A study of the blood flow restriction pressure of a tourniquet system to facilitate development of a system that can prevent musculoskeletal complications

2017 ◽  
Vol 12 (3) ◽  
pp. 139-145 ◽  
Author(s):  
Hiroyuki Maeda, MD, PhD ◽  
Hideaki Iwase, PhD ◽  
Akio Kanda, MD, PhD ◽  
Itaru Morohashi, MD, PhD ◽  
Kazuo Kaneko, MD, PhD ◽  
...  
Keyword(s):  
Blood Flow ◽  
Body Weight ◽  
Oxygen Saturation ◽  
Blood Flow Restriction ◽  
Behavioral Experiment ◽  
Tissue Oxygen Saturation ◽  
Control Group ◽  
Severe Bleeding ◽  
Tissue Oxygen ◽  
Flow Restriction

Background: After an emergency or disaster, subsequent trauma can cause severe bleeding and this can often prove fatal, so promptly stopping that bleeding is crucial to preventing avoidable trauma deaths. A tourniquet is often used to restrict blood flow to an extremity. In operation and hospital, the tourniquet systems currently in use are pneumatically actuated by an air compressor, so they must have a steady power supply. These devices have several drawbacks: they vibrate and are noisy since they are pneumatically actuated and they are far from portable since they are large and heavy.Introduction: Presumably, the drawbacks of pneumatic tourniquets could be overcome by developing a small, lightweight, vibration-free, quiet, and battery- powered tourniquet system. The current study built a small, vibration-free electrohydrodynamic (EHD) pump and then used that pump to restrict blood flow to the leg of rats in an experiment. This study explored the optimal conditions for effective restriction of blood flow by assessing biochemical and musculoskeletal complications following the restriction of blood flow, and this study also examined whether or not an EHD pump could be used to actuate a tourniquet system.Methods: A tourniquet cuff (width 12 mm × length 150 mm, material: polyolefin) was placed on the thigh of Wistar rats and pressure was applied for 2 hours by a device that uses EHD phenomena to generate pressure (an EHD pump). Animals were divided into four groups based on how much compressive pressure was applied with a tourniquet: 40 kPa (300 mm Hg, n = 13),  30 kPa (225 mm Hg, n = 12), 20 kPa (150 mm Hg, n = 15), or 0 kPa (controls, n = 25). Tissue oxygen saturation (regional oxygen saturation, denoted here as rSO2) was measured to assess the restriction of blood flow. To assess behavior once blood flow resumed, animal activity was monitored for third day and the amount of movement was counted with digital counters. Body weight was measured before and after the behavioral experiment, and changes in body weight were determined. Blood was sampled after a behavioral experiment and biochemically assessed and creatine kinase (CK) levels were measured.Results: Tissue oxygen saturation decreased significantly in each group. When a tourniquet was applied at a pressure of 30 kPa or more, tissue oxygen saturation decreased significantly. The amount of movement (the count) over third day decreased more when a tourniquet was applied at a higher pressure. The control group resumed the same amount of movement per day second after blood flow resumed. Animals to which a tourniquet was applied at a pressure of 20 or 30 kPa resumed the same amount of movement third day after blood flow resumed. In contrast, animals to which a tourniquet was applied at a pressure of 40 kPa did not resume the same amount of movement third day after blood flow resumed. After the behavioral experiment, animals to which a tourniquet was applied at a pressure of 40 kPa had a significantly lower body weight in comparison to the control group. After the behavioral experiment, animals to which a tourniquet was applied at a pressure of 40 kPa had significantly elevated CK levels in comparison to the control group.Discussion and Conclusion: A relationship between blood flow restriction pressure and tissue oxygen saturation was noted. rSO2 measurement can be used to assess the restriction of blood flow during surgery. On the basis of the decrease in rSO2, blood flow was effectively restricted at a pressure of 30 kPa or more. When, however, blood flow was restricted at a pressure of 40 kPa, weight loss and decreased movement were noted and CK levels increased after the behavioral experiment. Thus, complications had presumably developed due to damage to muscle tissue. These findings indicate that blood flow was effectively restricted in this experiment and they also indicate the existence of an optimal blood flow restriction pressure that does not cause musculoskeletal complications. The pressure in question was around 30 kPa. The tourniquet system that was developed here is actuated with an EHD pump that is still in the trial stages. That said, its pressure can readily be controlled and this pump could be used in a tourniquet system since it is quiet, vibration-free, and small. The pressure of this pump can be finely adjusted to prevent musculoskeletal complications.

Does blood flow restriction training increase the diameter of forearm vessels in chronic kidney disease patients? A randomized clinical trial

2018 ◽  
Vol 19 (6) ◽  
pp. 626-633 ◽  
Author(s):  
Jefferson BN Barbosa ◽  
Tuíra O Maia ◽  
Priscila S Alves ◽  
Shirley D Bezerra ◽  
Elaine CSC Moura ◽  
...  
Keyword(s):  
Clinical Trial ◽  
Chronic Kidney Disease ◽  
Blood Flow ◽  
Kidney Disease ◽  
Radial Artery ◽  
Handgrip Strength ◽  
Cephalic Vein ◽  
Blood Flow Restriction ◽  
Control Group ◽  
Flow Restriction

Introduction: Blood flow restriction training can be used as an alternative to conventional exercise in chronic kidney disease patients with indication of arteriovenous fistula. Objective: Evaluating the efficacy of blood flow restriction training in the diameter and distensibility change of the cephalic vein and the diameter and flow of the radial artery, muscle strength and forearm circumference in chronic kidney disease patients with arteriovenous fistula pre-creation. Methods: A blind randomized clinical trial consisting of 26 chronic kidney disease patients allocated into a blood flow restriction training group (blood flow restriction; n = 12) and a group without blood flow restriction training (control group; n = 14). Blood flow restriction was performed at 50% of systolic blood pressure and using 40% of handgrip strength as load for the isometric exercises in both groups. Results: An increase in the diameter of the cephalic vein in the 2 cm (p = 0.008) and 10 cm segments (p = 0.001) was observed in the control group. The diameter of the radial artery increased in all segments in the blood flow restriction group (2, 10 and 20 cm; p = 0.005, p = 0.021 and p = 0.018, respectively) and in the 10 and 20 cm segments (p = 0.017 and p = 0.026) in the control group. Handgrip strength only increased in the control group (p = 0.003). Conclusion: Physical training associated with blood flow restriction increased cephalic vein diameters in both groups and was effective in increasing the diameter of the radial artery; however, it did not demonstrate superiority over the exercise group protocol without blood flow restriction.

scholarly journals Blood Flow Restriction Therapy Preserves Whole Limb Bone and Muscle Following ACL Reconstruction

2019 ◽  
Vol 7 (3_suppl2) ◽  
pp. 2325967119S0019 ◽  
Author(s):  
Bradley Lambert ◽  
Corbin A. Hedt ◽  
Robert A. Jack ◽  
Michael Moreno ◽  
Domenica Delgado ◽  
...  
Keyword(s):  
Blood Flow ◽  
Bone Loss ◽  
Bone Mass ◽  
Acl Reconstruction ◽  
Blood Flow Restriction ◽  
Control Group ◽  
Type I ◽  
Leg Press ◽  
Flow Restriction ◽  
Post Surgery

Objectives: Patients often experience atrophy and bone loss immediately following anterior cruciate ligament (ACL) reconstruction. Rehabilitation (rehab) combined with blood flow restriction (BFR) therapy have been shown to mitigate muscle atrophy and reduce timelines for earlier return to function. Little is known about how BFR may impact bone loss. The objectives this study were to determine if BFR provides additional benefits when added to standard rehab in young active patients following ACL reconstruction with regards to preserving bone, recovering muscle, and regaining physical function. Methods: Fourteen active young adults (M=8, F=6; 23±7 yr; 170±10 cm, 75±14 kg) undergoing ACL repair via patellar tendon autograft were recruited, provided informed consent, and were randomized into two groups (CONTROL, n=7 & BFR, n=7) who performed 12wks of rehab beginning at 10 days post-surgery (2/wk). Both groups performed the same rehab protocol. However, during select exercises [quadriceps contractions wks1-3, bilateral leg press wk3-12, eccentric leg press wk4-12, hamstring curl wk4-6, eccentric hamstring curl wk7-12.], the BFR group exercised with 80% arterial limb occlusion using an automated tourniquet around the proximal thigh outfitted with Doppler (Delfi®). Exercise resistance was set at 20% of predicted 1-repetition maximum assessed in the contralateral limb. Exercises were performed for 4 sets of 30-15-15-15 repetitions separated by 30 s of rest. Functional assessments were performed at wk8 and wk12 post-surgery. Bone mineral density (BMD), bone mass, and lean muscle mass (LM) were measured using DEXA (Figure 1, GE®) at pre-surgery as well as wk6 and wk12 of rehab. Statistical Analysis: A 2(group) x 3(time) ANCOVA (co-varied on pre-surgery measures) was used to detect and compare changes in muscle and bone measures from pre-surgery at wk6 and wk12. A 2(group) x 2(time) ANOVA was used to detect and compare changes in functional outcomes tested at wk8 and wk12 between groups. Significant interactions were followed with a Tukey’s post hoc test for pairwise comparisons. Type I error was set at α=0.05. Results: Results are shown in Table 1. Both groups experienced similar decreases from pre-surgery measures in total LM at wk6 (p<0.05) with total lean mass in only the CONTROL group remaining diminished at wk12 (p<0.05). Whole leg LM in the injured limb was decreased in the CONTROL group, but not the BFR group, at both wk6 and wk12 (p<0.05). Thigh LM was found to be decreased in both groups at wk6 but to a greater extent in the CONTROL compared to the BFR group and remained decreased in only the CONTROL group at wk12. Whole leg bone mass was decreased in the control group at wk6 and in both groups wk12 (p<0.05). The CONTROL group was observed to have a decrease in BMD at the distal femur and proximal tibia as wk12 as well as the proximal fibula at wk6 and wk12 (p<0.05). Both groups demonstrated similar improvements in single leg squat distance, Y-balance, leg curl, and leg press from wk8 to wk12 of rehab (p<0.05). (Completed Data, N=32 anticipated by time of conference). Conclusion: In addition to recovering muscle to a greater extent than standard rehab alone, the addition of BFR to ACL rehab exercises appears to have a protective effect on bone. This effect also appears to not be limited to the site of cuff compression. Future studies are needed to examine the biochemical and mechanical mechanisms by which BFR may simultaneously act on bone and muscle. [Table: see text]

Effect of moderate intensity resistance training with blood flow restriction on muscle strength and girth in young adults –a randomized control trial

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Tanya Gujral ◽  
Jeyanthi Subburaj ◽  
Kiran Sharma
Keyword(s):  
Blood Flow ◽  
Resistance Training ◽  
Muscle Strength ◽  
Exercise Training ◽  
Blood Flow Restriction ◽  
Moderate Intensity ◽  
Control Group ◽  
Flow Restriction ◽  
Group A ◽  
Group B

Abstract Objectives To examine the effects of moderate intensity resistance training with blood flow restriction on muscle strength and forearm girth. Methods Total of 39 students enrolled in this study were divided into three groups that is group A (control group), group B and group C. Group A performed exercise training without restrictive pressure, group B & C performed exercise training with 50 and 75 mmHg respectively. Both the outcome measures were evaluated on day 1 and day 12th with the help of digital dynamometer and measuring tape. Results Repeated measure ANOVA with Post hoc analysis was done using SPSS software version 20. The result of the study showed significant (p≤0.05) within subject improvement in muscle strength and muscle girth in all the three groups. However, significant improvement in muscle strength was found in between group analysis (p≤0.05). Conclusions The results of the study can be concluded as the partial blood flow restriction (50 mmHg) with moderate intensity resistance training resulted in greater handgrip strength than the other two groups. No difference was found in forearm girth among the three groups, however within the group difference was found.

Evaluation of changes in the haemoglobin of skin and muscle tissue of the calf, as induced by topical application of a nonivamide/nicoboxil cream

2014 ◽  
Vol 92 (2) ◽  
pp. 149-154 ◽  
Author(s):  
Jan M. Warnecke ◽  
Thomas Wendt ◽  
Stefan Winkler ◽  
Matthias Schak ◽  
Thorsten Schiffer ◽  
...  
Keyword(s):  
Blood Flow ◽  
Oxygen Saturation ◽  
Optical Spectroscopy ◽  
Topical Application ◽  
Near Infrared ◽  
Nir Spectroscopy ◽  
Topical Administration ◽  
Tissue Oxygen Saturation ◽  
Tissue Oxygen

Topical agents like nonivamide and nicoboxil induce hyperaemisation and increase cutaneous blood flow and temperature. This study aimed to determine the effects of a nonivamide–nicoboxil cream on haemodynamics in the skin and calf muscle, via optical spectroscopy, discriminating between the changes for skin and muscle. Optical spectroscopy was applied in the visible (VIS) and near-infrared (NIR) wavelength range. The study determined the effect of the cream on changes in oxygenated (ΔoxyHb) and deoxygenated (ΔdeoxyHb) haemoglobin in skin and muscle, as well as on tissue oxygen saturation (SO2) in the skin of 14 healthy subjects. The left and right calves of the subjects were either treated with nonivamide–nicoboxil cream or were sham-administered. NIR spectroscopy allows noninvasive in-vivo examination of the oxygenation of human skeletal muscle. Topical administration of the nonivamide–nicoboxil cream significantly increased the concentration of oxygenated haemoglobin and tissue oxygen saturation in the skin, as well as the concentration of oxygenated haemoglobin in the muscle of the treated legs after 15 min, but with stronger and faster effects in the skin. The topical application of the nonivamide–nicoboxil cream increased blood flow in (smaller vessels of) the skin and muscle tissues.

Abstract 105: Changes in NIRS-Measured Cerebral Tissue Oxygen Saturation During Hyperventilation: A Comparison Between NIRO™ and INVOS™

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Tetsuo Hatanaka ◽  
Hiroshi Kaneko ◽  
Aki Nagase ◽  
Seishiro Marukawa
Keyword(s):  
Blood Flow ◽  
Oxygen Saturation ◽  
Healthy Volunteers ◽  
Near Infrared ◽  
Tissue Oxygen Saturation ◽  
Induced Response ◽  
Tissue Oxygen ◽  
Cerebral Tissue ◽  
End Tidal ◽  
Cerebral Tissue Oxygen Saturation

Introduction: Cerebral tissue oxygen saturation measured with transcranial near-infrared spectroscopy (NIRS) has been reported to predict neurological outcome of cardiac arrest patients. Because NIRS values are confounded by extracranial tissues, there can be considerable inter-device variation in the measured values. We compared hyperventilation-induced changes in NIRS values measured with 2 commercially available devices in healthy volunteers. Methods: After obtaining an approval from the ethics committee at Iseikai hospital and written informed consents, 29 healthy volunteers joined the study. Probes of NIRO™ 200NX (Hamamatsu Photonics, Japan) and INVOS™ 5100C (Covidien, USA) were applied respectively on the right and left side of the volunteers’ forehead. After obtaining the baseline values, the volunteers were asked to hyperventilate for 40 seconds attempting to reduce the end-tidal CO 2 by ~20 mmHg. Measurements were repeated, after 20 minutes of resting interval, with the probes applied on the contralateral sides. Hyperventilation-induced response of the NIRS value was categorized as “correct” when the average value over the 5 second period toward the end of the hyperventilation decreased by >15% the baseline or “erroneous” otherwise. Results: The mean (± SD) end-tidal CO 2 decreased from the baseline value of 36 ± 5.1 mmHg to 15.2 ± 4.4 mmHg during hyperventilation. Out of 58 measurements with each of the devices, NIRO values were “correct” in 54 (93.1%) measurements, whereas INVOS values were “correct” in 32 (52.2%) measurements. NIRO presented “erroneous” values on both sides of the forehead in no volunteers whereas INVOS presented “erroneous” values in 7 (35%) of 29 volunteers. Discussion: Hyperventilation consistently decreases cerebral blood flow in healthy subjects. Thus, the results of the present study suggest that NIRS devices may fail to reflect correct changes in cerebral tissue oxygen saturation in ~7% of measurements with NIRO and in ~48% with INVOS. The bilateral “erroneous” measurements with INVOS in 7 (35%) volunteers may suggest that INVOS is subject to confounding by extracranial tissues. A potential source of confounding may include the scalp where blood flow increases during hyperventilation.

scholarly journals Different cooling strategies between sets for 30 seconds does not have beneficial effect on resistance exercise with blood flow restriction

2020 ◽  
Vol 31 (1) ◽  
Author(s):  
Rodrigo Gianoni ◽  
Paulo Eduardo Pereira ◽  
Paulo Henrique Azevedo
Keyword(s):  
Blood Flow ◽  
Resistance Exercise ◽  
Rest Period ◽  
Dynamic Strength ◽  
Blood Flow Restriction ◽  
Control Group ◽  
Total Body Mass ◽  
Flow Restriction ◽  
Significant Difference ◽  
Sample Characterization

The ice application (cooling) has become popular during physical activities to improve performance. This study aimed to test whether different cooling places could increase the number of repetitions (volume) during resistance training with blood flow restriction (BFR). Ten women volunteered for this study. The sample characterization is presented in mean and standard deviation: age: 28.5 ± 8.6 years; height: 164.6 ± 8.3 cm; total body mass: 61.5 ± 7.1 maximal dynamic strength test (1RM): 236.5 ± 54.8 kg; 30% 1RM: 71.6 ± 16.5; SBP: 124.7 ± 7.7 mm Hg; 1.3 x SBP: 161.8 ± 10.4 mm Hg. The subjects performed five sessions of resistance exercise with BFR. Three sets were held in each session, with the intensity of 30% of 1RM until muscle failure; and 30-second rest period between sets. The cooling sites were: hands, neck, and tunnel temperature. One session without cooling was done and considered as control group. There was neither difference in the total number of repetitions of repetitions among interventions, nor significant difference among interventions for RPE (P = 0.49). Therefore, we do not recommend cooling to maintain a high number of repetitions during strength training with BFR.

scholarly journals The Proximal and Distal Effects of Blood Flow Restriction Therapy on Upper and Lower Extremity Strengthening: A Randomized Controlled Trial

2019 ◽  
Vol 7 (7_suppl5) ◽  
pp. 2325967119S0033
Author(s):  
Eric N. Bowman ◽  
Rami El-shaar ◽  
Heather Milligan ◽  
Greg Jue ◽  
Karen Mohr ◽  
...  
Keyword(s):  
Randomized Controlled Trial ◽  
Blood Flow ◽  
Lower Extremity ◽  
Controlled Trial ◽  
Lower Extremities ◽  
Blood Flow Restriction ◽  
Control Group ◽  
Flow Restriction ◽  
Low Intensity ◽  
Randomized Controlled

Objectives: Blood flow restriction (BFR) therapy consists of low-intensity exercise performed under reduced venous return due to an inflatable tourniquet. This produces similar physiologic and clinical effects to high-intensity routines with less joint and tissue stress. Postoperative patients may benefit from more efficient rehabilitation. Proximal and distal effects of BFR have been evaluated, however, minimal literature exists on its use in orthopaedic conditions. The purpose of this study was to determine the effects of low-intensity BFR therapy both proximal and distal, in the upper and lower extremities. Methods: This was a prospective, randomized controlled trial of healthy subjects completing a standardized 6-week course of BFR therapy. Subjects were randomized to BFR therapy on one extremity or to a control group. Subjects were excluded for cardiac, pulmonary, or hematologic disease, pregnancy, or previous surgery in the extremity. Data collected at baseline and completion included: limb circumferences, isokinetic, and manual strength testing. Results: Forty subjects completed the protocol. Average age was 27.7 years; 54% were female. For both upper and lower extremity groups, a statistically significant increase was observed in manual and isokinetic strength both proximal and distal to the BFR tourniquet when compared to both the non-tourniquet extremity and the control group (p<0.05). Limb circumference significantly increased in the upper (p<0.01) and lower extremities (p=0.02). A significant increase in manual strength was noted in shoulder abduction and scaption, and hip extension and abduction even in the non-tourniquet BFR extremity compared to the control group (p<0.05). Conclusion: Low-intensity BFR therapy led to greater increases in muscle strength and hypertrophy. Similar strengthening effects were seen in proximal and distal muscle groups. Strength increases in the contralateral BFR extremity may corroborate a systemic effect. This study provides data to further evaluate the efficacy and safety of BFR therapy in operative and non-operative orthopaedic conditions. [Table: see text]

scholarly journals Altered Oxygenation, Vascular and Ischemic Pain Responses in Adults with Sickle Cell Anemia

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 3399-3399
Author(s):  
Nathan S Fishman ◽  
Joseph Kim ◽  
Daniel Lichy ◽  
Kathleen Vaughan ◽  
Stephen Yoon ◽  
...  
Keyword(s):  
Blood Flow ◽  
Steady State ◽  
Oxygen Saturation ◽  
Sickle Cell ◽  
Sickle Cell Anemia ◽  
Pain Tolerance ◽  
Tissue Oxygen Saturation ◽  
Ischemic Pain ◽  
Tissue Oxygen ◽  
Pain Test

Abstract The clinical hallmark of sickle cell anemia is the vaso-occlusive pain crisis. Although the exact cause for severe vaso-occlusive painful events is unknown, sickle cell microvasculature occlusion is thought to be the proximate cause producing tissue hypoxia, reperfusion injury and acute pain. Endothelial dysfunction is a prominent characteristic of sickle cell anemia, and it is unclear to what extent this abnormal vascular response contributes to vaso-occlusion and pain. We sought to evaluate the effects of hypoxia on sickle cell pain by performing a forearm ischemic pain test as a potential in vivo model for vaso-occlusion. We hypothesized that sickle cell anemia patients would tolerate a shorter period of ischemia before reaching pain tolerance. We further hypothesized that sickle patients would show more hypoxia and increased vasodilation. Thirty adults with sickle cell anemia were recruited and matched by age and sex to 30 normal volunteers. We first performed a timed ischemic pain test with brachial artery occlusion until subjects first reported pain (pain threshold) and until maximum pain tolerated (pain tolerance). Sickle cell subjects first reported pain at 411 vs. 589 s for normal volunteers (mean, p=0.07). Occlusion time to pain tolerance was significantly shorter for sickle cell patients (637 vs. 918 s, mean, p=0.004). Despite this difference, both groups reported nearly identical pain scores at threshold and tolerance. Stepwise linear regression for all subjects against 8 variables likely to influence pain showed sickle status (p=0.002) and gender (p=0.0008) were independently associated with time to tolerance, supporting our initial hypothesis. Testing with continuous physiological monitoring was next repeated in sub-groups of 7 sickle cell and 9 normal subjects in an effort to understand the association between ischemia and pain progression. Before, during, and after brachial artery occlusion, oxygenated/deoxygenated hemoglobin concentration and tissue oxygen saturation were continuously monitored with near-infrared spectroscopy at the thenar eminence. We also recorded cutaneous blood flow with a Laser Speckle Contrast Imager (FLPI-2) in the volar aspect of forearm and continuous blood pressure and pulse in the contralateral arm. Monitoring was performed during steady state prior to occlusion (15 min), during occlusion until pain tolerance, and during recovery (20 min). At steady state, sickle cell subjects had higher median heart rate (68 vs. 62 bpm, p=0.05) and cutaneous blood flow (81.8 vs. 46.8 a.u., p<0.0001). They also had lower median oxygenated hemoglobin (51.3 vs. 68 μM, p<0.0001), tissue oxygen saturation (62 vs. 68%, p<0.0001) and blood pressure (110/75 vs. 126/80, p<0.0001). During occlusion, the absolute decline in blood flow, calculated as a difference between median steady state flow and flow at 2 min of occlusion, was greater with sickle group (40.8 vs. 20.63 a.u., p=0.05). However, sickle cell oxygenated hemoglobin decreased at a slower rate (-0.12 vs. -0.15, median, p<0.0001). As before, time to pain tolerance was shorter with sickle cell (566 vs. 1460 sec., median, p=0.009). Surprisingly, sickle subjects had higher median tissue oxygen saturation (28.9 vs. 25.7%, p=0.005) and oxygenated hemoglobin (22.9 vs. 20.0 μM, p=0.006) at pain tolerance, but blood flow was not different. Consistent with this pattern, recovery of oxygenated hemoglobin occurred at a slower rate in the sickle group (0.61 vs. 0.84, median, p<0.0001). Sickle subjects had a brief hyperemic recovery period during which they returned to lower baseline levels of tissue oxygen saturation and oxygenated hemoglobin, and the duration of this hyperemic recovery was the same in normal volunteers. Overall, sickle cell subjects have significantly lower steady state tissue oxygenation, but they are less tolerant of hypoxia and develop pain at higher oxygenated hemoglobin levels during ischemia. Despite higher oxygenated hemoglobin during ischemia, sickle cell subjects have a significantly higher absolute decline in blood flow during occlusion, suggesting an altered hypoxic response compared to controls. This might suggest a hypersensitive hypoxic pain response, possibly due to the presence of chronic pain, and altered oxygen sensing. The ischemic pain test is a potential in vivo model for early stage trials of drugs that alter either acute pain transmission or oxygen delivery to tissues. Disclosures No relevant conflicts of interest to declare.

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