Hemolysis usually happens instantly when red blood cells (RBCs) rupture under a high shear stress. However, it is also found to happen gradually in the extracorporeal membrane oxygenation (ECMO) under low but periodic squeezes. In particular, the gradual hemolysis is accompanied by a progressive change in morphology of RBCs. In this work, the gradual hemolysis is studied in a microfluidic device with arrays of narrow gaps the same as the constructions in ECMO. RBCs are seen to deform periodically when they flow through the narrow gaps, which causes the release of adenosine-triphosphate (ATP) from RBCs. The reduced ATP level in the cells leads to the fatigue of RBCs with the progressive changes in morphology and the gradual loss of deformability. An empirical model for the fatigue of RBCs is established under the periodic squeezes with controlled deformation, and it reveals a different way of the hemolysis that is dominated by the squeeze frequency. This finding brings a new insight into the mechanism of hemolysis, and it helps to improve the design of circulatory support devices.

Significance: Circulatory air embolisms resulting from surgical procedures or deep-sea diving can cause pathophysiological responses such as pulmonary hypertension and cardio-cerebral infarction. Despite significant research on embolism treatment, underlying processes of how moving bubbles get stuck in vessels have not been fully established. To further this mechanistic understanding, we developed microfluidic and in vivo experiments to observe bubble’s stopping process and revealed that aggregation of blood cells and thrombus formation occurs on the periphery of embolism’s tail because of flow recirculation. This localized thrombus formation triggers dramatic increase in flow resistance that stops bubble’s motion. This study brings insight into the critical stage of air embolism formation and may lead to strategies for prevention and treatment of this clinically significant event.

It has been reported that increased red blood cell distribution width (RDW) predicts adverse events in cardiovascular disease and in patients undergoing percutaneous coronary intervention. However, the role of serum RDW levels in drug-eluting stent (DES) restenosis remains unclear. We aimed to investigate the relationship between serum RDW levels and in-stent restenosis (ISR) after coronary stenting with DES in stable angina pectoris (SAP) patients. A total of 293 consecutive chronic SAP patients with coronary DES implantation were enrolled in this study. The ISR was analyzed by coronary angiography analysis at a mean follow-up of 8 months. According to whether ISR was detected, patients were divided into two groups: the ISR group (n=45) and the non-ISR group (n=247). Serum RDW was assessed both at admission and at the 8-month follow-up in all patients. Standard medication was continued throughout the investigation period. Baseline characteristics of the two groups were similar. Patients in the ISR group had significantly higher RDW levels compared with patients in the non-ISR group both at admission and at follow-up (P<0.01, respectively). Furthermore, the ISR group had significantly longer stent length and lower stent diameter compared with the non-ISR group (P<0.01, respectively). In a multivariate analysis, diabetes mellitus, current smoking, RDW levels, C-reactive protein levels, stent length, and stent diameter were associated independently with ISR. Serum RDW level may independently predict ISR at both admission and follow-up in SAP patients with coronary DES implantation, which indicates that a chronic inflammatory response might be involved in the pathogenesis of ISR.

There is a need to improve the efficacy and safety of endovascular techniques in venous thrombotic diseases, and microbubble enhanced sonothrombolysis is a promising approach. However, whether endovascular low-frequency ultrasound (LFUS) can be utilized in microbubble enhanced sonothrombolysis is unclear. Here, we present a catheter-based thrombolytic system that combines unfocused low-frequency low-intensity ultrasound with novel fibrin-targeted drug-loaded bifunctional microbubbles. We develop an in vitro flow model and an in vivo rabbit inferior vena cava (IVC) thrombosis model to evaluate the safety and efficacy of the thrombolytic system. The results indicate that microbubble enhanced sonothrombolysis with endovascular LFUS treatment for 30 min is equally effective compared to pure pharmacologic treatment. Furthermore, the thrombolytic efficacy of this system is safely and substantially improved by the introduction of a fibrin-targeted drug-loaded bifunctional microbubble with a reduction of the fibrinolytic agent dosage by 60%. The microbubble enhanced endovascular LFUS sonothrombolysis system with excellent thrombolytic efficacy may serve as a new therapeutic approach for venous thrombotic diseases.

Noncontacting finger seals are new compliant seal in gas turbine engine sealing technology. Their potential hydrodynamic and hydrostatic lifting capabilities make them preferable to brush seals and contacting finger seals. The work concerns the mechanism of dynamic leakage of noncontacting finger seal, and a novel dynamic leakage analysis model is proposed. The model combines seal dynamic analysis and seal leakage analysis together to estimate seal dynamic performance through seal leakage. The nature of dynamic leakage performance affected by the change of seal–rotor clearance is revealed. Dynamic leakage increasing is mainly affected by ratio of friction force to finger stiffness, finger mass natural frequency, and rotor excitation amplitude. Results show that the leakage increasing caused by the rotor eccentricity is inevitable. In the design optimization of the noncontacting finger seal, the ratio of friction force to finger stiffness and the rotor excitation should be as small as possible, and the finger natural frequency should be as large as possible.