Peak Pressure Research Articles

Damage behavior of the surrounding medium caused by different blast-induced dynamic and static loadings

The combination of the dynamic action of explosion stress wave and the static action of explosion gas expansion is what primarily drives rock-breaking blasting, and their different intensities lead to different blasting effects. Therefore, experiments were conducted to explore the damage behaviour of the surrounding medium caused by different blast-induced dynamic and static loadings using digital laser Schlieren and digital laser dynamic caustic systems. The results were as follows: In the air medium, when the explosives detonated, TATP (triacetone triperoxide) had the strongest quasi-static effect, and the highest velocity explosion shock wave and products compared with those of NHN (nickel hydrazine nitrate) and DDNP (diazodinitrophenol). Part of the TATP explosion product was ahead of the shock wave front, whereas for NHN and DDNP, their explosion products were behind the propagation of the shock wave front. The highest pressure peak of TATP was the result of the combined action of the shock wave and explosion product impacting the sensor. In the solid medium, NHN, the explosive with the strongest dynamic load, had the strongest stress wave and highest stress intensity factor peak of the main crack. The velocity reached the peak value at the early stage of propagation, and the dynamic action had a dominant effect on the cracking of the crack; the stronger the dynamic action, the higher the crack initiation energy. The stress intensity factor and propagation rate of the main crack of TATP with the strongest quasi-static effect decreased slower than those of the other explosives; therefore, the main crack propagation time and length were the longest. After cracking, the quasi-static effect dominated the process of crack propagation, where the stronger the quasi-static effect, the longer duration of the driving force of crack propagation. The research results provide a basis for customising explosives for different functions in practical engineering and realising the fine and efficient utilisation of explosion energy.

Phrenic Ampulla Emptying Dysfunction in Patients with Esophageal Symptoms.

Pharyngeal pump, esophageal peristalsis, and phrenic ampulla emptying play important roles in the propulsion of bolus from the mouth to the stomach. There is limited information available on the mechanism of normal and abnormal phrenic ampulla emptying. The goal of our study is to describe the relationship between bolus flow and esophageal pressure profiles during the phrenic ampulla emptying in normal subjects and patient with phrenic ampulla dysfunction. Pressure (using topography) and bolus flow (using changes in impedance) relationship through the esophagus and phrenic ampulla were determined in 15 normal subjects and 15 patients with retrograde escape of bolus from the phrenic ampulla into esophagus during primary peristalsis. During the phrenic ampulla phase, 2 high pressure peaks (proximal, related to lower esophageal sphincter and distal, related to crural diaphragm) were observed in normal subjects and patients during the phrenic ampulla emptying phase. The proximal was always higher than the distal one in normal subjects; in contrast, reverse was the case in patients with the retrograde escape of bolus from the phrenic ampulla into the esophagus. We propose that a strong after-contraction of the lower esophageal sphincter plays an important role in the normal phrenic ampullary emptying. A defective lower esophageal after-contraction, along with high crural diaphragm pressure are responsible for the phrenic ampulla emptying dysfunction.

Gait Training Interventions for Individuals with Chronic Ankle Instability: A Systematic Review & Meta-Analysis.

This review aimed to determine if gait training interventions influence lower extremity biomechanics during walking in individuals with chronic ankle instability (CAI). A literature search was conducted in PubMed, CINAHL, SPORTDiscus, and MEDLINE to identify English-language studies from inception through September 2022. Eligible studies included randomized control trials, repeated measures design, and descriptive laboratory studies measuring the effects during or following a gait training intervention on biomechanical outcomes (kinematics, kinetics, electromyography) during walking in individuals with CAI. Gait training interventions were broadly categorized into devices (destabilization devices, novel gait training device) and biofeedback (visual, auditory, and haptic delivery modes). Meta-analyses were conducted when appropriate using random-effects to compare pre-and post- gait training intervention mean differences and standard deviations. Thirteen studies were included. Meta-analyses were conducted for single session gait training studies only. Eleven studies reported kinetic outcomes. Our meta-analyses showed location of center of pressure (COP) was shifted medially from 0-90% (Effect Size [ES] range=0.35-0.82) of stance, contact time was decreased in medial forefoot (ES=0.43), peak pressure was decreased for lateral midfoot (ES=1.18) and increased for hallux (ES=0.59), pressure time integral was decreased for lateral heel (ES=0.33) and lateral midfoot (ES=1.22) and increased for hallux (ES=0.63). Three studies reported kinematic outcomes. Seven studies reported electromyography outcomes. Our meta-analyses revealed increased activity following initial contact (IC) for fibularis longus (ES=0.83). Gait training protocols improved some lower extremity biomechanical outcomes in individuals with CAI. Plantar pressure outcome measures seem to be most impacted by gait training programs with improvements in decreasing lateral pressure associated with increased risk for lateral ankle sprains. Gait training increased EMG activity post-IC for the fibularis longus. Few studies have assessed the impact of multi-session gait training on biomechanical outcome measures. Targeted gait trainning should be considered when treating patients with CAI.

The Antigravity Treadmill as a Postoperative and Injury Rehabilitation Tool: Reduction in Contact Forces and Muscle Activity With Reduced Weight Running.

To investigate the effects of reduced weight running on the antigravity (AG) treadmill on maintenance of normal muscle activation and reduction of plantar forces in healthy subjects. Descriptive laboratory study. Clinical sports medicine center. Twenty healthy subjects (10 male and 10 female) aged 18 to 29 years. Subjects running at 6.5 miles per hour on a standard treadmill and on the AG treadmill at 100%, 90%, 80%, 70%, 60%, and 50% of bodyweight levels. Dynamic plantar loading data were recorded using pressure insoles. Surface electromyography electrodes with imbedded accelerometers were used to estimate timing and magnitude of muscle activity, stride length, and cadence. There was a significant, sequential reduction in peak pressure, maximum force, and force time integral (FTI) with decreasing bodyweight. A 50% bodyweight reduction resulted in a 51% reduction in maximum force and a 59% reduction in FTI in the heel, as compared with 19% to 28% at the metatarsal heads. There was reduced contact area in the heel and midfoot at and below 70% BW. Lower limb muscle activity decreases with reduced bodyweight while maintain normal muscle recruitment timing. The AG treadmill provides a reduction in loading forces while maintaining normal muscle recruitment patterns. Decreased BW running preferentially unloads the hindfoot. The AG treadmill can be an effective rehabilitation tool following foot or ankle injury and may prove superior to other limited weight-bearing methods.

Urinary dysfunction after spinal cord injury: Comparing outcomes after thoracic spinal transection and contusion in the rat

Spinal cord injury (SCI) above the lumbosacral spinal cord induces loss of voluntary control over micturition. Spinal cord transection (SCT) was the gold standard method to reproduce SCI in rodents, but its translational value is arguable and other experimental SCI methods need to be better investigated, including spinal cord contusion (SCC). At present, it is not fully investigated if urinary impairments arising after transection and contusion are comparable. To explore this, we studied bladder-reflex activity and lower urinary tract (LUT) and spinal cord innervation after SCT and different severities of SCC. Severe-contusion animals presented a longer spinal shock period and the tendency for higher residual volumes, followed by SCT and mild-contusion animals. Urodynamics showed that SCT animals presented higher basal and peak bladder pressures. Immunostaining against growth-associated protein-43 (GAP43) and calcitonin gene-related peptide (CGRP) at the lumbosacral spinal cord demonstrated that afferent sprouting is dependent on the injury model, reflecting the severity of the lesion, with a higher expression in SCT animals. In LUT organs, the expression of GAP43, CGRP cholinergic (vesicular acetylcholine transporter (VAChT)) and noradrenergic (tyrosine hydroxylase (TH)) markers was reduced after SCI in the LUT and lumbosacral cord, but only the lumbosacral expression of VAChT was dependent on the injury model. Overall, our findings demonstrate that changes in LUT innervation and function after contusion and transection are similar but result from distinct neuroplastic processes at the lumbosacral spinal cord. This may impact the development of new therapeutic options for urinary impairment arising after spinal cord insult.

Recursive Engine In-Cylinder Pressure Reconstruction Using Sensor-Fused Engine Speed.

The engine in-cylinder pressure is a very important parameter for the optimization of internal combustion engines. This paper proposes an alternative recursive Kalman filter-based engine cylinder pressure reconstruction approach using sensor-fused engine speed. In the proposed approach, the fused engine speed is first obtained using the centralized sensor fusion technique, which synthesizes the information from the engine vibration sensor and engine flywheel angular speed sensor. Afterwards, with the fused speed, the engine cylinder pressure signal can be reconstructed by inverse filtering of the engine structural vibration signal. The cylinder pressure reconstruction results of the proposed approach are validated by two combustion indicators, which are pressure peak Pmax and peak location Ploc. Meanwhile, the reconstruction results are compared with the results obtained by the cylinder pressure reconstruction approach using the calculated engine speed. The results of sensor fusion can indicate that the fused speed is smoother when the vibration signal is trusted more. Furthermore, the cylinder pressure reconstruction results can display the relationship between the sensor-fused speed and the cylinder pressure reconstruction accuracy, and with more belief in the vibration signal, the reconstructed results will become better.

Regulation of Catalysts on Tightly Packaged Solid Propellant Energetic Particles: High Combustion Performance with Low Temperature Sensitivity.

Although the effectiveness of combustion catalysts promoting the combustion performance of solid propellant (SP) was identified in many research studies, its regulation on the temperature sensitivity coefficient of burning rate (δp) has been rarely explored, where SP with low δp is a big challenge with little progress. Herein, several ammonium perchlorate (AP)-enriched (>70 wt %) pomegranate-structured SP energetic particles (SPPs), AP/nitrocellulose (NC)/Al (SPP), SPP/CoWO4-rGO (SPP-Co), SPP/Bi2WO6-rGO (SPP-Bi), and SPP/CuCo2O4/GO (SPP-Cu), were prepared by the electrospray granulation method, tightly packaging AP with high-efficiency catalysts to promote its reactivity and reduce temperature sensitivity. The pressurization rates of SPPs in a constant volume combustion chamber at 50, 0, and -40 °C were obtained to determine δp. The burning rates of SPP-Co, SPP-Bi, and SPP-Cu loose strips are 0.319, 0.312, and 0.356 m/s, which are increased by 11.1%, 8.7%, and 24.0% compared to that of SPP (0.287 m/s), respectively. The peak pressures and pressurization rates of SPP-Co, SPP-Bi, and SPP-Cu at 0 °C are increased by 18.8%, 10.1%, and 9.1% and 62.3%, 67.1%, and 64.1% compared with SPP, respectively, indicating that these catalysts significantly accelerate the combustion process. Compared with SPP, the δp of SPP-Co, SPP-Bi, and SPP-Cu decreased by 26.6%, 60.6%, and 24.7% at 0-50 °C and 19.5%, 61.6%, and 27.6% at -40-0 °C, respectively. It suggests that the Bi2WO6-rGO catalyst reduces the δp by 61% at -40-50 °C, exhibiting the optimal δp regulation performance. This research introduces a novel approach to lower the δp from the chemical by tightly packaging temperature-sensitive AP with high-efficiency catalysts.

Using Flexible-Printed Piezoelectric Sensor Arrays to Measure Plantar Pressure during Walking for Sarcopenia Screening.

Sarcopenia is an age-related syndrome characterized by the loss of skeletal muscle mass and function. Community screening, commonly used in early diagnosis, usually lacks features such as real-time monitoring, low cost, and convenience. This study introduces a promising approach to sarcopenia screening by dynamic plantar pressure monitoring. We propose a wearable flexible-printed piezoelectric sensing array incorporating barium titanate thin films. Utilizing a flexible printer, we fabricate the array with enhanced compressive strength and measurement range. Signal conversion circuits convert charge signals of the sensors into voltage signals, which are transmitted to a mobile phone via Bluetooth after processing. Through cyclic loading, we obtain the average voltage sensitivity (4.844 mV/kPa) of the sensing array. During a 6 m walk, the dynamic plantar pressure features of 51 recruited participants are extracted, including peak pressures for both sarcopenic and control participants before and after weight calibration. Statistical analysis discerns feature significance between groups, and five machine learning models are employed to screen for sarcopenia with the collected features. The results show that the features of dynamic plantar pressure have great potential in early screening of sarcopenia, and the Support Vector Machine model after feature selection achieves a high accuracy of 93.65%. By combining wearable sensors with machine learning techniques, this study aims to provide more convenient and effective sarcopenia screening methods for the elderly.

Intraoperative Lung Mechanics In Post-Covid Healthy Pregnants Who Required Cesarean Section: A Randomized Controlled Trial

Objective: This study aimed to investigate whether lung mechanics were affected in patients recovering from Covid-19 without ARDS who did not undergo lung imaging during the active infection period. Methods: The study included pregnant patients undergoing cesarean section operations. Participants were divided into two groups: those who had recovered from Covid-19 within the past year (group 1, n=50) and those who had never been infected with Covid-19 (group 2, n=50). The study included 100 patients divided into two groups: those who had recovered from Covid-19 within the last year (group 1, n=50) and those who had never experienced Covid-19 infection (group 2, n=50). Peak pressure (Ppeak), plateau pressure (Pplato), dynamic compliance (Cdyn), and positive end-expiratory pressure (PEEP) values, measured by the anesthesia machine, were recorded at specified time intervals following intubation. Results: Comparisons of Ppeak, Pplato, ΔP, Cdyn, and R data at specified times (1 min, 5 min, 10 min, 20 min, 30 min, and 40 min) showed no significant differences between the groups (p>0.05). Conclusion: No significant differences in lung mechanics were found between the Covid-19-recovered patient group and the control group. Differences observed in SpO2, MAP, and Cdyn values in both groups are considered to be expected changes associated with routine procedures of general anesthesia

Numerical Investigation of the Effect of Intake Closing Timing on Flow Field and Combustion Process in an Elliptical Rotary Engine

Abstract The aim of this research is to investigate the effect of intake closing timing (ICT) on the flow field and combustion process in elliptical rotary engines. The model that can accurately describe the working process of the elliptical rotary engine was established, five kinds of ICTs were designed, and the influence of ICT on the flow field and combustion process was studied. The results show that the advance of the ICT can increase the intake mass flowrate and reduce the back flowrate, the volumetric efficiency is 86.1% at a 145-deg crank angle (°CA) before top dead center (BTDC), which is 7.6% higher than 125 °CA BTDC. The advance of the ICT improves the consumption speed, makes the combustion reaction more intense, and shortens the combustion time. When the ICT is 145 °CA BTDC, the crank angle when the burned mass fraction is 90% (CA90) is 19.4 °CA earlier than 125 °CA BTDC, the peak mass of hydroxy in a cylinder is 41.6% higher, and the peak pressure in a cylinder is 25.9% higher. With the advance of the ICT, the pressure and heat release in the cylinder are significantly increased, the peak temperature in the cylinder is increased, the rate of carbon monoxide generation is accelerated, and the mass of nitrogen oxide emission is significantly increased. However, advancing the ICT cannot improve the indicated thermal efficiency of the elliptical rotary engine. This analysis provides a comprehensive understanding of the ICT of elliptical rotary engines.

Dynamics of fuel-lean and stoichiometric methane-air explosion venting: Experiments and simulations

The computational explosion venting analyzer (EVA), a zero-dimensional (0D) model based on the conservation of mass and energy, is being developed to model centrally- and rear-ignited explosions. For this purpose, a series of explosion venting experiments in a cylinder with vent areas of 132.7, 86.6, 67.9 cm2 (corresponding to the vent area ratios of K=0.47,0.31,0.24, respectively) is performed. Two equivalence ratios of ϕ=0.8 and 1 are considered to represent the fuel-lean and stoichiometric methane-air mixtures, respectively. The dynamics of explosions is studied through the observation of flame propagation and pressure measurements. In rear ignition experiments, laminar, so-called “finger flame” propagation is observed, while in the case of center ignition, a flame initially expands spherically and then is pulled by the vent, acquiring a half-elliptical and half-spherical shape. The peak pressures obtained from rear ignition exceed their counterparts in the center ignition experiments. The EVA is compared with the experimental matrix. No turbulence is implemented in stoichiometric simulations, and slight turbulence has been accounted for in the lean mixture simulations. It is found that the large vent, generally, imposes more disturbances on the flame shape and the fuel-lean mixtures are more prone to the diffusional-thermal instabilities. It is shown that such a simple numerical tool, as the EVA is, can estimate a complicated problem such as pressure evolution resulted from a vented gas explosion.

A Study on the Factors Controlling the Kinematics of a Reactivated and Slow-Moving Landslide in the Eastern Liguria Region (NW Italy) through the Integration of Automatic Geotechnical Sensors

This paper deals with the investigation of factors influencing the movement patterns of a reactivated slow-moving landslide situated in the eastern Liguria region (NW Italy) through the analysis of extensive ground-based hydrological and geotechnical monitoring data. Subsurface horizontal displacement and pore water pressure data were acquired simultaneously by means of automatic sensors positioned at pre-existing and localized failure zones. The joint examination of field measurements enabled us to explore the connections between rain, pore water pressure, and displacements. The results of continuous displacement monitoring showed that the landslide kinematics involved phases of extremely slow movements alternated with periods of relative inactivity. Both stages occurred prevalently at seasonal scale displaying similar durations. The slow-motion phases took place at relatively constant pore water pressure and were ascribed to mechanisms of viscous shear displacements along failure surfaces. Inactive phases entailed no significant deformations, mostly corresponding to prolonged dry periods. The two motion patterns were interrupted by episodic sharp deformations triggered by delayed (preparation periods from 4 to 11 days) rainfall-induced pore water pressure peaks, which were ascribed to sliding mechanisms taking place through rigid-plastic frictional behaviour. During these deformation events, hysteresis relationships between pore water pressure and displacement were found, revealing far more complex hydro-mechanical behaviour.

Deep Learning Methods to Analyze the Forces and Torques in Joints Motion

This paper proposes a composite model that combines convolutional neural network models and mechanical analysis to determine the forces acting on an object. First, we establish a model using Newtonian mechanics to analyze the forces experienced by the human body during movement, particularly the forces on joints. The model calculates the mapping relationship between the object’s movement and the forces on the joints. Then, by analyzing a large number of fencing competition videos using a deep learning model, we extract video features to study the torques and forces on human joints. Our analysis of numerous images reveals that, in certain movement patterns, the peak pressure on the knee joint can be two to three times higher than in a normal state, while the driving knee can withstand peak torques of 400–600 Nm. This straightforward model can effectively capture the forces and torques on the human body during movement using a deep neural network. Furthermore, this model can also be applied to problems involving non-rigid body motion.

Characteristics analysis of flame propagation and its coupling effect with other parameters in LPG pipeline

AbstractTo study the flame propagating characteristic and its coupling effect with other parameters in the LPG pipeline, a typical pipeline model with two equal‐length branches perpendicular to each other is designed for experiment and simulation. Then, gas explosion scenarios are experimentally tested and numerically simulated, which is followed by the analysis of flame shape changing with time and peak temperature changing with space. Results show that when passing through the bifurcation, flame propagates to vertical branch B in a sharp knife shape affected by the strong vortex, reflected airflow, and compressed pressure wave in the pipeline with a diameter of 0.125 m. At the monitoring point that is 0.4 m away from the bifurcation point, the peak temperature of the vertical branch B is 57.87% bigger than that of the horizontal branch C, and its arrival time is 80% longer than that of the horizontal branch C, due to the existence of flame in vertical branch B. What's more, in both branches, the coupling results between peak temperature and peak velocity agree very well with the growth function, while the coupling results between peak temperature and peak pressure agree well with the decay function, providing aids to the optimal layout design of industrial pipeline branches as well as to the explosion suppression measures.

Use of pressure muscle index to guide pressure support ventilation setting: a study protocol and statistical plan for a prospective randomised controlled proof-of-concept trial

IntroductionAlthough pressure support ventilation is one of the most commonly used assisted ventilation modes in intensive care units, there is still a lack of precise strategies for setting pressure support....

Investigation on NOx control of a CI engine through the collective effect of hydrogen and biodiesel blend at modified compression ratio

The main challenges with using biodiesel in CI engines are higher NOx emissions and reduced brake thermal efficiency. These biodiesel-related issues can be handled by concurrently introducing gaseous fuels along with primary fuel into CI engines. This study examines the effects of hydrogen in a dual fuel mode operation with diesel and Calophyllum inophyllum biodiesel blend (B20) at different compression ratios on the engine's performance, combustion, and emission characteristics. A single-cylinder, 4-stroke, variable compression ratio engine operating at 1500 rpm was used for the research. A standard compression ratio (SCR) of 17.5 and a modified compression ratio (MCR) of 15.5 at a constant hydrogen flow rate of 6 L per minute (lpm) were used with diesel and B 20. The addition of hydrogen with diesel and B20 resulted in higher cylinder pressure and heat release rate when compared to pure diesel and B20 operation. This resulted in a shorter delay period (by an average of 9.4 % and 7.1 %) with lower peak pressure than pure diesel and B20 operation. During the dual fuel mode of H2 with B 20 at a modified compression ratio, the maximum heat release rate was decreased and its occurrence was retarded. NOx, UBHC, and CO emissions of the engine were decreased significantly by an average of 20.8% 43.7, %, and 22 % respectively with 37.7 % increase in smoke opacity. The increase in NOx emission with the use of H2 with diesel was reduced by operating H2 with B20 and at a reduced compression ratio. This lower emission was achieved with a compromise of a marginal decrease in engine brake thermal efficiency.

Dynamic Simulation Model and Performance Optimization of a Pressurized Pulsed Water Jet Device

Pulsed water jet technology has broad application prospects in the field of rock breaking. The pressurized pulsed water jet (PPWJ) is a new type of pulsed jet that offers high-amplitude pressurization, variable pulse pressure and frequency, and a high energy usage rate. To achieve a more destructive and powerful pulsed water jet, a dynamic simulation model of the device was established by using the AMESim software (v1400) based on the operational principle of PPWJs, and the simulation model was validated against the experimental results. The relationships between the key structural parameters of the PPWJ device and the pulse parameters were quantitatively investigated. The pulse pressure and frequency can be increased by appropriately increasing the nozzle diameter or boost ratio, and the pulse pressure will drop if the nozzle diameter or boost ratio exceeds a threshold value. Increasing the maximum displacement or action area of the piston will increase pulse length while decreasing pulse frequency; a proper match of the maximum displacement or action area of the piston will assure pulse peak pressure. The maximum outer diameter of the piston only affects the pulse frequency. The key structural parameters of the device were optimized on that foundation. Compared to the original device, the optimized device resulted in an increase in pulse frequency and jet output energy, leading to larger diameter and volume of erosion pits at the same stand-off distance and erosion time. The findings of this study offer valuable scientific insights for achieving efficient rock breaking with PPWJ.

Effect of Flexible Tank Wall on Seismic Response of Horizontal Storage Tank

Horizontal storage tanks are integral to the petrochemical industry but pose significant risks during earthquakes, potentially causing severe secondary disasters. Current seismic designs predominantly assume rigid tank walls, which can lead to an underestimation of seismic responses. This study introduces a novel analysis method for assessing the dynamic response of flexible-walled horizontal storage tanks. By separating the liquid velocity potential into convective and impulsive components and integrating these with beam vibration theory, we developed a simplified mechanical model. A parameter analysis and dynamic response research were conducted using numerical methods. Results indicate that flexible tank walls amplify seismic responses, including liquid dynamic pressure peaks, base shear, and overturning bending moments, compared to rigid walls. Additionally, the impact of flexible walls is more pronounced in tanks with larger radii, aspect ratios, diameter–thickness ratios, and H/R ratios. These findings highlight the necessity for revised seismic design approaches that consider wall flexibility to enhance the safety and resilience of horizontal storage tanks.

Abstract Mo105: End Systolic Pressure and Ejection Timing Correlate with Impaired Relaxation

Impaired relaxation is a common feature in most cases of diastolic dysfunction, including heart failure with preserved ejection fraction. Isovolumetric relaxation is typically characterized by τ, an exponential time constant, but may be broken into relaxation and stiffness-like parameters (µ and Ek). Recent in vitro work suggests that strain during late systole (protodiastolic period) modifies relaxation. We hypothesize that late systolic pressure and time indexes correlate with myocardial relaxation. Thirty-four (34) simultaneous aortic and left ventricular micromanometric (Millar) pressure traces were obtained from a comprehensive database of clinical cardiac catheterization patients. These patients underwent coronary artery disease screening and presented but did not have arterial blockages. Pressure and time parameters were calculated over a five-minute interval. Relaxation rate (1/τ), and stiffness (Ek) correlated to end systolic parameters in an orthogonal pattern to relaxation (µ). 1/τ showed strong correlations with time from peak pressure to aortic valve divided by ejection time (t54/t52, r = .675, p < .01) and moderate correlation to the pressure decline after peak pressure to aortic valve pressure divided by the pulse pressure (P45/P42, r = .577, p < .01). In parallel Ek showed moderate correlation with t54/t52 (r = .592, p < .01), and a moderate correlation with P45/P42 (r = .470, p < .01), the pressure at aortic valve closure (r = -.420, p < .05), and aortic augmentation index (AIx, r = -.360, p < .05). Finally, µ presented a moderate correlation to P45/P42 (r = .501, p < .05), the pressure at aortic valve closure (r = .404, p < .05), and AIx (r = -.357, p < .05). As predicted, ventricular relaxation in patients correlates with late systolic hemodynamics. Parameters or combinations of parameters may predict relaxation rates or correlate to in vivo late systolic strain. Prospective studies evaluating end systolic strain and relaxation merit consideration. Overall, these observations are consistent with in vitro studies that suggest that impaired cessation of contraction is a regulator of relaxation.

The relationship between intraosseous catheter tip placement, flow rates, and infusion pressures in a high bone density cadaveric swine (Sus scrofa) model.

Intraosseous (IO) infusion is a life-preserving technique when intravenous access is unobtainable. Successful IO infusion requires sufficiently high flow rates to preserve life but at low enough pressures to avoid complications. However, IO catheter tips are often misplaced, and the relative flow rates and pressures between IO catheter tips placed in medullary, trabecular, and cortical bone are not well described, which has important implications for clinical practice. We developed the Zone Theory of IO Catheter Tip Placement based on bone density and proximity to the venous central sinus and then tested the influence of catheter tip placement locations on flow rates and pressures in a cadaveric swine model. Three cross-trained participants infused 500mL of crystalloid fluid into cadaveric swine humerus and sternum (N=210 trials total) using a push‒pull method with a 60 cm3 syringe. Computed tomography scans were scored by radiologists and categorized as zone 1 (medullary space), zone 2 (trabecular bone), or zone 3 (cortical bone) catheter tip placements. Differences between zones in flow rates, mean pressures, and peak pressures were assessed using analysis of variance and analysis of covariance to account for participant and site differences at the p<0.05 threshold. Zone 1 and zone 2 placements were essentially identical in flow rates, mean pressures, and peak pressures (each p>0.05). Zone 1 and zone 2 placements were significantly higher in flow rates and lower in pressures than zone 3 placements (each p<0.05 or less). Within the limitations of an unpressurized cadaveric swine model, the present findings suggest that IO catheter tip placements need not be perfect to acquire high flow rates at low pressures, only accurate enough to avoid the dense cortical bone of zone 3. Future research using in vivo animal and human models is needed to better define the clinical impact of IO catheter placement on infusion flow rates and pressures.