Cold Thresholds Research Articles

High-dose desloratadine decreases wheal volume and improves cold provocation thresholds compared with standard-dose treatment in patients with acquired cold urticaria: A randomized, placebo-controlled, crossover study

Increased dosing of nonsedating antihistamines is recommended by the current European Academy of Allergology and Clinical Immunology/Global Allergy and Asthma European Network/European Dermatology Forum guidelines on patients with acquired cold urticaria (ACU) who do not respond satisfactorily to the standard dose. Prospective data supporting this recommendation are scant. We sought to assess the effects of 5 and 20 mg of desloratadine and placebo on cold-induced urticarial reactions in patients with ACU. In this prospective, randomized, double-blind, 3-way crossover trial, patients with ACU (n = 30) received placebo, 5 mg of desloratadine, and 20 mg of desloratadine every day each for 7 days separated by 14-day washout periods. At the end of each treatment, patients underwent cold provocation with the TempTest 2.0/2.1 system, and urticarial reactions were assessed by using digital 3-dimensional time-lapse photography and thermography; the critical temperature threshold (CTT) and critical stimulation time threshold (CSTT) were measured. Adverse events (AEs) reported during the study were assessed. Compared with placebo, 7 days of desloratadine at 5 and 20 mg/d significantly reduced the volume of cold-induced wheals and areas of hyperthermic skin and improved CTT and CSTT results. Desloratadine at 20 mg/d significantly reduced cold-induced wheal volume and CTT and CSTT values versus desloratadine at 5 mg/d. Desloratadine was well tolerated, with no increased rate of somnolence or other AEs with 20 mg of desloratadine. Desloratadine at standard and high doses significantly improved objective signs of ACU provoked by cold exposure. Desloratadine at 4 times the standard dose significantly reduced ACU lesion severity versus 5 mg of desloratadine without an increase in AEs. This study supports current guidelines that increased desloratadine dosing might benefit patients with urticaria who do not respond to standard doses.

Climate‐driven range extension of a sea urchin: inferring future trends by analysis of recent population dynamics

AbstractPatterns of climate‐forced range shift in the marine environment are informed by investigating the population dynamics of an ecologically important sea urchin (Centrostephanus rodgersii– Diadematidae) across its newly extended range in Tasmania (southeastern Australia). A growth model of C. rodgersii is developed allowing estimation of a sea urchin age profile and, in combination with abundance data, we correlate the sea urchin population dynamic with respect to environmental signals across the range extension region. Growth patterns did not vary across the extension region; however, there was a strong pattern of decreasing sea urchin age with increasing distance from the historic range. The sequential poleward discovery of the sea urchin, a pattern of declining age and a general poleward reduction in abundance along the eastern Tasmanian coastline are consistent with a model of range extension driven by recent change in patterns of larval dispersal. We explore this hypothesis by correlating C. rodgersii population characteristics with respect to the East Australian Current (EAC), i.e. the chief vector for poleward larval dispersal, and reveal patterns of declining sea urchin age and abundance with increasing distance from this oceanic feature. Furthermore, C. rodgersii is generally limited to sites where average winter temperatures are warmer than the cold threshold for its larval development. Potential dispersal and physiological mechanisms defining the range extension appear to be strongly coupled to the EAC which has undergone recent poleward advance and resulted in coastal warming in eastern Tasmania. Predicted climate change conditions for this region will favour continued population expansion of C. rodgersii not only via atmospheric‐forced ocean warming, but also via ongoing intensification of the EAC driving continued poleward supply of larvae and heat.

Thermal discrimination thresholds: a comparison of different methods

Thermal testing was carried out on 55 healthy subjects in order to establish normal results and reproducibility of warm and cold thresholds. Diurnal variations of thresholds were investigated in a further 30 normal subjects. Then the sensitivity of different testing procedures was investigated in 33 patients with diabetes mellitus, but without severe polyneuropathy. Forced choice testing takes 6 times longer than the method of limits, and the results are not considerably different. It is thought that the forced choice algorithm does not provide a method for clinical routine. Another new approach, the double random staircase method, may help to exclude bias without taking too much time.

Mechano- and thermosensitivity of regenerating cutaneous afferent nerve fibers

Crush lesion of a skin nerve is followed by sprouting of myelinated (A) and unmyelinated (C) afferent fibers into the distal nerve stump. Here, we investigate quantitatively both ongoing activity and activity evoked by mechanical or thermal stimulation of the nerve in 43 A- and 135 C-fibers after crush lesion of the sural nerve using neurophysiological recordings in anesthetized rats. The discharge patterns in the injured afferent nerve fibers and in intact (control) afferent nerve fibers were compared. (1) Almost all (98%) A-fibers were mechanosensitive, some of them exhibited additionally weak cold/heat sensitivity; 7% had ongoing activity. (2) Three patterns of physiologically evoked activity were present in the lesioned C-fibers: (a) C-fibers with type 1 cold sensitivity (low cold threshold, inhibition on heating, high level of ongoing and cold-evoked activity; 23%): almost all of them were mechanoinsensitive and 40% of them were additionally heat-sensitive; (b) C-fibers with type 2 cold sensitivity (high cold threshold, low level of ongoing and cold-evoked activity; 23%). All of them were excited by mechanical and/or heat stimuli; (c) cold-insensitive C-fibers (54%), which were heat- and/or mechanosensitive. (3) The proportions of C-fibers exhibiting these three patterns of discharge to physiological stimuli were almost identical in the population of injured C-fibers and in a population of 91 intact cutaneous C-fibers. 4. Ongoing activity was present in 56% of the lesioned C-fibers. Incidence and rate of ongoing activity were the same in the populations of lesioned and intact type 1 cold-sensitive C-fibers. The incidence (but not rate) of ongoing activity was significantly higher in lesioned type 2 cold-sensitive and cold insensitive C-fibers than in the corresponding populations of intact C-fibers (42/93 fibers vs. 11/72 fibers).

ヒトの手掌部の温冷感覚特性の評価とその活用法の検討

Tactile sense as third human sensoria has been presently considered to apply to use for developing device of information presentation at international level. In this study, we focused on thermal and cold sensorial characteristic that has fully been not used until now, and investigated thermal and cold sensitivity and considered the possibility of effective use of the sense for some sort of working in daily life. Concretely, we examined threshold level of thermal and cold sense by reference to 30 degrees Celsius (°C). Spontaneously, the influence of positions (tip of thirst finger, ball of the thumb and tip of fourth finger) in palma on the threshold was investigated. And we also assessed the possibility of use of the thermal and cold sense as e-mail reception trigger during PC work. The results show that thermal and cold thresholds on ball of the thumb were smallest in the three positions (thermal threshold: 6°C, cold one: 4°C). It was also found that we can use the thermal and cold sense as e-mail reception trigger during PC work. From this study, these knowledge may be assistance to develop some interface for handicapped people (especially, hearing-impaired people and visual impairment) and weak sight-or-hearing aged persons.

Modelling the non-linear multiple-lag effects of ambient temperature on mortality in Santiago and Palermo: a constrained segmented distributed lag approach

Objectives:Exposure to ambient temperature can affect mortality levels for days or weeks following exposure, making modelling such effects in regression analysis of daily time-series data complex.Methods:We propose a new approach...

Surgical Techniques: Dorsal Slit Surgery for Clitoral Phimosis

Female sexual dysfunction (FSD) is multifactorial, with psychological and organic elements. Genital sensation, an important component of sexual response, has until recently not been subjected to adequate clinical appraisal. During the past 15 years we have performed Quantitative Sensory Testing (QST) to assess genital sensation in healthy women and women with FSD.To review available evidence of QST in the investigation of genital sensation in women with FSD.We examined data obtained from assessment of genital sensation in normal women and those with different conditions, including multiple sclerosis, pelvic floor disorders, effect of hysterectomy, and vulvar vestibulitis.Use of QST for assessment of FSD.Normograms for healthy women were used to measure parameters during arousal, orgasm, and the refractory phase. Using QST, genital sensation was found to be impaired in women with multiple sclerosis. Clitoral vibratory sensation most significantly correlated with FSD parameters. Women with greater deficit in vibratory sensation encountered more sexual dysfunction. Women with urinary incontinence had a significant decrease in sensitivity to warm, cold, and vibratory thresholds in the anterior vaginal wall and clitoral area. A study comparing women with and without pelvic organ prolapse showed mean thresholds for vibratory and warm stimuli to be significantly higher and mean thresholds for cold stimuli to be significantly lower in the group with prolapse. QST of women undergoing hysterectomy showed a significant decrease in sensation to cold, warm, and vibratory stimuli at the anterior and posterior vaginal wall; clitoral thermal and vibratory sensation thresholds remained unchanged after surgery. In a study of vulvar vestibulitis, patients reported significantly lower heat pain thresholds compared with controls.QST appears useful for evaluating various gynecologic disorders associated with disturbed sexual function and with multiple sclerosis, which might be accompanied by disturbed genital sensation.

Comparison between sensory testing modalities for the evaluation of afferent nerve functioning in the genital area

Determine the reproducibility and relationship between current perception threshold testing (CPT) and quantitative sensory testing (QST) in the genital area. Sixteen women underwent CPT and QST of the vagina. CPT was done at 2,000, 250, and 5 Hz (corresponding to A-beta, A-delta, and C fibers, respectively), and QST testing was done using thermal (C fibers), vibratory (A-beta fibers), and cold (A-delta and C fibers) sensation. Ten women underwent repeated testing 1 week later. Thermal and vibratory thresholds correlated with CPT at 5 and 2,000 Hz (rho = 0.77, P = 0.002 and rho = 0.6, P = 0.01, respectively). Repeated thermal, vibratory, and cold thresholds had good concordance correlation (rho_(c) = 0.83, rho_(c) = 0.96, rho_(c) = 0.77). CPT at 5 and 2,000 Hz were also strongly correlated (rho_(c) = 69, rho_(c) = .7). CPT and QST testing stimulate similar afferent nerve fiber populations in the vagina.

High resolution topographical mapping of warm and cold sensitivities

Objective This study aims to explore the thermal sensitivity distribution (topographical mapping) over the glabrous skin of the hand in males and females. Methods Warm (WT) and cold (CT) thresholds were measured in 25 healthy volunteers (12 females), applying a multi-site test of 23 locations on the volar part of the hand. Results The palm area was more sensitive than the fingers to both warm ( P < 0.001) and cold ( P < 0.001) stimuli. On the palm itself, the proximal part was the most sensitive ( P < 0.05). Heterogeneity was also found to both warm and cold sensibilities within dermatomes ( P < 0.05) as well as to cold sensitivity across dermatomes ( P < 0.001). Females were more sensitive than males to both warm ( P < 0.001) and cold sensations ( P < 0.001). In addition, painful components were frequently reported as accompanying warm/cold sensations during mild warming/cooling. Conclusions The thermal sensitivity distribution over the glabrous skin of the hand is highly heterogeneous. Significance It is appropriate to precisely define testing locations when conducting thermal examinations on the hand.

Analysis of clinical usefulness of the heat flux technique: predictability of the recovery from neurosensory disturbances in the chin undergoing mandibular sagittal split ramus osteotomy

To examine the prognosis of the neurosensory disturbance (NSD) in the chin after bilateral sagittal split ramus osteotomy (BSSRO), using the heat flux technique. Twenty-nine patients (total 58 sides) undergoing BSSRO were examined. The warm sensory threshold (WHF) and cold sensory threshold (CHF) in the chins of these patients were measured by the heat flux technique. Touch sensory threshold (TS) was measured by an Semmes-Weinstein esthesiometer. Touch sensory disturbance was subjectively evaluated by visual analog scale. At all of the postoperative time points, there were no significant differences in the incidence rate among all tests (chi-squared test; P > .05). WHF, CHF, and TS were significantly correlated with the subjective evaluation. Recovery from NSD was delayed in cases that the postoperative variation of 2 weeks was >400 W/m(2) in WHF and CHF and the filament marking at 2 weeks after surgery was >3.5 in TS. The heat flux technique appears to be a useful method for the prediction of the recovery from NSD in the chin.

Quantitative testing of pain perception in subjects with PTSD – Implications for the mechanism of the coexistence between PTSD and chronic pain

Post-traumatic stress disorder (PTSD) often co-occurs with chronic pain. Neither the underlying mechanism of this comorbidity nor the nature of pain perception among subjects with PTSD is well defined. This study is the first systematic and quantitative evaluation of pain perception and chronic pain in subjects with PTSD. The study group consisted of 32 outpatients with combat- and terror-related PTSD, 29 outpatients with anxiety disorder and 20 healthy controls. Quantitative somatosensory testing included the measurement of warm, cold, light touch and heat-pain thresholds and responses to acute suprathreshold heat and mechanical stimuli. Chronic pain was characterized, and levels of PTSD and anxiety symptomatology were assessed by self-report questionnaires. Subjects with PTSD exhibited higher rates of chronic pain, more intense chronic pain and more painful body regions compared with the other two groups. PTSD severity correlated with chronic pain severity. Thresholds of subjects with PTSD were significantly higher than those of subjects with anxiety and healthy controls, but they perceived suprathreshold stimuli as being much more intense than the other two groups. These results suggest that subjects with PTSD exhibit an intense and widespread chronic pain and a unique sensory profile of hyposensitivity to pain accompanied by hyper-reactivity to suprathreshold noxious stimuli. These features may be attributed to the manner with which PTSD subjects emotionally interpret and respond to painful stimuli. Alternatively, but not mutually exclusive, the findings may reflect altered sensory processing among these subjects.

Early diabetic neuropathy: thermal thresholds and intraepidermal nerve fibre density in patients with normal nerve conduction studies

To determine whether neuropathy in diabetic patients with normal nerve conduction studies could be detected by measurements of thermal thresholds and quantification of intraepidermal nerve fibre (IENF) density, and to evaluate differences in parameters between patients with and without neuropathic symptoms. A total of 22 patients with and 37 patients without sensory symptoms suggesting distal neuropathy were included. Measurements of warm and cold perception thresholds and skin biopsy for quantification of IENFs were performed distally on the leg. Reference data were used to normalize test results for age and height or gender of individual patients by calculating the Z-scores. IENF density was significantly reduced in both symptomatic and asymptomatic patients compared to controls (p < 0.001), and in patients with symptoms compared to those without (p = 0.01). Thermal thresholds were significantly elevated (more abnormal) in patients with symptoms compared to controls (p < 0.01), but only for cold perception threshold (CPT) (p < 0.001) in the asymptomatic group. When comparing symptomatic and asymptomatic patients, there was no statistically significant difference in thermal thresholds. Depletion of IENFs in skin biopsy was the most frequent abnormal finding in the subgroup of patients with neuropathic symptoms (36 %) followed by abnormal CPT (27 %). Patients with diabetes and normal nerve conduction studies had significantly lower IENF density and higher CPT than controls, whether they had symptoms of polyneuropathy or not. In patients with neuropathic symptoms, abnormal IENF density predominated and seemed thus to be the most sensitive tool of detecting small diameter nerve fibre involvement.

The diagnostic criteria for small fibre neuropathy: from symptoms to neuropathology

Small fibre neuropathy (SFN), a condition dominated by neuropathic pain, is frequently encountered in clinical practise either as prevalent manifestation of more diffuse neuropathy or distinct nosologic entity. Aetiology of SFN includes pre-diabetes status and immune-mediated diseases, though it remains frequently unknown. Due to their physiologic characteristics, small nerve fibres cannot be investigated by routine electrophysiological tests, making the diagnosis particularly difficult. Quantitative sensory testing (QST) to assess the psychophysical thresholds for cold and warm sensations and skin biopsy with quantification of somatic intraepidermal nerve fibres (IENF) have been used to determine the damage to small nerve fibres. Nevertheless, the diagnostic criteria for SFN have not been defined yet and a ‘gold standard’ for clinical practise and research is not available. We screened 486 patients referred to our institutions and collected 124 patients with sensory neuropathy. Among them, we identified 67 patients with pure SFN using a new diagnostic ‘gold standard’, based on the presence of at least two abnormal results at clinical, QST and skin biopsy examination. The diagnosis of SFN was achieved by abnormal clinical and skin biopsy findings in 43.3% of patients, abnormal skin biopsy and QST findings in 37.3% of patients, abnormal clinical and QST findings in 11.9% of patients, whereas 7.5% patients had abnormal results at all the examinations. Skin biopsy showed a diagnostic efficiency of 88.4%, clinical examination of 54.6% and QST of 46.9%. Receiver operating characteristic curve analysis confirmed the significantly higher performance of skin biopsy comparing with QST. However, we found a significant inverse correlation between IENF density and both cold and warm thresholds at the leg. Clinical examination revealed pinprick and thermal hypoesthesia in about 50% patients, and signs of peripheral vascular autonomic dysfunction in about 70% of patients. Spontaneous pain dominated the clinical picture in most SFN patients. Neuropathic pain intensity was more severe in patients with SFN than in patients with large or mixed fibre neuropathy, but there was no significant correlation with IENF density. The aetiology of SFN was initially unknown in 41.8% of patients and at 2-year follow-up a potential cause could be determined in 25% of them. Over the same period, 13% of SFN patients showed the involvement of large nerve fibres, whereas in 45.6% of them the clinical picture did not change. Spontaneous remission of neuropathic pain occurred in 10.9% of SFN patients, while it worsened in 30.4% of them.

International study of temperature, heat and urban mortality: the ‘ISOTHURM’ project

This study describes heat- and cold-related mortality in 12 urban populations in low- and middle-income countries, thereby extending knowledge of how diverse populations, in non-OECD countries, respond to temperature extremes. The cities were: Delhi, Monterrey, Mexico City, Chiang Mai, Bangkok, Salvador, São Paulo, Santiago, Cape Town, Ljubljana, Bucharest and Sofia. For each city, daily mortality was examined in relation to ambient temperature using autoregressive Poisson models (2- to 5-year series) adjusted for season, relative humidity, air pollution, day of week and public holidays. Most cities showed a U-shaped temperature-mortality relationship, with clear evidence of increasing death rates at colder temperatures in all cities except Ljubljana, Salvador and Delhi and with increasing heat in all cities except Chiang Mai and Cape Town. Estimates of the temperature threshold below which cold-related mortality began to increase ranged from 15 degrees C to 29 degrees C; the threshold for heat-related deaths ranged from 16 degrees C to 31 degrees C. Heat thresholds were generally higher in cities with warmer climates, while cold thresholds were unrelated to climate. Urban populations, in diverse geographic settings, experience increases in mortality due to both high and low temperatures. The effects of heat and cold vary depending on climate and non-climate factors such as the population disease profile and age structure. Although such populations will undergo some adaptation to increasing temperatures, many are likely to have substantial vulnerability to climate change. Additional research is needed to elucidate vulnerability within populations.

The effect of acupuncture duration on analgesia and peripheral sensory thresholds

BackgroundAcupuncture provides a means of peripheral stimulation for pain relief. However, the detailed neuronal mechanisms by which acupuncture relieves pain are still poorly understood and information regarding optimal treatment settings is still inadequate. Previous studies with a short burst of unilateral electroacupuncture (EA) in the Tendinomuscular Meridians (TMM) treatment model for pain demonstrated a transient dermatomally correlated bilateral analgesic effect with corresponding peripheral modality-specific sensory threshold alterations. However, the impact of EA duration on the analgesic effect in this particular treatment model is unknown. To obtain mechanistically and clinically important information regarding EA analgesia, this current prospective cross-over study assesses the effects of EA duration on analgesia and thermal sensory thresholds in the TMM treatment model.MethodsBaseline peripheral sensory thresholds were measured at pre-marked testing sites along the medial aspects (liver and spleen meridians) of bilateral lower extremities. A 5-second hot pain stimulation was delivered to the testing sites and the corresponding pain Visual Analog Scale (VAS) scores were recorded. Three different EA (5Hz) stimulation durations (5, 15 and 30 minutes) were randomly tested at least one week apart. At the last 10 seconds of each EA session, 5 seconds of subject specific HP stimulation was delivered to the testing sites. The corresponding pain and EA VAS scores of de qi sensation (tingling) during and after the EA were recorded. The measurements were repeated immediately, 30 and 60 minutes after the EA stimulation. A four-factor repeat measures ANOVA was used to assess the effect of stimulation duration, time, location (thigh vs. calf) and side (ipsilateral vs. contralateral) of EA on sensory thresholds and HP VAS scores.ResultsA significant (P < 0.01) main effect of time and location with warm, cold and hot pain thresholds at the four testing sites without any significant difference in duration effect was observed. Similar time and location effects were observed with HP VAS with the longer durations (15 and 30 minutes) of stimulation showed a slower onset, but a more sustainable bilateral analgesic benefit than the short stimulation duration (5 minutes). The 15-minute stimulation resulted in an earlier onset of analgesic effect than the 30-minute stimulation paradigm.ConclusionLonger durations of EA stimulation provide a more sustainable analgesic benefit to hot noxious stimulation than a shorter duration of stimulation. The increase of cold threshold with sustained warm threshold temperature elevation as observed in the longer durations of EA suggests that as the duration of EA lengthened, there is a gradual shifting from an initial predominantly spinally mediated analgesic effect to a supraspinally mediated modulatory mechanism of thermal pain. The 15-minute stimulation appeared to be the optimal setting for treating acute pain in the lower extremities.

Cold Acclimation Threshold Induction Temperatures in Cereals

To acquire a competitive advantage and ensure survival when exposed to low‐temperature extremes, cool season plants must be programmed to respond to temperatures favorable for growth and environmental cues that signal seasonal changes. This project was initiated to determine (i) the cold acclimation threshold induction temperatures (ITs) in wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), and rye (Secale cereale L.) and (ii) their relationship to plant freezing tolerance at full acclimation. A wide range of genotypic specific IT and initial rapid acclimation responses that were inversely related to decreases in temperatures below the threshold was observed both within and among species, indicating that cereals monitor temperature with a high level of precision. Hardy wheat cultivars had a 5.7°C warmer activation temperature than tender genotypes when the vernalization gene was neutralized in near‐isogenic lines, and a 12°C difference in IT of hardy rye compared with tender barley cultivars emphasized the high cold adaptation potential of rye. This early response to decreasing temperatures means that hardy rye had a longer time to prepare for the extremes of winter and was in a better position to cope with unexpected frosts during the growing season. Differences in IT were closely related to the differences in freezing tolerance at full acclimation. However, a longer vegetative stage also meant that winter habit genotypes were more responsive to extended periods at acclimation temperatures in the threshold range.

Cutaneous Amitriptyline in Human Volunteers

Amitriptyline is effective in relieving neuropathic pain. Its site of action is thought to be supraspinal and spinal, but a peripheral effect on fibers is also suggested. This double-blind study examined the effects of transcutaneous amitriptyline diluted in hydroalcoholic solution in healthy young male volunteers. Six treatments were randomly applied on different areas of the skin of the back: amitriptyline at 0 (vehicle), 25, 50, and 100 mm; saline (control); and lidocaine-prilocaine cream as a positive control. Up to 24 h after application, mechanical thresholds for touch and nociception, and thermal thresholds for cold, warm, and heat sensation were recorded for each area. Blood samples were collected to assess plasma levels of amitriptyline. A late recording of the tactile thresholds was performed 1 and 3 weeks after the treatment session. The thresholds for all sensations did not differ between the vehicle and saline. Lidocaine-prilocaine cream displayed a short-lasting anesthetic effect for all sensations, although this was not significant for warm sensation. Amitriptyline, at the three concentrations studied, induced a mild and short-lasting increase of the tactile and mechanical nociceptive thresholds. It significantly decreased cold thresholds (down to 21.8 degrees C, P = 0.01 vs. 27.5 degrees C for control) and heat thresholds (down to 40.1 degrees C, P = 0.004 vs. 43.4 degrees C for control). These two effects were no longer significant after the fourth hour of observation. Amitriptyline did not change warm thresholds. There was no apparent systemic absorption effect of the drug. It is hypothesized that amitriptyline has a differential effect on different fiber structures.

Hypoxia induces no change in cutaneous thresholds for warmth and cold sensation

Hypoxia can affect perception of temperature stimuli by impeding thermoregulation at a neural level. Whether this impact on the thermoregulatory response is solely due to affected thermoregulation is not clear, since reaction time may also be affected by hypoxia. Therefore, we studied the effect of hypoxia on thermal perception thresholds for warmth and cold. Thermal perception thresholds were determined in 11 healthy overweight adult males using two methods for small nerve fibre functioning: a reaction-time inclusive method of limits (MLI) and a reaction time exclusive method of levels (MLE). The subjects were measured under normoxic and hypoxic conditions using a cross-over design. Before the thermal threshold tests under hypoxic conditions were conducted, the subjects were acclimatized by staying 14 days overnight (8 h) in a hypoxic tent system (Colorado Altitude Training: 4,000 m). For normoxic measurements the same subjects were not acclimatized, but were used to sleep in the same tent system. Measurements were performed in the early morning in the tent. Normoxic MLI cold sensation threshold decreased significantly from 30.3 ± 0.4 (mean ± SD) to 29.9 ± 0.7°C when exposed to hypoxia (P < 0.05). Similarly, mean normoxic MLI warm sensation threshold increased from 34.0 ± 0.9 to 34.5 ± 1.1°C (P < 0.05). MLE measured threshold for cutaneous cold sensation was 31.4 ± 0.4 and 31.2 ± 0.9°C under respectively normoxic and hypoxic conditions (P > 0.05). Neither was there a significant change in MLE warm threshold comparing normoxic (32.8 ± 0.9°C) with hypoxic condition (32.9 ± 1.0°C) (P > 0.05). Exposure to normobaric hypoxia induces slowing of neural activity in the sensor-to-effector pathway and does not affect cutaneous sensation threshold for either warmth or cold detection.

Comparison of perception threshold testing and thermal‐vibratory testing

Current perception threshold testing (CPT) is thought to selectively activate and measure three types of afferent nerves. However, it has not been standardized or compared with better-studied methods of sensory testing. Our objectives were to determine the relationship between CPT (2000 Hz, 250 Hz, 5 Hz) and quantitative sensory testing (QST) using vibratory and heat thresholds, and to assess the test-retest reliability of both methods. Twenty-seven healthy women were enrolled. Each woman underwent CPT and QST on the volar part of the arm. Sensory thresholds were determined by the method of limits; 20 women underwent repeated CPT testing and QST after 1 week to determine test-retest reliability. Thermal thresholds were moderately correlated with CPT at 5 Hz (rho = 0.49, P = 0.009), as were vibratory thresholds and CPT at 2000 Hz (rho = 0.5, P = 0.008). In contrast to CPT measurements, warm and vibratory and cold thresholds were correlated 1 week apart (rho = 0.73, P = 0.0001; rho = 0.83, P = 0.0001; and rho = 0.47, P = 0.0037, respectively). CPT testing and QST seem to be measuring similar afferent nerve-fiber populations, but QST has better test-retest reliability than CPT testing, justifying its role in clinical or research studies.

Acute effects of vibration on thermal perception thresholds

This study focuses on the acute effects of vibration and how vibrations influence the measures of the thermal perception thresholds during different vibration magnitudes, frequencies, and durations. The fingers of ten healthy subjects, five males and five females, were exposed to vibration under 16 conditions with a combination of different frequency, intensity and exposure time. The vibration frequency was 31.5 and 125 Hz and exposure lasted between 2 and 16 min. The energy-equivalent frequency weighted acceleration, according to ISO 5349-1, for the experimental time of 16 min was 2.5 or 5.0 m/s(2) (r.m.s.), corresponding to a 8-h equivalent acceleration, A(8) of 0.46 and 0.92 m/s(2), respectively. A measure of the thermal perception of cold and warmth was conducted before the different exposures to vibration. Immediately after the vibration exposure the acute effect was measured continuously on the exposed index finger for the first 75 s, followed by 30 s of measures at every minute for a maximum of 10 min. If the subject's thermal thresholds had not recovered, the measures continued for a maximum of 30 min with measurements taken every 5 min. For all experimental conditions and 30 s after exposure, the mean changes of the thresholds compared with the pre-test were found to be 0.05 and -0.67 degrees C for the warmth and cold thresholds, respectively. The effect of the vibration exposure was only significant on the cold threshold and only for the first minute after exposure when the threshold was decreased. The warmth threshold was not significantly affected at all. The frequency and the exposure time of the vibration stimuli had no significant influence on the perception thresholds for the sensation of cold or warmth. Increased equivalent frequency weighted acceleration resulted in a significant decrease of the subjects' cold threshold, not the warmth. The thresholds were unaffected when changes in the vibration magnitude were expressed as the frequency weighted acceleration or the unweighted acceleration. When testing for the thermotactile thresholds, exposure to vibration on the day of a test might influence the results. Until further knowledge is obtained the previous praxis of 2 h avoidance of vibration exposure before assessment is recommended.