Continuous flow left ventricular assist devices: a valid option for heart failure patients

Recent outstanding clinical advances with new mechanical circulatory systems (MCS) have led to additional strategies in the treatment of end stage heart failure (HF). Heart transplantation (HTx) can be postponed and for certain patients even replaced by smaller implantable left ventricular assist devices (LVAD). Mechanical support of the failing left ventricle enables appropriate hemodynamic stabilisation and recovery of secondary organ failure, often seen in these severely ill patients. These new devices may be of great help to bridge patients until a suitable cardiac allograft is available but are also discussed as definitive treatment for patients who do not qualify for transplantation. Main indications for LVAD implantation are bridge to recovery, bridge to transplantation or destination therapy. LVAD may be an important tool for patients with an expected prolonged period on the waiting list, for instance those with blood group 0 or B, with a body weight over 90 kg and those with potentially reversible secondary organ failure and pulmonary artery hypertension. However, LVAD implantation means an additional heart operation with inherent peri-operative risks and complications during the waiting period. Finally, cardiac transplantation in patients with prior implantation of a LVAD represents a surgical challenge. This review summarises the current knowledge about LVAD and continuous flow devices especially since the latter have been increasingly used worldwide in the most recent years. The review is also based on the institutional experience at Berne University Hospital between 2000 and 2012. Apart from short-term devices (Impella, Cardiac Assist, Deltastream and ECMO) which were used in approximately 150 cases, 85 pulsatile long-term LVAD, RVAD or bi-VAD and 44 non-pulsatile LVAD (mainly HeartMateII and HeartWare) were implanted. After an initial learning curve, one-year mortality dropped to 10.4% in the last 58 patients.

Point-of-care prothrombin time testing in paediatric intensive care: an observational study of the ease of use of two devices

Two major difficulties arise when taking blood samples in children: the challenge of venous access and the comparatively large amount of blood required.

A novel interface for hybrid mock circulations to evaluate ventricular assist devices

This paper presents a novel mock circulation for the evaluation of ventricular assist devices (VADs), which is based on a hardware-in-the-loop concept. A numerical model of the human blood circulation runs in real time and computes instantaneous pressure, volume, and flow rate values. The VAD to be tested is connected to a numerical-hydraulic interface, which allows the interaction between the VAD and the numerical model of the circulation. The numerical-hydraulic interface consists of two pressure-controlled reservoirs, which apply the computed pressure values from the model to the VAD, and a flow probe to feed the resulting VAD flow rate back to the model. Experimental results are provided to show the proper interaction between a numerical model of the circulation and a mixed-flow blood pump.

Radiation exposure in whole-body computed tomography of multiple trauma patients: bearing devices and patient positioning

Whole-body computed tomography (WBCT) plays an important role in the management of severely injured patients. We evaluated the radiation exposure of WBCT scans using different positioning boards and arm positions.

Continuous Formation and Separation of Calcium-Alginate Capsules Containing Viable Mammalian Cells in Microfluidic Devices

Microfluidic devices can be used for many applications, including the formation of well-controlled emulsions. In this study, the capability to continuously create monodisperse droplets in a microfluidic device was used to form calcium-alginate capsules.Calcium-alginate capsules have many potential uses, such as immunoisolation of cells and microencapsulation of active drug ingredients or bitter agents in food or beverage products. The gelation of calcium-alginate capsules is achieved by crosslinking sodiumalginate with calcium ions. Calcium ions dissociated from calcium carbonate due to diffusion of acetic acid from a sunflower oil phase into an aqueous droplet containing sodium-alginate and calcium carbonate. After gelation, the capsules were separated from the continuous oil phase into an aqueous solution for use in biological applications. Typically, capsules are separated bycentrifugation, which can damage both the capsules and the encapsulated material. A passive method achieves separation without exposing the encapsulated material or the capsules to large mechanical forces, thereby preventing damage. To achieve passiveseparation, the use of a microfluidic device with opposing channel wa hydrophobicity was used to stabilize co-laminar flow of im of hydrophobicity is accomplished by defining one length of the channel with a hydrogel. The chosen hydrogel was poly (ethylene glycol) diacrylate, which adheres to the glass surface through the use of self-assembled monolayer of 3-(trichlorosilyl)-propyl methacrylate. Due to the difference in surface energy within the channel, the aqueous stream is stabilized near a hydrogel and the oil stream is stabilized near the thiolene based optical adhesive defining the opposing length of the channel. Passive separation with co-laminar flow has shown success in continuously separating calcium-alginatecapsules from an oil phase into an aqueous phase. In addition to successful formation and separation of calcium alginate capsules,encapsulation of Latex micro-beads and viable mammalian cells has been achieved. The viability of encapsulated mammalian cells was determined using a live/dead stain. The co-laminar flow device has also been demonstrated as a means of separating liquid-liquidemulsions.

Continuous, Passive Liquid-Liquid Extraction and Emulsion Separation Within Microfluidic and Millifluidic Devices

Liquid-liquid extraction (LLE) is a method used to separate compounds based on their relative activity in two immiscible phases. By significantly reducing the scale of liquid-liquid extraction to the micro- and milli-fluidic levels, this separation process can bemade suitable for low volume, high value materials.

Efficient Liquid Liquid Extraction By Emulsion Formation and Separation in Robust Milli-Fluidic Devices

Conventional liquid liquid extraction (LLE) methods require large volumes of fluids to achieve the desired mass transfer of a solute, which is unsuitable for systems dealing with a low volume or high value product. An alternative to these methods is to scale down the process. Millifluidic devices share many of the benefits of microfluidic systems, including low fluid volumes, increased interfacial area-to-volume ratio, and predictability. A robust millifluidic device was created from acrylic, glass, and aluminum. The channel is lined with a hydrogel cured in the bottom half of the device channel. This hydrogel stabilizes co-current laminar flow of immiscible organic and aqueous phases. Mass transfer of the solute occurs across the interface of these contacting phases. Using a y-junction, an aqueous emulsion is created in an organic phase. The emulsion travels through a length of tubing and then enters the co-current laminar flow device, where the emulsion is broken and each phase can be collected separately. The inclusion of this emulsion formation and separation increases the contact area between the organic and aqueous phases, therefore increasing the area over which mass transfer can occur. Using this design, 95% extraction efficiency was obtained, where 100% is represented by equilibrium. By continuing to explore this LLE process, the process can be optimized and with better understanding may be more accurately modeled. This system has the potential to scale up to the industrial level and provide the efficient extraction required with low fluid volumes and a well-behaved system.

Vibrating Membrane Devices Deliver Aerosols More Efficient than Standard Devices: A Study in a Neonatal Upper Airway Model

Abstract Background: Aerosol therapy in preterm infants is challenging, as a very small proportion of the drug deposits in the lungs. Aim: Our aim was to compare efficiency of standard devices with newer, more efficient aerosol delivery devices. Methods: Using salbutamol as a drug marker, we studied two prototypes of the investigational eFlow(®) nebulizer for babies (PARI Pharma GmbH), a jet nebulizer (Intersurgical(®) Cirrus(®)), and a pressurized metered dose inhaler (pMDI; GSK) with a detergent-coated holding chamber (AeroChamber(®) MV) in the premature infant nose throat-model (PrINT-model) of a 32-week preterm infant (1,750 g). A filter or an impactor was placed below the infant model's "trachea" to capture the drug dose or particle size, respectively, that would have been deposited in the lung. Results: Lung dose (percentage of nominal dose) was 1.5%, 6.8%, and 18.0-20.6% for the jet nebulizer, pMDI-holding chamber, and investigational eFlow nebulizers, respectively (p<0.001). Jet nebulizer residue was 69.4% and 10.7-13.9% for the investigational eFlow nebulizers (p<0.001). Adding an elbow extension between the eFlow and the model significantly lowered lung dose (p<0.001). A breathing pattern with lower tidal volume decreased deposition in the PrINT-model and device residue (p<0.05), but did not decrease lung dose. Conclusions: In a model for infant aerosol inhalation, we confirmed low lung dose using jet nebulizers and pMDI-holding chambers, whereas newer, more specialized vibrating membrane devices, designed specifically for use in preterm infants, deliver up to 20 times more drug to the infant's lung.

Intracardiac devices for stroke prevention

Stroke is a significant cause of serious disability and death worldwide. A substantial proportion of strokes are related to an underlying cardiac embolic source, most commonly in association with atrial arrhythmias (fibrillation/flutter). Atrial fibrillation is considered a major risk factor for stroke. Although long-term prophylactic oral anticoagulation has been shown to be very effective in reducing stroke in patients with atrial fibrillation, it has a number of major limitations and is not feasible in all patients. In such cases, the use of percutaneously (transvenous) implanted left atrial appendage occlusive devices or surgical appendage obliteration is being explored. Similarly, the presence of a patent foramen ovale, especially in the presence of an atrial septal aneurysm, is now recognized as an important potential mediator of paradoxical cardiogenic embolism. Percutaneous patent foramen ovale closure is becoming increasingly established as a safe and effective means of preventing recurrent strokes in the presence of a patent foramen ovale. In this account, the authors discuss the intracardiac devices and techniques available and the relative merits of their use for stroke prevention.