) were higher for females during the initial 30 min of recovery by between 0.46 degrees C and 0.64 degrees C for T(VM) and by between 0.53 degrees C and 0.70 degrees C for T(TB). In parallel, females showed a 5 to 7 mmHg greater reduction in MAP during recovery relative to males (P = 0.002) and a significantly lower CVC (P = 0.020) and sweat rate (P = 0.034). Therefore, it is concluded that females demonstrate a greater and more prolonged elevation in postexercise esophageal temperature and active and inactive muscle temperatures, which is paralleled by a greater postexercise hypotensive response.     

Body weight and tympanic temperature change in professional rugby league players during night and day games: a study in the field

This study investigated the impact of day and night games in the professional rugby league on body weight and tympanic temperature change in participants. Twenty-five players contracted to an English Super League club had their pre- and postgame body weight and tympanic temperatures recorded during 10 games played during the official professional rugby league season, representing a total of 165 player appearances. The mean (+/-SD) ambient temperature and relative humidity was 12.3 degrees C (+/-6.0) and 83.3% (+/-11.4), respectively. Body weight was recorded using a set of calibrated Soehnle digital scales with players wearing underwear only and towel-dried of all sweat (postmatch). Tympanic temperature was recorded using a Braun ThermoScan Pro LT instant thermometer. Players were allowed to ingest fluid ad libitum throughout each match. Wet and dry bulb temperatures were recorded at the commencement and completion of each match. Significant changes in pregame to postgame body weight and tympanic temperature were found, but these were not influenced by the time of day that the game was played. The mean decrease in body weight was 0.86 kg (SE 0.085, p < 0.000), and the mean increase in tympanic temperature was 0.34 degrees C (SE 0.070, p < 0.000). No significant differences in body weight or tympanic temperature change were found between forwards and backs. Participation in the English professional rugby league can produce significant decreases in body weight and increases in body temperature that may lead to impaired performance. It is important for participants, coaches, and administrators to introduce strategies that will minimize the impact of environmental conditions on thermoregulation and ultimately player performance.     

Effect of menstrual cycle phase on the ventilatory response to rising body temperature during exercise

To examine the effect of menstrual cycle on the ventilatory sensitivity to rising body temperature, ten healthy women exercised for ~60 min on a cycle ergometer at 50% of peak oxygen uptake during the follicular and luteal phases of their cycle. Esophageal temperature, mean skin temperature, mean body temperature, minute ventilation, and tidal volume were all significantly higher at baseline and during exercise in the luteal phase than the follicular phase. On the other hand, end-tidal partial pressure of carbon dioxide was significantly lower during exercise in the luteal phase than the follicular phase. Plotting ventilatory parameters against esophageal temperature revealed there to be no significant menstrual cycle-related differences in the slopes or intercepts of the regression lines, although minute ventilation and tidal volume did significantly differ during exercise with mild hyperthermia. To evaluate the cutaneous vasodilatory response, relative laser-Doppler flowmetry values were plotted against mean body temperature, which revealed that the mean body temperature threshold for cutaneous vasodilation was significantly higher in the luteal phase than the follicular phase, but there were no significant differences in the sensitivity or peak values. These results suggest that the menstrual cycle phase influences the cutaneous vasodilatory response during exercise and the ventilatory response at rest and during exercise with mild hyperthermia, but it does not influence ventilatory responses during exercise with moderate hyperthermia.     

The temperature of the air within the external auditory meatus compared with esophageal temperature during anaesthesia and surgery

• 1.1.|Air temperature within the external auditory meatus, sensed by a thermistor insulated from the walls of the aural canal, was compared with the temperature recorded from a probe in the esophagus in patients under general anaesthesia.
• 2.2.|In the first study of 14 patients, aural temperatures at the time of induction of anaesthesia were more than 3°C lower, and the changes during surgery were more variable, than those recorded from the esophagus.
• 3.3.|In a second study of 35 patients in which heat loss from the external ear was reduced by ear protectors, there was also a poor correlation between temperatures of the ear and esophagus. Aural temperature was initially lower and rose over time in most cases whereas esophageal temperature generally decreased.
• 4.4.|These results suggest that air temperature within the aural canal is not a useful estimate of deep body temperature since it reflects mainly skin temperature.

     

Hypohydration affects forearm vascular conductance independent of heart rate during exercise.

Elevated body core temperature stimulates cutaneous vasodilation, which can be modified by nonthermal factors. To test whether hypohydration affects forearm vascular conductance discretely from relative alterations in heart rate (HR), eight trained cyclists exercised progressively for 20 min each at 60, 120, and 180 W [approximately 22, 37, and 55% of maximal cycling O2 consumption (VO2peak), respectively] in a warm humid environment (dry bulb temperature 30 degrees C; wet bulb temperature 24 degrees C). Esophageal temperature and forearm blood flow were measured every 30 s, and mean arterial pressure and HR were measured at rest and during each exercise intensity (minutes 15, 35, and 55). In the hypovolemic (HP) compared with the euvolemic (EU) state, blood volume was contracted by 24-h fluid restriction an average of 510 ml, and this difference was sustained throughout exercise. The esophageal temperature and HR responses were similar between EU and HP states at 60 and 120 W but were significantly (P < 0.05) higher in HP by the end of 180 W. In contrast, the forearm blood flow response was significantly (P < 0.05) depressed during exercise at 120 and 180 W in HP, whereas mean arterial pressure remained similar between conditions. When body core temperature is elevated in a hypohydrated state, forearm vascular conductance is reduced at exercise intensities of approximately 37% VO2peak, which is independent of relative changes in HR. These findings are consistent with the notion that during exercise an attenuated cutaneous vasodilation is elicited by alterations in regionalized sympathetic outflow, which is unaccompanied by activation of cardiac pacemaker cells.     

Effects of exposure to a simulated altitude of 3,500 m on calves and oxen

Nine calves and nine oxen were divided into 6 groups and exposed in a climatised low pressure chamber to the following conditions: 2 weeks at 400 m and 4 weeks at 3,500 m. High altitude produced the following changes: increases in heart rate and pulmonary artery pressure, both these changes being larger in the calves than in the oxen. During 4 weeks continuous exposure to 3,500 m, heart rate declined, whereas pulmonary arterial pressure rose. There were increments in respiratory rate, blood-pH, leucocyte number, rectal temperature, blood lactate and blood pyruvate, but no changes in the lactate/pyruvate ratio. Increases in erythrocyte number, haemoglobin, haematocrit, blood specific gravity and blood viscosity were more pronounced in the oxen than in the calves. Feed intake in all animals tended to be depressed in the first half of the high altitude periode. Water intake showed a fall during the first day at 3,500 m, but recovered thereafter. It is concluded that in response to high altitude the calves activated preferentially the circulatory, the oxen the erythropoetic system.     

Sweating and tympanic temperature during warm water immersion compared between Vietnamese and Japanese living in Hanoi

The present study compared between Japanese and Vietnamese subjects living in Hanoi, the local evaporation rate by sweating and the tympanic temperature during legs immersion in warm water. Seven Vietnamese and seven Japanese (who had lived in Hanoi for 1-2 years) participated in the experiments, which were performed in April, 2001 in Hanoi (Vietnam). It was found that the tympanic temperature at which subjects started to sweat in the forearm was significantly higher in Vietnamese than in Japanese. In addition, the local amount of evaporation was significantly lower in Vietnamese subjects. We discussed the physiological reason for such different thermoregulatory responses in terms of different levels of set-point in the core temperature between Vietnamese and Japanese. It was concluded that the Vietnamese inhabitant commenced the sweating at higher tympanic temperature to identical warm stimuli and had lower sweating rate and higher tympanic temperature during the 40 min immersion of both legs to warm water than the Japanese inhabiting Hanoi for 1-2 years.     

Effects of temperature on properties of flight neurons in the locust

High ambient temperatures increase the wing-beat frequency in flying locusts, Locusta migratoria. We investigated parameters of circuit and cellular properties of flight motoneurons at temperatures permissive for flight (20–40 °C). As the thoracic temperature increased motoneuronal conduction velocity increased from an average of 4.40 m/s at 25 °C to 6.73 m/s at 35 °C, and the membrane time constant decreased from 11.45 ms to 7.52 ms. These property changes may increase locust wing-beat frequency by affecting the temporal summation of inputs to flight neurons in the central circuitry. Increases in thoracic temperature from 25–35 °C also resulted in a hyperpolarization of the resting membrane potentials of flight motoneurons from an average of-41.1 mV to -47.5 mV, and a decrease of input resistances from an average of 3.45 M to 2.00 M. Temperature affected the measured input resistance both by affecting membrane properties, and by altering synaptic input. We suggest that the increase in conduction velocity Q₁₀=1.53) and the decrease of membrane time constant (Q₁₀=0.62) would more than account for the wing-beat frequency increase (Q₁₀=1.15). Hyperpolarization of the resting membrane potential (Q₁₀=1.18) and reduction in input resistance (Q₁₀=0.54) may be involved in automatic compensation of temperature effects.Abbreviations ANOVA analysis of variance - CPG central pattern generator - DL dorsal longitudinal muscles - EMG electromyographic - MN motoneuron - PSP post synaptic potential - Q₁₀ temperature coefficient - RMP resting membrane potential - S.D. standard deviation - SR stretch receptor     

Respiratory heat loss and core temperatures during submaximal exercise

1. 1. This study examined the effect of inhaling air supersaturated with water on changes of core temperatures in submaximally exercising males.

2. 2. During exercise with inhalation of supersaturated relative to low-air-humidity air, a significant elevation in tympanic temperature (P = 0.009) and a significant decrease in esophageal temperature (P = 0.004) were observed.

3. 3. Forehead skin temperatures significantly decreased during humidified air inhalation (P = 0.02) supporting that this treatment induced greater thermolytic responses that cooled the skin.

4. 4. The results are consistent with the conclusion that heat loss from the upper airways directly influenced human cerebral temperatures as indexed by tympanic temperatures.

     

Effect of Short-term Cooling at –70°C in an Air Cryogenic Sauna on Body Temperature and Lipid Profile of Healthy People

The investigation was aimed at evaluation of level and rate of cutaneous and tympanic temperature drop due to a single short-timed (3 min) cooling in a cryosauna (–70°С), and adaptation-indicative physiological parameters, including blood catecholamines, ACTH, lipoproteins and free fatty acids. The subjects were seven healthy men. Exposure to cold invariably reduced the internal (tympanic) and cutaneous temperature by 1°С and 7°С on average, respectively. Tympanic temperature remained 0.4°С low on the average for more than 20 min after exposure. Cutaneous temperature was 1°С below the norm for an hour after cooling. For one hour after the short-term cold exposure, blood norepinephrine remained increased, and so did the blood concentrations of high-density lipoprotein cholesterol and free fatty acids. These results demonstrate brief adaptive changes following a single exposure at–70°C.     

128层螺旋CT肺动脉造影对急性肺栓塞患者栓塞程度和右心功能的评估价值研究

目的:探讨128层螺旋CT肺动脉造影(CTPA)对急性肺栓塞(APE)患者栓塞程度和右心功能的评估价值。方法:选取2016年7月到2018年6月期间在我院行CTPA检查确诊并接受治疗的APE患者100例记为观察组,根据观察组患者的病情将其分为高危组(57例)和非高危组(43例),同时根据观察组患者肺栓塞部位及预后将患者分为中心肺栓塞死亡组(8例)、中心肺栓塞存活组(38例)、周围肺栓塞组(54例)。另选择同期于我院进行CTPA检查的无肺栓塞患者50例记为对照组。记录所有患者的右心功能参数[右心室短轴最大径(RVMSA)、左心室短轴最大径(LVMSA)以及二者的比值(RV:LV)],计算APE患者的CT肺动脉阻塞指数,并分析APE患者CT肺动脉阻塞指数与右心功能指标的相关性。结果:观察组的RVMSA、RV:LV均明显高于对照组(P0.05),高危组的CT肺动脉阻塞指数、RVMSA、RV:LV均明显高于非高危组(P0.05)。中心肺栓塞死亡组的CT肺动脉阻塞指数、RVMSA、RV:LV均明显高于中心肺栓塞存活组和周围肺栓塞组,中心肺栓塞存活组的CT肺动脉阻塞指数、RVMSA、RV:LV均明显高于周围肺栓塞组(P0.05)。经Pearson相关分析显示,APE患者CT肺动脉阻塞指数与RVMSA、RV:LV均呈正相关(P0.05),与LVMSA无明显的相关性(P0.05)。结论:CTPA检查可有效评估APE患者的栓塞程度和右心功能,且栓塞程度与右心功能存在相关性,CTPA检查有助于APE患者的诊断和病情评估。     

Esophageal wall blood perfusion during contraction and transient lower esophageal sphincter relaxation in humans

We recently reported that esophageal contraction reduces esophageal wall perfusion in an animal study. Our aim was to determine esophageal wall blood perfusion (EWBP) during esophageal contraction and transient lower esophageal sphincter relaxations (TLESRs) in humans. We studied 12 healthy volunteers. A custom-designed laser Doppler probe was anchored to the esophageal wall, 4-6 cm above the LES, by use of the Bravo pH system so that the laser light beam stay directed toward the esophageal mucosa. A high-resolution manometry equipped with impedance electrodes recorded esophageal pressures and reflux events. Synchronized pressure, impedance, pH, and EWBP recordings were obtained during dry and wet swallows and following a meal. Stable recordings of laser Doppler EWBP were only recorded when the laser Doppler probe was firmly anchored to the esophageal wall. Esophageal contractions induced by dry and wet swallows resulted in 46 ± 9% and 60 ± 10% reduction in the EWBP, respectively (compared to baseline). Reduction in EWBP was directly related to the amplitude (curvilinear fit) and duration of esophageal contraction. Atropine reduced the esophageal contraction amplitude and decreased the EWBP reduction associated with esophageal contraction. TLESRs were also associated with reduction in the EWBP, albeit of smaller amplitude (29 ± 3%) but longer duration (19 ± 2 s) compared with swallow-induced esophageal contractions. We report 1) an innovative technique to record EWBP for extended time periods in humans and 2) contraction of circular and longitudinal muscle during peristalsis and selective longitudinal muscle contraction during TLESR causes reduction in the EWBP; 3) using our innovative technique, future studies may determine whether esophageal wall ischemia is the cause of esophageal pain/heartburn.     

Noctural Asthma: Role of Nocturnal Gastroesophageal Reflux

Gastroesophageal reflux (GER) is common in those with asthma, with 77% of asthmatics complaining of heartburn, with 41% experiencing reflux-associated respiratory symptoms. Likewise, 24% of those with asthma that is difficult to control have “clinically silent” GER. There are no studies examining nocturnal reflux symptoms in asthmatics. Esophageal dysmotility is also common, and abnormal esophageal acid contact times on 24h esophageal pH tests were found in 82% of asthmatics examined consecutively. Most asthmatics with GER also have abnormal esophageal acid contact times while in the supine position, reflecting sleep time. Endoscopic evidence of esophagitis was found in 43% of asthmatics. Two mechanisms of bronchoconstriction induced by esophageal acid have been proposed: a vagally mediated reflex, by which esophageal acid in the distal esophagus causes reflex bronchoconstriction, and microaspiration. Although there is conflicting evidence, distal esophageal acid causes a decrease in peak expiratory flow rates, an increase in respiratory resistance, and an increase in minute ventilation. If microaspiration is present, there is further augmentation of this airway response. Although only a few studies have been performed in those with nocturnal asthma with GER, one study in a pediatric population showed that esophageal acid infusions caused more airway responses at 04:00 than at 24:00. Also, asthmatic children with nocturnal asthma symptoms have a higher re-flux score, with a positive correlation between reflux score and nighttime-associated wheezing. Despite these findings in children, a study performed in sleeping adults with nocturnal asthma noted no alterations in airflow resistance with esophageal acid, concluding that GER contributed little to the nocturnal worsening of asthma. There are also gastroesophageal circadian issues that may influence GER in asthmatics. Gastric acid secretion peaks at approximately 21:00, and gastric emptying is delayed when a meal is given at 20:00 versus 08:00. Esophageal acid clearance is delayed significantly during sleep, and acid clearance occurs during arousals. Upper esophageal sphincter (UES) pressure also decreases with sleep onset, which may predispose to microaspiration. Further research is needed to clarify what role nocturnal reflux has on nocturnal asthma and airway inflammation and whether circadian rhythm factors alter airway responses to esophageal acid.     

Quantitative radionuclide assessment of total pulmonary vascular volume changes

Current techniques do not permit continuous and noninvasive assessments of changes in total pulmonary intravascular volume. Hence, the present study was undertaken to determine whether quantitative radionuclide imaging can be used to determine the direction and estimate the magnitude of total pulmonary vascular volume changes. The pulmonary circulation was separately perfused at a constant rate via the pulmonary artery and drained at a constant pressure via the left atrium in nine dogs. Changes in pulmonary intravascular volume were recorded as reciprocal changes in extracorporeal reservoir volume during phenylephrine or isoproterenol administration, a 20% increase in pulmonary artery flow or a 5 mmHg (1 mmHg = 133.32 Pa) decrease in left atrial pressure. Erythrocytes were labeled with technetium-99m and pulmonary volume changes were determined from tissue attenuation, blood radioactivity, and changes in total pulmonary radioactivity obtained with a gamma-camera. During each of the interventions, count changes correlated with volume changes (r greater than or equal to 0.75). The technique reliably detected volume changes as small as 10 mL. For all 531 individual pairs of radionuclide- and reservoir-determined volume changes, the correlation between reservoir-determined and radionuclide-estimated pulmonary intravascular volume changes was 0.87. The standard error of the radionuclide estimate was 21 mL. Hence, the present study demonstrates that quantitative radionuclide imaging can be used to continuously and noninvasively determine total pulmonary vascular volume changes.     

Responses of central and cerebral hemodynamics to active orthostasis in healthy subjects

Regular trends in changes in cerebral and central hemodynamics were studied in 28 healthy men aged 20–26 years during active orthostatic stress. The hemodynamic parameters of the blood flow in the middle cerebral artery (MCA), systemic hemodynamics, and parameters of pulmonary ventilation were recorded simultaneously for 10 min while a subject was in a horizontal position and for the same period after the position had been changed to vertical (active rising). In healthy subjects, several types of responses of cerebral and central hemodynamics were detected during active orthostasis.     

Factors affecting the accuracy of esophageal balloon measurement of pleural pressure in dogs.

Simultaneous measurement of esophageal and tracheal pressures during an occluded inspiratory effort was used to assess the accuracy of the esophageal balloon for measuring pleural pressure in dogs. Esophageal balloons were inserted in five mongrel dogs, and an occlusion test was performed with the balloon tip 5, 10, 15, 20, and 25 cm above the esophageal sphincter; at lung volumes of functional residual capacity (FRC) and FRC + 600 ml; and in supine and right- and left-side lying postures. The protocol was repeated in paralyzed animals. This time the occlusion test was performed by injecting air into a plethysmograph to change the body surface pressure, simulating pressure changes produced by respiratory efforts in spontaneously breathing animals. In 47% of the tests in spontaneously breathing dogs, the slope of esophageal vs. tracheal pressure varied greater than 10% from unity. After paralysis the slope did not vary greater than 5% from unity under any circumstance. These data indicate that the poorer performance of the occlusion test in nonparalyzed dogs is due to active tension in the walls of the esophagus and stress induced in the intrathoracic soft tissues by the descent of the diaphragm during a breathing effort.