Background  The role of mechanical distension (stretch and tension) on intestinal contractility is poorly understood. Methods  We introduce a novel isovolumic myograph to quantify the intestinal contractility in response to mechanical stimulation. To evaluate the role of distension on contractility, an external restraint was used to restrict intestinal distension or ...

Complex relationships exist between gut contractility and the flow of digesta. We propose here a Smoothed Particle Hydrodynamics model coupling the flow of luminal content and wall flexure to help investigate these relationships. The model indicates that a zone of muscular relaxation preceding the contraction is an important element for ...

BackgroundThe mechanism by which blood pressure increases during renovascular hypertension is incompletely understood. We, therefore, tested the hypothesis that in the 2-kidney, 1-clip (2K-1C) rat, in which hypertension develops due to increased angiotensin II (Ang II) levels, there is increased expression and phosphorylation of Na,K-ATPase at Ser-11 and Ser-18 in ...

A chronic increase in the concentration of sodium in the CSF (↑ CSF [Na]) may be critically important for the development of salt-dependent hypertension. In agreement with this concept, increasing CSF [Na] chronically by intracerebroventricular (i.c.v.) infusion of Na-rich artificial CSF (aCSF-HiNa) in rats produces hypertension by the same brain ...

Intra-abdominal pressure (IAP) and intra-abdominal hypertension (IAH) are associated with significant morbidity and mortality in critically ill patients. Our aim was to assess the effects of IAH on liver function using the noninvasive liver function monitoring system LiMON and to assess the prognostic value of IAP in critically ill patients. ...

Treatment of the pregnant ewe with glucocorticoids early in pregnancy results in offspring with hypertension. This study examined if glucocorticoids can reduce nephron formation or alter gene expression for sodium channels in the late gestation fetus. Sodium channel expression was also examined in 2 month old lambs whilst arterial pressure ...

ABSTRACT: Dynamic variables of fluid responsiveness are useful guides for fluid management in patients under controlled positive pressure ventilation. In the previous issue of Critical Care, Jacques and colleagues show that these variables remain reliable predictors of fluid responsiveness in a porcine model of intra-abdominal hypertension, but threshold values are ...

We perform numerical simulations to determine the shear stress and pressure of steady-state shear flow in a soft-disk model in two dimensions at zero temperature in the vicinity of the jamming transition ϕ_{J}. We use critical point scaling analyses to determine the critical behavior at jamming, and we find that ...

The acute acclimatization to high altitude is underpinned by a diuresis (and to a lesser extent a natriuresis) that facilitates a reduction in plasma volume. This allows a haemoconcentration to occur that increases the oxygen carrying capacity of a given volume of blood, a vital effect in the presence of ...

The reported incidence of pressure ulcers in critically ill infants and children is 18% to 27%. Patients at risk for pressure ulcers and nursing interventions to prevent the development of the ulcers have not been established. To determine the incidence of pressure ulcers in critically ill children, to compare the ...

Achievement of a mean blood pressure (MBP) target is one of the hemodynamic goals to ensure an adequate blood perfusion pressure in critically ill patients. Arterial catheter allows for a continuous and precise monitoring of arterial pressure signal. In addition to giving a precise MBP monitoring, analysis of the blood ...

Purpose. Strategies for volume assessment of critically ill patients are limited, yet early goal-directed therapy improves outcomes. Central venous pressure (CVP), Bioimpedance Vectorial Analysis (BIVA), and brain natriuretic peptide (BNP) are potentially useful tools. We studied the utility of these measures, alone and in combination, to predict changing oxygenation. Methods. ...

Tortuous or twisted veins are often seen in the retina, cerebrum, and legs (varicose veins) of one-third of the aged population, but the underlying mechanisms are poorly understood. While the collapse of veins under external pressure has been well documented, the bent buckling of long vein segments has not been ...

The stability of blood vessels under lumen blood pressure is essential to the maintenance of normal vascular function. Differential buckling equations have been established recently for linear and nonlinear elastic artery models. However, the strain energy in bent buckling and the corresponding energy method have not been investigated for blood ...

Measurement of dissolved gases in groundwater is becoming increasingly common and important. Many of these measurements involve monitoring or sampling within wells or from water pumped from wells. We used total dissolved gas pressure (TDGP) sensors placed in the screened section of various wells (4 to 72 m deep) to ...

A non-membrane micro surface tension pump (MISPU) was fabricated on a glass microchip by one-step glass etching. It needs no material other than glass and is driven by digital gas pressure. The MISPU can be seen working like a piston pump inside the glass microchip under a microscope. The design ...

A mock circulatory system (MCS) was designed to replicate a physiological environment for in vitro testing and was assessed with the intra-aortic balloon pump (IABP). The MCS was comprised of an artificial left ventricle (LV), connected to a 14-branch polyurethane-compound aortic model. Physiological distribution of terminal resistance and compliance according ...

OBJECTIVES: Lymph transportation through the body is partly controlled by the intrinsic pumping of lymphatic vessels. Although an understanding of this process is important for medical application, little is currently known because it is difficult to measure. Here, we introduce an easy, safe, and cost-effective technique for measuring lymphatic pumping ...

There is potential for inappropriate use of transfusion administration sets when used in combination with modern infusion pumps with consequences for patient safety. The aims of our study were to (i) establish if the design and testing of transfusion sets specified in International Standard ISO 1135-4 are adequate for their ...

A new pulse duplicator was designed for evaluation of the performance of ventricular assist devices through pressure-volume (P-V) diagrams of the native heart. A linear drive system in combination with a pusher-plate mechanism was designed as a drive system to implement the passive fill mechanism during diastole of the mock ...

The packing of submicrometer sized silica beads inside a microchannel was enabled by a novel method which avoids the complication and limitations of generating a frit using conventional approaches and the restriction of flow using a submicrometer sized weir. A micrometer sized weir and two short columns of 5 μm ...

A pulsatility-based control algorithm with a self-adapting pulsatility reference value is proposed for an implantable rotary blood pump and is to be tested in computer simulations. The only input signal is the pressure difference across the pump, which is deduced from measurements of the pump's magnetic bearing. A pulsatility index ...

The ventricular performance is dependent on the drainage effect of rotary blood pumps (RBPs) and the performance of RBPs is affected by the ventricular pulsation. In this study, the interaction between the ventricle and RBPs was examined using the pressure-volume (P-V) diagram of the ventricle and dynamic head pressure-bypass flow ...

Debate exists regarding the merits and limitations of continuous versus pulsatile flow mechanical circulatory support. To characterize the hemodynamic differences between each mode of support, we investigated the acute effects of continuous versus pulsatile unloading of the failing left ventricle in a bovine model. Heart failure was induced in male ...

This study demonstrated the concept of using speed modulation in a continuous-flow total artificial heart (CFTAH) to shape arterial pressure waveforms and to adjust pressure pulsatility. A programmable function generator was used to determine the optimum pulsatile speed profile. Three speed profiles [sinusoidal, rectangular, and optimized (a profile optimized for ...

In this work we have systematically studied the behavior of solenoid pumps (SMP) as a function of flow rate and flow resistance. Using a new, economic, and miniature control unit, we achieved improvements of the systems versatility, transportability, and pressure robustness. A further important improvement with respect to pressure resistance ...

During extracorporeal life support (ECLS), blood is exposed to a myriad of unphysiological factors that can affect outcome. One aspect of this is the sub-atmospheric pressure generated by the ECLS pump and imparted to blood elements along the pump inlet line. This pressure can be measured on the inlet line ...

In a univentricular Fontan circulation, modest augmentation of existing cavopulmonary pressure head (2-5 mm Hg) would reduce systemic venous pressure, increase ventricular filling, and thus substantially improve circulatory status. An ideal means of providing mechanical cavopulmonary support does not exist. We hypothesized that a viscous impeller pump, based on the ...

In this study, we report the design of a microchip-based hydraulic pump that comprises three glass conduits arranged in a T-geometry, one of which has a 2 mm long segment shallower (0.5-3 microm in depth) than the remaining 15 microm deep microfluidic network. Upon application of an electric field across ...

Recent studies into rotary biventricular support have indicated that inadequate left/right flow balancing may lead to vascular congestion and/or ventricular suckdown. The implementation of a passive controller that automatically adjusts left/right flow during total and partial cardiac support would improve physiological interaction. This has encouraged the development of a biventricular ...

We have developed an ultraminiature centrifugal pump, TinyPump, with a priming volume of 5 ml. The in vivo performance of TinyPump was compared with that of HPM-05 for left ventricular support. Each pump group included seven rabbits weighing 3.4-3.8 kg. One rabbit in the TinyPump group and two rabbits in ...

Noninvasive blood pressure measurements are difficult when arterial pulsations are reduced, as in patients supported by continuous flow left ventricular assist devices (cf-LVAD). We evaluated the feasibility of measuring noninvasive arterial blood pressure with the Nexfin monitor during conditions of reduced arterial pulsatility. During cardiopulmonary bypass(CPB) in which a roller ...

This note describes a compact electromagnetic hydraulic pump (EMHP) designed primarily to build a microdriving system for a robot joint actuator. A characteristic mathematical model integrating electricity, magnetism, and hydraulics is constructed to represent the working process of the EMHP. Tests show that a volumetric flow rate of up to ...

We succeeded in growing high quality single crystals of URu(2)Si(2) and performed thermal expansion measurements under pressure. Applying a magnetic field along the [001] direction in the tetragonal structure, the so-called hidden-order phase reappears after the suppression of the antiferromagnetic phase above the critical pressure P(x). We determined the pressure-temperature-field ...

OBJECTIVE: To describe the inadvertent creation of a connection between lumens of a multilumen catheter by use of an in-line intravenous hand pressure pump. DESIGN: Case report. SETTING: Operating theater. PATIENT: All lumens of a 4F triple lumen catheter were verified patent by irrigation with saline before insertion into an ...

BACKGROUND: We studied the hemodynamic effects of inducing an artificial pulse in a continuous-flow total artificial heart consisting of 2 axial-flow pumps in a mock circulatory system. METHODS: We varied the amplitude (maximum minus minimum speed), beat rate and systolic duration of the left pump, right pump or both. Mean ...

BACKGROUND: In this study, we describe the potential advantages of a continuous-flow total artificial heart (CFTAH) comprising two small, non-pulsatile pumps with optimized responsiveness to the pressure gradient. METHODS: We modified a MicroMed DeBakey axial-flow pump by increasing its inducer-impeller inlet angle, thereby increasing its pressure responsivity. We obtained the ...

We have developed a prototype, in vitro anthropomorphic model for simulating pressure-guided, subxiphoid access procedures done to enable minimally invasive epicardial cardiac procedures including treatments for ventricular tachycardia. Life-size replicas of the heart and lungs were modelled using anatomically accurate surrogates. The dynamic pressure-frequency profiles of simulated pericardial fluid surrounding ...

BACKGROUND: Full mechanical support with a left ventricular assist device (LVAD) is often limited to very sick patients, as the only survival option. This European multicenter study analyzes the effect of partial mechanical support as bridge-to-transplant in a less sick heart failure patient group. METHODS: The CircuLite Synergy device is ...

BACKGROUND: Needle cricothyrotomy and subsequent transtracheal jet ventilation (TTJV) is one of the last options to restore oxygenation while managing an airway emergency. However, in cases of complete upper airway obstruction, conventional TTJV is ineffective and dangerous. We transformed a small, industrial ejector into a simple, manual ventilator providing expiratory ...

A simple way was proposed to make a monolithic column for a high pressure electroosmotic pump (EOP). It is in-situ synthesized inside the silica capillary from potassium silicate solution and no frit is required. Compared with common approaches to make columns for EOP, the present method is robust and fast ...

This paper presents a simple-to-construct, low dead volume pump capable of generating a wide range of positive and negative pressures for microfluidic applications. The pump generates pressure or vacuum by changing the volume of air confined inside a syringe and is able to generate pressures between -95 and +300 kPa ...

Published studies of the past decades have established that mass transfer across the dialyzer membrane is governed by diffusion, convection and osmosis. While the former is independent of the pressure in the liquids, the latter two are pressure dependent and are enhanced when the pressure difference across the membrane is ...

A mock circulation system has been developed to approximate key anatomic features and simulate the pressures and flows of an infant. Pulsatile flow is generated by 10 cc pulsatile ventricles (Utah infant ventricular assist device). Systemic vasculature is mimicked through the use of 3/8" ID bypass tubing with two flexible ...

The undulation pump ventricular assist device (UPVAD) is a small implantable ventricular assist device using an undulation pump. The UPVAD can produce pulsatile flow by changing the motor rotation speed of the UPVAD. Because the undulation pump is a volume displacement type pump, the inflow sucking occurs easily. The purpose ...

Pressure-volume relationship permits conceptual integration with time-varying elastance, stress-strain relationship, and pressure-volume area. It has also superior usefulness to other indexes, both as a load-independent index of ventricular contractility and as a determinant of ventricular pump function.

We describe a case of a patient assisted by extracorporeal life support, in which we obtained the dynamic filling index, a measure for venous volume during extracorporeal life support, and used this index to assess cardiac load-responsiveness during acute reloading. While reloading, the obtained findings on cardiac pump function by ...

The Intra-Aortic Balloon Pump (IABP) is frequently used to mechanically support the heart. There is evidence that IABP improves microvascular flow during cardiogenic shock but its influence on the human microcirculation in patients deemed ready for discontinuing IABP support has not yet been studied. Therefore we used sidestream dark field ...

A pump-free and low-cost negative pressure sampling device for injecting well-defined non-biased sample plugs into the separation channel of MCE was developed. It was composed of a pipet bulb, a 3-way electromagnetic valve and a single voltage supply at constant voltage. A sub-atmospheric pressure was created by hand-pressing air out ...

Less than optimal outcomes for hypoplastic left heart syndrome may be related to unstable in-parallel circulation. Mechanical lung assist by (1) superior vena cava to right atrium pump with oxygenation (oxygenator assist), or (2) superior vena cava to pulmonary artery pump (pump assist) may permit successful neonatal in-series palliation. Nineteen ...