Hand Immersion Research Articles

Hand cooling induces changes in the kinetics of oxygen uptake

The objective of this investigation was to assess the impact of elevated catecholamine concentrations, induced through cold-water hand immersion, on the oxygen consumption (V̇O2) kinetics during intense exercise, and to contrast this effect with that of the priming effect. Ten active participants underwent three 8-minute constant work rate exercises (CWR) at ∆25%, with one CWR preceded by hand cooling (2 min at 0 °C, HC) and two consecutive CWR to induced priming effect on the second bout (SB). Pulmonary gas exchange and blood samples were analyzed to measure levels of epinephrine (E) and norepinephrine (NE). Results demonstrated a significant increase in the primary phase amplitude of V̇O2 kinetics in response to both hand HC (33.9 mL.min−1.kg−1; CI [32.2;35.7], p < 0.001) and SB (34.6 mL.min−1.kg−1; CI [33.0;36.3], p < 0.001) relative to the control (32.7 mL.min−1.kg−1; CI [31.5;35.1]). Additionally, the amplitude of the V̇O2 slow component was reduced for both HC (3.2 mL.min−1.kg−1; CI [2.2;4.1], p = 0.018) and SB (2.9 mL.min−1.kg−1; CI [1.8;4.2], p = 0.009) in comparison to control (3.9 mL.min−1.kg−1; CI [2.9;4.2]). These findings suggest that the increase in E and NE induced by hand cooling prior to exercise modifies V̇O2 kinetics in a manner akin to the priming effect. This research underscores the potential role of catecholamines in facilitating the priming effect and its subsequent impact on V̇O2 kinetics. However, further studies are necessary to clearly establish this link.

Understanding inter-individual variability of experimental pain habituation and conditioned pain modulation in healthy individuals

Although reduced experimental pain habituation is proposed as a proxy of diminished endogenous pain modulatory capacity in chronic pain, prior studies show contradictory findings. Even across healthy participants, pain habituation varies substantially, which may relate to another measure of endogenous pain modulation, i.e., conditioned pain modulation (CPM). Hence, this study investigated the relationship between pain habituation and CPM. Pain habituation was assessed in 45 healthy participants between two blocks of 15–20 contact-heat stimuli applied to the hand. Habituation of subjective pain ratings and objective neurophysiological readouts (contact-heat evoked potential (CHEP) and palmar sympathetic skin response (SSR)) was investigated. CPM was assessed by comparing heat pain thresholds before and after hand immersion in a noxious cold (9 °C) and lukewarm water bath (32 °C, to control for repeated measures effects). Pain habituation showed a large variability, with subjective but not objective pain habituation correlating with cold-induced CPM effects (r = 0.50; p = 0.025). This correlation was not observed for ‘true’ CPM effects (corrected for repeated measures effects) nor for CPM effects induced by a lukewarm water bath. These findings suggest that the observed variability in subjective pain habituation may be influenced by both descending endogenous pain modulation and peripheral adaptation processes associated with repeated measures. Objective pain habituation readouts, i.e., CHEPs and SSRs, capture different, complementary aspects of endogenous pain modulation.

Short-latency afferent inhibition is reduced with cold-water immersion of a limb and remains reduced after removal from the cold stimulus.

The experience of pain that is induced by extremely cold temperatures can exert a modulatory effect on motor cortex circuitry. Although it is known that immersion of a single limb in very cold water can increase corticomotor excitability it is unknown how afferent input to the cortex shapes excitatory and inhibitory processes. Therefore, the purpose of this study was to examine motor-evoked potentials (MEP), short-latency afferent inhibition (SAI) and long-latency afferent inhibition (LAI) in response to immersion of a single hand in cold water. Transcranial magnetic stimulation (TMS) was used to assess MEPs, and peripheral nerve stimulation of the median nerve paired with TMS was used to measure SAI and LAI in motor circuits of the ipsilateral hemisphere. Measurements were obtained from electromyography (EMG) of the first dorsal interosseous (FDI) at baseline, during cold-water immersion, and during recovery from cold-water immersion. The intervention caused unconditioned MEPs to increase during exposure to the cold stimulus (P=0.008) which then returned to baseline levels once the hand was removed from the cold water. MEP responses were decoupled from SAI responses, where SAI was reduced during exposure to the cold stimulus (P=0.005) and remained reduced compared to baseline when the hand was removed from the cold water (P=0.002). The intervention had no effect on LAI. The uncoupling of SAI from MEPs during the recovery period suggests that the mechanisms underlying the modulation of corticospinal excitability by sensory input may be distinct from those affecting intracortical inhibitory circuits. HIGHLIGHTS: What is the central question of this study? Does immersion of a limb in very cold water influence corticospinal excitability and the level of afferent inhibition exerted on motor cortical circuits? What is the main finding and its importance? In additional to perception of temperature, immersion in 6°C water also induced perceptions of pain. Motor evoked potential (MEP) amplitude increased during immersion, and short-latency afferent inhibition (SAI) of the motor cortex was reduced during immersion; however, these responses differed after the limb was removed from the cold stimulus, as MEPs returned to normal levels while SAI remained suppressed.

Posttraumatic headache: pain related evoked potentials (PREP) and conditioned pain modulation (CPM) to assess the pain modulatory function

Posttraumatic headache (PTH) is common following traumatic brain injury and impacts quality of life. We investigated descending pain modulation as one possible mechanism for PTH and correlated it to clinical measures. Pain-related evoked potentials (PREP) were recorded in 26 PTH-patients and 20 controls after electrical stimulation at the right hand and forehead with concentric surface electrodes. Conditioned pain modulation (CPM) was assessed using painful cutaneous electric stimulation (PCES) on the right hand as test stimulus and immersion of the left hand into 10 °C-cold water bath as conditioning stimulus based on changes in pain intensity and in amplitudes of PCES-evoked potentials. All participants completed questionnaires assessing depression, anxiety, and pain catastrophising. PTH-patients reported significantly higher pain ratings during PREP-recording in both areas despite similar stimulus intensity at pain threshold. N1P1-amplitudes during PREP and CPM-assessment were lower in patients in both areas, but statistically significant only on the hand. Both, PREP-N1-latencies and CPM-effects (based on the N1P1-amplitudes and pain ratings) were similar in both groups. Patients showed significantly higher ratings for anxiety and depression, which did not correlate with the CPM-effect. Our results indicate generalized hyperalgesia for electrical stimuli in both hand and face in PTH. The lacking correlation between pain ratings and EEG parameters indicates different mechanisms of pain perception and nociception.

The Leuven Prolonged Acute Stress Test (L-PAST): A novel paradigm to induce a subjective and glucocorticoid stress response for at least ninety minutes

Laboratory stress tests typically administer stress acutely, ranging from 3 to 15 minutes. However, everyday stressors usually last longer than ten minutes (e.g., examination stressors, work stressors, and social stressors. Moreover, in some studies, it may be relevant to induce stress for a longer period to affect certain psychological or physiological parameters. To this end, we developed a novel stress test that intends to induce psychosocial stress for 90 minutes. The Leuven Prolonged Acute Stress Test (L-PAST) combines physical (hand immersion in cold water), cognitive (mental arithmetic), and psychosocial (social evaluation and feelings of failure) stress elements of two well-known laboratory stress tests, the Maastricht Acute Stress Test (MAST) and the Montreal Imaging Stress Test (MIST). Fifty healthy women were subjected to both the L-PAST and a sham (control) test in a randomized and counterbalanced manner. The stress response was determined by salivary cortisol measurements and assessment of subjective stress ratings at regular time points during the time preceding the stress period (5 min), the stress period (90 min), and the recovery period (35 min). Cognitive reactivity to failure and subjective pain levels were also assessed at various time points. The childhood trauma questionnaire (CTQ) and the perceived stress scale (PSS) were administered prior to the testing phase. As expected, linear mixed models revealed that the stress response was significantly higher during the L-PAST as indicated by a significant time point by condition interaction effect for both the cortisol response (F(10,450)=12.21, p < 0.0001, ηp2=0.11) and the subjective stress response (F(13,637)=13.98, p < 0.0001, ηp2 = 0.12). Moreover, there was a significant time point by condition interaction effect for cognitive reactivity to failure (F(13,637) = 7.97, p < 0.0001, ηp2 = 0.07) and subjective pain (F(13,637) = 38.52, p < 0.0001, ηp2 = 0.27), indicating that the levels were higher during the L-PAST at most stress induction time points. Lastly, higher CTQ scores were associated with higher subjective pain levels during the L-PAST (F(1,44)=6.05, p = 0.02). Collectively, our results confirm the efficacy of the L-PAST in inducing a prolonged subjective as well as cortisol stress response.

Heart rate variability and cold-induced vascular dilation after stimulation of two different areas of the ear: a prospective, single-blinded, randomized crossover study

BackgroundBoth noninvasive transauricular vagus nerve stimulation (taVNS) and traditional medical practice (TMP), such as auriculotherapy, use the auricle as a starting point for stimulation, but with two different conceptual frameworks: taVNS depends on vagal afferences to account for its effects, whereas TMP requires stimulation of the ear with high topographical accuracy regardless of the afferent nerves. The aim of this study was to measure heart rate variability (HRV) and cold water–induced vasodilation (CIVD) after puncturing two different ear points with the same afference but that should have opposite effects according to TMP.MethodsTen healthy subjects were investigated in this single-blinded crossover study over three sessions. In the first session, sympathetic activation was performed via cold water immersion of the right hand, with recordings taken from multiple fingers. HRV was assessed in the time domain (square root of the mean squared differences of NN intervals (RMSSD)) and frequency domain (low (LF) and high frequencies (HF)). In the second and third sessions, the same skin immersion test was performed, and mechanical stimulation was applied to the ear at two different points on the internal surface of the antitragus, one with alleged parasympathetic activity and the other with alleged sympathetic activity. The stimulation was done with semipermanent needles.ResultsStimulation of the point with alleged parasympathetic activity immediately resulted in a significant decrease in RMSSD in 75% of the subjects and in LF in 50% of the subjects, while stimulation of the point with alleged sympathetic activity resulted in an increase in HF and RMSSD in 50% of the subjects. Stimulation of these points did not affect the CIVD reflex. The 20 min cold water immersion induced an immediate decrease in LF and the LF/HF ratio and an increase in HF. The skin temperature of the nonimmersed medius significantly decreased when the contralateral hand was immersed, from 34.4 °C to 31.8 °C.ConclusionsStimulation of two different ear points innervated by the same afferent nerves elicited different HRV responses, suggesting somatotopy and a vagal effect beyond vagal afferences. These results are not in accordance with the claims of TMP.Trial registrationNCT04130893 (18/10/2019) clinicaltrials.com.

Effect of catecholamines stimulation via hand cooling and the priming effect on the oxygen consumption kinetics

Introduction&#x0D; Priming effect has been shown to accelerate the oxygen consumption (V̇O2) kinetics. This phenomenon could be explained by muscle oxygen (O2) enhanced delivery, motor unit recruitment or intracellular O2 enhanced utilization (Goulding et al. 2023). Catecholamines such as epinephrine (E) and norepinephrine (NE) are known to impact the cardiovascular system as well as the respiratory system and metabolic effects (Zouhal et al. 2008). The aim of this study is two folds. Observing the effect of increased E and NE induced by cold-water hand immersion on V̇O2 kinetic during heavy intensity exercise bout (HCWR). Compare the effect of cold-water hand immersion and previous HCWR on V̇O2 kinetic to see if the sympathetic system could partially explain the priming effects.&#x0D; Methods&#x0D; Ten healthy active males (mean ± SD, age 23 ± 5 years, body mass 71 ± 6.5 kg) participated in this study. An incremental test was performed on ergometer to prescribe the intensity for the HCWR exercise (∆ 25%). Participants did an 8 min HCWR normal bout (NO), followed by 8 min rest and a second bout (SB) and hand cooling bout (HC) at heavy intensity in a randomized order. For the HC condition, participants put hands in cold water (0°C) for 2 min then directly did the HCWR. Blood samples has been taken at rest, before and directly after the HCWR.&#x0D; Results&#x0D; Just before exercise, all conditions were different, but HC E (1.095 ± 0.64 nmol/ml) increased by 347% while HC NE (6.98 ± 1.89 nmol/ml) matched values from SB NE (6.89 ± 2.22 nmol/ml). At the end of exercise, no significant difference has been found between NO E (1.44 ± 1.06) and HC E (1.54 ± 1.38 nmol/ml) while SB E (2.35 ± 1.55 nmol/ml) was significantly higher than both conditions but no differences have been found between HC (20.15 ± 8.76 nmol/ml) and SB (20.41 ± 9.74 nmol/ml) NE. V̇O2 kinetic has been sped up for both HC and SB by increasing the absolute primary prime amplitude of HC (33.88 ± 0.96 ml/min/kg),SB (34.60 ± 0.86ml/min/kg) compared to NO (32.75 ± 0.65 ml/min/kg) and reducing the prime amplitude of HC (3.22 ± 0.51 ml/min/kg), SB (2.90 ± 0.64 ml/min/kg) vs NO (3.87 ±0 .56 ml/min/kg) of the slow component of V̇O2.&#x0D; Discussion/Conclusion&#x0D; Catecholamines stimulation via hand cooling accelerated the V̇O2 kinetics enhancing the primary phase and reducing the slow component. This effect seemed to follow the priming effect but with less intensity. Increased O2 delivery appeared to be a common feature of both conditions, Motor neuron excitability due to increased NE was also a likely hypothesis, as both HC and SB had the same values just before exercise. Finally, intra-muscular enhancement illustrated by improved intracellular partial pressure kinetics and mitochondrial O2 utilization might explain the effects of catecholamines and part of the priming effect. Mitochondrial “warm-up” could be influenced by both catecholamines and priming effect resulting in a better production of adenosine triphosphate.&#x0D; References&#x0D; Goulding, R. P., Burnley, M., &amp; Wüst, R. C. I. (2023). How priming exercise affects oxygen uptake kinetics: From underpinning mechanisms to endurance performance. Sports Medicine, 53, 959-976. https://doi.org/10.1007/s40279-023-01832-1&#x0D; Zouhal, H., Jacob, C., Delamarche, P., &amp; Gratas-Delamarche, A. (2008). Catecholamines and the effects of exercise, training and gender. Sports Medicine 38, 401-423. https://doi.org/10.2165/00007256-200838050-00004

Spatial summation of pain is associated with pain expectations: Results from a home-based paradigm.

The purpose of this study was to reproduce the previously observed spatial summation of pain effect (SSp) using non-laboratory procedures and commercial equipment. An additional aim was to explore the association between expectations and SSp. The Cold Pressor Task (CPT) was used to induce SSp. Healthy participants (N = 68) immersed their non-dominant hands (divided into 5 segments) into cold water (CPT). Two conditions were used 1) gradual hand immersion (ascending condition) and 2) gradual hand withdrawal (descending condition). Pain intensity was measured on a Visual Analogue Scale (VAS). Psychological factors, such as the participants' expectations of pain intensity were also measured on a VAS. Results showed significant SSp (χ2(4) = 116.90, p < 0.001), reproduced with non-laboratory equipment in a home-based set-up. Furthermore, two novel findings were observed: i) there was a significant correlation between expectations and perceived pain, indicating a link between pain expectations and SSp, ii) spatial summation increased with the increase in duration exposure to the noxious stimulus (Wald χ2(8) = 80.80, p < 0.001). This study suggests that SSp is associated with pain expectations and can be formed by a mixture of excitatory and inhibitory mechanisms potentially driven by temporal characteristics of neural excitation. Moreover, this study proposes a new feasible way to induce SSp using a home-based set-up.

Cold-induced vasodilation during sequential immersions of the hand.

A common practice for those operating in cold environments includes repetitive glove doffing and donning to perform specific tasks, which creates a repetitive cycle of hand cooling and rewarming. This study aimed to determine the influence of intraday repeated hand cooling on cold-induced vasodilation (CIVD), sympathetic activation, and finger/hand temperature recovery. Eight males and two females (mean ± SD age: 28 ± 5year; height: 181 ± 9cm; weight: 79.9 ± 10.4kg) performed two 30-min hand immersions in cold (4.3 ± 0.92°C) water in an indoor environment (18°C). Both immersions (Imm1; Imm2) were performed on the same day and both allowed for a 10-min recovery. CIVD components were calculated for each finger (index, middle, ring) during each immersion. CIVD onset time (index, p = 0.546; middle, p = 0.727; ring, p = 0.873), minimum finger temperature (index, p = 0.634; middle, p = 0.493; ring, p = 0.575), and mean finger temperature (index, p = 0.986; middle, p = 0.953; ring, p = 0.637) were all similar between immersions. Recovery rates generally demonstrated similar responses as well. Findings suggest that two sequential CIVD tests analyzing the effect of prior cold exposure of the hand does not impair the CIVD response or recovery. Such findings appear promising for those venturing into cold environments where hands are likely to be repeatedly exposed to cold temperatures.

Investigating manual performance when using push buttons following cold water hand immersion

The purpose of this study was to investigate manual performance of humans when using push buttons following cold water hand immersion. An experiment involving 29 human participants was carried out to measure the activation rate of twelve different shaped push buttons mounted on a novel test apparatus after their dominant hand was immersed in cold (2 °C) and thermoneutral (34 °C) water for 2 min. A series of standardized hand dexterity tests were completed to assess the participants' baseline tactile sensitivity in a dry thermoneutral state. The mean baseline performance of participants indicates that they were representative of the general population. The button test apparatus was developed specifically for this experiment and was comprised of 12 different buttons at different locations on the panel which were varying in size, surface shape and texture. After the participants immersed their dominant hand in the assigned temperature condition, their index finger was guided to the centre of the panel, and they were instructed to find and press as many buttons as they could in a 2-min time period using only their index finger. For the button panel test, the participants’ view was obstructed from seeing the buttons. The results of the study indicate that temperature does not influence the activation rate of the push buttons on the button test apparatus. In addition, button size (large) was the most significant factor, followed by shape (protruding), however button texture was not a significant parameter. Given that exposure to cold water reduces manual performance, along with anecdotal evidence from survival training centres that users sometimes struggle to activate PLBs, the motivation for this research was to understand how humans interact with these devices in cold water emergency situations. It is expected that the results of this research will be useful for designers of emergency signalling devices used for rescue at sea.

Cold water immersion of the hand and forearm during half-time improves intermittent exercise performance in the heat

The present study aimed to investigate the effect of cold water immersion of the hand and forearm during half-time (HT) on intermittent exercise performance and thermoregulation by imitating intermittent athletic games in the heat. In a randomized crossover design, 11 physically active men performed the first half (first and second block) and second half (third and fourth block) intermittent cycling exercise protocol, which consisted of a 5-s maximal power pedalling (body weight × 0.075 kp) every minute separated by 25-s of unloaded pedalling and rest (30 s) in the heat (33°C, 50% relative humidity). The two-halves were separated by a 15-min HT. During HT, the participants were assigned to the CON (sedentary resting) or COOL (immersion of hands and forearms in cold water at 15–17°C) condition. The mean power output in the second half was significantly greater (third and fourth block:p&amp;lt; 0.05) in the COOL than in the CON condition. Moreover, there was a significant decrease in the rectal (0.54 ± 0.17°C,p&amp;lt; 0.001) and mean skin (1.86 ± 0.34°C,p&amp;lt; 0.05) temperatures of the COOL condition during HT. Furthermore, the heart rate (16 ± 7 bpm,p&amp;lt; 0.05) and skin blood flow (40.2 ± 10.5%,p&amp;lt; 0.001) decreased at the end of HT in the COOL condition. In the second half, thermal sensation was more comfortable in the COOL condition (p&amp;lt; 0.001). Cold water immersion of the hand and forearm during HT improved physiological and reduced perceived heat stress. Moreover, it prevented a reduction in intermittent exercise performance in the second half.

Modulation of Pain Sensitivity by a Hyperventilatory Breathing Exercise and Cold Exposure Training.

Evidence indicates that healthy individuals who follow a training program comprised hyperventilatory breathing exercises and cold exposure can voluntarily activate their sympathetic nervous system and attenuate their systemic inflammatory response during experimental endotoxemia (intravenous administration of bacterial endotoxin). Furthermore, trained participants reported less endotoxemia-induced flu-like symptoms. However, it remained to be determined whether the effects on symptoms are due to the mitigated inflammatory response or involve direct analgesic effects of (elements of) the training program. In the present study, we used Nijmegen-Aalborg Screening Quantitative sensory testing (NASQ) to objectively map pain sensitivity using non-invasive stimuli to address this question. First, NASQ parameters were evaluated in 20 healthy volunteers before, during, and after the conduct of the hyperventilatory breathing exercise. Second, NASQ measurements were performed before and after 48 healthy volunteers followed different modalities of the training program: breathing exercise training, cold exposure training, the combination of both, or no training. Lastly, NASQ measurements were performed in these 48 subjects during experimental endotoxemia. Electrical pain detection thresholds increased during the breathing exercise (p = 0.001) as well as four hours afterwards (p = 0.03). Furthermore, cold exposure training resulted in lower VAS scores during hand immersion in ice water (p < 0.001). Systemic inflammation induced by administration of endotoxin nullified the decreased pain perception during the ice water test in subjects trained in cold exposure. A hyperventilatory breathing exercise decreases pain perception induced by an electrical stimulus. Furthermore, cold exposure training may decrease pain perception induced by hand immersion in ice water.

0163 Impact of cold-water hand immersion on cognitive performance and sleepiness during sleep inertia

Abstract Introduction Sleep inertia is a state of impaired cognitive performance upon awakening that dissipates with time awake. Manipulation of the distal-to-proximal skin temperature gradient using cold water has been hypothesized as a potential countermeasure to sleep inertia, but not previously explored (Krauchi et al., 2004). This study examined the effects of cold-water hand immersion on subsequent cognitive performance and sleepiness during sleep inertia. Methods Ten healthy adults (mean±standard deviation [SD] age 23.2±4.96 years; 6M, 4F) have thus far completed an ongoing 8-day protocol. Prior to an overnight in-laboratory visit, participants maintained habitual 8h sleep schedules for 1 week at home. In-laboratory sleep opportunities were timed to coincide with habitual sleep time. Following at least 5-min of electroencephalogram (EEG) verified continuous slow wave sleep (SWS), participants were awakened twice during the night to submerge their non-dominant hand in warm (34 C) or ice-cold water (0 C) for 3 min in a randomized, crossover design. Sleep inertia was assessed with a Mathematical Addition Test (ADD) and the Karolinska Sleepiness Scale (KSS) at ~ 5, 15, and 25 min after each awakening. Outcomes included number of correct responses and median reaction time for correct responses on the ADD and KSS scores. Data were analyzed with mixed-model ANOVA with condition, condition order and time since awakening as fixed factors and subject as a random factor. Results The average (Mean±SD) amount of SWS prior awakening was similar before the cold 7.0±2.3 min and warm 6.6±1.0min conditions (p&amp;gt;0.10). Following cold water immersion, subjective sleepiness was reduced and the median reaction time for correct responses was faster compared with warm water immersion (main effects of condition, p’s&amp;lt; 0.05). The number of correct responses was not significantly different between conditions, nor were there any significant interaction effects among the fixed factors. Conclusion These preliminary findings indicate that cold-water hand immersion may reduce sleepiness and increase the speed of arithmetic calculations during sleep inertia, which could have important implications for military and first responders performing after awakenings from sleep. Support (if any) Office of Naval Research MURI N00014-15-1-2809; NIH RHL165343A and CTSA Grant UL1 TR002535; Undergraduate Research Opportunities Grant, University of Colorado Boulder.

Comparison between Speckle Plethysmography and Photoplethysmography during Cold Pressor Test Referenced to Finger Arterial Pressure.

Speckle Plethysmography (SPG) and Photoplethysmography (PPG) are different biophotonics technologies that allow for measurement of haemodynamics. As the difference between SPG and PPG under low perfusion conditions is not fully understood, a Cold Pressor Test (CPT-60 s full hand immersion in ice water), was used to modulate blood pressure and peripheral circulation. A custom-built setup simultaneously derived SPG and PPG from the same video streams at two wavelengths (639 nm and 850 nm). SPG and PPG were measured at the right index finger location before and during the CPT using finger Arterial Pressure (fiAP) as a reference. The effect of the CPT on the Alternating Component amplitude (AC) and Signal-to-Noise Ratio (SNR) of dual-wavelength SPG and PPG signals was analysed across participants. Furthermore, waveform differences between SPG, PPG, and fiAP based on frequency harmonic ratios were analysed for each subject (n = 10). Both PPG and SPG at 850 nm show a significant reduction during the CPT in both AC and SNR. However, SPG showed significantly higher and more stable SNR than PPG in both study phases. Harmonic ratios were found substantially higher in SPG than PPG. Therefore, in low perfusion conditions, SPG seems to offer a more robust pulse wave monitoring with higher harmonic ratios than PPG.

Spatial Tuning in Nociceptive Processing Is Driven by Attention

When the source of nociception expands across a body area, the experience of pain increases due to the spatial integration of nociceptive information. This well-established effect is called spatial summation of pain (SSp) and has been the subject of multiple investigations. Here, we used cold-induced SSp to investigate the effect of attention on the spatial tuning of nociceptive processing. Forty pain-free volunteers (N = 40, 20 females) participated in this experiment. They took part in an SSp paradigm based on three hand immersions into cold water (5°C): Participants either immersed the radial segment (“a”), ulnar segment (“b”) or both hand segments (“a+b”) and provided overall pain ratings. In some trials based on “a+b” immersions, they were also asked to provide divided (ie, first pain in “a” then in “b”; or reversed) and directed attention ratings (ie, pain only in “a” or “b”). Results confirmed a clear SSp effect in which reported pain during immersions of “a” or “b” was less intense than pain during immersions of “a+b” (P < .001). Data also confirmed that spatial tuning was altered. SSp was abolished when participants provided two ratings in a divided fashion (P < .001). Furthermore, pain was significantly lower when attention was directed only to one segment (“a” OR “b”) during “a+b” immersion (P < .001). We conclude that spatial tuning is dynamically driven by attention as reflected in abolished SSp. Directed attention was sufficient to focus spatial tuning and abolish SSp. Results support the role of cognitive processes such as attention in spatial tuning. PerspectiveThis article presents experimental investigation of spatial tuning in pain and offers mechanistic insights of contiguous spatial summation of pain in healthy volunteers. Depending on how pain is evaluated in terms of attentional derivative (overall pain, directed, divided attention) the pain is reduced and spatial summation abolished.

Inaccuracy of surgical irrigation fluid temperature hand assessment.

Fluids are often used for irrigation during surgical procedures. The temperature of the fluid directly affects the exposed tissue and body temperature. The recommended practice is to use euthermic fluids to be homeostatic and optimise patient care. Hand checking the fluid temperature by surgeons and scrub practitioners is the commonly used method. This subjective measurement leaves room for error and can lead to inaccuracies. The purpose of the study is to assess the accuracy of the currently used method of checking irrigation fluids temperature by hand immersion. Two sets of fluids were prepared. One was made at 37°C and the other was 30°C. Participants immersed their hands in the containers and then report if each of the two sets is (1) appropriately warm for irrigation, (2) too cool and (3) too warm. Data were collected and interpreted. Results showed that about half of participants in our study perceived normal physiologic fluid temperature as too hot for use in irrigation, 30°C fluid was perceived as appropriate and physiologic by about a quarter of participants. Perception of surgical irrigation fluid temperature by hand immersion is inaccurate. Standard objective methods of measuring the temperature are recommended.

Influence of acute beetroot juice supplementation on cold-induced vasodilation and fingertip rewarming.

Vasoactive ingredients in beetroot (BR) such as nitrate are known to induce vasodilation in temperate conditions. This study investigated the effect of BR ingestion on cold induced vasodilation (CIVD) and rewarming of finger skin temperature (Tfing) during and after hand immersion in cold water. Twenty healthy males (mean ± SD; age 22.2 ± 0.7 years, height 172.6 ± 6.0cm, body mass 61.3 ± 11.7kg) repeated a hand cold water immersion test twice with prior BR or water beverage ingestion (randomised order). They rested for 2h in thermoneutral conditions (27°C, 40% relative humidity) after consuming the beverage, then immersed their non-dominant hand in 8°C water for 30min. They then rewarmed their hand in the ambient air for 20min. Skin temperature at seven body sites, Tfing, finger skin blood flow (SkBFfing), and blood pressure were measured. During hand immersion parameters of CIVD (Tfing and SkBFfing) were not different between BR and water conditions although skin temperature gradient from proximal to distal body sites was significantly smaller with BR (P < 0.05). During rewarming, SkBFfing and cutaneous vascular conductance were significantly higher with BR than with water (P < 0.05). The rewarming speed in Tfing and SkBFfing was significantly faster with BR at 15- (BR 1.24 ± 0.22 vs water 1.11 ± 0.26°C/min) and 20-min rewarming (P < 0.05). Additionally, individuals with slower rewarming speed with water demonstrated accelerated rewarming with BR supplementation. BR accelerated rewarming in Tfing and SkBFfing after local cold stimulus, whereas, CIVD response during hand cold immersion was not affected by BR ingestion.

Effect of the cold pressor test on coronary flow reserve by cardiac magnetic resonance in patients with hereditary TTR+ amyloidosis

Abstract Background Cold pressor test (CPT) is a potent alpha-adrenergic vasoconstrictor stimulus and evaluates the sympathetic reactivity of the cardiovascular system during the immersion of a hand in cold water, its effect on coronary flow reserve (CFR) in patients with hereditary TTR+ amyloidosis is unknown. Purpose To evaluate CFR by CPT in hereditary TTR+ amyloidosis patients with different cardiac involvement regarding the distribution of late gadolinium enhancement (LGE) by cardiac magnetic resonance imaging (CMRI) and compare with healthy volunteers Methods It was a cross-sectional study of 22 hereditary TTR+ amyloidosis patients with different patterns of LGE (absence/minimum or extensive involvement), and 4 healthy controls without LGE. CPT was performed with immersion of one hand in four Celsius degrees temperated water. Phase-contrast images were acquired on rest and during stress (after four minutes of a hand immersion). Volume quantification was made in posterior analysis to determine flow differences. Results No statistically significant differences were found regarding left ventricular (LV) volumes, LV mass, LV ejection fraction, and atrial volumes comparing the three groups of patients. CFR was abnormal in both groups of TTR+ amyloidosis patients compared with higher values in healthy subjects. Nevertheless, no statistically significant differences were determined. Conclusions Hereditary TTR+ amyloidosis subjects presented with abnormal values of CFR even with minimal or non-LGE by CMRI in the setting of infiltration. This response hypothesized small vessel involvement due to early infiltration by amyloid deposits before LGE development. Funding Acknowledgement Type of funding sources: None.

Inhibition of current perception thresholds in A-delta and C fibers through somatosensory stimulation of the body surface

Somatosensory stimulation of the body surface, such as through tactile and noxious stimulation, is widely known to inhibit pain. However, no studies have measured the threshold changes due to somatosensory stimulation of each nerve fiber (Aβ, Aδ, and C) separately. We examined the changes in the current perception thresholds of Aδ, C, and Aβ fibers induced by non-noxious and noxious somatosensory stimulation of the body surface. The current stimuli were sinusoidal waves at frequencies of 2000 Hz, 250 Hz, and 5 Hz, which selectively stimulated the Aβ, Aδ, and C fibers, respectively. In the case of non-noxious stimulation, lightly rubbing the dorsal side of the forearm with a brush showed no significant physiological or clinical changes in the current perception thresholds of the Aδ, and C fibers; a significant increase was observed only in the Aβ fibers. However, applying noxious stimulation to the body surface through hand immersion in cold water increased pain thresholds in both the Aδ and C fibers, and sensory threshold of the Aβ fibers; changes in tactile thresholds were not significant. Inhibition of sensory information by nociceptive inputs may selectively suppress nociceptive stimuli.

Hyper-connectivity between the left motor cortex and prefrontal cortex is associated with the severity of dysfunction of the descending pain modulatory system in fibromyalgia.

IntroductionThe association between descending pain modulatory system (DPMS) dysfunction and fibromyalgia has been previously described, but more studies are required on its relationship with aberrant functional connectivity (FC) between the motor and prefrontal cortices.ObjectivesThe objective of this cross-sectional observational study was to compare the intra- and interhemispheric FC between the bilateral motor and prefrontal cortices in women with fibromyalgia, comparing responders and nonresponders to the conditioned pain modulation (CPM) test.MethodsA cross-sectional sample of 37 women (23 responders and 14 nonresponders to the CPM test) with fibromyalgia diagnosed according to the American College of Rheumatology criteria underwent a standardized clinical assessment and an FC analysis using functional near-infrared spectroscopy. DPMS function was inferred through responses to the CPM test, which were induced by hand immersion in cold water (0–1°C). A multivariate analysis of covariance for main effects between responders and nonresponders was conducted using the diagnosis of multiple psychiatric disorders and the use of opioid and nonopioid analgesics as covariates. In addition, we analyzed the interaction between the CPM test response and the presence of multiple psychiatric diagnoses.ResultsNonresponders showed increased FC between the left motor cortex (lMC) and the left prefrontal cortex (lPFC) (t = −2.476, p = 0.01) and right prefrontal cortex (rPFC) (t = −2.363, p = 0.02), even when both were considered as covariates in the regression analysis (lMC–lPFC: β = −0.127, t = −2.425, p = 0.021; lMC–rPFC: β = −0.122, t = −2.222, p = 0.033). Regarding main effects, a significant difference was only observed for lMC–lPFC (p = 0.035). A significant interaction was observed between the psychiatric disorders and nonresponse to the CPM test in lMC−lPFC (β = −0.222, t = −2.275, p = 0.03) and lMC−rPFC (β = −0.211, t = −2.2, p = 0.035). Additionally, a significant interaction was observed between the CPM test and FC in these two region-of-interest combinations, despite the psychiatric diagnoses (lMC−lPFC: β = −0.516, t = −2.447, p = 0.02; lMC−rPFC: β = −0.582, t = −2.805, p = 0.008).ConclusionsHigher FC between the lMC and the bilateral PFC may be a neural marker of DPMS dysfunction in women with fibromyalgia, although its interplay with psychiatric diagnoses also seems to influence this association.