Artificial organs最新文献

Background: We previously reported the EXTEND (EXTra-uterine Environment for Neonatal Development) system provides physiologic support of fetal lambs (105-111 days gestational age; GA) via a pumpless arteriovenous circuit using a commercially available oxygenator (Maquet-Ox). However, for anticipated human subjects at 23-28 weeks of GA, a smaller oxygenator is required. To meet this requirement, a proprietary oxygenator (Experimental Oxygenator: Exp-Ox) was developed.

Methods: Fourteen lambs (mean GA 99 days, mean weight at cannulation 1.36 kg) were placed on the EXTEND system. Thereafter, Exp-Ox was connected in parallel with the Maquet-Ox, and its durability and hemocompatibility were assessed over a prolonged use of up to 21 days, utilizing a dual oxygenator platform. Blood flow to Exp-Ox was increased over time using a tubing clamp to maintain the anticipated human fetal flow rates (50-165 mL/min).

Results: Throughout the study, there was no deterioration in the oxygen and CO₂ exchange function. The pressure drop in the Exp-Ox remained unchanged over time, with no statistically significant difference, whereas the calculated Exp-Ox resistance (pressure drop/blood flow) decreased since the change in pressure drop increased at a slower rate than the increase in blood flow. The quantitative clot burden in the Exp-Ox following completion of the study ranged from 0.03% to 2.55%, with no correlation to study duration.

Conclusions: The study demonstrated the Exp-Ox maintained its ability to transfer oxygen and CO2 and sustained hemocompatibility for up to 21 days at anticipated fetal flow rates on the EXTEND system.

Background: One of the main challenges in control algorithm design for full closed-loop automated insulin delivery systems is the trade-off between the effective compensation of meal-related disturbances and ensuring user safety during the postprandial and fasting periods.

Methods: This paper proposes and evaluates the performance of a switched tuning strategy, a promising but relatively underexplored solution in this domain. This method employs two distinct tunings of a primary control algorithm: an aggressive tuning for meal compensation and a conservative tuning for fasting periods. The analysis considers implementing the switched strategy for three control algorithms: model predictive control and proportional-derivative control, both widely used for glucose regulation, and a linear quadratic Gaussian control, an optimal algorithm previously validated in clinical settings under a switched structure. Additionally, to obtain a more comprehensive understanding of the switched strategy implications, two nonswitched controllers are implemented for each control algorithm: an aggressive and a conservative tuning strategy.

Results: The switched strategy significantly improves the trade-off between meal compensation and safety, increasing the time within the target range of 70-180 [mg/dL] for all three algorithms. For proportional-derivative control, the time in range increases from 69.1% with the conservative tuning and 83.1% with the aggressive to 86.6% with the switched structure. For model predictive control, the improvement is from 73.4% and 74.1% to 85.8%. Last, linear quadratic Gaussian control increases from 65.0% and 70.4% to 85.6%.

Conclusion: The findings suggest that the switched strategy may be a feasible and straightforward approach for enhancing meal compensation without increasing the risk of postprandial hypoglycemia in people with diabetes.

Background: Ex vivo heart perfusion (EVHP) is a promising approach for preserving donor hearts in a near-physiological state. However, the perfusion pressure and flow require adjustment to meet the requirements of aerobic metabolism, which may cause hemolysis and coagulation, consequently impairing myocardial function. The aim of this study is to investigate the impact of transient control performance of pulsatile flow on hemolysis and coagulation in EVHP.

Methods: Fresh porcine blood was circulated for 4 h in a mock loop equipped with a pulsatile pump and a self-designed compliant chamber, operating under conditions of a mean flow rate of 1 L/min and a mean pressure of 75 mmHg. Two typical proportional-integral-derivative (PID) control responses (underdamped response and overdamped response) were implemented to compare the impact of transient performance on hemolysis and coagulation. Blood samples were collected from the in vitro loop and analyzed for plasma free hemoglobin (PfHb), thrombin-antithrombin complex (TAT) and P-selectin levels.

Results: The experimental results demonstrated that the transient control performance of pulsatile flow had a significant impact on hemolysis and coagulation as circulation time increased. Compared to the overdamped response, the underdamped response resulted in more hemolysis and a higher risk of thrombosis. However, both the overdamped response and the underdamped response exhibited comparable levels of platelet activation.

Conclusion: During the control process of EVHP, frequent adjustments of perfusion pressure and flow should be minimized. Additionally, oscillations and overshoots in transient responses should be avoided to reduce hemolysis and thrombosis.

Background: This systematic review evaluates the current evidence pertaining to the application of artificial intelligence (AI) and machine learning (ML) in left ventricular assist device (LVAD) implantation. Specifically, the potential of AI/ML in risk stratification, predicting complications, and improving patient outcomes is explored, whereas also identifying key challenges and elucidating avenues of future research.

Methods: A comprehensive search was conducted across EMBASE, MEDLINE, Cochrane, PubMed, and Google Scholar databases to identify studies on AI/ML in LVAD implantation up to March 2024. Articles were selected if they utilized AI/ML techniques in LVAD settings and met predefined criteria. A total of 17 studies were included after a rigorous screening and appraisal process.

Results: The included studies highlighted the use of ML in five main areas: (1) mortality prediction, where ML models demonstrated higher accuracy compared to traditional models; (2) adverse event prediction, including aortic regurgitation and suction events; (3) myocardial recovery, with ML models outperforming traditional stratification methods; (4) deciphering thrombosis risk, with ML identifying key predictors such as younger age and higher BMI; and (5) right ventricular failure prognostication, within which ML models leveraged hemodynamic and imaging data for superior prediction accuracy. Despite such prevalent advances, challenges including data heterogeneity, lack of causality, and limited generalizability persist.

Conclusion: AI and ML possess transformative potential in optimizing LVAD management, offering both advanced prediction of commonly encountered risk occurrence and personalized care respectively. However, identified issues in AI/ML application, including data interpretability, dataset diversity, and integration into clinical workflows, must be addressed in order to enhance their broader adoption and impact.

Background: Limb ischemia is a serious complication of venoarterial (VA) extracorporeal membrane oxygenation (ECMO), potentially resulting in amputation, rhabdomyolysis, or death. This study aimed to evaluate the effectiveness of near-infrared spectroscopy (NIRS) monitoring in the early detection and prevention of limb ischemia in peripheral VA ECMO.

Methods: We retrospectively reviewed 166 patients who underwent peripheral VA ECMO between January 2018 and December 2022. Patients were categorized into two groups based on the implementation of NIRS monitoring (Before-NIRS [n = 83] vs. After-NIRS [n = 83]). An inverse probability of treatment weighting (IPTW)-adjusted analysis was conducted.

Results: Baseline characteristics were not significantly different between the groups. The ECMO weaning success rate was significantly higher in the After-NIRS group (45.9% vs. 63.4%, p = 0.026). However, survival to discharge did not differ significantly (31.8% vs. 42.7%, p = 0.174). The incidences of rhabdomyolysis and acute limb ischemia were significantly lower in the After-NIRS group (10.6% vs. 1.2% and 11.8% vs. 0%, respectively). In the After-NIRS group, a decrease in NIRS values was observed in three patients, prompting timely placement of distal perfusion catheters. None of these patients developed limb ischemia.

Conclusions: After the implementation of NIRS monitoring, no cases of limb ischemia were observed. NIRS enables early identification of limb malperfusion, facilitates timely intervention, and reduces unnecessary distal perfusion catheter placement. As a non-invasive, real-time monitoring modality, NIRS offers continuous assessment of limb perfusion and plays a valuable role in the early prevention of limb ischemia in patients undergoing peripheral VA ECMO.

Background: Extracorporeal membrane oxygenation (ECMO) provides mechanical circulatory and respiratory support. However, thrombus formation in the circuit can lead to hemorrhagic complications, requiring improvements in ECMO anti-thrombogenicity. Few studies have reported the effect of pulsatile flow on thrombus formation in ECMO circuits. This study evaluated how pulsatile flow affects thrombus formation inside the membrane oxygenator.

Methods: This study was conducted in pigs (n = 5) using an experimental model in which each pig was connected to two different ECMO circuits: one with steady flow (via the jugular vein and carotid artery) and the other with pulsatile flow (via the femoral vein and artery). The pulsatile waveform was generated as an upward sinusoidal waveform added to the baseline frequency. Both circuits were set to a mean flow rate of 2 L/min and operated for 4 h without anticoagulation. Thrombus formation in the membrane oxygenators was observed during and after circulation. The thrombus area was quantified using image analysis.

Results: All experiments were completed with stable hemodynamics. The pressure in the pulsatile circuit was confirmed to be a pulsatile waveform. The thrombus area in the steady flow circuits was 81.5%, 10.6%, 42.1%, 60.2%, and 96.7%, while those in the pulsatile flow circuits were 6.2%, 5.2%, 8.4%, 9.9%, and 65.8%, respectively. The thrombus area in the pulsatile flow circuit tended to be smaller than that in the steady flow circuit.

Conclusions: Pulsatile flow with a specific waveform may reduce thrombus formation in membrane oxygenators, potentially enhancing the anti-thrombogenicity of ECMO circuits.

Background: We had previously established an adequate cryopreservation process for hepatocyte spheroids for the development of an off-the-shelf bioartificial liver (BAL) system. The purpose of this study is to evaluate the efficacy of a BAL system containing cryopreserved immobilized porcine hepatocyte spheroids in a porcine model of acute liver failure (ALF).

Methods: ALF pigs were divided into three groups. The control group consisted of treatment-naïve pigs (n = 5), the blank group consisted of pigs that were attached to the BAL system not containing hepatocyte spheroids for 12 h (n = 5), and the BAL group consisted of pigs that were attached to the BAL containing hepatocyte spheroids for 12 h (n = 5).

Results: Analysis of specific oxygen uptake rates showed that the hepatocytes sustained vigorous activity throughout the 12-h period of BAL operation. Median survival time of pigs was 24.0 h in the BAL group, 17.0 h in the blank group, and 15.0 h in the control group. The BAL group showed significantly prolonged survival according to Kaplan-Meier survival analysis compared to the blank group (p = 0.04) and control group (p = 0.04). Serum ammonia levels were significantly increased in the blank group (p < 0.01) and control group (p < 0.01), compared to the BAL group during the treatment period of the porcine ALF models. Prothrombin time (PT) was significantly lower in the BAL group compared to the blank group (p = 0.04) and control group (p = 0.01).

Conclusions: A BAL system with a bioreactor containing cryopreserved immobilized hepatocyte spheroids showed effective clearance of serum ammonia, preservation of renal function, and improved survival in a porcine model of ALF.

Introduction and objective: The artificial urinary sphincter (AUS) is currently the gold standard treatment for stress urinary incontinence in men, and it's also a treatment option for women in Europe. UroActive is a new electronic device that offers remotely adjustable settings, including device pressure. This study aims to compare the range of Maximal Urethral Closure Pressures (MUCPs) covered by UroActive with those covered by the current AMS800 in male and female cadavers.

Methods: Six cadavers (3 males and 3 females) were implanted with an occlusive cuff (OC) positioned around the bulbar urethra in men and around the bladder neck in women. A MUCP measurement was performed for each of the 3 different AMS800 Pressure-Regulating Balloons (PRBs): 51-60, 61-70, and 71-80 cmH₂O, that were successively connected to the OC. The AMS800 PRB was then replaced by the UroActive Control Unit (CU), and MUCP measurements were performed at set pressures from 10 to 150 cmH₂O.

Results: UroActive device remained fully functional (wireless communication, calibration) throughout the study period. UroActive CU achieved MUCPs values that encompassed the entire range observed with the 3 different AMS800 PRBs. A strong positive correlation between set device pressures sent to UroActive CU and MUCPs was noted in both males (r² = 0.984) and females (r² = 0.948).

Conclusion: The findings suggest that UroActive provides a wide adjustable range of urethral closure pressures, potentially offering an alternative to AMS800 for managing stress urinary incontinence in both men and women. Further clinical studies are necessary to confirm its safety and effectiveness in patients.