Normalized Index Of Hemolysis Values Research Articles

CARD13: INDUS: Economical Maglev Centrifugal Blood Pump for Developing Countries- Preliminary In-Vitro Hemolysis Testing

Purpose of Study: The Centrimag® is widely used for acute extracorporeal circulatory support. However, it is prohibitively expensive for low- and lower-middle-income countries (LMICs). In order to lower the costs associated with the use of Centrimag®, our India-US consortium is developing an economical centrifugal pump (INDUS), to improve accessibility of this lifesaving device. As a first step, a 3D printed magnetically levitated centrifugal pump head was designed and fabricated (Figure 1), that can fit into a standard Centrimag® motor unit. The objective of this study is to compare the hemolysis caused by the INDUS versus the original Centrimag® system in a mock circulatory loop, under realistic hemodynamic conditions. Methods: The prototype INDUS pump head was inserted into a simple mock-loop consisting of a blood reservoir, inlet and outlet tubing connections and the pump (Figure 2). A 3D printed clamp was used to control the resistance and develop pressure head. Pressure sensors were used to monitor pressure to a laptop using the DataQ system and non-contact Transonic flow probe provided a measure of the flow rate. The hemolysis tests were conducted as per the ASTM F1841-97 Standards using 400±20 mL of fresh, citrated, veni-puncture bovine blood at 30-35% haematocrit. The samples were collected at 0 Hr (baseline), 30 min., 1 Hr, 2 Hr, 3 Hr, and 4 Hr. The flow rate was maintained at 5±0.25 LPM and pressure at 110±15 mmHg. The samples were centrifuged, and the plasma was measured for plasma free hemoglobin, using a Multimode Reader. The normalized index of hemolysis (NIH) was calculated for both the pumps. Results: The NIH values for the original Centrimag® and the 3D printed INDUS were 0.00118 and 0.00166 respectively (Figure 3). Conclusion: The INDUS pump does not cause excessive hemolysis compared to the original Centrimag® pump. These encouraging in-vitro results encourages us to proceed with developing an injection moulded version and to launch further basic biocompatibility testing toward the goal of providing an inexpensive mechanical blood pump that can be accessible to patients in India and other LMICs.Figure 1. 3D Printed prototype of INDUS Pump (IAAHP: Indo-American Artificial Heart Program).Figure 2. Mock loop with Indus pump circulating bovine blood for hemolysis test.Figure 3. NIH comparison for Indus and Centrimag® pumps

Hemodynamic investigation and in vitro evaluation of a novel mixed-flow blood pump.

Ventricular assist devices (VADs) are considered an effective treatment for patients with advanced heart failure, while complications associated with blood damage remain a burden. Structure design innovation has the potential to reduce hemolysis and improve hemocompatibility. In this research, a novel mixed-flow blood pump that integrates structural features of the axial and centrifugal VADs was proposed. The pump consists of an inducer, a mixed impeller supported by two ceramic pivot bearings, and a volute. The flow field and laminar viscous shear stress were analyzed by the in silico simulation. The hydraulic and hemolytic performance were evaluated in vitro by using a 3D printed pump. The flow field distribution showed that streamlines in the connection area were smoothly transitioned through structural integration and no irregular flow occurred in the entire flow channel. The axial blades work as a fluid accelerator (generating 18.56% of the energy), and the centrifugal blades provide the main pressure head. The proportion of fluid inside the pump exposed to low laminar viscous shear stress (<50Pa) and high laminar viscous shear stress (>150Pa) was 99.02% and 0.03%, respectively. The in vitro hemolysis test results showed that the NIH (Normalized Index of Hemolysis) value of the mixed pump is 0.0079±0.0039g/100L (n=6). It can be concluded that the mixed flow structure is effective at improving hydraulic performance, eliminating flow disturbance, and minimizing shear stresses. This novel pump design is expected to provide a new direction for the development of next-generation VADs.

Development of a real-time blood damage monitoring device for cardiopulmonary bypass system using near-infrared spectroscopy.

The optical properties of hemoglobin could indicate the degree of hemolysis. We aimed to utilize this to develop a real-time blood damage monitoring device for cardiopulmonary bypass (CPB) systems. The real-time blood damage monitoring device comprised a near-infrared spectroscopy optical module with a fiber spectrometer and monitoring platform and computer software developed using LabVIEW 2017. The fiber spectrometer operated at wavelengths of 545, 660, and 940nm and contained a detector fiber bundle (source-detector distance = 1.0-2.5cm). CPB operation was simulated using an artificial heart-lung machine with a flow rate of 3, 4, or 5L/min. Four hundred milliliter of anticoagulated porcine blood was continuously rotated for 4h. The transmittance, reflectivity, and absorbance of the blood were measured using the optical device at a frequency of 25Hz and then digitally averaged into 1-s interval. Samples of damaged blood were collected at regular intervals for in vitro hemolysis tests to calculate the normalized index of hemolysis (NIH). All experiments were repeated three times. We prepared 28 blood bags containing 400ml of anticoagulant. Paired t test was used to examine the test-retest reliability of the differences between the three methods and control samples. Statistical tests revealed significant differences in the mean values between the test and control groups over time (P< 0.01). Relationship was established between the real-time monitoring results and the NIH values. An effective blood damage detection method that combined in vitro hemolysis tests and near-infrared spectroscopy was achieved. The results demonstrate the clinical potential of a real-time, low-cost, and reliable blood damage monitoring device to improve the safety of CPB operation.

Evaluation of in vitro hemolysis and platelet activation of a newly developed maglev LVAD and two clinically used LVADs with human blood.

In vitro hemolysis testing remains one of the most important performance measures to judge the hemocompatibility of a left ventricular assist device (LVAD). Clinically relevant operating conditions and appropriate testing blood are essential to infer in vitro data for potential clinical use. This in vitro study was carried out to evaluate and compare the hemolytic performance of a newly developed magnetically levitated (maglev) LVAD (CH-VAD) with two clinically used LVADs (HVAD and HeartMate II (HMII)) using fresh human blood. A small volume (~300 mL) in vitro circulating flow loop was constructed with a LVAD generated flow of 4.5 L/min at the nominal or reported clinical operating speed for each LVAD. The blood was circulated in the loop for 4 hours with samples drawn at baseline and hourly. Plasma-free hemoglobin (PFH) concentrations in the hourly blood samples were determined with spectrophotometry. Normalized index of hemolysis (NIH) was calculated to compare the hemolytic performance of the CH-VAD and the two reference LVADs. Platelet activation was measured with flow cytometry. The experimental test for each device was repeated at least 7 times. The data from this study showed that all the three LVADs generated very low hemolysis (NIH <0.01 g/100L). The CH-VAD was found to have a significantly lower NIH value (0.00135 ± 0.00032 g/100L) compared to the HVAD (0.00525 ± 0.00183 g/100L) and the HMII (0.00583 ± 0.00182 g/100L). No statistically significant difference in device-generated hemolysis was found between the HVAD and the HMII. The level of platelet activation induced by the CH-VAD is significantly lower than those by the HVAD and the HMII. The data suggest that the shear-induced hemolysis and platelet activation of the CH-VAD are acceptable relative to the two LVADs currently in clinical use.

In Vitro Characterization of the Pittsburgh Pediatric Ambulatory Lung.

Acute and chronic respiratory failure are a significant source of pediatric morbidity and mortality. Current respiratory support options used to bridge children to lung recovery or transplantation typically render them bedridden and can worsen long-term patient outcomes. The Pittsburgh Pediatric Ambulatory Lung (P-PAL) is a wearable pediatric blood pump and oxygenator (0.3 m surface area) integrated into a single compact unit that enables patient ambulation. The P-PAL is intended for long-term use and designed to provide up to 90% of respiratory support in children weighing 5-25 kg. Computational fluid dynamics and numerical gas exchange modeling were used to design the P-PAL and predict its performance. A P-PAL prototype was then used to obtain pressure versus flow curves at various impeller rotation rates using a blood analog fluid. In vitro oxygen exchange rates were obtained in blood in accordance with ISO standard 7199. The normalized index of hemolysis (NIH) was measured over a 6 hour period at blood flow rates of 1 and 2.5 L/min. The P-PAL provided blood flows of 1-2.5 L/min against the pressure drop associated with its intended-use pediatric cannulas. The oxygen exchange rate reached a maximum of 108 ml/min at a blood flow rate of 2.5 L/min and met our respiratory support design target. Device-induced hemolysis was low with NIH values of 0.022-0.027 g/100 L in the intended blood flow rate range. In conclusion, the current P-PAL design met our pumping, oxygenation, and hemolysis specifications and has the potential to improve treatment for pediatric respiratory failure.

HEMOLYSIS CHARACTERISTICS OF A NEW TYPE-INTRAVENOUS LUNG ASSIST DEVICE

The purpose of this study was to investigate the effect of multiple mechanical forces in hemolysis. Specific attention was focused on the effect of membrane vibration. This study was design to identify membrane vibration dependence on hemolysis, and provide verification data for a developing a device. For the hemolysis test, the plasma free hemoglobin concentration was measured spectrophotometrically with a Shimadzu assay kit. The normalized index of hemolysis(NIH) was calculated according to a linear regression analysis method. The normalized index of hemolysis for the oxygenator(NIHO) has been modified according to the ASTM standards. The NIH value, which was obtained from the circuit without an oxygenator, was subtracted from the circuit with an oxygenator to eliminate the effects of the roller pump or other artifacts. This value was defined as the value of NIHO. The blood flow was fixed at 1 L/min as in an ECMO condition and 5 L/min as a cardiopulmonary bypass condition (V/Q ratio = 1). The NIH values of the circuit, including the intravenous lung assist device, were 0.0014(g/100L) by exciting a piezo-vibrator with the sine wave magnitude of DC 10V and 0.0018(g/100L) at 50 V. The NIH values of the circuit without the oxygenator were 0.00043 (g/100L) by exciting a piezo-vibrator with the sine wave magnitude of DC 10V and 0.00072 (g/100L) at 50 V. By subtracting these numbers, The NIHO value could he determined as 0.00097(g/l00L) and 0.00108(g/100L) by exciting a piezo-vibrator with the sine wave magnitude of DC 10V and 50 V, respectively

Feasibility of a tiny Gyro centrifugal pump as an implantable ventricular assist device.

The Gyro pumps were developed for long-term circulatory support. The first generation Gyro pump (C1E3) achieved 1 month paracorporeal circulatory support in chronic animal experiments; the second generation (PI702) implantable ventricular assist device (VAD) was successful for over 6 months. The objective of the next generation Gyro pump is for use as a long-term totally implantable VAD and for pediatric circulatory support. This tiny Gyro pump (KP101) was fabricated with the same design concept as the other Gyro pumps. The possibility of an implantable VAD was determined after performance and hemolysis test results were compared to those of the other Gyro pumps. The pump housing and impeller were fabricated from polycarbonate with an impeller diameter of 35 mm. The diameter and height of the pump housings are 52.3 mm and 29.9 mm, respectively. At this time, a DC brushless motor drives the KP101, which is the same as that for the C1E3. The pump performance was measured in 37% glycerin water at 37 degrees C. Hemolysis tests were performed utilizing a compact mock loop filled with fresh bovine blood in a left ventricular assist device (LVAD) condition at 37 degrees C. The KP101 achieved the LVAD conditions of 5 L/min and 100 mm Hg at 2,900 rpm; generated 10 L/min against 100 mm Hg at 3,200 rpm; 3 L/min against 90 mm Hg at 2,600 rpm; and 2 L/min against 80 mm Hg at 2,400 rpm. In addition, the pump efficiency during this experiment was 12.5%. The other Gyro pumps. that is, the C1E3, PI601, and PI701, in an LVAD condition require 1,600, 2,000, and 2,000 rpm, respectively. The KP101 produced a normalized index of hemolysis (NIH) value of 0.005 g/100 L. With regard to the NIH, the other Gyro pumps, namely the C1E3, PI601, and PI701 demonstrated 0.0007, 0.0028, and 0.004 g/100 L, respectively. The KP101 produced an acceptable pressure flow curve for a VAD. The NIH value was higher than that of other Gyro pumps, but is in an acceptable range.

Evaluation of Platelet Damage in Two Different Centrifugal Pumps Based on Measurements of α‐Granule Packing Proteins

Mechanical trauma caused by centrifugal pumps is usually evaluated in terms of hemolysis. However, platelet damage caused by centrifugal pumps has not been studied well. We evaluated platelet damage in 2 different centrifugal pumps, the Medtronic BioMedicus BP-80 and the Terumo Capiox, in vitro and compared the results in terms of hemolysis. To evaluate platelet damage, the rate of increase (RI) for beta-thromboglobulin (beta-TG) and platelet factor-4 (PF-4) were measured by enzyme immunoassay. RI was defined as follows: RI for beta-TG is deltabeta-TG/deltaN and RI for PF-4 is deltaPF-4/deltaN where deltabeta-TG is the increase in beta-TG, deltaPF-4 is the increase in PF-4, and deltaN is the increase of the passing number, which is defined in the following equation: N = Qt/V (t, time; V, priming volume; Q, flow rate). Each pump was tested in a mock circuit for 3 h under a flow rate of 5 L/min and a pressure head of 100 mm Hg using fresh human heparinized blood (n = 5). For comparison, the normalized index of hemolysis (NIH) values were calculated for both pumps. The NIH values did not indicate a significant difference between the Capiox and the BP-80 pumps (Capiox vs. BP-80, 0.0021 +/- 0.0004 vs. 0.0034 +/- 0.0007, NS). However, the RI values for beta-TG and PF-4 in the Capiox were significantly lower than in the BP-80 (beta-TG, 0.198 +/- 0.047 vs. 0.376 +/- 0.049; PF-4, 0.080 +/- 0.014 vs. 0.268 +/- 0.043, p < 0.05). In conclusion, although there was no significant difference between the 2 pumps in terms of hemolysis, the Capiox centrifugal pump induced less platelet damage than the BP-80. The results suggest that measurements of RI for beta-TG and PF-4 are more sensitive parameters than NIH values for evaluating blood cell damage.