Ejection Pressure Research Articles

Effects of Liraglutide on Cardiac Function and Myocardial Infarct Size in the Setting of Obesity

Glucagon like peptide‐1 (GLP‐1) based therapies have been shown to improve cardiac function and protect against myocardial ischemic injury in non‐obese animals. However, whether these therapies confer protection against ischemic damage in the setting of obesity has not been established. Obese Ossabaw swine were subjected to a gradually developing coronary occlusion by placement of an ameroid occluder on the left anterior descending coronary artery. Animals then received daily subcutaneous injections of saline or the stable GLP‐1 analogue, liraglutide (0.005‐0.015 mg/kg/day) for 30 days. Following this treatment period, animals were anesthetized and an open chest procedure was performed to assess cardiac and systemic responses to administration of the sympathomimetic compound, dobutamine (0.3‐30 μg/kg/min). Liraglutide treatment had no effect on baseline hemodynamic variables, including mean pressure (P = 0.32), stroke volume (P = 0.80), heart rate (P = 0.26), or ejection fraction (P = 0.80). Dobutamine administration dose‐dependently increased heart rate, systolic ejection pressure, dP/dtmax, stroke work, and decreased contraction time, left ventricular end diastolic volume, and stroke volume. Dobutamine‐induced changes were unaffected by liraglutide administration. Excised hearts were sliced into 1cm thick sections and stained with tetrazolium to quantify the area of myocardial infarction. Overall, total myocardial infarct size was not significantly different in between groups (P = 0.41). These findings indicate that liraglutide does not significantly affect cardiac function or myocardial infarct size in the setting of obesity.

Sonication-free dispersion of large-area graphene oxide sheets using internal pressure from release of intercalated carbon dioxide

A new concept to disperse graphene sheets without sonication, significant size reduction, and any further removal of intercalating materials, is demonstrated using ejection pressure of CO2 gas captured by water molecules dissolved in the interlayer of graphene and the ice structure surrounding it. After graphene oxide (GO) layers are swelled with water molecules, CO2 gas is dissolved in the swelled interlayer of GO. The CO2 gas within the GO layers is well maintained by the transformation of excess water molecules outside of interlayer to solid ice at low temperature (around −30°C). The resulting CO2-incorporating GOs are well dispersed in various solvents by the ejection pressure of stored CO2 without sonication, and without additional treatment for removal of the intercalating material as surrounding ices spontaneously melt. We show that the lateral length of these well-dispersed GO sheets is 10 times larger than that of GO sheets obtained by the conventional sonication method.

Comparative in Vitro Research of the Human Aortic Bioprosthesis

Abstract Evaluate of the usefulness and reliability of structures based on the analysis of recorded parameters determining the flow through the Human Aortic Bioprosthesis (HAB) have been dealt with. By flow parameters changes determining the performance environment of prosthesis analyzed change of the motion dynamics of the valve leaflets as a function of pressure, thereby determining the degree of alignment of the prosthesis to the performance conditions. Based on the gathered measurement data a comparative analysis of flow rate valve prostheses for different frequency values of the piston pump imitating the heart, different ejection capacity and pressure conditioning work environment prosthesis were studied. Interpretation of the recorded image gave the basis for determining the Effective Orifice Area (EOC).

Effect of Particle Size on Direct Compaction of Urea Fertilizer

The effect of particle size on compaction properties and characteristics of urea tablets manufactured from available urea granules (TG tablets) and ground urea powders (TP tablets) was investigated. The compaction properties, namely, plastic work, elastic work, friction work, and maximum ejection pressure were analyzed from the force-displacement profile of the compaction process. Five applied pressures ranging between 37.67 MPa and 188.35 MPa were used to compact the materials using a universal testing machine. Characteristics of the tablets tested were mechanical strength and the release of ammonium ion through dissolution test. The results demonstrated that TG tablets underwent high plastic work and elastic work but low friction work compared to the TP tablets. TG tablets released lower amount of ammonium ion compared to the TP tablets at almost all applied pressures, except at 75.34 MPa. This study provides a valuable data for evaluating the behavior of urea in the form of granules and powders during the compaction process as well as the suitability in choosing the form of raw material for the production of urea tablets.

Preparation and characterization of two types of separate collagen nanofibers with different widths using aqueous counter collision as a gentle top-down process

Two types of single collagen nanofibers with different widths were successfully prepared from native collagen fibrils using aqueous counter collision (ACC) as a top-down process. A mild collision of an aqueous suspension at a 100 MPa ejection pressure yielded nanofibers, termed CNF100, which have an inherent axial periodicity and are ∼100 nm in width and ∼10 μm in length. In contrast, ACC treatment at 200 MPa provided a non-periodic, shorter and thinner nanofiber, termed CNF10, that was ∼10 nm in width and ∼5 μm in length. Both nanofibers exhibited the inherent triple helix conformation of native collagen supramolecules. Even a medial collision that exceeded the above ACC pressures provided solely a mixture of the two nanofiber products. The two nanofiber types were well characterized, and their tensile strengths were estimated based on their sonication-induced fragmentation behaviors that related to their individual fiber morphologies. As a result, CNF10, which was found to be a critical minimum nanofibril unit, and CNF10 exhibited totally different features in sizes, morphology, tensile strength and viscoelastic properties. In particular, as the mechanical strength of the molecular scaffold affects cell differentiation, the two collagen nanofibers prepared here by ACC have the potential for controlling cell differentiation in possibly different ways, as they have different mechanical properties. This encourages the consideration of the application of CNF100 and CNF10 in the fabrication of new functional materials with unique properties such as a scaffold for tissue engineering.

Hyperbilirubinemia modulates myocardial function, aortic ejection, and ischemic stress resistance in the Gunn rat.

Mildly elevated circulating unconjugated bilirubin (UCB) is associated with protection against hypertension and ischemic heart disease. We assessed whether endogenously elevated bilirubin in Gunn rats modifies cardiovascular function and resistance to ischemic insult. Hearts were assessed ex vivo (Langendorff perfusion) and in vivo (Millar catheterization and echocardiography), and left ventricular myocardial gene expression was measured via quantitative real-time PCR. Ex vivo analysis revealed reduced intrinsic contractility in the Gunn myocardium (+dP/dt: 1,976 ± 622 vs. 2,907 ± 334 mmHg/s, P < 0.01; -dP/dt: -1,435 ± 372 vs. -2,234 ± 478 mmHg/s, P < 0.01), which correlated positively with myocardial UCB concentration (P < 0.05). In vivo analyses showed no changes in left ventricular contractile parameters and ejection (fractional shortening and ejection fraction). However, Gunn rats exhibited reductions in the rate of aortic pressure development (3,008 ± 461 vs. 4,452 ± 644 mmHg/s, P < 0.02), mean aortic velocity (439 ± 64 vs. 644 ± 62 mm/s, P < 0.01), and aortic volume time integral pressure gradient (2.32 ± 0.65 vs. 5.72 ± 0.74 mmHg, P < 0.01), in association with significant aortic dilatation (12-24% increase in aortic diameter, P < 0.05). Ex vivo Gunn hearts exhibited improved ventricular function after 35 min of ischemia and 90 min of reperfusion (63 ± 14 vs. 35 ± 12%, P < 0.01). These effects were accompanied by increased glutathione peroxidase and reduced superoxide dismutase and phospholamban gene expression in Gunn rat myocardium (P < 0.05). These data collectively indicate that hyperbilirubinemia in Gunn rats 1) reduces intrinsic cardiac contractility, which is compensated for in vivo; 2) induces aortic dilatation, which may beneficially influence aortic ejection velocities and pressures; and 3) may improve myocardial stress resistance in association with beneficial transcriptional changes. These effects may contribute to protection from cardiovascular disease with elevated bilirubin.

My paper 20years later: Effect of positive end-expiratory pressure on right ventricular function in humans.

In 1992, we published a report on the effect of positive end-expiratory pressure (PEEP) on right ventricular (RV) function in humans. We measured RV volumes and pressures and pericardial pressure (Ppc) as PEEP was increased from zero to 15 cm H20 in 12 patients after thoracotomy, using a pulmonary arterial catheter equipped with a rapid responding thermistor that allowed measurement of RV ejection fraction (RVef), while Ppc was measured via a pericardial balloon catheter. RV end-diastolic volume (EDV) was estimated as the ratio of stroke volume (SV) to RVef, whereas RV end-systolic volume (ESV) were estimated as RV EDV-SV. PEEP increased Ppc and Pra, but RVef unaltered. There was no relation between either RV filling pressure (Pra-Ppc) and EDV or the change in RV filling pressure and EDV, although EDV varied significantly with PEEP (p<0.05). The relations between EDV and both SV and RVef were weak (r=0.54 and 0.55, respectively). RVef varied inversely with ESV (r=-0.77), although it showed no relation to transmural peak pulmonary artery pressure (r=0.28). However, both absolute and relative changes in EDV corresponded closely with respective ESV values (r=0.94). We concluded that EDV varies independently of changes in filling pressure and that changes in ESV occur independently of changes in ejection pressure. These data can be explained by assuming that the RV shape changes can dissociate changes in RV EDV from changes in RV wall stress (preload). Thus, changes in RV EDV may or may not alter SV but should proportionately change ESV to a degree dependent on election pressure and contractility. Subsequent studies confirmed our findings which can be summarized as 1) RV filling is independent of Pra; thus central venous pressure cannot be used to estimate RV preload; and 2) for cardiac output to increase by the Starling mechanism the RV must dilate increasing RV ESV. Since the pericardium limits absolute biventricular volume, there is a finite limit to which cardiac output can increase by the Starling mechanism defined not by left ventricular contractility but by RV function. And 3) if fluid loading causes Pra to increase without increasing cardiac output, then resuscitation should stop as the patient is going into acute cor pulmonale. These truths help bedside clinicians understand the echocardiographic and hemodynamic signatures of both RV failure and volume responsiveness.

Validation of the pulse decomposition analysis algorithm using central arterial blood pressure.

BackgroundThere is a significant need for continuous noninvasive blood pressure (cNIBP) monitoring, especially for anesthetized surgery and ICU recovery. cNIBP systems could lower costs and expand the use of continuous blood pressure monitoring, lowering risk and improving outcomes.The test system examined here is the CareTaker® and a pulse contour analysis algorithm, Pulse Decomposition Analysis (PDA). PDA’s premise is that the peripheral arterial pressure pulse is a superposition of five individual component pressure pulses that are due to the left ventricular ejection and reflections and re-reflections from only two reflection sites within the central arteries.The hypothesis examined here is that the model’s principal parameters P2P1 and T13 can be correlated with, respectively, systolic and pulse pressures.MethodsCentral arterial blood pressures of patients (38 m/25 f, mean age: 62.7 y, SD: 11.5 y, mean height: 172.3 cm, SD: 9.7 cm, mean weight: 86.8 kg, SD: 20.1 kg) undergoing cardiac catheterization were monitored using central line catheters while the PDA parameters were extracted from the arterial pulse signal obtained non-invasively using CareTaker system.ResultsQualitative validation of the model was achieved with the direct observation of the five component pressure pulses in the central arteries using central line catheters. Statistically significant correlations between P2P1 and systole and T13 and pulse pressure were established (systole: R square: 0.92 (p < 0.0001), diastole: R square: 0.78 (p < 0.0001). Bland-Altman comparisons between blood pressures obtained through the conversion of PDA parameters to blood pressures of non-invasively obtained pulse signatures with catheter-obtained blood pressures fell within the trend guidelines of the Association for the Advancement of Medical Instrumentation SP-10 standard (standard deviation: 8 mmHg(systole: 5.87 mmHg, diastole: 5.69 mmHg)).ConclusionsThe results indicate that arterial blood pressure can be accurately measured and tracked noninvasively and continuously using the CareTaker system and the PDA algorithm. The results further support the physical model that all of the features of the pressure pulse envelope, whether in the central arteries or in the arterial periphery, can be explained by the interaction of the left ventricular ejection pressure pulse with two centrally located reflection sites.

Ambulatory blood pressure monitoring in prepubertal idiopathic dilated cardiomyopathy children

BACKGROUND AND OBJECTIVES: Ambulatory blood pressure monitoring is recommended for several diseases in childhood; however, there are no reports about its use in the monitoring of children with dilated cardiomyopathy so far. We evaluated the pattern of ambulatory blood pressure monitoring in children with dilated cardiomyopathy and correlated it to height, weight, and body mass index. METHODS: Prepubertal children with dilated cardiomyopathy were assessed by ambulatory blood pressure monitoring. Data were collected for systolic and diastolic blood pressure. Means, for 24hours, daytime, and nighttime, dipping pattern and levels above the normal expected values were computed. RESULTS: Children with cardiomyopathy have the same blood pressure as normal kids. Weight was moderately but significantly correlated to nighttime systolic blood pressure. Children with left ventricular ejection fraction < 50% have 6% less diastolic blood pressure dipping. These same children were also receiving higher doses of carvedilol and captopril. CONCLUSIONS: Children with idiopathic dilated cardiomyopathy have the same blood pressure values and blood pressure dipping patterns on ambulatory blood pressure monitoring as normal healthy children are expected to have. Children with low left ventricular ejection pressure have lower dipping pattern.

Ejection fractions and pressure–heart rate product to evaluate cardiac efficiency

Ejection fractions, derived from ventricular volumes, and double product, related to myocardial oxygen consumption, are important diagnostic parameters, as they describe the efficiency with which oxygen is consumed. Present technology often allows only intermittent determination of physiological status. This deficiency may be overcome if ejection fractions and myocardial oxygen consumption could be determined from continuous blood pressure and heart rate measurements. The purpose of this study is to determine the viability of pressure-derived ejection fractions and pressure-heart rate data in a diverse patient population and the use of ejection fractions to monitor patient safety. Volume ejection fractions, derived from ventricular volumes, EF(V), are defined by the ratio of the difference of end-diastolic volume, EDV, and end-systolic volume, ESV, to EDV. In analogy, pressure ejection fraction, EF(P), may be defined by the ratio of the difference of systolic arterial pressure, SBP, and diastolic arterial pressure, DBP, to SBP. The pressure-heart rate (heart rate: HR) is given by the product of systolic pressure and heart rate, SBP × HR. EF(P) and SBP × HR data were derived for all patients (n = 824) who were admitted in 2008 to the ICU of a university hospital at the specific time 30min prior to leaving the ICU whether as survivors or non-survivors. The results are displayed in an efficiency/pressure-heart rate diagram. The efficiency/pressure-heart rate diagram reveals one subarea populated exclusively by survivors, another subarea populated statistically significant by non-survivors, and a third area shared by survivors and non-survivors. The efficiency/pressure-heart rate product relationship may be used as an outcome criterion to assess survival and to noninvasively monitor improvement or deterioration in real time to improve safety in patients with diverse dysfunctions.

Estimating Right Ventricular Stroke Work and the Pulsatile Work Fraction in Pulmonary Hypertension

The mean pulmonary artery pressure (mPAP) replaces mean systolic ejection pressure (msePAP) in the classic formula of right ventricular stroke work (RVSW) = (mPAP - RAP) × stroke volume, where RAP is mean right atrial pressure. Only the steady work is thus taken into account, not the pulsatile work, whereas pulmonary circulation is highly pulsatile. Our retrospective, high-fidelity pressure study tested the hypothesis that msePAP was proportional to mPAP, and looked at the implications for RVSW. Eleven patients with severe, precapillary pulmonary hypertension (PH) (six patients with idiopathic pulmonary arterial hypertension and five with chronic thromboembolic PH; mPAP = 57 ± 10 mm Hg) were studied at rest and during mild to moderate exercise. Eight non-PH control subjects were also studied at rest (mPAP = 16 ± 2 mm Hg). The msePAP was averaged from end diastole to dicrotic notch. In the full data set (53 pressure-flow points), mPAP ranged from 14 to 99.5 mm Hg, cardiac output from 2.38 to 11.1 L/min, and heart rate from 53 to 163 beats/min. There was a linear relationship between msePAP and mPAP (r² = 0.99). The msePAP matched 1.25 mPAP (bias, -0.5 ± 2.6 mm Hg). Results were similar in the resting non-PH group and in resting and the exercising PH group. This implies that the classic formula markedly underestimates RVSW and that the pulsatile work may be a variable 20% to 55% fraction of RVSW, depending on RAP and mPAP. At rest, RVSW in patients with PH was twice as high as that of the non-PH group (P < .05), but pulsatile work fraction was similar between the two groups (26 ± 4% vs 24 ± 1%) because of the counterbalancing effects of high RAP (11 ± 5 mm Hg vs 4 ± 2 mm Hg), which increases the fraction, and high mPAP, which decreases the fraction. Our study favored the use of an improved formula that takes into account the variable pulsatile work fraction: RVSW = (1.25 mPAP - RAP) × stroke volume. Increased RAP and increased mPAP have opposite effects on the pulsatile work fraction.

Functionality of galenIQ 721 as excipient for direct compression tablets

Article history: Received on: 21/02/2013 Revised on: 09/03/2013 Accepted on: 25/03/2013 Available online: 27/04/2013 The purpose of the work is the comparative evaluation of GalenIQ 721, against known excipients such as Pharmatose M200 and Alfacel type 102. The evaluated parameters included compactibility curves, tablet ejection pressure, disintegration time and flowability of individual powders and mixtures of the excipients and amoxicillin. The surrogate and explicit compactibility of Alfacel 102 (492 N; 7.9 N) is superior, followed by GalenIQ 721 (310 N; 0.93 N) and Pharmatose M200 (203 N; -2.8 N). The lubricity of Alfacel 102 is superior (ejection pressure Pe=0.590 MPa), followed by GalenIQ 721 (Pe=6.45 MPa) and Pharmatose M200 (Pe=6.51 MPa). Disintegrability of tablets was better by GalenIQ (0.33 s/N), followed by Alfacel 102 (2.48 s/N) and Pharmatose M200 (4.47 s/N).GalenIQ 721 displays a powder fluidity of (14.4 g/s), followed by Alfacel 102 (7.88 g/s) and Pharmatose M200 (0.99 g/s). The tableting functionality of GalenIQ 721 is better than that of Pharmatose M200 but inferior of that of Alfacel 102. Although the GalenIQ 721 characteristics, predominantly brittle, are expected to be more stable to changes in formula composition and process conditions than those of Alfacel 102, plastic behavior.

Planar Flow Casting of Fe71Si13.5B9Nb3Cu1Al1.5Ge1 Ribbons

In this study, the planar flow casting (PFC) technique for producing wide amorphous ribbons of Fe71Si13.5B9Nb3Cu1Al1.5Ge1 alloy is investigated. Various ribbons of the mentioned alloy were produced through applying different values of wheel speed and ejection pressure. In addition, effects of wheel speed (13, 23, and 33 m/s) on the structure, degree of amorphicity, and surface quality of the ribbons were examined. The results showed that the trends of thickness variation with increasing wheel speed and ejection pressure for Fe71Si13.5B9Nb3Cu1Al1.5Ge1 ribbons are in good agreement with what the Bernoulli equation in fluid dynamics predicts for the PFC process. Further, based on x-ray diffraction and differential scanning calorimeter results, it was shown that the degree of amorphicity increases by increasing the wheel speed. Besides, surface roughness measurements and scanning electron microscope micrographs of the ribbons revealed that the surface quality of the prepared ribbons improved by increasing the wheel speed.

Intraventricular ejection pressure gradient derived from acceleration measurement by phase contrast CMR as a new marker of left ventricular contractility: feasibility study and preliminary results in dilated cardiomyopathy

Background Intra-ventricular pressure gradient along the direction of the outflow tract is generated by the impulse response of the myocardial contraction. This spatial pressure gradient, derived from the maximal acceleration estimates within the left ventricular (LV) ejection flow, has been validated in vitro by using MRI and was found strongly related to the inotropic state of the LV as demonstrated in animal and human echocardiographic studies. This acceleration may be less dependant on load conditions than others LV systolic function parameters, especially LV ejection fraction (LVEF). Aim: (1) to evaluate the feasibility of LV ejection flow acceleration (Acc) estimates by spatial and temporal derivative of velocities recorded by CMR using phase contrast sequence, (2) to compare the acceleration values to LVEF in patients with Dilated Cardiomyopathy (LVEF<50%) and in control subjects. Methods

Issues on Puddle Formation During Rapid Solidification of Fe–Si–B–Nb–Cu Alloy Using Planar Flow Melt Spinning Process

The present investigation deals with the processing of rapidly solidified 10–40 mm wide, 30–50 μm thick and 10–30 m long continuous amorphous ribbons of Fe–Si–B–Nb–Cu alloy using a planar flow melt spinning (PFMS) equipment. As the formation of quality amorphous ribbon depends on the melt puddle formed between the nozzle and the rotating copper wheel, the effect of different processing parameters such as nozzle wheel gap, ejection pressure etc. on the shape and stability of puddle has been studied using a high-speed imaging system and correlated with ribbon formation. Simultaneously, a two-dimensional numerical model has been developed to simulate the puddle formation during the PFMS process. The model is based on a computational fluid dynamics technique, called volume of fluid using transient heat transfer and fluid flow equations with the evolution of free boundaries. Different simulations have been performed to study the effect of process parameters on the puddle formation. The simulated results have been verified with the experimental observations considering same set of process parameters. It has been observed that the present simulations have produced exact replica of the experimental observations. Further parametric analysis as well as analysis of simulated result has been carried out to understand how the different process parameters affect the formation of quality amorphous ribbons during PFMS process.

Microseparation, fluid pressure and flow in failures of metal-on-metal hip resurfacing arthroplasties

ObjectivesMetal-on-metal (MoM) hip resurfacing was introduced into clinical practice because it was perceived to be a better alternative to conventional total hip replacement for young and active patients. However, an increasing number of reports of complications have arisen focusing on design and orientation of the components, the generation of metallic wear particles and serum levels of metallic ions. The procedure introduced a combination of two elements: large-dimension components and hard abrasive particles of metal wear. The objective of our study was to investigate the theory that microseparation of the articular surfaces draws in a high volume of bursal fluid and its contents into the articulation, and at relocation under load would generate high pressures of fluid ejection, resulting in an abrasive water jet.MethodsThis theoretical concept using MoM resurfacing components (head diameter 55 mm) was modelled mathematically and confirmed experimentally using a material-testing machine that pushed the head into the cup at a rate of 1000 mm/min until fully engaged.ResultsThe mathematical model showed the pattern but not the force of fluid ejection, the highest pressures were expected when the separation of the components was only a fraction of one millimetre. The experimental work confirmed the results; with the mean peak ejection pressure of 43 763 N/m2 equivalent to 306 mmHg or 5 psi.ConclusionsThe mechanical effect of the high-pressure abrasive water jet is the likely cause of the spectrum of complications reported with metal-on-metal resurfacing. Investigating serum levels of metallic elements may not be the best method for assessing the local mechanical effects of the abrasive water jet.

Myocardial Longitudinal Peak Systolic Acceleration (pSac): Relationship to Ejection Phase, Pressure, and Contractility

Acceleration has been measured both noninvasively and invasively, during both isovolumic contraction and early ejection and has been shown to reflect contractility, especially through correlation with dP/dt(max) . In this study timing and amplitude of mitral valve annulus acceleration assessed by tissue Doppler were measured and related to diastolic and systolic events. Invasive load independent measures of contractility, based on pressure-volume relationships, were derived, and pacing was done to modulate and control heart rate. Peak systolic acceleration (pSac) of the mitral valve annulus was shown to occur slightly later but timely related to dP/dt(max) (P < 0.05), while peak preejection acceleration (pPac) was related to diastolic events. During inotropy and preload modulation dP/dt(max) was found to be the strongest determinant of pSac (β= 0.9 ± 0.1; P < 0.001 and β= 1.3 ± 0.4; P < 0.001, respectively, log-transformed variables). PSac increased with pacing at a higher rate (β= 0.1 ± 0.0 cm/sec(2), P = 0.03). Furthermore, pSac indexed to end-diastolic volume (EDV) was linearly correlated to load independent contractility parameters (E(max), R = 0.7; ESPVR, R = 0.7; and PRSW, R = 0.5), and proved stable toward changes in preload and afterload. The relation between dP/dt(max)/EDV and pSac/EDV was stable throughout the study. In conclusion we found that peak systolic longitudinal acceleration (pSac) of the mitral valve annulus during aortic valve opening is strongly associated with dP/dt(max). Indexed to EDV, pSac may represent a load independent noninvasive contractility parameter. We consider pSac a candidate marker of long-axis contractility which should be viewed upon as the long-axis contribution to dP/dt(max).

Exercise blood pressure response during assisted circulatory support: Comparison of the total artifical heart with a left ventricular assist device during rehabilitation

The total artificial heart (TAH) consists of two implantable pneumatic pumps that replace the heart and operate at a fixed ejection rate and ejection pressure. We evaluated the blood pressure (BP) response to exercise and exercise performance in patients with a TAH compared to those with a with a continuous-flow left ventricular assist device (LVAD). We conducted a single-center, retrospective study of 37 patients who received a TAH and 12 patients implanted with an LVAD. We measured the BP response during exercise, exercise duration and change in tolerated exercise workload over an 8-week period. In patients with a TAH, baseline BP was 120/69 ± 13/13, exercise BP was 118/72 ± 15/10 and post-exercise BP was 120/72 ± 14/12. Mean arterial BP did not change with exercise in patients with a TAH (88 ± 10 vs 88 ± 11; p = 0.8), but increased in those with an LVAD (87 ± 8 vs 95 ± 13; p < 0.001). Although the mean arterial BP (MAP) was negatively correlated with metabolic equivalents (METs) achieved during exercise, the association was not statistically significant (β = -0.1, p = 0.4). MAP correlated positively with METs achieved in patients with LVADs (MAP: β = 0.26, p = 0.04). Despite the abnormal response to exercise, patients with a TAH participated in physical therapy (median: 5 days; interquartile range [IQR] 4 to 7 days) and treadmill exercise (19 days; IQR: 13 to 35 days) early after device implantation, with increased exercise intensity and duration over time. During circulatory support with a TAH, the BP response to exercise was blunted. However, aerobic exercise training early after device implantation was found to be safe and feasible in a supervised setting.

Experimental and Computational Analysis of Water-Droplet Formation and Ejection Process Using Hollow Microneedle

In this paper, we present the possibility of liquid delivery using fabricated hollow silicon dioxide microneedles of approximately 2 µm in diameter. As a fundamental study, the water-droplet formation and ejection process was examined via dynamic observations during water ejection tests and computational fluid dynamics (CFD) analysis. The experimental results indicated that fluid flow in a microneedle follows the Hagen–Poiseuille law, i.e., the flow rate is approximately directly proportional to the fourth power of the inner diameter. Moreover, the ejection pressure and maximum droplet curvature obtained using the proposed microfluid ejection model were in good agreement with the experimental results. The resulting ejection pressure is equal to the theoretical pressure difference of a spherical droplet, which is determined using the Young–Laplace equation. The maximum curvature of a droplet formed at the tip of a microneedle can be estimated on the basis of the contact angle theory expressed by the Young equation.

Experimental and Computational Analysis of Water-Droplet Formation and Ejection Process Using Hollow Microneedle

In this paper, we present the possibility of liquid delivery using fabricated hollow silicon dioxide microneedles of approximately 2 µm in diameter. As a fundamental study, the water-droplet formation and ejection process was examined via dynamic observations during water ejection tests and computational fluid dynamics (CFD) analysis. The experimental results indicated that fluid flow in a microneedle follows the Hagen–Poiseuille law, i.e., the flow rate is approximately directly proportional to the fourth power of the inner diameter. Moreover, the ejection pressure and maximum droplet curvature obtained using the proposed microfluid ejection model were in good agreement with the experimental results. The resulting ejection pressure is equal to the theoretical pressure difference of a spherical droplet, which is determined using the Young–Laplace equation. The maximum curvature of a droplet formed at the tip of a microneedle can be estimated on the basis of the contact angle theory expressed by the Young equation.