Lung thermography during the initial reperfusion period to assess pulmonary function in cellular ex vivo lung perfusion.

Background: Thermography is a noninvasive technology to detect low temperatures in poorly circulated areas. In ex vivo lung perfusion (EVLP), lungs are rewarmed to body temperature during the initial 1 h. Currently, the effect of graft thermal changes during the rewarming phase on pulmonary function is unknown.

Impact of gap size and groove design of hydrodynamic bearing on plasma skimming effect for use in rotary blood pump.

Plasma skimming can exclude red blood cells from high shear regions in the gaps formed by hydrodynamic bearings in rotary blood pumps. We investigated the effect of the gap size and groove design on the plasma skimming efficiency. Spiral groove bearings (SGBs) were installed into a specially designed test rig for in vitro experiments performed using human blood.

In vitro hemocompatibility investigation for the development of low-flow centrifugal blood pumps with less platelet clogging.

Low-flow blood pumps rated under 1 L/min are emerging for new medical applications, such as hemofiltration in acute use. In those pumps, platelet adhesion and aggregation have to be carefully considered because of clogging risk in the filter part. To find an acceptable hemocompatibility that can be applied to low-flow centrifugal blood pump design, the platelet aggregation index, clogging on a micromesh filter, and the hemolysis index were investigated using a low-flow blood pump designed for hemofiltration use.

Quantitative investigation of platelet aggregation under high shear force for anti-platelet aggregation in vitro tests.

Blood pumps are often used for hemofiltration in patients with renal failure. To design effective centrifugal blood pumps for hemofiltration, it is important to suppress clogging caused by platelet aggregation. However, the optimal conditions for conducting anti-platelet aggregation tests in vitro have not yet been established.

Investigating the cause of hemolysis in patients supported by a pulsatile ventricular assist device.

A survey conducted by Abiomed, Inc. revealed that 10 of 60 patients who received ventricular assistance via the AB5000 ventricular assist device (VAD) experienced hemolysis. The present study was conducted to investigate which factors influence hemolysis under pulsatile-flow VADs such as the AB5000.

Improvement of hemolysis performance in a hydrodynamically levitated centrifugal blood pump by optimizing a shroud size.

We have developed a hydrodynamically levitated centrifugal blood pump. In the blood pump having hydrodynamic bearings, the narrow bearing gap has a potential for high hemolysis. The purpose of the this study is to improve hemolysis performance in a hydrodynamically levitated centrifugal blood pump by optimizing a shroud size.

Real-time, non-invasive thrombus detection in an extracorporeal circuit using micro-optical thrombus sensors.

Introduction: Real-time, non-invasive monitoring of thrombus formation in extracorporeal circuits has yet to be achieved. To address the challenges of conventional optical thrombus detection methods requiring large devices that limit detection capacity, we developed a micro-optical thrombus sensor.

Methods: The proposed micro-optical thrombus sensor can detect the intensity of light scattered by blood at wavelengths of 660 and 855 nm.

Suitable hemolysis index for low-flow rotary blood pumps.

A suitable index is needed for hemolysis tests that use low-flow pumps, such as pediatric blood pumps or blood purification pumps. To create such an index, the present study investigates the change of plasma-free hemoglobin in the pump circuit with time and the change of the hemolysis rate with flow rate and impeller rotational speed. The results show that the hemolysis rate or the increase rate of the total free hemoglobin are suitable measures for hemolysis evaluation for low-flow pumps.

Plasma skimming efficiency of human blood in the spiral groove bearing of a centrifugal blood pump.

This work investigates the plasma skimming effect in a spiral groove bearing within a hydrodynamically levitated centrifugal blood pump when working with human blood having a hematocrit value from 0 to 40%. The present study assessed the evaluation based on a method that clarified the limitations associated with such assessments. Human blood was circulated in a closed-loop circuit via a pump operating at 4000 rpm at a flow rate of 5 L/min.

Development of a real-time and quantitative thrombus sensor for an extracorporeal centrifugal blood pump by near-infrared light.

We developed an optical thrombus sensor for a monopivot extracorporeal centrifugal blood pump. In this study, we investigated its quantitative performance for thrombus detection in acute animal experiments of left ventricular assist using the pump on pathogen-free pigs. Optical fibers were set in the driver unit of the pump.

Optical Dynamic Analysis of Thrombus Inside a Centrifugal Blood Pump During Extracorporeal Mechanical Circulatory Support in a Porcine Model.

Complications due to pump thrombus remain the weak point of mechanical circulatory support (MCS), such as the use of a left ventricular assist device (LVAD) or extracorporeal membrane oxygenation, leading to poor outcomes. Hyperspectral imaging (HSI) is an effective imaging method using a hyperspectral (HS) camera, which comprises a spectrophotometer and a charge-coupled device camera to discriminate thrombus from whole blood. Animal experiments were conducted to analyze dynamic imaging of thrombus inside a prototype of a hydrodynamically levitated centrifugal blood pump using an HSI system.

Reaction mechanism of blood coagulation factors in shear flow field.

Thrombus formation in blood pumps is a major problem. It has been reported that the shear rate is closely related to thrombus formation in blood pumps; however, the mechanism of blood coagulation in a shear flow field is not yet fully understood. The purpose of this study is to evaluate the effect of shear loading on the reaction of blood coagulation factors quantitatively.

Long-term durability test of axial-flow ventricular assist device under pulsatile flow.

A long-term durability test was conducted on a newly developed axial-flow ventricular assist device (VAD) with hydrodynamic bearings. The mock circulatory loop consisted of a diaphragm pump with a mechanical heart valve, a reservoir, a compliance tank, a resistance valve, and flow paths made of polymer or titanium. The VAD was installed behind the diaphragm pump.

Plasma Skimming in a Spiral Groove Bearing of a Centrifugal Blood Pump.

Plasma skimming is a phenomenon in which discharge hematocrit is lower than feed hematocrit in microvessels. Plasma skimming has been investigated at a bearing gap in a spiral groove bearing (SGB), as this has the potential to prevent hemolysis in the SGB of a blood pump. However, it is not clear whether plasma skimming occurs in a blood pump with the SGB, because the hematocrit has not been obtained.

Properties of a monopivot centrifugal blood pump manufactured by 3D printing.

An impeller the same geometry as the impeller of a commercial monopivot cardiopulmonary bypass pump was manufactured using 3D printing. The 3D-printed impeller was integrated into the pump casing of the commercially available pump to form a 3D-printed pump model. The surface roughness of the impeller, the hydraulic performance, the axial displacement of the rotating impeller, and the hemolytic properties of the 3D-printed model were measured and compared with those of the commercially available model.

In vitro thrombogenesis resulting from decreased shear rate and blood coagulability.

In vitro antithrombogenic testing with mock circulation is a useful type of pre-evaluation in ex vivo testing of mechanical assist devices. For effective in vitro testing, we have been developing a clear quantitative thrombogenesis model based on shear stress and blood coagulability. Bovine blood was used as the test medium.

Effect of Impeller Geometry on Lift-Off Characteristics and Rotational Attitude in a Monopivot Centrifugal Blood Pump.

The effect of the flow path geometry of the impeller on the lift-off and tilt of the rotational axis of the impeller against the hydrodynamic force was investigated in a centrifugal blood pump with an impeller supported by a single-contact pivot bearing. Four types of impeller were compared: the FR model with the flow path having both front and rear cutouts on the tip, the F model with the flow path having only a front cutout, the R model with only a rear cutout, and the N model with a straight flow path. First, the axial thrust and the movement about the pivot point, which was loaded on the surface of the impeller, were calculated using computational fluid dynamics (CFD) analysis.

Optical aggregometry of red blood cells associated with the blood-clotting reaction in extracorporeal circulation support.

The aggregability of red blood cell (RBCs) is associated with the contribution of plasma proteins, such as fibrinogen and lipoproteids, to blood-clotting. Hence, we hypothesized that RBC aggregability reflects the blood-clotting reaction. A noninvasive optical monitoring method to measure RBC aggregability for the assessment of blood-clotting stage during mechanical circulatory support was developed.

Development of a photon-cell interactive monte carlo simulation for non-invasive measurement of blood glucose level by Raman spectroscopy.

Turbidity variation is one of the major limitations in Raman spectroscopy for quantifying blood components, such as glucose, non-invasively. To overcome this limitation, we have developed a Raman scattering simulation using a photon-cell interactive Monte Carlo (pciMC) model that tracks photon migration in both the extra- and intracellular spaces without relying on the macroscopic scattering phase function and anisotropy factor. The interaction of photons at the plasma-cell boundary of randomly oriented three-dimensionally biconcave red blood cells (RBCs) is modeled using geometric optics.

Bearing gap adjustment for improvement of levitation performance in a hydrodynamically levitated centrifugal blood pump.

The purpose of the present study is to investigate a bearing gap adjustment for improvement of levitation performance in a hydrodynamically levitated centrifugal blood pump to realize a blood pump with a low hemolysis level. The impeller levitates axially by balancing a gravitational force, buoyancy, a magnetic force, and hydrodynamic forces on the top and bottom sides of the impeller. To adjust the levitation position of the impeller, the balance of acting forces on the impeller was adjusted by changing the shroud area on the bottom impeller.

Evaluation of erythrocyte flow at a bearing gap in a hydrodynamically levitated centrifugal blood pump.

We have developed a hydrodynamically levitated centrifugal blood pump for extracorporeal circulatory support. In the blood pump, a spiral groove bearing was adopted for a thrust bearing. In the spiral groove bearing, separation of erythrocytes and plasma by plasma skimming has been postulated to occur.