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BACKGROUND: Chest compression at a rate of 100-120 compressions per minute (cpm) during cardiopulmonary resuscitation (CPR) is associated with the highest survival rates. Performing compressions at a faster rate may exhaust the rescuers. OBJECTIVES: To compare a new cue of 'two compressions per second' to the traditional cue of '100-120 compressions per minute' on compression rate in CPR training. METHODS: In this cluster-randomized study, students from two senior high schools were assigned into two groups. For the experimental group, the cue for the compression rate was 'two compressions per second'. For the control group, the cue was '100-120 cpm'. Except the different cues, all participants underwent the same standardized CPR training program. Verbal compression rate-related feedback was not obtained during practice. Quality indicators of chest compressions were recorded by a sensorized manikin. The primary outcome measure was mean compression rate at course conclusion. The secondary outcome measures were individual compression quality indicators at course conclusion and 3 months after training. RESULTS: We included 164 participants (85 participants, experimental group; 79 participants, control group). Both groups had similar characteristics. The experimental group had a significantly lower mean compression rate at course conclusion (144.3 ± 16.17 vs. 152.7 ± 18.38 cpm, p = 0.003) and at 3 months after training (p = 0.09). The two groups had similar mean percentage of adequate compression rate (≥ 100 cpm), mean compression depth, and mean percentage of complete recoil at course conclusion and 3 months after training. CONCLUSION: The new cue of 'two compressions per second' resulted in participants having a lower compression rate, although it still exceeded 120 cpm.

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The exponential growth in data volume has necessitated the adoption of alternative storage solutions, and DNA storage stands out as the most promising solution. However, the exorbitant costs associated with synthesis and sequencing impeded its development. Pre-compressing the data is recognized as one of the most effective approaches for reducing storage costs. However, different compression methods yield varying compression ratios for the same file, and compressing a large number of files with a single method may not achieve the maximum compression ratio. This study proposes a multi-file dynamic compression method based on machine learning classification algorithms that selects the appropriate compression method for each file to minimize the amount of data stored into DNA as much as possible. Firstly, four different compression methods are applied to the collected files. Subsequently, the optimal compression method is selected as a label, as well as the file type and size are used as features, which are put into seven machine learning classification algorithms for training. The results demonstrate that k-nearest neighbor outperforms other machine learning algorithms on the validation set and test set most of the time, achieving an accuracy rate of over 85% and showing less volatility. Additionally, the compression rate of 30.85% can be achieved according to k-nearest neighbor model, more than 4.5% compared to the traditional single compression method, resulting in significant cost savings for DNA storage in the range of $0.48 to 3 billion/TB. In comparison to the traditional compression method, the multi-file dynamic compression method demonstrates a more significant compression effect when compressing multiple files. Therefore, it can considerably decrease the cost of DNA storage and facilitate the widespread implementation of DNA storage technology.

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Aim: Propose new metrics of impulsiveness of manual chest compressions (CCs) that account for shape and duration, separate the characteristics of the compressive part of the CC cycle from those of the recoil part, and are uncorrelated to CC depth and rate. Methods: We conducted a retrospective analysis of adult out-of-hospital cardiac arrest monitor-defibrillator recordings having CPR data. Specifically, episodes of adult patients with ≥ 1000 compressions free of leaning were examined. CCs were obtained from the depth signal of the valid episodes, and we calculated the novel metrics: compression area index (CAI), recoil area index (RAI), compression impulsiveness index (CII) and recoil impulsiveness index (RII). Generalized linear mixed-effects models and Jonckheere-Terpstra trend analyses were employed to measure differences between populations and trends, and the absolute value of Pearson's correlation coefficient |r| was used to report dependence between variables. Statistics are reported as median and interquartile range. Results: We analyzed 982,340 CCs corresponding to 453 episodes, for which we calculated their CAI, RAI and duty cycle (DC). We analyzed the metrics for various populations: age, sex, any ROSC achieved and disposition, and found that CAI was significantly different according to patient disposition and RAI relative to age and sex (p<0.05). None of the metrics was correlated strongly to depth or rate (|r| values of 0.22 or smaller), and all of them varied for CC series corresponding to the same rescuer over the course of resuscitation (ptrend<0.05). However, we observed that the metrics are not balanced, in that for any value of DC, CAI and RAI span almost their entire ranges. Conclusion: The proposed metrics correctly and completely describe manual CC waveforms, improve upon the DC, since they depend on the signal waveform, and provide additional information to current indicators of quality CPR, depth and rate. Furthermore, they allow to differentiate the compressive and recoil parts of the CC cycle, reflecting influence of the rescuer (via CAI or CII) and of the biomechanics of the patient's chest (via RAI or RII). Thus, they have the potential to contribute to better understanding CPR dynamics and, eventually, to enhanced quality of CPR practice as additional indicators of proper manual CC technique.

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Aim: The aim of this study was to evaluate chest compression rates (CCR) with and without the use of a metronome during treatment of out-of-hospital cardiac arrest (OHCA). Methods: We performed a retrospective cohort investigation of non-traumatic OHCA cases treated by Seattle Fire Department from January 1, 2013, to December 31, 2019. The exposure was a metronome running during CPR at a rate of 110 beats per minute. The primary outcome was the median CCR for all periods of CPR with a metronome compared to periods without a metronome. Results: We included 2,132 OHCA cases with 32,776 minutes of CPR data; 15,667 (48%) minutes had no metronome use, and 17,109 (52%) minutes had a metronome used. Without a metronome, the median CCR was 112.8 per minute with an interquartile range of 108.4 - 119.1, and 27% of minutes were above 120 or less than 100. With a metronome, the median CCR was 110.5 per minute with an interquartile range of 110.0-112.0, and less than 4% of minutes were above 120 or less than 100. The compression rate was 109, 110, or 111 in 62% of minutes with a metronome compared to 18% of minutes with no metronome. Conclusion: The use of a metronome during CPR resulted in increased compliance to a predetermined compression rate. Metronomes are a simple tool that improves achievement of a target compression rate with little variance from that target.

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Mechanoluminescence (ML) has received widespread attention because of potential application in stress sensors and imaging. However, pursuing highly efficient ML remains a challenge due to multifactorial limitations such as pressure and loading rate. Here, we systematically investigate pressure- and rate-dependent ML in Mn2+ and Eu3+ co-doped ZnS in a gigapascal pressure range by using a high-pressure dynamic diamond anvil cell and microsecond time-resolved fluorescent methods and demonstrate the giant tunability in both ML efficiency and wavelength. Compressed from ambient pressure to 11 GPa at different compression rates, ZnS: Mn2+, Eu3+ exhibits a volcano shape in ML emission efficiency with an optimum at ∼3.5 GPa and ∼211.1 GPa/s, at least 1000-fold higher than that measured in the MPa range. The pressure-dependent ML is accompanied with a tunable yellow-to-red emission color change. A combination of high-pressure X-ray diffraction and photoluminescence measurements reveals that the pressure- and rate-dependent ML behavior derives from pressure-induced strengthening of the crystal piezoelectric field and enhanced interaction between the host lattice and doped ions with a significant change of the energy level of the Mn ion. Significantly, the highly efficient ML of ZnS: Mn2+, Eu3+ at the GPa level is reproducible under a compression-decompression process and can be manipulated on a micron scale, implying great potential in mechanical-optical energy conversion and application in dynamic pressure imaging, stress sensors, and multicolor displays.

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AIM: Characterise how changes in chest compression depth and rate affect variations in end-tidal CO2 (ETCO2) during manual cardiopulmonary resuscitation (CPR) in out-of-hospital cardiac arrest (OHCA). METHODS: Retrospective analysis of adult OHCA monitor-defibrillator recordings having concurrent capnogram, compression depth, transthoracic impedance and ECG, and with atleast 1,000 compressions. Within each patient, during no spontaneous circulation, nearby segments with changes in chest compression depth and rate were identified. Average ETCO2 within each segment was standardised to compensate for ventilation rate variability. Contributions of relative variations in depth and rate to relative variations in standardised ETCO2 were characterised using linear and non-linear models. Normalisation between paired segments removed intra and inter-patient variation and made coefficients of the model independent of the scale of measurement and therefore directly comparable. RESULTS: A total of 394 pairs of segments from 221 patients were analysed (33% female, median (IQR) age 66 (55-74) years). Chest compression depth and rate were 50.4 (43.2-57.0)mm and 111.1 (106.5-116.1)compressions per minute. ETCO2 before and after standardization was 32.1 (23.0-41.4)mmHg and 28.5 (19.4-38.7)mmHg. Linear model coefficient of determination was 0.89. Variation in compression depth mainly explained ETCO2 variation (coefficient 0.95, 95% confidence interval (CI): 0.93-0.98) while changes in compression rate did not (coefficient 0.04, 95% CI: 0.01-0.07). Non-linear trend analysis confirmed the results. CONCLUSION: This study quantified the relative importance of chest compression characteristics in terms of their impact on CO2 production during CPR. With ventilation rate standardised, variation in chest compression depth explained variations in ETCO2 better than variation in chest compression rate.

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PURPOSE: To improve cardiac arrest survival, international resuscitation guidelines emphasize measuring the quality of cardiopulmonary resuscitation (CPR). We aimed to investigate CPR quality during in-hospital cardiac arrest (IHCA) and study long-term survival outcomes. PATIENTS AND METHODS: This was a cohort study of IHCA from December 2011 until November 2014. Data were collected from the hospital switch board, patient records, and from defibrillators. Impedance data from defibrillators were analyzed manually at the level of single compressions. Long-term survival at 1-, 3-, and 5 years is reported. RESULTS: The study included 189 IHCAs; median (interquartile range (IQR)) time to first rhythm analysis was 116 (70-201) seconds and median (IQR) time to first defibrillation was 133 (82-264) seconds. Median (IQR) chest compression rate was 126 (119-131) per minute and chest compression fraction (CCF) was 78% (69-86). Thirty-day survival was 25%, while 1-year-, 3-year-, and 5-year survival were 21%, 14%, and 13%, respectively. There was no significant association between any survival outcomes and CCF, whereas chest compression rate was associated with survival to 30 days and 3 years. Overall, 5-year survival was associated with younger age (median 68 vs 74 years, p=0.003), less comorbidity (Charlson comorbidity index median 3 vs 5, p<0.001), and witnessed cardiac arrest (96% vs 77%, p=0.03). CONCLUSION: We established a systematic collection of IHCA CPR quality data to measure and improve CPR quality and long-term survival outcomes. Median time to first rhythm check/defibrillation was <3 minutes, but median chest compression rate was too fast and median CCF slightly below 80%. More than half of 30-day survivors were still alive at 5 years.

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AIM: To evaluate an algorithm that uses an end-tidal carbon dioxide (ETCO2) target of ≥ 30 torr to guide specific changes in chest compression rate and epinephrine administration during cardiopulmonary resuscitation (CPR) in paediatric swine. METHODS: Swine underwent asphyxial cardiac arrest followed by resuscitation with either standard or ETCO2-guided algorithm CPR. The standard group received chest compressions at a rate of 100/min and epinephrine every 4 min during advanced life support consistent with the American Heart Association paediatric resuscitation guidelines. In the ETCO2-guided algorithm group, chest compression rate was increased by 10 compressions/min for every minute that the ETCO2 was < 30 torr, and the epinephrine administration interval was decreased to every 2 min if the ETCO2 remained < 30 torr. Short-term survival and physiologic data during active resuscitation were compared. RESULTS: Short-term survival was significantly greater in the ETCO2-guided algorithm CPR group than in the standard CPR group (16/28 [57.1%] versus 4/28 [14.3%]; p = 0.002). Additionally, the algorithm group had higher predicted mean ETCO2, chest compression rate, diastolic and mean arterial pressure, and myocardial perfusion pressure throughout resuscitation. Swine in the algorithm group also exhibited significantly greater improvement in diastolic and mean arterial pressure and cerebral perfusion pressure after the first dose of epinephrine than did those in the standard group. Incidence of resuscitation-related injuries was similar in the two groups. CONCLUSIONS: Use of a resuscitation algorithm with stepwise guidance for changes in the chest compression rate and epinephrine administration interval based on a goal ETCO2 level improved survival and intra-arrest hemodynamics in this porcine cardiac arrest model.

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Eustachian tube dysfunction (ETD) and middle ear barotrauma (MEB) are common reported complications during hyperbaric oxygen treatment. Our Phase I study data was the first to demonstrate a statistically significant decrease in the occurrence of symptomatic ETD and MEB. The Phase I Trial suggested the total time interval and rate (slope) of compression (ROC) may be a determining factor in ETD and MEB. This Phase II study investigates an optimal rate of compression to reduce ETD and MEB when considering each multiplace treatment (with multiple patients) as the unit of observation as a group, rather than for each individual patient. Data were collected prospectively on 1,244 group patient-treatment exposures, collectively including 5,072 individual patient-treatment/exposures. We randomly assigned patient-treatment group exposures to four different time interval and rate (slope) of compression. These compression rates and slopes were identical to those used in the Phase I trial. All patients experiencing symptoms of MEB requiring compression stops were evaluated post treatment for the presence of ETD and MEB using the O'Neill Grading System (OGS) for ETD. Data were analyzed using the IBM-SPSS statistical software program. A statistically significant decrease in the number of compression holds was observed in the 15-minute compression schedule, correlating to the results observed in the Phase I trial. The 15-minute linear compression profile continues to demonstrate the decreased need for patient symptomatic compression stops (as in the Phase I trial) using a USN TT9 during elective hyperbaric oxygen treatments in a Class A multiplace hyperbaric chamber. Trial Registration: ClinicalTrials.gov Identifier: NCT04776967.

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OBJECTIVES: A systematic review to determine if cardiopulmonary resuscitation (CPR) guided by either real-time or post-event feedback could improve CPR quality or patient outcome compared to unguided CPR in out-of-hospital cardiac arrest (OHCA). METHODS: Four databases were searched; PubMed, Embase, CINAHL, and Cochrane Library in August 2020 for post 2010 literature on OHCA in adults. Critical outcomes were chest compression depth, rate and fraction. Important outcomes were any return of spontaneous circulation, survival to hospital and survival to discharge. RESULTS: A total of 9464 studies were identified with 61 eligibility for full text screening. A total of eight studies was included in the meta-analysis. Five studies investigated real-time feedback and three investigated post-event feedback. Meta-analysis revealed that real-time feedback statistically improves compression depth and rate while post-event feedback improved depth and fraction. Feedback did not statistically improve patient outcome but an improvement in absolute numbers revealed a clinical effect of feedback. Heterogenity varied from "might not be important" to "considerable". CONCLUSION: To significantly improve CPR quality real-time and post-event feedback should be combined. Neither real-time nor post event feedback could statistically be associated with patient outcome however, a clinical effect was detected. The conclusions reached were based on few studies of low to very low quality. PROSPERO REGISTRATION: CRD42019133881.

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Weaning is a critical period for the health of rabbits, with a high sensitivity to digestive diseases. Allowing early consumption of solid feed in the nest of the suckling rabbit could help to maintain its health around weaning. In general, previous studies have focused on feed intake of rabbits when they are able to leave the nest, i.e. around 16 days. Herein, we provide a unique dataset of the dynamics of the onset of feed intake in suckling rabbits from 8 days to weaning. We quantified the solid feed intake behaviour and determined the dietary preferences for pellets according to their physical properties using nine pellets differing in diameter or compression rate. Additionally to the data provided in Paës et al. [1] we provide (i) the description of the nine pellets processing (ii) the description of the 3 point-scale system for nest quality evaluation, (iii) details on the device used to provide pellets in the nest, (iv) milk intake data and milk intake curve calculation and (v) pellet intake data according to physical characteristics.

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AIM: The mathematical method used to calculate chest compression (CC) rate during cardiopulmonary resuscitation varies in the literature and across device manufacturers. The objective of this study was to determine the variability in calculated CC rates by applying four published methods to the same dataset. METHODS: This study was a secondary investigation of the first 200 pediatric cardiac arrest events with invasive arterial line waveform data in the ICU-RESUScitation Project (NCT02837497). Instantaneous CC rates were calculated during periods of uninterrupted CCs. The defined minimum interruption length affects rate calculation (e.g., if an interruption is defined as a break in CCs ≥ 2 s, the lowest possible calculated rate is 30 CCs/min). Average rates were calculated by four methods: 1) rate with an interruption defined as ≥ 1 s; 2) interruption ≥ 2 s; 3) interruption ≥ 3 s; 4) method #3 excluding top and bottom quartiles of calculated rates. American Heart Association Guideline-compliant rate was defined as 100-120 CCs/min. A clinically important change was defined as ±5 CCs/min. The percentage of events and epochs (30 s periods) that changed Guideline-compliant status was calculated. RESULTS: Across calculation methods, mean CC rates (118.7-119.5/min) were similar. Comparing all methods, 14 events (7%) and 114 epochs (6%) changed Guideline-compliant status. CONCLUSION: Using four published methods for calculating CC rate, average rates were similar, but 7% of events changed Guideline-compliant status. These data suggest that a uniform calculation method (interruption ≥ 1 s) should be adopted to decrease variability in resuscitation science.

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AIM: Maximum velocity during chest recoil has been proposed as a metric for chest compression quality during cardiopulmonary resuscitation (CPR). This study investigated the relationship of the maximum velocities during compression and recoil phases with compression depth and rate in manual CPR. METHODS: We measured compression instances in out-of-hospital cardiac arrest recordings using custom Matlab programs. Each compression cycle was characterized by depth and rate, maximum compression and recoil velocities (CV and RV), and compression and recoil durations (total and effective). Mean compression and recoil velocities were computed as depth divided by compression and recoil durations, respectively. We correlated CV and RV with their corresponding mean velocities (total and effective), characterized by Pearson's correlation coefficient. RESULTS: CV/RV were strongly correlated with their corresponding mean velocities, with a median r of 0.83 (0.77-0.88)/0.82 (0.76-0.87) in per patient analysis, 0.86/0.88 for all the population. Correlation with mean effective velocities had a median r of 0.91 (0.87-0.94)/0.92 (0.89-0.94) in per-patient, 0.92/0.94 globally (p < 0.001). Total and effective compression and recoil durations were inversely proportional to compression rate. We observed similar RV values among compressions regardless of whether they were compliant with recommended depth and rate. Conversely, we observed different RV values among compressions having the same depth and rate, but presenting very distinct compression waveforms. CONCLUSION: CV and RV were highly correlated with compression depth and compression and recoil times, respectively. Better understanding of the relationship between novel and current quality metrics could help with the interpretation of CPR quality studies.

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Introduction: Symptomatic Eustachian tube dysfunction (ETD) and middle ear barotrauma (MEB) are the most common reported complications during hyperbaric oxygen (HBO2) treatment. There is no standardized rate of compression (ROC) reported to decrease the incidence rates of ETD and MEB during hyperbaric treatments. Few studies actually demonstrate that the ROC decreases the incidence of ETD or MEB. Methods: Our study was designed to determine an optimal hyperbaric chamber compression rate that might reduce the incidence of symptomatic ETD leading to MEB during the compression phase of treatment in a multiplace hyperbaric chamber. Data was collected prospectively over 2,807 elective patient treatments compressed using a U.S. Navy Treatment Table 9 (USN TT9) with a modified ROC. ROC was assigned using two variables, time (10 vs.15 minutes) and slope (linear vs. non-linear compression). Patients were exposed to all four compression schedules in a consecutive daily fashion. We recorded any patient requiring a stop during initial compression due to ear discomfort. Anyone requiring a stop was evaluated post treatment for MEB. Findings were compared to our standard 10-minute linear ROC. Evaluation of the tympanic membrane was accomplished using video otoscopy. Barotrauma when present was classified using both the Teed and O'Neill grading systems. Data was analyzed using basic statistical methods. Results: When comparing four different rates of compression during an elective USN TT9 in a multiplace (Class A) chamber there is a decreased incidence for symptomatic ETD when using a 15-minute linear compression schedule (p-value ⟨0.05). Conclusion: Using a 15-minute linear compression schedule is associated with less symptomatic ETD and less MEB when performing an elective 45 fsw (USN TT9) hyperbaric treatment in a Class A chamber. Asymptomatic ETD and MEB were not considered in this study.

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INTRODUCTION: High-quality chest compressions (CCs) are associated with high survival rates and good neurological outcomes in cardiac arrest patients. The 2015 American Heart Association (AHA; Dallas, Texas USA) Guidelines for Resuscitation defined and recommended high-quality CCs during cardiopulmonary resuscitation (CPR). However, CPR providers struggle to achieve high-quality CCs. There is a debate about the use of backboards during CPR in literature. Some studies suggest backboards improve CC quality, whereas others suggest that backboards can cause delays. This is the first study to evaluate all three components of high-quality CCs: compression depth, recoil depth, and rate, at the same time with a high number of subjects. This study evaluated the impact of backboards on CC quality during CPR. The primary outcome was the difference in successful CC rates between two groups. METHODS: This was a randomized, controlled, single-blinded study using a high-fidelity mannequin. The successful CC rates, means CC depths, recoil depths, and rates achieved by 6th-grade undergraduate medical students during two minutes of CPR were compared between two randomized groups: an experimental group (backboard present) and a control group (no backboard). RESULTS: Fifty-one of all 101 subjects (50.5%) were female, and the mean age was 23.9 (SD = 1.01) years. The number and the proportion of successful CCs were significantly higher in the experimental group (34; 66.7%) when compared to the control group (19; 38.0%; P = .0041). The difference in mean values of CC depth, recoil depth, and CC rate was significantly higher in the experiment group. CONCLUSION: The results suggest that using a backboard during CPR improves the quality of CCs in accordance with the 2015 AHA Guidelines.Sanri E, Karacabey S. The impact of backboard placement on chest compression quality: a mannequin study. Prehosp Disaster Med. 2019;34(2):182-187.

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PURPOSE: To investigate the influence of the size of low intensity zone (LIZ) (T1 image) on the vertebral body and the increase in the compression rate in patients with osteoporotic vertebral compression fracture. MATERIALS AND METHODS: In a retrospective study, 187 patients (198 segments) who were followed-up for at least 3 months and diagnosed with thoracolumbar vertebral compression fracture between October 2011 and October 2016, and treated with conservative therapies, such as bed rest and thoraco-lumbar-sacral orthosis. We measured the size of the vertebral LIZ, and fractures on the upper and lower endplates were observed on the initial magnetic resonance imaging. We analyzed the correlation with the increase in compression rate at the last follow-up. Comparisons of the increase in the compression rate were analyzed through a correlation analysis. RESULTS: The larger the size of the LIZ the greater the difference in the increase of the compression rate. The group with the initially LIZ (80%–100%) was significantly increased to 23.87%±17.90% (p=0.007). In case of fracture of upper and lower endplates, an increase in the compression rate was 19.39%±12.59% in the upper endplate fracture, which was significantly higher than that in the absence of endplate fracture (p=0.002). CONCLUSION: The larger the size of the LIZ (T1 image) and superior endplate fracture observed on the initial magnetic resonance imaging after fracture, the greater the increase in the compression rate. In particular, when the size of the LIZ is greater than 80%, the compression rate was significantly increased.

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BACKGROUND: The knee joint performs mechanical functions with various loading and unloading processes. Past studies have focused on the kinematics and elastic response of the joint with less understanding of the rate-dependent load response associated with viscoelastic and poromechanical behaviors. METHODS: Forty-five fresh porcine knee joints were used in the present study to determine the loading-rate-dependent force-compression relationship, creep and relaxation of normal, dehydrated and meniscectomized joints. RESULTS: The mechanical tests of all normal intact joints showed similar strong compression-rate-dependent behavior: for a given compression-magnitude up to 1.2 mm, the reaction force varied 6 times over compression rates. While the static response was essentially linear, the nonlinear behavior was boosted with the increased compression rate to approach the asymptote or limit at approximately 2 mm/s. On the other hand, the joint stiffness varied approximately 3 times over different joints, when accounting for the maturity and breed of the animals. Both a loss of joint hydration and a total meniscectomy greatly compromised the load support in the joint, resulting in a reduction of load support as much as 60% from the corresponding intact joint. However, the former only weakened the transient load support, but the latter also greatly weakened the equilibrium load support. A total meniscectomy did not diminish the compression-rate-dependence of the joint though. CONCLUSIONS: These findings are consistent with the fluid-pressurization loading mechanism, which may have a significant implication in the joint mechanical function and cartilage mechanobiology.

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As per the AHA 2015 and ERC 2015 guidelines for resuscitation, chest compression depth should be between 5 and 6 cm with a rate of 100-120 compressions per minute. Theoretical validation of these guidelines is still elusive. We developed a computer model of the cardiopulmonary resuscitation (CPR) system to validate these guidelines. A lumped element computer model of the cardiovascular system was developed to simulate cardiac arrest and CPR. Cardiac output was compared for a range of compression pressures and frequencies. It was observed from our investigation that there is an optimum compression pressure and rate. The maximum cardiac output occurred at 100 mmHg, which is approximately 5.7 cm, and in the range of 100 to 120 compressions per minute with an optimum value at 110 compressions per minute, validating the guidelines. Increasing the pressure or the depth of compression beyond the optimum, limits the blood flow by depleting the volume in the cardiac chambers and not allowing for an effective stroke volume. Similarly increasing the compression rate beyond the optimum degrades the ability of the chambers to pump blood. The results also bring out the importance of complete recoil of the chest after each compression with more than 400% increase in cardiac output from 90% recoil to 100% recoil. Our simulation predicts that the recommendation to compress harder and faster is not the best counsel as there is an optimum compression pressure and rate for high-quality CPR.

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OBJECTIVE: To observe different bone cement dispersion types of PVP, PKP and manipulative reduction PVP and their effects in the treatment of senile osteoporotic vertebral compression fractures and the bone cement leakage rate. METHODS: The clinical data of patients with osteoporotic vertebral compression fractures who underwent unilateral vertebroplasty from January 2012 to January 2015 was retrospectively analyzed. Of them, 56 cases including 22 males and 34 females aged from 60 to 78 years old were treated by PVP operation; Fouty-eight cases including 17 males and 31 females aged from 61 to 79 years old were treated by PKP operation; Forty-three cases including 15 males and 28 females aged from 60 to 76 years old were treated by manipulative reduction PVP operation. AP and lateral DR films were taken after the operation; the vertebral bone cement diffusion district area and mass district area were calculated with AutoCAD graphics processing software by AP and lateral DR picture, then ratio(K) of average diffusion area and mass area were calculated, defining K<50% as mass type, 50%<=K<=100% as mixed type and K>100% as diffusion type. Different bone cement dispersion types of PVP, PKP and manipulative reduction PVP operation were analyzed. According to bone cement dispersion types, patients were divided into diffusion type, mixed type and mass type groups.Visual analogue scale (VAS), vertebral body compression rate, JOA score and bone cement leakage rate were observed. RESULTS: All patients were followed up for 12-24 months with an average of 17.2 months. There was significant difference in bone cement dispersion type among three groups (P<0.05). The constituent ratio of diffusion type, mixed type and mass type in PVP operation was 46.43%, 35.71%, 17.86%, in PKP was 16.67%, 37.50% , 45.83%, and in manipulative reduction PVP was 37.21%, 44.19% and 18.60%, respectively. PVP operation and manipulative reduction PVP were mainly composed of diffusion type and mixed type, while PKP was mainly composed of mass type and mixed type. There was no significant difference in VAS score, JOA score and bone cement leakage rate among three groups. There was statistically significant difference in postoperative vertebral body compression rate among three bone cement dispersion types(P<0.05), postoperative vertebral body compression rate in diffusion type group at 24 h postoperatively and final follow-up was (17.31±5.06)% and(18.58±4.91)%, respectively. In mixed type group, it was(14.21±5.15)% and(14.59±5.07)%, respectively. In mass type group, it was(13.89±5.02)% and(14.28±4.94)%, respectively. CONCLUSIONS: Bone cement dispersion type is different in PVP, PKP and manipulative reduction PVP operation. The bone cement dispersion of mass type and mixed type to recovery of compressed vertebral body is better than diffusion type, and there is no obvious difference in clinical effect in different bone cement dispersion type early and middle term.

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