Skin temperature biofeedback for Raynaud's disease: A double-blind study

The lack of control procedures inherent in most of the experiments conducted to assess the effectiveness of skin temperature biofeedback in the treatment of Raynaud's disease renders the results inconclusive. In this study, control groups and a double-blind approach are adopted. Thirty-six patients, carefully screened for a diagnosis of primary Raynaud's disease, were assigned to a skin temperature increase group (N=12), to an EMG relaxation control group (N=12), or to a notreatment control group (N=12). All patients kept records of their symptoms for the duration of the study. Each subject in the two training groups received 20 sessions, the last 2 conducted under cold stress. Data analysis according to original group assignment, as well as following regrouping of subjects according to several learning criteria, showed that while all patients reported a marked decrease in the number of vasospastic attacks, no significant differences were found among the three groups on the clinical measures used to assess symptomatic relief. The general improvement reported must therefore be attributed to nonspecific factors.This study was supported in part by Rehabilitation Services Administration Grant No. 16-P-56810/5–17 to the University of Minnesota Medical Rehabilitation Research and Training Center. We are grateful to Gail Gaebe, Carla Grossman, Steve Janousek, Linda Rubbelke, and Scott Williamson, who served as blind assistants, and to Steve Sheffield for his technical support.     

The relative efficacy of autogenic phrases and autogenic-feedback training in teaching hand warming to children

There are few well-controlled biofeedback temperature training studies in the literature that have used children as subjects. The purposes of this study were (1) to evaluate whether children can learn to increase hand temperature, controlling for methodological factors that have been overlooked in previous experiments, and (2) to determine whether adding thermal biofeedback to autogenic phrases results in improved ability to produce voluntary increases in hand temperature over the use of autogenic phrases alone. Twenty-six subjects (ages 9–11) were divided into two groups of 13 subjects each. All subjects participated in four 35 to 45-minute sessions consisting of a stabilization phase, a training phase, and a post-training phase on 4 consecutive days. One group was trained to increase finger temperature with autogenic phrases only, and the other was trained with autogenic phrases plus thermal feedback. None of the subjects in either group learned to increase hand temperature significantly within sessions. There was a consistent and reliable decreasing trend within each session; however, finger temperature did increase (.27° F) for the first 8 minutes of the training phase. There was a significant increase in hand temperature from day 1 to days 3 and 4, and there were significant increases in temperature during the stabilization phase alone. There were no differential effects of treatments. Methodological issues concerning stabilization, the potential confounding effect of boredom and fatigue, and different training methods for children are discussed.     

Skin and core temperature response to partial- and whole-body heating and cooling

1. Human subjects were exposed to partial- and whole-body heating and cooling in a controlled environmental chamber to quantify physiological and subjective responses to thermal asymmetries and transients.

2. Skin temperatures, core temperature, thermal sensation, and comfort responses were collected for 19 local body parts and for the whole body.

3. Core temperature increased in response to skin cooling and decreased in response to skin heating.

4. Hand and finger temperatures fluctuated significantly when the body was near a neutral thermal state.

5. When using a computer mouse in a cool environment, the skin temperature of the hand using the mouse was observed to be 2–3 °C lower than the unencumbered hand.     

The use of temperature biofeedback in the treatment of chronic pain due to causalgia

A patient with chronic pain due to a reflex sympathetic dystrophy in his hand and arm was successfully treated with temperature biofeedback after several months of conservative standard medical care brought little relief. Over the 18 treatment sessions the patient learned to emit a reliable handwarming response of 1 to 1.5°C. Coincident with his learning, the pain in his hand and arm decreased markedly and remained absent at 1-year follow-up.The author wishes to acknowledge the assistance of Dr. Kit S. Mays and the staff of the Pain Clinic of the University of Tennessee Center for the Health Sciences.     

Preliminary Investigation: Acupoint-Skin Conductance in Stroke Survivors

It has been reported that patients with rheumatoid arthritis or asthma have skin conductance over the acupoints that is lower than that of their healthy counterparts; this has been regarded as indirect evidence of the existence of acupoints and the energy-based model of diseases. In order to investigate the potential application of acupoint-skin conductance measurement that may reflect pathology of ischemic stroke, the present study recruited 34 stroke survivors with hemiparesis, whose skin conductance of a hand acupoint and an adjacent non-acupoint and the finger temperature in both affected and unaffected hands were simultaneously measured; the data revealed that the skin conductance and finger temperature were statistically higher in the unaffected hand than that of the affected, and the skin conductance of the acupoint and the non-acupoint were comparable in the affected and unaffected hands respectively. We attribute the observed drop in the skin conductance to the diminished peripheral blood flow of the affected hand that is signified by relatively lower finger temperature. As such, it should be advisable when studying skin conductance over acupoints, monitoring the adjacent non-acupoint skin and local vascular circulation is essential.     

Finger dexterity, skin temperature, and blood flow during auxiliary heating in the cold.

The primary purpose of the present study was to compare the effectiveness of two forms of hand heating and to discuss specific trends that relate finger dexterity performance to variables such as finger skin temperature (T(fing)), finger blood flow (Q(fing)), forearm skin temperature (T(fsk)), forearm muscle temperature (Tfmus), mean weighted body skin temperature (Tsk), and change in body heat content (DeltaH(b)). These variables along with rate of body heat storage, toe skin temperature, and change in rectal temperature were measured during direct and indirect hand heating. Direct hand heating involved the use of electrically heated gloves to keep the fingers warm (heated gloves condition), whereas indirect hand heating involved warming the fingers indirectly by actively heating the torso with an electrically heated vest (heated vest condition). Seven men (age 35.6 +/- 5.6 yr) were subjected to each method of hand heating while they sat in a chair for 3 h during exposure to -25 degrees C air. Q(fing) was significantly (P < 0.05) higher during the heated vest condition compared with the heated gloves condition (234 +/- 28 and 33 +/- 4 perfusion units, respectively), despite a similar T(fing) (which ranged between 28 and 35 degrees C during the 3-h exposure). Despite the difference in Q(fing), there was no significant difference in finger dexterity performance. Therefore, finger dexterity can be maintained with direct hand heating despite a low Q(fing). DeltaH(b), Tsk, and T(fmus) reached a low of -472 +/- 18 kJ, 28.5 +/- 0.3 degrees C, and 29.8 +/- 0.5 degrees C, respectively, during the heated gloves condition, but the values were not low enough to affect finger dexterity.     

Effects of high altitudes on finger cooling test in Japanese and Tibetans at Qinghai Plateau

The influences of both hypobaric hypoxia and cold on peripheral circulation were studied using the finger cooling test (measurement of the decrease in finger temperature, measured at the dorsal surface of the finger, during immersion of the hand in 0° C water for 20 min) at Qinghai Plateau. The same test was carried out at simulated altitudes in a 25° C climatic chamber to separate the hypobaric hypoxia influence from that of cold. In Japanese subjects at Qinghai Plateau there was a significant difference between finger skin temperatures (FSTs) during 20 min of 0° C water immersion at altitudes of 2260 m and 4860 m by ANOVA. Mean finger skin temperature during the 20-min immersion (5–20 min, MST) measured at 4860 m was significantly lower than that at 2260 m. In Tibetan subjects, there was also a significant difference between FSTs at 2260 m and at 4860 m by ANOVA. MST at 4860 m tended to be lower than that at 2260 m. In the 25° C climatic chamber, there was a significant difference between FSTs of Japanese expedition members at 2000 m and at 4000 m by ANOVA. MST was higher at 4000 m than at 2000 m, contrary to the data obtained in Qinghai. In conclusion, the higher skin temperature in response to local cold immersion, which would have been caused by stronger hypobaric hypoxia, must have been masked by the lower ambient temperature.     

Psychophysiological Patterns During Cell Phone Text Messaging: A Preliminary Study

This study investigated the psychohysiological patterns associated with cell phone text messaging (texting). Twelve college students who were very familiar with texting were monitored with surface electromyography (SEMG) from the shoulder (upper trapezius) and thumb (abductor pollicis brevis/opponens pollicis); blood volume pulse (BVP) from the middle finger, temperature from the index finger, and skin conductance (SC) from the palm of the non-texting hand; and respiration from the thorax and abdomen. The counter-balanced procedure consisted of a 2 min pre-baseline, 1 min receiving text messages, 2 min middle baseline, 1 min sending text messages and 2 min post-baseline. The results indicated that all subjects showed significant increases in respiration rate, heart rate, SC, and shoulder and thumb SEMG as compared to baseline measures. Eighty-three percentage of the participants reported hand and neck pain during texting, and held their breath and experienced arousal when receiving text messages. Subjectively, most subjects were unaware of their physiological changes. The study suggests that frequent triggering of these physiological patterns (freezing for stability and shallow breathing) may increase muscle discomfort symptoms. Thus, participants should be trained to inhibit these responses to prevent illness and discomfort.     

Cold-induced vasodilation and vasoconstriction in the finger of tropical and temperate indigenes

While heat acclimatization reflects the development of heat tolerance, it may weaken an ability to tolerate cold. The purpose of this study was to explore cold-induced vasodilation (CIVD) responses in the finger of tropical indigenes during finger cold immersion, along with temperate indigenes. Thirteen tropical male indigenes (subjects born and raised in the tropics) and 11 temperate male indigenes (subjects born and raised in Japan and China) participated. Subjects immersed their middle finger at 4.3±0.8 °C water for 30 min. Rectal temperature, skin temperatures, finger skin blood flow, blood pressure and subjective sensations were recorded during the test. The results showed that: (1) the tropical group demonstrated a lower minimum (T_min), maximum (T_max) and mean finger temperature (T_mean) compared to those of the temperate group (P<0.05); (2) seven tropical indigenes demonstrated a late-plateau type of CIVD pattern, which is characterized by a pronounced 1st vasoconstriction and a single CIVD with a faint and weak 2nd vasoconstriction, whereas no temperate indigene demonstrated the late-plateau type; and (3) the hand temperature at the end of finger immersion was 3 °C lower in the tropical than the temperate group (P<0.05). These results indicate that tropical indigenes have less active responses of arterio-venous anastomoses in the finger and weaker vasoconstrictions after the first CIVD response during finger cold immersion, which can be considered as being more vulnerable to cold injury of the periphery in severe cold.     

Elderly bioheat modeling: changes in physiology,thermoregulation, and blood flow circulation

A bioheat model for the elderly was developed focusing on blood flow circulatory changes that influence their thermal response in warm and cold environments to predict skin and core temperatures for different segments of the body especially the fingers. The young adult model of Karaki et al. (Int J Therm Sci 67:41–51, 2013) was modified by incorporation of the physiological thermoregulatory and vasomotor changes based on literature observations of physiological changes in the elderly compared to young adults such as lower metabolism and vasoconstriction diminished ability, skin blood flow and its minimum and maximum values, the sweating values, skin fat thickness, as well as the change in threshold parameter related to core or skin temperatures which triggers thermoregulatory action for sweating, maximum dilatation, and maximum constriction. The developed model was validated with published experimental data for elderly exposure to transient and steady hot and cold environments. Predicted finger skin temperature, mean skin temperature, and core temperature were in agreement with published experimental data at a maximum error less than 0.5 °C in the mean skin temperature. The elderly bioheat model showed an increase in finger skin temperature and a decrease in core temperature in cold exposure while it showed a decrease in finger skin temperature and an increase in core temperature in hot exposure.     

Comparability of skin temperatures from three sites on the hand

Skin temperature from three recording sites (web dorsum and two digital sites) on one hand were compared over a 30-minute period during which room temperature was raised from 66° to 80°F causing skin temperatures to range from 78.5° to 92.3°F. The web dorsum remained significantly warmer than either digital site at the lowest skin temperatures; no significant inter-site differences were seen as skin temperature gradually increased. These findings imply that none of the three sites is more advantageous than the others when recording hand temperature values around or above 85°F. However, at the lower levels of skin temperature, there is a floor below which the web dorsum is no longer a sensitive indicator. More generally, basic data of this type provide a necessary but often absent foundation for routine practice of clinical biofeedback.We gratefully acknowledge the assistance of Kelly Peters in the data collection and of Steve Krause and Rick Scott in the data analysis.     

A new mathematical model to simulate AVA cold-induced vasodilation reaction to local cooling

The purpose of this work was to integrate a new mathematical model with a bioheat model, based on physiology and first principles, to predict thermoregulatory arterio-venous anastomoses (AVA) and cold-induced vasodilation (CIVD) reaction to local cooling. The transient energy balance equations of body segments constrained by thermoregulatory controls were solved numerically to predict segmental core and skin temperatures, and arterial blood flow for given metabolic rate and environmental conditions. Two similar AVA–CIVD mechanisms were incorporated. The first was activated during drop in local skin temperature (<32 °C). The second mechanism was activated at a minimum finger skin temperature, T _{CIVD, min}, where the AVA flow is dilated and constricted once the skin temperature reached a maximum value. The value of T _CIVD,min was determined empirically from values reported in literature for hand immersions in cold fluid. When compared with published data, the model predicted accurately the onset time of CIVD at 25 min and T _CIVD,min at 10 °C for hand exposure to still air at 0 °C. Good agreement was also obtained between predicted finger skin temperature and experimentally published values for repeated immersion in cold water at environmental conditions of 30, 25, and 20 °C. The CIVD thermal response was found related to core body temperature, finger skin temperature, and initial finger sensible heat loss rate upon exposure to cold fluid. The model captured central and local stimulations of the CIVD and accommodated observed variability reported in literature of onset time of CIVD reaction and T _CIVD,min.     

Correlated fluctuations of daytime skin temperature and vigilance

Skin temperature shows spontaneous ultradian fluctuations during everyday-life wakefulness. Previous work showed that mild manipulations of skin temperature affect human sleep and vigilance, presumably by influencing neuronal systems involved in both thermal sensing and arousal regulation. We therefore examined whether fluctuations in skin temperature are associated with those in vigilance level under conditions similar to everyday-life situations requiring sustained attention. Eight healthy participants (30.1 ± 8.1 years, M ± SD) participated in a 2-day protocol, during which vigilance and skin temperature were assessed 4 times per day in a silent, dimly lit, temperature-controlled room. Vigilance was assessed by measuring reaction speed and lapses on a novel sustained vigilance task specifically designed to increase lapse rate and range of reaction times. Skin temperature was sampled at 30-second intervals from 3 locations: distal, intermediate, and proximal temperatures were obtained from the middle finger (T(finger) ), the wrist (T(wrist)), and the infraclavicular area (T(chest)), respectively. Furthermore, 3 distal to proximal gradients were calculated. Mixed-effect regression analyses were used to evaluate the association of the fluctuations in temperatures and gradients and those in response speed and lapse probability. Especially the spontaneous fluctuations in proximal temperature were negatively associated with fluctuations in response speed and positively with lapse rate. If individual T(chest) temperature ranges were classified into 10 deciles, they accounted for 23% of the variance in response speed and 11% of the variance in lapse rate. The findings indicate coupling between the spontaneous fluctuations in skin temperature and vigilance during the day and are compatible with the hypothesis of overlap in brain networks involved in the regulation of temperature and vigilance. From an applied point of view, especially proximal skin temperature assessment may be of use in vigilance monitoring.     

Finger temperatures during military field training at 0 to −29 °C

1. Skin and rectal temperatures were recorded continuously in 70 measurements during typical tasks of infantry and artillery training at 0 to −29 °C. The duration of the measurements varied from 55 min to 9.5 h.

2. The distribution of finger skin temperatures was quite similar at ambient temperature ranges 0 to −10 °C and −10 to −20 °C, while at −20 to −30 °C the finger temperatures were clearly lower.

3. At different ambient temperature ranges, 20–69% of finger temperatures were low enough to cause cold thermal sensations.

4. Sensation of cold was experienced at a finger temperature of 11.6±3.7 °C (mean±SD).     

Hand temperature norms for headache, hypertension, and irritable bowel syndrome

Hand temperature norms are presented for 221 headache patients (migraine, mixed, and tension), 105 hypertensives, 45 irritable bowel syndrome patients, and 56 normal controls under conditions of resting baseline, self-relaxation, volitional handwarming, mental arithmetic, and cold pressor. The two vascular headache groups (migraine and mixed) had significantly lower hand temperatures across conditions.     

Relationship between body heat content and finger temperature during cold exposure.

The purpose of the present experiment was to examine the relationship between rate of body heat storage (S), change in body heat content (DeltaH(b)), extremity temperatures, and finger dexterity. S, DeltaH(b), finger skin temperature (T(fing)), toe skin temperature, finger dexterity, and rectal temperature were measured during active torso heating while the subjects sat in a chair and were exposed to -25 degrees C air. S and DeltaH(b) were measured using partitional calorimetry, rather than thermometry, which was used in the majority of previous studies. Eight men were exposed to four conditions in which the clothing covering the body or the level of torso heating was modified. After 3 h, T(fing) was 34.9 +/- 0.4, 31.2 +/- 1.2, 18.3 +/- 3.1, and 12.1 +/- 0.5 degrees C for the four conditions, whereas finger dexterity decreased by 0, 0, 26, and 39%, respectively. In contrast to some past studies, extremity comfort can be maintained, despite S that is slightly negative. This study also found a direct linear relationship between DeltaH(b) and T(fing) and toe skin temperature at a negative DeltaH(b). In addition, DeltaH(b) was a better indicator of the relative changes in extremity temperatures and finger dexterity over time than S.     

Seasonal changes in thermal responses of urban residents to cold exposure

To determine whether urban circumpolar residents show seasonal acclimatisation to cold, thermoregulatory responses and thermal perception during cold exposure were examined in young men during January-March (n=7) and August-September (n=8). Subjects were exposed for 24 h to 22 and to 10 degrees C. Rectal (T(rect)) and skin temperatures were measured throughout the exposure. Oxygen consumption (VO(2)), finger skin blood flow (Q(f)), shivering and cold (CDT) and warm detection thresholds (WDT) were assessed four times during the exposure. Ratings of thermal sensations, comfort and tolerance were recorded using subjective judgement scales at 1-h intervals. During winter, subjects had a significantly higher mean skin temperature at both 22 and 10 degrees C compared with summer. However, skin temperatures decreased more at 10 degrees C in winter and remained higher only in the trunk. Finger skin temperature was higher at 22 degrees C, but lower at 10 degrees C in the winter suggesting an enhanced cold-induced vasoconstriction. Similarly, Q(f) decreased more in winter. The cold detection threshold of the hand was shifted to a lower level in the cold, and more substantially in the winter, which was related to lower skin temperatures in winter. Thermal sensations showed only slight seasonal variation. The observed seasonal differences in thermal responses suggest increased preservation of heat especially in the peripheral areas in winter. Blunted vasomotor and skin temperature responses, which are typical for habituation to cold, were not observed in winter. Instead, the responses in winter resemble aggravated reactions of non-cold acclimatised subjects.     

Do chronic primary insomniacs have impaired heat loss when attempting sleep?

For good sleepers, distal skin temperatures (e.g., hands and feet) have been shown to increase when sleep is attempted. This process is said to reflect the body's action to lose heat from the core via the periphery. However, little is known regarding whether the same process occurs for insomniacs. It would be expected that insomniacs would have restricted heat loss due to anxiety when attempting sleep. The present study compared the finger skin temperature changes when sleep was attempted for 11 chronic primary insomniacs [mean age = 40.0 years (SD 13.3)] and 8 good sleepers [mean age = 38.6 years (SD 13.2)] in a 26-h constant routine protocol with the inclusion of multiple-sleep latency tests. Contrary to predictions, insomniacs demonstrated increases in finger skin temperature when attempting sleep that were significantly greater than those in good sleepers (P = 0.001), even though there was no significant differences in baseline finger temperature (P = 0.25). These significant increases occurred despite insomniacs reporting significantly greater sleep anticipatory anxiety (P < 0.0008). Interestingly, the core body temperature mesor of insomniacs (37.0 +/- 0.2 degrees C) was significantly higher than good sleepers (36.8 +/- 0.2 degrees C; P = 0.03). Whether insomniacs could have impaired heat loss that is masked by elevated heat production is discussed.     

Cross-Limb Interference during Motor Learning

It is well known that following skill learning, improvements in motor performance may transfer to the untrained contralateral limb. It is also well known that retention of a newly learned task A can be degraded when learning a competing task B that takes place directly after learning A. Here we investigate if this interference effect can also be observed in the limb contralateral to the trained one. Therefore, five different groups practiced a ballistic finger flexion task followed by an interfering visuomotor accuracy task with the same limb. Performance in the ballistic task was tested before the training, after the training and in an immediate retention test after the practice of the interference task for both the trained and the untrained hand. After training, subjects showed not only significant learning and interference effects for the trained limb but also for the contralateral untrained limb. Importantly, the interference effect in the untrained limb was dependent on the level of skill acquisition in the interfering motor task. These behavioural results of the untrained limb were accompanied by training specific changes in corticospinal excitability, which increased for the hemisphere ipsilateral to the trained hand following ballistic training and decreased during accuracy training of the ipsilateral hand. The results demonstrate that contralateral interference effects may occur, and that interference depends on the level of skill acquisition in the interfering motor task. This finding might be particularly relevant for rehabilitation.     

Effects of Combining 2 Weeks of Passive Sensory Stimulation with Active Hand Motor Training in Healthy Adults

The gold standard to acquire motor skills is through intensive training and practicing. Recent studies have demonstrated that behavioral gains can also be acquired by mere exposure to repetitive sensory stimulation to drive the plasticity processes. Single application of repetitive electric stimulation (rES) of the fingers has been shown to improve tactile perception in young adults as well as sensorimotor performance in healthy elderly individuals. The combination of repetitive motor training with a preceding rES has not been reported yet. In addition, the impact of such a training on somatosensory tactile and spatial sensitivity as well as on somatosensory cortical activation remains elusive. Therefore, we tested 15 right-handed participants who underwent repetitive electric stimulation of all finger tips of the left hand for 20 minutes prior to one hour of motor training of the left hand over the period of two weeks. Overall, participants substantially improved the motor performance of the left trained hand by 34%, but also showed a relevant transfer to the untrained right hand by 24%. Baseline ipsilateral activation fMRI-magnitude in BA 1 to sensory index finger stimulation predicted training outcome for somatosensory guided movements: those who showed higher ipsilateral activation were those who did profit less from training. Improvement of spatial tactile discrimination was positively associated with gains in pinch grip velocity. Overall, a combination of priming rES and repetitive motor training is capable to induce motor and somatosensory performance increase and representation changes in BA1 in healthy young subjects.