Carotid artery velocity time integral and corrected flow time measured by a wearable Doppler ultrasound detect stroke volume rise from simulated hemorrhage to transfusion

Objective Doppler ultrasonography of the common carotid artery is used to infer stroke volume change and a wearable Doppler ultrasound has been designed to improve this workflow. Previously, in a human model of hemorrhage and resuscitation comprising approximately 50,000 cardiac cycles, we found a strong, linear correlation between changing stroke volume, and measures from the carotid Doppler signal, however, optimal Doppler thresholds for detecting a 10% stroke volume change were not reported. In this Research Note, we present these thresholds, their sensitivities, specificities and areas under their receiver operator curves (AUROC). Results Augmentation of carotid artery maximum velocity time integral and corrected flowtime by 18% and 4%, respectively, accurately captured 10% stroke volume rise. The sensitivity and specificity for these thresholds were identical at 89% and 100%. These data are similar to previous investigations in healthy volunteers monitored by the wearable ultrasound.

Human-In-The-Loop Optimization of A Wearable Robot Using Foot Pressure Sensors

Background: Individuals with below-knee amputation (BKA) experience increased physical effort when walking, and the use of a robotic ankle-foot prosthesis (AFP) can reduce such effort. Our prior study on a robotic AFP showed that walking effort could be reduced if the robot is personalized to the wearer. The personalization is accomplished using human-in-the-loop (HIL) optimization, in which the cost function is based on a real-time physiological signal indicating physical effort. The conventional physiological measurement, however, requires a long estimation time, hampering real-time optimization due to the limited experimental time budget. In addition, the physiological sensor, based on respiration uses a mask with rigid elements that may be difficult for the wearer to use. Prior studies suggest that a symmetry measure using a less intrusive sensor, namely foot pressure, could serve as a metric of gait performance. This study hypothesized that a function of foot pressure, the symmetric foot force-time integral, could be used as a cost function to rapidly estimate the physical effort of walking; therefore, it can be used to personalize assistance provided by a robotic ankle in a HIL optimization scheme. Methods: We developed a new cost function derived from a well-known clinical measure, the symmetry index, by hypothesizing that foot force-time integral (FFTI) symmetry would be highly correlated with metabolic cost. We conducted experiments on human participants (N = 8) with simulated amputation to test the new cost function. The study consisted of a discrete trial day, an HIL optimization training day, and an HIL optimization data collection day. We used the discrete trial day to evaluate the correlation between metabolic cost and a cost function using symmetric FFTI percentage. During walking, we varied the prosthetic ankle stiffness while measuring foot pressure and metabolic rate. On the second and third days, HIL optimization was used to find the optimal stiffness parameter with the new cost function using symmetric FFTI percentage. Once the optimal stiffness parameter was found, we validated the performance with comparison to a weight-based stiffness and control-off conditions. We measured symmetric FFTI percentage during the stance phase, prosthesis push-off work, metabolic cost, and user comfort in each condition. We expected the optimized prosthetic ankle stiffness based on the newly developed cost function could reduce the energy expenditure during walking for the individuals with simulated amputation. Results: We found that the cost function using symmetric foot force-time integral percentage presents a reasonable correlation with measured metabolic cost (Pearson’s R > 0.62). When we employed the new cost function in HIL ankle-foot prosthesis parameter optimization, 8 individuals with simulated amputation reduced their cost of walking by 15.9% (p = 0.01) and 16.1% (p = 0.02) compared to the weight-based and control-off conditions, respectively. The symmetric FFTI percentage for the optimal condition tended to be closer to the ideal symmetry value (50%) compared to weight-based (p = 0.23) and control-off conditions (p = 0.04). Conclusion: This study suggests that foot force-time integral symmetry using foot pressure sensors can be used as a cost function when optimizing a wearable robot parameter.

Effectiveness of the Fixtoe Device® in Plantar Pressure Reduction: A Preliminary Study.

Background: Metatarsalgia is a common foot condition. The metatarsophalangeal stabilizing taping technique described by Yu et al. has shown good clinical results as a provisional treatment in propulsive metatarsalgia. 35 The Fixtoe Device®, a novel orthopedic device, intends to simulate stabilizing tape. However, to date, there is no evidence of its effectiveness.Methods: The aim of this study was to assess plantar pressure changes using the Fixtoe Device®, in comparison with the traditional method (stabilizing tape) in a young, healthy sample thorough a cross-sectional study. Maximal pressure (Kpa) and pressure-time integral (Kpa/s) in the second metatarsal head were measured in twenty-four healthy volunteers. Registers were taken in four different conditions: barefoot, traditional stabilizing tape, Fixtoe Device® without metatarsal pad, and Fixtoe Device® with metatarsal pad. Results: Mean second metatarsal head maximal pressure and mean pressure-time integral showed statistical difference among the four analyzed conditions (p < 0.0001 in both cases). The improvement in maximal pressure and pressure-time integral obtained in each intervention also showed significance (p < 0.0001 in both cases). Comparing the improvement of the Fixtoe Device® with and without metatarsal pad with that of tape condition showed a moderate to high and moderate effect size for both peak pressure and pressure-time integral reduction.Conclusions: The Fixtoe Device® reduces median maximal pressure and median pressure-time integral under the second metatarsal head in healthy young individuals. The Fixtoe Device® shows higher effectiveness than the traditional second metatarsophalangeal joint stabilizing taping technique. To our knowledge, this is the first investigation proving the effectiveness of the recently developed Fixtoe Device® in terms of plantar pressure modification, which leads the way to its use in clinics.

Volume Overload Initiates an Immune Response in the Right Ventricle at the Neonatal Stage

Background: Pulmonary regurgitation caused by the correction or palliation of pediatric tetralogy of Fallot (TOF) leads to chronic right ventricular (RV) volume overload (VO), which induces adolescent RV dysfunction. A better understanding of the molecular mechanism by which VO initiates neonatal RV remodeling may bring new insights into the post-surgical management of pediatric TOF.Methods and Results: We created a fistula between the abdominal aorta and inferior vena cava on postnatal day 1 (P1) using a rat model to induce neonatal VO. Echocardiography revealed that the velocity and velocity- time-integral of the pulmonary artery (PA) were significantly elevated, and hematoxylin and eosin (H&amp;E) staining showed that the diameter of the RV significantly increased. RNA-seq analysis of the RV on P7 indicated that the top 10 enriched Gene Ontology (GO) terms and the top 20 enriched terms in the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were associated with immune responses. Flow-cytometric analysis demonstrated that the number of CD4+and CD8+ immune cells were significantly augmented in the VO group compared with the sham group.Conclusions: A neonatal cardiac VO rat model on P1 was successfully created, providing a platform for studying the molecular biology of neonatal RV under the influence of VO. VO - induces an immune response at the neonatal stage (from P1 to P7), suggesting that immune responses may be an initiating factor for neonatal RV remodeling under the influence of VO and that immunosuppressants may be used to prevent pediatric RV remodeling caused by VO.

Lower limb kinetic comparisons between the chasse step and one step footwork during stroke play in table tennis

Background Biomechanical footwork research during table tennis performance has been the subject of much interest players and exercise scientists. The purpose of this study was to investigate the lower limb kinetic characteristics of the chasse step and one step footwork during stroke play using traditional discrete analysis and one-dimensional statistical parameter mapping. Methods Twelve national level 1 table tennis players (Height: 172 ± 3.80 cm, Weight: 69 ± 6.22 kg, Age: 22 ± 1.66 years, Experience: 11 ± 1.71 year) from Ningbo University volunteered to participate in the study. The kinetic data of the dominant leg during the chasse step and one step backward phase (BP) and forward phase (FP) was recorded by instrumented insole systems and a force platform. Paired sample T tests were used to analyze maximum plantar force, peak pressure of each plantar region, the force time integral and the pressure time integral. For SPM analysis, the plantar force time series curves were marked as a 100% process. A paired-samples T-test in MATLAB was used to analyze differences in plantar force. Results One step produced a greater plantar force than the chasse step during 6.92–11.22% BP (P = 0.039). The chasse step produced a greater plantar force than one step during 53.47–99.01% BP (P < 0.001). During the FP, the chasse step showed a greater plantar force than the one step in 21.06–84.06% (P < 0.001). The one step produced a higher maximum plantar force in the BP (P = 0.032) and a lower maximum plantar force in the FP (P = 0) compared with the chasse step. The one step produced greater peak pressure in the medial rearfoot (P = 0) , lateral rearfoot (P = 0) and lateral forefoot (P = 0.042) regions than the chasse step during BP. In FP, the chasse step showed a greater peak pressure in the Toe (P = 0) than the one step. The one step had a lower force time integral (P = 0) and greater pressure time integral (P = 0) than the chasse step in BP, and the chasse step produced a greater force time integral (P = 0) and pressure time integral (P = 0.001) than the one step in the FP. Conclusion The findings indicate that athletes can enhance plantarflexion function resulting in greater weight transfer, facilitating a greater momentum during the 21.06–84.06% of FP. This is in addition to reducing the load on the dominant leg during landing by utilizing a buffering strategy. Further to this, consideration is needed to enhance the cushioning capacity of the sole heel and the stiffness of the toe area.