Foot temperature in healthy individuals: effects of ambient temperature and age

An Innovative Non-Invasive Method for Early Detection and Monitoring of Acute Compartment Syndrome

Background: Acute compartment syndrome is a major surgical emergency with complex pathophysiology and a highly unpredictable pattern of evolution. We hypothesized that the onset of acute compartment syndrome of the leg or forearm is associated with variations in the surface temperature of the distal segment (foot or hand) with a distinct pattern, which acts as an early warning sign. Materials and Methods: We developed a monitoring device that consists of two thermic sensors attached to a modular limb splint, which continuously measure the temperature difference between the proximal and distal regions of the limb (i.e., arm-hand, thigh-foot). Firstly, we investigated both the arm-hand and thigh-foot temperature gradients of hospitalized patients' healthy limbs (43 patients, 56 upper limbs, 64 lower limbs) in order to establish a baseline. Secondly, we examined the correlation between the thermic gradients and intracompartmental pressure values in compartment syndrome limbs (20 patients, 6 upper limbs, 14 lower limbs). Results: For the control group, the mean values for the normal limb thermic gradients were -0.17 °C for the upper limbs. and 0.03 °C for the lower limbs. In the impending compartment syndrome group (defined by intracompartmental pressure values), the mean index was -0.38 °C. In the fully developed compartment syndrome group, the mean value was 4.11 °C. Discussions: Analysis was performed using the ANOVA one-way statistical method. This showed significant differences between the compartment syndrome group and the impending and control groups. A decreasing trend in the thermic gradient in patients with impending compartment syndrome compared with the control group was noted. Conclusions: The thermic gradient of limbs presenting signs of impending compartment syndrome decreases as a result of the increased temperature of the distal segment. This pattern can be used as an early diagnostic method for acute compartment syndrome. This technique is non-invasive and bears no risk to the patient, allowing facile continuous monitoring during immobilization.

When cooling of the skin is perceived as warmth: Enhanced paradoxical heat sensation by pre-cooling of the skin in healthy individuals

A paradoxical heat sensation (PHS) is the misperception of warmth when the skin is cooled. PHS is uncommon in healthy individuals but common in patients with neuropathy and is associated with reduced thermal sensitivity. Identifying conditions that contribute to PHS may indirectly help us understand why some patients experience PHS. We hypothesized that pre-warming increased the number of PHS and that pre-cooling had minimal effect on PHS. We tested 100 healthy participants' thermal sensitivity on the dorsum of their feet by measuring detection and pain thresholds to cold and warm stimuli and PHS. PHS was measured using the thermal sensory limen (TSL) procedure from the quantitative sensory testing protocol of the German Research Network on Neuropathic Pain and by using a modified TSL protocol (mTSL). In the mTSL we examined the participants' thermal detection and PHS after pre-warming of 38°C and 44°C and pre-cooling of 26°C and 20°C. Compared to a baseline condition, the number of PHS responders was significantly increased after pre-cooling (20°C: RR = 1.9 (1.1; 3.3), p = 0.023 and 26°C: RR = 1.9 (1.2; 3.2), p = 0.017), but not significantly after pre-warming (38°C: RR = 1.5 (0.86; 2.8), p = 0.21 and 44°C: RR = 1.7 (.995; 2.9), p = 0.078). Pre-warming and pre-cooling increased the detection threshold of both cold and warm temperatures. We discussed these findings in relation to thermal sensory mechanisms and possible PHS mechanisms. In conclusion, PHS and thermosensation are closely related and pre-cooling can induce PHS responses in healthy individuals.

Using AI and passive medical radiometry for diagnostics (MWR) of venous diseases

We studied the possibility of using artificial intelligence (AI) passive microwave radiometry (MWR) for the diagnostics of venous diseases. MWR measures non-invasive microwave emission (internal temperature) from human body 4 cm deep. The method has been used for early diagnostics in cancer, back pain, brain, COVID-19 pneumonia, and other diseases. In this paper, an AI model based on MWR data is proposed. The model was used to predict the disease state of phlebology patients. We have used MWR and infrared (skin temperature) data of the lower extremities to design a feature space and construct a classification algorithm. Our method has a sensitivity above 0.8 and a specificity above 0.7. At the same time, our method provides an advisory outcome in terms which are understandable for clinicians.

Early diagnosis of diabetic peripheral neuropathy based on infrared thermal imaging technology

AIMS

The purpose of this study was to detect and compare the surface temperature of plantar vessels in mild diabetic peripheral neuropathy (DPN) patients and healthy controls, to explore a simple, convenient and reliable method for early diagnosis of DPN, and to explore the influence of sex and age on vascular surface temperature.

MATERIALS AND METHODS

In this study, 60 mild DPN patients (30 males and 30 females) and 60 healthy volunteers were randomly recruited according to their age and sex. Intra-class correlation coefficient was used to evaluate the repeatability of skin temperature measurement in the vascular area. A general linear model was used to analyse the difference of skin temperature between mild DPN patients and healthy controls.

RESULTS

The infrared detection results of skin temperature corresponding to blood vessels showed excellent test-retest reliability. There was no significant difference in skin temperature between sex and age. But there were significant differences in skin temperature between mild DPN patients and healthy controls, except for the posterior tibial artery.

CONCLUSIONS

For mild DNP patients, in case of no obvious abnormality in the infrared detection of lower extremity arterial surface temperature, the small vessels have shown early abnormal body surface temperature, that is, the surface temperature of related vessels increased. The research conclusions of this article not only enable us to better understand the correlation between body surface temperature and hemodynamic parameters, but also provide an in vivo, non-invasive, and convenient way of thinking and methods for early diagnosis of DPN.

Effects of Nurse and Care Worker-led Foot-Care Program on Older People's Foot Conditions: Before and After Intervention Study

INTRODUCTION

An increasing number of older people with frailty in Japan use geriatric day care centers. Older people who have been certified as requiring long-term care attend centers during the day and receive nursing care help with bathing, excretion, meals, and functional training services. Many older people have foot problems with need foot care by nurses and care workers (NCWs) at geriatric day care centers.

OBJECTIVE

This study explored the effects of NCWs' foot-care programs on the foot conditions of older people attending daytime services.

METHODS

A before-after intervention study was conducted at geriatric day care centers for older people, where the foot-care program was presented by NCWs for two months. The foot conditions of 23 clients (8 men, 15 women, mean age = 78.6 years, standard deviation = 9.2) were assessed before and after the program. Changes in foot condition and clients' perceptions after the study were analyzed through descriptive statistics, McNemar, and paired t-tests.

RESULTS

Although dramatic changes in foot conditions were not observed, some conditions were improved or maintained. Changes were observed in mean dry skin scores (p < .01; right foot: 1.6→1.1, left foot: 1.6→1.1), skin lesions and long nails (skin lesions R: 0.2→0.1; long nail R: 1.4→1.0, L: 1.1→0.8), and edema (R: 43.5%→39.1%, L: 52.2%→47.8%). Further, clients started perceiving that foot health is important and discussed their feet with staff more often.

CONCLUSION

The NCWs' foot-care program was effective in maintaining and improving foot health in older people and positively affected their perception of foot care.

Objective measurement of adherence to wearing foot orthoses using an embedded temperature sensor

The objective of this study was to evaluate the validity of a temperature sensor for the measurement of adherence to wearing foot orthoses. Ten participants were provided with foot orthoses containing an embedded temperature sensor and wore the orthoses for a randomly-determined duration over a five-day period. Sensor-detected wear time was compared to a reference standard (objectively measured wear time using a smart-phone application). Ambient temperature and physical activity were recorded with a temperature gauge and wearable activity tracker, respectively. A simple peak detection algorithm which identified the largest one-minute changes in sensor temperature provided highly accurate wear time values (r = 0.999, coefficient of variation=0.2%). Ambient temperature and physical activity did not significantly influence temperature sensor scores. These findings demonstrate that the temperature sensor provides accurate foot orthosis wear time data and may therefore be a useful tool for documenting adherence in clinical practice and intervention studies.

Unilateral remote temperature monitoring to predict future ulceration for the diabetic foot in remission

OBJECTIVE

Daily remote foot temperature monitoring is an evidence-based preventive practice for patients at risk for diabetic foot complications. Unfortunately, the conventional approach requires comparison of temperatures between contralaterally matched anatomy, limiting practice in high-risk cohorts such as patients with a wound to one foot and those with proximal lower extremity amputation (LEA). We developed and assessed a novel approach for monitoring of a single foot for the prevention and early detection of diabetic foot complications. The purpose of this study was to assess the sensitivity, specificity, and lead time associated with unilateral diabetic foot temperature monitoring.

RESEARCH DESIGN AND METHODS

We used comparisons among ipsilateral foot temperatures and between foot temperatures and ambient temperature as a marker of inflammation. We analyzed data collected from a 129-participant longitudinal study to evaluate the predictive accuracy of our approach. To evaluate classification accuracy, we constructed a receiver operator characteristic curve and reported sensitivity, specificity, and lead time for four different monitoring settings.

RESULTS

Using this approach, monitoring a single foot was found to predict 91% of impending non-acute plantar foot ulcers on average 41 days before clinical presentation with a resultant mean 4.2 alerts per participant-year. By adjusting the threshold temperature setting, the specificity could be increased to 78% with corresponding reduced sensitivity of 53%, lead time of 33 days, and 2.2 alerts per participant-year.

CONCLUSIONS

Given the high incidence of subsequent diabetic foot complications to the sound foot in patients with a history of proximal LEA and patients being treated for a wound, practice of daily temperature monitoring of a single foot has the potential to significantly improve outcomes and reduce resource utilization in this challenging high-risk population.

A Novel Method to Determine Dynamic Temperature Trends Applied to In-Shoe Temperature Data During Walking

Body temperature is one of the fundamental measures considered in the assessment of health and well-being, with various medical conditions known to give rise to abnormal changes in temperature. In particular, abnormal variations in dynamic temperature patterns during walking or exercise may be linked to a range of foot problems, which are of particular concern in diabetic patients.A number of studies have investigated normative temperature patterns of a population by considering data from multiple participants and averaging results after an acclimatisation interval. In this work we demonstrate that the temperature patterns obtained using such an approach may not be truly representative of temperature changes in a population, and the averaging process adopted may yield skewed results.An alternative approach to determine generic reference temperature patterns based on a minimization of root mean square differences between time-shifted versions of temperature data collected from multiple participants is proposed. The results obtained indicate that this approach can yield a general trend that is more representative of actual temperature changes across a population than conventional averaging methods. The method we propose is also shown to better capture and link the effects of factors that influence dynamic temperature trends, which could in turn lead to a better understanding of underlying physiological phenomena.

Brief Report: Monosodium Urate Monohydrate Crystal Deposits Are Common in Asymptomatic Sons of Patients With Gout: The Sons of Gout Study

OBJECTIVE

To estimate the prevalence and distribution of asymptomatic monosodium urate monohydrate (MSU) crystal deposition in sons of patients with gout.

METHODS

Patients with gout were mailed an explanatory letter with an enclosed postage-paid study packet to mail to their son(s) age ≥20 years old. Sons interested in participating returned a reply form and underwent telephone screening. Subsequently, they attended a study visit at which blood and urine samples were obtained and musculoskeletal ultrasonography was performed, with the sonographer blinded with regard to the subject's serum urate level. Images were assessed for double contour sign, intraarticular or intratendinous aggregates/tophi, effusion, and power Doppler signal. Logistic regression was used to examine associations. Adjusted odds ratios (OR_adj ) and 95% confidence intervals (95% CIs) were calculated.

RESULTS

One hundred thirty-one sons (mean age 43.8 years, mean body mass index 27.1 kg/m² ) completed assessments. The serum urate level was ≥6 mg/dl in 64.1%, and 29.8% had either a double contour sign or intraarticular aggregates/tophi in ≥1 joint. All participants with MSU deposition had involvement of 1 or both first metatarsophalangeal joints. Intratendinous aggregates were present in 21.4% and were associated with intraarticular MSU crystal deposits (OR_adj 2.96 [95% CI 1.17-7.49]). No participant with a serum urate level of ≤5 mg/dl had MSU crystal deposition seen on ultrasonography, and 24.2% of those with serum urate levels between 5 and 6 mg/dl had ultrasonographic MSU deposition. MSU crystal deposition was associated with increasing serum urate levels (OR_adj 1.61 [95% CI 1.10-2.36] for each increase of 1 mg/dl).

CONCLUSION

Asymptomatic sons of patients with gout frequently have hyperuricemia and MSU crystal deposits. In this study MSU crystal deposits were present in participants with serum urate levels of ≥5 mg/dl. Evaluation of subjects without a family history of gout is needed to determine whether the threshold for MSU crystal deposition is also lower in the general population.

The thermoregulation of healthy individuals, overweight-obese, and diabetic from the plantar skin thermogram: a clue to predict the diabetic foot

Background: Thermoregulation is a complex autonomic process to keep or to dissipate heat in the human body.

Methods: In this work, by means of the thermogram of the plantar skin, the thermoregulation of healthy individuals, overweight–obese, and diabetic is discussed.

Results: The thermograms of the plantar skin, for the healthy individuals, are: (1) symmetrical, the temperature distribution of the right foot being a mirror image of that of the left foot ; (2) the thermograms of women, on average, are 3°C colder than those of the men; and (3) the temperature distributions decrease distally from the medial longitudinal arch. The plantar skin thermograms of overweight–obese individuals show: (1) increased average temperature of both feet and for both genders; (2) no symmetry between the left and right feet thermograms; and (3) the temperature distribution is still decreasing from the medial longitudinal arch to the periphery of the foot. However, the standard deviation, for each averaged temperature of the angiosomes, shows greater uncertainty. Most thermograms of diabetic individuals show temperature increase on the plantar skin, and are mostly symmetric between left and right feet.

Conclusions: An asymmetric thermogram of the plantar skin of diabetic individuals, where one foot is hotter than the other, may mean that the coldest foot is losing the capacity to communicate properly with the central nervous system and/or that vasoconstriction/vasodilatation is having problems in regulating the passing of blood through the vessels. Thus, the asymmetric thermograms of diabetic patients, and particularly those coldest regions of foot are of interest, because of the reduction of the local autonomic sensing and the lack of achieving properly the passing of the blood.

A Study of Thermistor Performance within a Textile Structure

Textiles provide an ideal structure for embedding sensors for medical devices. Skin temperature measurement is one area in which a sensor textile could be particularly beneficial; pathological skin is normally very sensitive, making the comfort of anything placed on that skin paramount. Skin temperature is an important parameter to measure for a number of medical applications, including for the early detection of diabetic foot ulcer formation. To this end an electronic temperature-sensor yarn was developed by embedding a commercially available thermistor chip into the fibres of a yarn, which can be used to produce a textile or a garment. As part of this process a resin was used to encapsulate the thermistor. This protects the thermistor from mechanical and chemical stresses, and also allows the sensing yarn to be washed. Building off preliminary work, the behaviour and performance of an encapsulated thermistor has been characterised to determine the effect of encapsulation on the step response time and absolute temperature measurements. Over the temperature range of interest only a minimal effect was observed, with step response times varying between 0.01–0.35 s. A general solution is presented for the heat transfer coefficient compared to size of the micro-pod formed by the encapsulation of the thermistor. Finally, a prototype temperature-sensing sock was produced using a network of sensing yarns as a demonstrator of a system that could warn of impending ulcer formation in diabetic patients.

When Do Skeletal Class III Patients Wear Their Reverse Pull Headgears?

Objective. The aim of this study is to evaluate the factors that affect wearing time and patient behavior during reverse pull headgear therapy with a newly designed reverse pull headgear. Methods. In clinical practice, new reverse pull headgears were applied to fifteen patients. The patients were monitored during reverse pull headgear therapy and the data were evaluated. Statistical analysis was made. Results. During the study, patients were monitored successfully and the evaluations showed that patients wear the new reverse pull headgears mostly at night. There are differences between days of week and hours of day. Weekends are more popular than weekdays for wearing reverse pull headgear. Conclusions. This new type of reverse pull headgears can be used successfully in clinical practice and can help the clinician. Study showed that the most important factor that affects the cooperation of reverse pull headgear patient is aesthetic appearance.

Foot model for tracking temperature of safety boot insoles: application to different insole materials in firefighter boots

This research is based on the development of a human foot model to study the temperature conditions of a foot bottom surface under extreme external conditions. This foot model is made by combining different manufacturing techniques to enable the simulation of bones and tissues, allowing the placement of sensors on its surface to track the temperature values of different points inside a shoe. These sensors let researchers capture valuable data during a defined period of time, making it possible to compare the features of different safety boots, socks or soles, among others. In this case, it has been applied to compare different plantar insole materials, placed into safety boots on a high-temperature surface.

Distal-proximal skin temperature gradient prior to sleep onset in infants for clinical use

BACKGROUND

The objective of this study was to explore the possibility of using distal-proximal skin temperature gradient (DPG) to predict sleep-onset latency of night-time sleep for infants at home.

METHODS

Foot (for distal) and abdominal (for proximal) skin temperature during sleep onset in healthy infants, aged 4-9 months, was continuously recorded using a temperature logger at home. Sleep-onset latency during each study night was defined as the interval from lights-off to sleep onset, determined on actigraphy. Association of DPG profile after lights-off with sleep-onset latency on the study nights was evaluated.

RESULTS

Data for 43 nights from 28 infants were available for analysis. With regard to low DPG (<-2.5°C) at lights-off, >60% of infants fell asleep within 30 min if DPG was increased to ≥-2.5°C within 15 min after lights-off. If DPG remained at <-2.5°C at 15 min after lights-off, however, only 20% of infants fell asleep within 30 min. In addition, if infants were still awake at 15 min after lights-off and the DPG at that time was <-2.5°C, they were not likely to quickly fall asleep (predictive value was 0.875).

CONCLUSIONS

Increase in DPG by 15 min after lights-off is a key determinant for sleep-onset latency.

Personalized foot orthoses with embedded temperature sensing: Proof of concept and relationship with activity

Plantar foot surface temperature has been identified as a clinically relevant physiological variable. Embedding sensors in foot orthoses (FOs) may allow long term monitoring of these temperatures, with compliance via the detection of periods of activity being a potential clinical utilization. This study aimed to test novel designs for FOs with embedded sensing that were produced via additive manufacturing and determine if foot temperature measurements could be used to detect periods of increased activity. FOs with embedded temperature sensors were developed and tested in 10 healthy participants over four day wear periods. Activity monitoring was used to estimate energy expenditure during testing. A threshold-based algorithm was developed to identify time periods of high activity from foot temperature data. Group differences in estimated energy expenditure between time periods below and above the threshold were significant in both the training and validation sets (p<0.001). Significant differences were also seen at individual participant level (p<0.001 in all cases). These results demonstrate the feasibility of using FOs with embedded sensing to monitor plantar surface foot temperatures during normal daily activities and for extended periods and show that periods of increased activity can be identified using foot temperature data.

Decreased skin temperature of the foot increases gait variability in healthy young adults

We investigated the effects of reduction in plantar skin temperature on gait. Thirty-four healthy subjects (20 men and 14 women; mean age 22.2±2.5 years; mean height 166.8±8.3cm) walked 16m under two different conditions - normal conditions (NC) with the skin at a basal temperature, and cold conditions (CC) after cooling of the plantar skin to about 15°C. Wireless motion-recording sensor units were placed on the back at the level of L3 and on both heels to measure acceleration and angular velocity. Gait velocity and mean stride, stance and swing times were calculated. The variability of lower limb movement was represented by the coefficients of variation (CVs) of stride, stance and swing times, and that of trunk movement was represented by autocorrelation coefficients (ACs) in three directions (vertical: VT; mediolateral: ML; and anteroposterior: AP). Gait velocity was significantly lower under CC conditions than under NC (p<0.0001). None of the temporal parameters were changed by plantar cooling. However, all parameters of gait variability were significantly worse under CC, and AC-VT, AC-ML, and AC-AP were significantly lower under CC than under NC, even after adjusting for gait velocity (p=0.0005, 0.0071, and 0.0126, respectively). Our results suggest that reducing plantar skin temperature induces gait variability among healthy young adults. Further studies are now needed to explore the relationship between plantar skin temperature and gait in the elderly.

Sensory functions in the foot soles in victims of generalized torture, in victims also beaten under the feet (falanga) and in healthy controls - A blinded study using quantitative sensory testing

Background

Falanga torture (beatings on the foot soles) produces local chronic pain and severe walking difficulties. We have previously reported signs of neuropathic pain in the feet of falanga victims. The objective here was to clarify underlying pain mechanisms by quantifying sensory impairments in the feet of torture victims who had experienced both generalized torture and those who had been exposed to falanga in addition. An ethnically matched control group was available.

Methods

We employed quantitative sensory testing (QST) by investigators blinded to whether the patients, 32 male torture victims from the Middle East, had (n=15), or had not (n=17) been exposed to falanga. Pain intensity, area and stimulus dependence were used to characterize the pain as were interview data on sensory symptoms. QST included thresholds for touch, cold, warmth, cold-pain, heat-pain, deep pressure pain and wind-up to cutaneous noxious stimuli in the foot soles. Clinical data on anxiety and depression were retrieved.

Results

Almost all falanga victims had moderate or strong pain in their feet and in twice as large an area of their foot soles as other torture victims. One-third of the latter had no pain in their feet and many reported slight pain; in spite of this, there were no differences in foot sole QST data between the tortured groups. A comparison with normal data indicated that both tortured groups had hypoesthesia for all cutaneous sensory fibre groups except those transmitting cold and heat pain, in addition to deep mechano-nociceptive hyperalgesia.

Conclusion

A comparison of the QST data between victims having been exposed to generalized torture and victims who in addition had been exposed to falanga, showed no differences on the group level. The sensory disturbances in relation to our control group are compatible with central sensitization and de-sensitization, pointing to a core role of central mechanisms. A further analysis to create individual sensory profiles from our measurements is in progress.