Influence of circumferential annular grooving design of impeller on suspended fluid force of axial flow blood pump

Aiming at insufficient suspension force on the impeller when the hydraulic suspension axial flow blood pump is start at low speed, the impeller suspension stability is poor, and can’t quickly enter the suspended working state. By establishing the mathematical model of the suspension force on the impeller, then the influence of the circumferential groove depth of the impeller on the suspension force is analyzed, and the annular groove depth on the impeller blade in the direction of fluid inlet and outlet was determined as (0.26, 0.02 mm). When the blood pump starts, there is an eccentricity between the impeller and the pump tube, the relationship between the suspension force and the speed of the impeller under different eccentricities is analyzed. Combined with the prototype experiment, the circumferential annular grooving design of the impeller can make the blood pump rotate at about 3500 rpm into the suspension state, when the impeller is at 8000 rpm, the impeller can basically achieve stable suspension at the eccentricity of 0.1 mm in the gravity direction, indicating that the reasonable circumferential annular grooving design of the impeller can effectively improve the suspension hydraulic force of the impeller and improve the stability of the hydraulic suspension axial flow blood pump.

Smart syringe using actuator and force sensor for epidural anesthesia injection

The anesthesia process in the epidural space is quite difficult as it requires a high level of skill. Therefore, a medical accident occurs, and intensive training is required. In order to reduce these medical accidents, medical technology is being developed, which provides safe and accurate treatment services. This paper proposes a smart syringe design for safe and accurate anesthesia in the epidural space. The smart syringe is designed to measure the electrical sensing waveform by using a sensor instead of the sense of the hand during anesthesia and show the position of the needle through external monitoring. To design a smart syringe, a force sensor, actuator, and CPU were used, and a 3D printer was used to produce the outer shape. An animal test was conducted to evaluate the performance test of the smart syringe, and satisfactory results were obtained by measuring the needle insertion process of the smart syringe and the position of the needle through the animal experiment.

Ensuring hemodialysis adequacy by dialysis dose monitoring with UV spectroscopy analysis of spent dialyzate

Introduction: Patients’ session-to-session variation has been shown to influence outcomes, making critical the monitoring of dialysis dose in each session. The aim of this study was to detect the intra-patient variability of blood single pool Kt/V as measured from pre-post dialysis blood urea and from the online tool Adimea®, which measures the ultraviolet absorbance of spent dialyzate. Methods: This open, one-armed, prospective non-interventional study, evaluates patients on bicarbonate hemodialysis or/and on hemodiafiltration. Dialysis was performed with B. Braun Dialog+ machines equipped with Adimea®. In the course of the prospective observation, online monitoring with Adimea® in each session was established without the target warning function being activated. A sample size of 97 patients was estimated. Results: A total of 120 patients were enrolled in six centers in China (mean age 51.5 ± 12.2 years, 86.7% males, 24.2% diabetics). All had an AV-fistula. The proportion of patients with blood Kt/V < 1.20 at baseline was 48.3%. During follow-up with Adimea®, the subgroup with Kt/V > 1.20 at baseline remains at the same adequacy level for more than 90% of the patients. Those with a Kt/V < 1.20 at baseline, showed a significant increase of Kt/V to 60% of the patients reaching the adequacy level >1.20. The coefficient of variation for spKt/V as evaluated by Adimea® was 9.6 ± 3.4%, not significantly different from the 9.6 ± 8.6% as blood Kt/V taken at the same time. Conclusion: Online monitoring of dialysis dose by Adimea® improves and maintains dialysis adequacy. Implementing online monitoring by Adimea into daily practice moves the quality of dialysis patient care a significant step forward.

The influence of surface roughness on the damage of von Willebrand Factor under shear flow condition

Despite technological advances in mechanical circulatory support devices to treat end-stage heart failure, blood damage induced by non-physiological shear stress in operation often triggered clinical hemocompatibility complications. The loss of high molecular weight von Willebrand Factor (HMW-VWF) has been considered as an essential cause of gastrointestinal bleeding. In addition to the mechanics factors, interface factors may also affect blood damage, especially the surface characteristics. In this study, the effect of surface roughness on VWF damage under flow condition was investigated. A roller pump circulation experimental platform with a roughness embedded sample chamber was constructed to provide blood shearing flow condition. VWF molecular weight analysis, VWF antigen (VWF-Ag) concentration assay, and VWF ristocetin cofactor activity (VWF-Rico) assay were performed on the sheared blood samples. These variables are the main functional indicators of VWF. It was found that the surface roughness induced VWF damage is mainly caused by the loss of HMW-VWF rather than reducing the total amount of VWF. The threshold value of surface roughness for a rapid increase in the degradation of HMW-VWF under low flow rate was obtained between Ra 0.4 and 0.6 μm, which was smaller than the threshold for hemolysis. Our findings indicated that VWF is more sensitive to the interface factor of surface roughness than red blood cells, thus has a higher requirement for blood pump design. It could provide reference for the material design and processing in developing mechanical circulatory support devices.

Comparison of household income in in-hospital outcomes after implantation of left ventricular assist device

Introduction: Due to the inability to keep up with the demand for heart transplantation, there is an increased utilization of left ventricular assist devices (LVAD). However, paucity of data exists regarding the association of household income with in-hospital outcomes after LVAD implantation. Methods: Retrospective cohort study using the NIS to identify all patients ⩾18 years who underwent LVAD implantation from 2011 to 2017. Statistical analysis was performed comparing low household income (⩽50th percentile) and high income (>50th percentile). Results: A total of 25,503 patients underwent LVAD implantation. The low-income group represented 53% and the high-income group corresponded to 47% of the entire cohort. The low-income group was found to be younger (mean age 55 ± 14 vs 58 ± 14 years), higher proportion of females (24% vs 22%), and higher proportion of blacks (32% vs 16%, p < 0.001 for all). The low-income group was found to have higher prevalence of hypertension, chronic pulmonary disease, smoking, dyslipidemia, obesity, and pulmonary hypertension ( p < 0.001 for all). However, the high-income cohort had higher rate of atrial tachyarrhythmias and end-stage renal disease ( p < 0.001). During hospitalization, patients in the high-income group had increased rates of ischemic stroke, acute kidney injury, acute coronary syndrome, bleeding, and need of extracorporeal membrane oxygenation ( p < 0.001 for all). We found that the unadjusted mortality had an OR 1.30 (CI 1.21–1.41, p < 0.001) and adjusted mortality of OR 1.14 (CI 1.05–1.23, p = 0.002). Conclusion: In patients undergoing LVAD implantation nationwide, low-income was associated with increased comorbidity burden, younger age, and fewer in-hospital complications and all-cause mortality.

Effects of the atrium on intraventricular flow patterns during mechanical circulatory support

Simulations of the ventricular flow patterns during left ventricular assist device (LVAD) support are mainly performed with idealized cylindrical inflow, neglecting the influence of the atrial vortex. In this study, the influence of the left atrium (LA) on the intra-ventricular flow was investigated via Computational Fluid Dynamics (CFD) simulations. Ventricular flow was simulated by a combined Eulerian (carrier flow)/Lagrangian (particles) approach taking into account either the LA or a cylindrical inflow section to mimic a fully support condition. The flow deviation at the mitral valve, the blood low-velocity volume as well as the residence time and shear stress history of the particles were calculated. Inclusion of the LA deflects the flow at the mitral valve by 25°, resulting in an asymmetric flow jet entering the left ventricle. This reduced the ventricular low-velocity volume by 40% (from 6.4 to 3.9 cm3), increased (40%) the shear stress experienced by particles and correspondingly increased (27%) their residence time. Under the studied conditions, the atrial geometry plays a major role in the development of intraventricular flow patterns. A reliable prediction of blood flow dynamics and consequently thrombosis risk analysis within the ventricle requires the consideration of the LA in computational simulations.

Rescue extracorporeal life support as a bridge to durable left ventricular assist device

Background: The ideal timing of a durable assist device implantation in patients with end-stage heart failure presenting with INTERMACS profile I is still controversial. The data on extracorporeal life support (ECLS) bridge to durable left ventricular assist device (LVAD) in these patients is limited. Materials and methods: We retrospectively analyzed the outcomes of 35 patients in acute cardiogenic shock (CS) who, between December 2013 and September 2020, were bridged with ECLS to durable LVAD. The mean age was 52.3 ± 12.0 years. The primary endpoints of this study were in-hospital, 30-day, 6-month, and 1-year mortality. The secondary endpoint was the development of any postoperative adverse events and other characteristics during the follow-up period. We also assessed the impact of the rescue ECLS on the recovery of the end-organ function. Results: In-hospital, 30-day, 6-month, and 1-year survival was 65.6%, 75.9%, 69.2%, and 62.7% respectively. The median time on ECLS was 7 days (IQR 5.0–13.0). We observed a high incidence of a severe right heart failure (22.9%), acute kidney injury on dialysis (68.6%), and respiratory failure (77.1%). Bridge with ECLS provided a significant recovery of liver and kidney function prior to durable LVAD implantation. Conclusion: The concept of bridging patients presenting in end-stage heart failure and cardiogenic shock with ECLS prior to durable LVAD implantation is a feasible method to ensure acceptable survival rates and significant recovery of the end-organ function.

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. We conducted circulation testing in vitro using fresh porcine blood and two centrifugal pumps with different impeller inlet shapes. The Negative Log Platelet Aggregation Threshold Index (NL-PATI), which reflects the ability of residual platelets to aggregate, and flow rate were measured during reflux for 60 min, and the Normalized Index of Hemolysis (NIH (g/20 min)) was calculated. In addition, blood cell clogging after reflux was observed on the micromesh filter by SEM, and the adhesion rate was calculated. Our results showed that the platelet clogging on the micromesh filter occurred when the average NL-PATI was greater than 0.28 and the average NIH (g/20 min) was greater than 0.01. In contrast, platelet clogging on the micromesh was suppressed when NL-PATI was less than 0.17 and the NIH (g/20 min) was less than 0.003. These values might be used as acceptable hemocompatibility of low-flow centrifugal blood pumps with suppressed platelet clogging for hemofiltration pumps.

Donor variability alters differentiation and mechanical cohesion of tissue-engineered constructs with human endothelial/MSC co-culture

To move towards clinical applications, tissue engineering (TE) should be validated with human primary cells and offer easy connection to the native vascularisation. Based on a sheet-like bone substitute developed previously, we investigated a mesenchymal stem cells/endothelial cells (MSCs/ECs) coculture to enhance pre-vascularisation. Using MSCs from six independent donors whose differentiation potential was assessed towards two lineages, we focused on donor variability and cell crosstalk regarding bone differentiation. Coculture was performed on calcium phosphate granules in a specific chamber during 1 month. MSCs were seeded first then ECs were added after 2 weeks, with respective monocultures as control groups. Cell viability and organisation (fluorescence, electronic microscopy), differentiation (ALP staining/activity, RT-qPCR) and mechanical cohesion were analysed. Adaptation of the protocol to coculture was validated (high cell viability and proliferation). Activity and differentiation showed strong trends towards synergistic effects between cell types. MSCs reached early mineralisation stage of maturation. The delayed addition of ECs allowed for their attachment on developed MSCs’ matrix. The main impact of donor variability could be here the lack of cell proliferation potential with some donors, leading to low differentiation and mechanical cohesion and therefore absence of sheet-like shape successfully obtained with others. We suggest therefore adapting protocols to cell proliferation potentials from one batch of cells to the other in a patient-specific approach.

Lung ultrasound and the role of lung aeration score in patients with acute respiratory distress syndrome on extracorporeal membrane oxygenation

Objective: This was a pilot study to determine the utility of daily lung ultrasound (LUS) in patients requiring veno-venous extracorporeal membrane oxygenation (VV-ECMO) for acute respiratory distress syndrome (ARDS). Design: This was a prospective, observational study. Setting: The study took place in the intensive care unit at Royal Papworth Hospital in Cambridge, UK. Participants: We recruited adult patients receiving VV-ECMO for ARDS. Interventions: All patients received a lung computed tomography (CT) scan and LUS on admission. Bedside chest radiography (CXR) and LUS were done on a daily basis until patients were decannulated. Measurements and main results: Daily LUS aeration scores were calculated according to the appearance of four defined patterns. An independent radiologist calculated corresponding scores for CT and CXR, retrospectively. These were checked for correlation with LUS aeration scores. There were statistically significant correlations between LUS versus CT ( r = 0.868, p = 0.002) and LUS versus CXR ( r = 0.498, p = 0.018) with good agreement and no evidence of proportional bias. LUS was able to detect 13.5% of pleural effusions and 54.2% of pneumothorax that were not picked up on CXR. In most of the patients who were weaned off VV-ECMO, a progressive reduction of LUS aeration scores corresponding to lung re-aeration was observed. Conclusions: LUS correlated with findings on CT and CXR for quantifying lung aeration and the clinical presentation of patients. LUS also picked up more pleural effusions and pneumothorax than CXR. Together with traditional imaging techniques, the routine use of LUS should be considered for this patient group.