An in vitro methodology for evaluating the mechanical properties of aortic vascular prostheses

The main problem in the replacement of pathological segments of the aorta with vascular prostheses consists of matching the fluid admittance of the host artery and the graft. This mismatch results from the different compliance between natural and prosthetic vessels and from the plastic dilatation of the prosthesis diameter that occurs after implantation. An experimental procedure was set up for evaluating the mechanical properties of aortic vascular prostheses. An MTS 858 MiniBionix testing machine was equipped with a purposely designed testing apparatus, which allows loading a ring-shaped prosthesis specimen with forces that can be related easily to the transmural pressure acting on the prostheses in vivo. The reference pressure waveforms are simulated from a lumped parameter model of the cardiovascular system. Preliminary tests on 3 different (woven, warp knitted, and carbon-coated warp knitted fabric) aortic prostheses point out a good reproducibility of the results. The fabric strongly affects the circumferential elasticity and the dimensional stability of the graft. Simulation of hypertension promotes larger diameter dilatation and reduction in compliance. Agreement between in vitro and clinical diameter measurements has been assessed for 8 prosthesis samples and found to be adequate. This method is thus a potentially useful means for preclinical evaluation of compliance of vascular prostheses for the purpose of matching to native vessels.     

A comparison of CORVITA and expanded polytetrafluoroethylene vascular grafts implanted in the abdominal aortas of dogs

The utility of CORVITA vascular grafts, composed of an inner layer of meshed polyurethane fibers and an outer layer of meshed Dacron reinforcement, for replacement of the abdominal aorta was assessed in a canine model and compared with expanded polytetrafluoroethylene (ePTFE) grafts. CORVITA or ePTFE vascular grafts were implanted and left in place for 3 or 6 months. After removal, they were inspected macroscopically and histologically. Microspectrophotometry was used to quantify smooth muscle cells (SMCs), elastin (EL), and collagen (CL) in the media of the native artery. The patency rate of the CORVITA grafts after 6 months was 100%, whereas that of the ePTFE grafts was only 50%. Moreover, stenoses were apparent in all of the ePTFE grafts, but in only 43% of the CORVITA grafts. The intimal thickness at the distal anastomosis was significantly greater at 3 months in the ePTFE grafts (P<0.01), and there were significantly more SMCs in the host arterial media at the proximal and distal anastomoses in these grafts. Thus, better long-term patency can be expected with CORVITA grafts than with ePTFE grafts. This conferred advantage is most likely attributable to the less pronounced intimal hyperplasia which results from the proliferation of SMCs in the media of the native artery.     

Adding vancomycin to bone cement: research on its influence on mechanical and fixation strength using rabbit femoral prostheses

Objective: To compare the influence of different methods of adding vancomycin on the strength of bone cement used for fixing rabbits' femoral prostheses. Methods: Eighteen New Zealand white rabbits (36 femora) were allocated to three groups of six rabbits (12 femora) each: a control group, an experimental group 1 and experimental group 2. The bone cement used in the control group was mixed manually without vancomycin; in experimental group 1 it was mixed manually with 5% (2 g/40 g) vancomycin; and in experimental group 2 it was mixed in a vacuum with 5% (2 g/40 g) vancomycin. The cement combinations were then used to fill the marrow cavity of rabbit femurs to fix prostheses. An electronic universal testing machine (EUTM) was used to test the pullout force of the prostheses with bone cement 48 hours later. Student's paired t‐test was used for statistical analysis. Results: It was found that the maximum load of pullout force was 559.3 ± 82.3 N in the control group; 523.6 ± 86.5 N in experimental group 1; and 645.1 ± 105.9 N in experimental group 2. Statistical analysis showed there was no significant difference between the control group and experimental group 1 (P > 0.05). However, there were significant differences between the control group and experimental group 2 (P < 0.05); and between experimental group 1 and experimental group 2 (P < 0.05). Conclusion: When bone cement and vancomycin were mixed manually in a low concentration (<5%) vancomycin had no influence on the strength of the bone cement. However, bone cement and vancomycin mixed at the same concentrations in a vacuum did have a statistically significant effect on the strength of the bone cement.     

犬自体静脉与腹膜碎片镶嵌种植人工血管的研究

目的:探讨加速人工血管内皮化,提高人工血管移植后通畅率的途径.方法:犬自体静脉与腹膜碎片镶嵌种植人工血管,行股动脉移植.结果与结论:细胞镶嵌种植后的人工血管在短期内形成了管腔内皮化,提高了人工血管移植通畅率.光、电镜及免疫组化观察,证实了移植血管新生内膜的细胞组成.内膜厚度测定,种植组与对照组间差异显著(P<0.01 ),内皮化后抑制了内膜的增生.腹膜间皮细胞与内皮细胞在形态及功能上的相似性,使其同样具有很好的应用前景.镶嵌种植技术为一快速、简便的人工血管内皮化方法,具有较高的临床应用价值.     

The mineral and mechanical properties of bone in chronic experimental diabetes

The long-term effects of experimentally induced diabetes on bone were studied in eight male Lewis rats, intravenously (i.v.) injected with 65 mg/kg of streptozocin (STZ) and maintained for 12 months. Eight untreated age-matched rats served as controls. In the STZ-treated rats, experimentally induced diabetes was documented by the presence of hyperglycemia at 24 h and at 3 and 12 months. Significantly less weight was gained and less growth occurred in the STZ-treated rats despite careful attention to feeding and hydration. Mineral alterations were detected in the bones of the animals with experimental diabetes. Decreased hydroxyapatite crystal perfection, decreased Ca/P of the ash, and decreased ash content in the tibial metaphyses with increased ash content in the tibial diaphyses, was noted relative to controls. Bone osteocalcin content was increased in the metaphyses of the STZ-treated rats. While absolute measures of stiffness, torsional strength and energy absorption were decreased in the bones of the STZ-treated animals, when torsional strength and stiffness were normalized for differences in both growth and geometry, the normalized stiffness values for the diabetic bones were increased. The results suggest that in experimental diabetes certain aspects of bone mineralization are adversely affected and lead to reduced strength-related properties. However, a compensatory increase in stiffness occurs. The reason for this increase, although not known, may be related to changes in bone crystal structure.     

管腔内支架力学性能的体外实验现状及存在问题

管腔内支架已经广泛用于治疗人体各种管腔狭窄疾病。良好的力学性能是支架植入成功的前提。体外实验能直接测量支架的力学性能,近似反映支架在体内的受力情况,是研制支架必不可少的手段。本文就国内外多种支架的力学性能,特别是径向支撑力的实验研究、支架力学性能的体外实验装置存在的问题和发展前景进行综述。     

丙泊酚的药效及对脂代谢的影响

目的观察丙泊酚的药效学及对家兔脂代谢的影响。方法家兔12只,随机分为1%丙泊酚组(Ⅰ组)和2%丙泊酚组(Ⅱ组),每组6只。两组丙泊酚单次首次剂量均为6mg/kg,以0.6mg/s从家兔耳缘静脉分别匀速注射,观察和记录家兔头正位反射消失时间。注射完毕后接麻醉注射泵以400μg·kg-1·min-1的速度持续输注丙泊酚6h,记录心率、血压和呼吸等生命体征变化及停药后苏醒时间。并于静注前、静注完毕、持续输注5、30min及1、3、6h和苏醒时分别抽血行血气分析,检测血药浓度及血清甘油三酯(TG)、总胆固醇(TC)、高密度脂蛋白(HDL)、低密度脂蛋白(LDL)的浓度。结果Ⅰ组家兔血清TG浓度在持续输注1、3和6h与静注前比较均有显著增高(P<0.01),血清TC浓度仅在持续输注6h较静注前增高(P<0.01);Ⅱ组在6h的血清TG浓度高于用药前(P<0.01),但同时点仍低于Ⅰ组(P<0.01)。结论2%丙泊酚与1%丙泊酚的药效相似,但2%丙泊酚能明显延缓脂代谢紊乱的发生时间。     

Long-term effect of orchidectomy on cortical bone from rat femur: Bone mass and mechanical properties

Summary The study comprised seven groups of intact rats killed at 9, 12, 15, and 24 months of age, and three groups of rats castrated at the age of 9 months and killed together with the intact rats 3, 6, and 15 months after castration. The composition, dimension, and mechanical properties of intact bone as well as the constituent bone collagen from femoral diaphyses were investigated in relation to both age (9–24 months) and castration. Castration had no effect on density and only minor effect on ash and collagen contents. An age-related increase in bone mass, cross-sectional area, and wall thickness of the diaphyses was arrested (bone mass, area) or even reversed (to a decrease in wall thickness) after castration. Therefore, a growing difference, pronounced from 6 months after castration, between intact and castrated rats was observed in bone mass, cross-sectional area, and wall thickness. The compressive mechanical strength of intact bone normalized with regard to cross-sectional area was unaffected by castration, whereas castration tended to increase the stiffness of the bone collagen. When observed in a polarization microscope, two different zones in cross sections of the diaphyses were apparent. The average diameter of the border line separating the two zones was independent of age and castration. By measuring the average thickness of each of the two zones, age-related periosteal bone formation and endosteal bone resorption were demonstrated. After castration, the rate of bone formation was reduced and the rate of bone resorption was accelerated. Castration was thus found to affect the composition and the quality of the cortical bone to a minor extent only. On the other hand, the quantity of cortical bone was markedly reduced from 6 months after castration due to both an inhibited rate of bone formation and an accelerated rate of bone resorption.     

Impact of current cryopreservation procedures on mechanical and functional properties of human aortic homografts

We evaluated the impact f standard cryopreservation on mechanical and functional properties of human aortic homografts. From 14 human heart-valve donors, the thoracic descending aorta was obtained. Effects of cryopreservation on mechanical (elastic properties and breaking stress) and smooth muscle cell (SMC) and endothelium function were tested. Cryopreservation (cryo) did not significantly affect Young's modulus of elastin (fresh: 3.1 ± 1.0, cryo: 2.7 ± 0.9 × 10⁵ Nm^–2), collagen recruitment pressure (fresh: 1.1 ± 0.3, cryo: 1.1 ± 0.4 × 10⁴ Nm^–2), distensibility (fresh: 3.8 ± 1.8, cryo: 3.6 ± 1.6 × 10⁵ N^–1m²), or breaking stress (fresh: 2.4 ± 1.0, cryo: 2.2 ± 1.0 × 10⁶ Nm^–2). Following explantation, no endothelium-dependent relaxation was found. SMC function and endothelium-independent relaxation were mainly intact after explantation but significantly decreased after cryopreservation. Aortic mechanical properties are not influenced by cryopreservation. Following explantation, almost no endothelial cell function is present, and SMC contractility is strongly affected after cryopreservation. Received: 3 March 2000 Accepted: 27 April 2001     

过氧化脂质对淋巴细胞功能影响的实验研究

体外观察了过氧化亚油酸(LOOH)对淋巴细胞的影响,并进一步观察烧伤后体内过氧化脂质(LPO)水平变化及淋巴细胞功能变化,以探讨烧伤免疫抑制的机制。体外实验采用正常小鼠脾淋巴细胞与LOOH一起培养或温育,测定增殖反应、IL-2及LPO。体内实验采用小鼠11％～12％TBSA III度烧伤模型测定脾淋巴细胞功能以及血浆、肝、脾中LPO。结果表明:LOOH可抑制淋巴细胞增殖反应及IL-2生成、诱发淋巴细胞脂质过氧化,Vit E可减轻LOOH的这些作用;烧伤后体内LPO水平明显升高、脾淋巴细胞增殖反应及IL-2生成明显降低,Vit E组或SOD组的这些变化与正常组相比,无显著性差别。提示:烧伤后体内脂质过氧化亢进以及LPO增多可能是烧伤免疫抑制的机制之一。     

过氧化脂质对淋巴细胞功能影响的实验研究

体外观察了过氧化亚油酸（ＬＯＯＨ）对淋巴细胞的影响，并进一步观察烧伤后体内过氧化脂质（ＬＰＯ）水平变化及淋巴细胞功能变化，以探讨烧伤免疫抑制的机制。体外实验采用正常小鼠脾淋巴细胞与ＬＯＯＨ一起培养或温育，测定增殖反应、ＩＬ－２及ＬＰＯ。体内实验采用小鼠１１％～１２％ＴＢＳＡⅢ度烧伤模型测定脾淋巴细胞功能以及血浆、肝、脾中ＬＰＯ。结果表明：ＬＯＯＨ可抑制淋巴细胞增殖反应及ＩＬ－２生成、诱发淋巴细胞脂质过氧化，ＶｉｔＥ可减轻ＬＯＯＨ的这些作用；烧伤后体内ＬＰＯ水平明显升高、脾淋巴细胞增殖反应及ＩＬ－２生成明显降低，ＶｉｔＥ组或ＳＯＤ组的这些变化与正常组相比，无显著性差别。提示：烧伤后体内脂质过氧化亢进以及ＬＰＯ增多可能是烧伤免疫抑制的机制之一。     

Congenital lack of COX-2 affects mechanical and geometric properties of bone in mice

We compared the mechanical properties of bones from mice lacking either a functional cycloxygenase-1 (C57BL6/DBA COX-1–/–; n = 9) or COX-2 (C57BL6/DBA COX-2–/–; n = 9) gene and wild type mice (C57BL6/DBA; n = 10). Twenty-eight right femora from 3-month-old male mice were used to determine bulk structural and material properties of bone by three-point bending. Bone matrix properties were also measured by nanoindentation to access the changes in bulk mechanical properties due to changes in bone matrix or bone geometry. The bulk material properties (elastic modulus, P < 0.05; ultimate stress, P < 0.01) of COX-2–/– bones were lower than those of wild-type mice whereas the bulk structural properties (stiffness, P > 0.2; breaking force, P > 0.1) were similar to those of the wild-type mice. COX-2–/– mice had a longer moment of inertia but their cortical bones were thinner and contained many more intra-cortical pores compared with the bones of the other two groups. Finally, the bone matrix properties of COX-1–/– mice, COX-2–/– mice and their heterozygous littermates were similar to those of C57BL6/DBA wild-type mice. Deseased on December 30, 2002     

Cortical bone mass,composition, and mechanical properties in female rats in relation to age,long-term ovariectomy,and estrogen substitution

Summary The study comprised 12 groups of female rats: 6 groups of intact rats killed at 2, 6, 9, 12, 15, and 24 months of age, 4 groups of rats ovariectomized at 6 months and killed together with the intact rats at 9, 12, 15, and 24 months of age, and 2 groups of rats (one intact and one ovariectomized) treated with estrogen (2 g estradiol valerate/rat/week s.c.) for 8 months before they were killed at 24 months of age. The composition, dimensions, and mechanical strength of intact bone and bone collagen from femoral diaphyses were investigated in relation to age, ovariectomy, and estrogen administration. Up to 6–9 months of age, the axial length, percentage ash, density, and compressive mechanical stress increased, whereas percentage collagen decreased. An age-related increase in bone mass, crosssectional area, and wall thickness and a decrease in mechanical quality of bone collagen were apparent from 2 to 24 months of age. An age-related periosteal bone formation and the absence of endosteal bone resorption were demonstrated in intact rats. Compared with intact rats, ovariectomy was followed by an increase in body weight, a tendency to reduced percentage ash and a depressed bone mass, crosssectional area, and wall thickness of femoral diaphyses. The compressive mechanical stress of intact bone and the mechanical quality of bone collagen were unaffected by ovariectomy. Ovariectomy did not influence the periosteal bone formation but induced an endosteal bone resorption not present in the intact rats. The estrogen treatment of the ovariectomized rats normalized the body weight of the rats and brought to an end the endosteal bone resorption induced by ovariectomy. Estrogen treatment of both ovariectomized and intact rats tended to reduced the rate of periosteal bone formation.     

The effects of test environment and cyclic stretching on the failure properties of human patellar tendons

There is a need to document the mechanical properties of patellar tendon allografts used for reconstructive surgery of the damaged anterior cruciate ligament, especially the effects of irradiation sterilization. The purpose of this study was to investigate the influences of in vitro test environment and low-level cyclic stretching prior to failure tests on nonirradiated and irradiated human graft tissues. Bilateral patellar tendons were split and each half processed accordingly. Some graft tissues were stretched cyclically at 2.5 mm deformation before failure. Experiments were performed in a 37 degrees C saline bath or with tissues moistened with a drip of the same. The irradiated grafts relaxed less and generated less slack length in the drip environment than the nonirradiated controls. Cyclic stretching did not alter failure characteristics of either graft tissue. While no significant differences in the tensile responses or failure characteristics were noted for irradiated and nonirradiated grafts in the drip, in the bath environment the nonirradiated tissues had greater strength and modulus. This resulted in there being a significant difference between irradiated and nonirradiated tissue responses in a heated saline bath environment. These experimental results exemplify the need to control in vitro test environments in the evaluation of various sterilization and preservation protocols for soft tissue allografts.     

Flavonoid-rich beverage effects on lipid profile and blood pressure in diabetic patients

AIM: To compare freeze-dried strawberry(FDS) beverage and strawberry-flavored drink effects on lipid profile and blood pressure in type 2 diabetic(T2D) patients.METHODS: In a randomized, double-blind, controlled trial, 36 subjects with T2D(23 females; mean ± SE age: 51.57 ± 10 years) were randomly divided into two groups. Participants consumed two cups of either pure FDS beverage(each cup containing 25 g freeze-dried strawberry powder equivalent to one serving of fresh strawberries; intervention group) or an iso-caloric drinkwith strawberry flavoring(similar to the FDS drink in fiber content and color; placebo group) daily for 6 wk. Anthropometric measurements, 3 d, 24 h dietary recall, and fasting blood samples were collected at baseline and at weeks 6 intervention. After lying down and relaxing for approximately 10 min, each participant's blood pressure was recorded in triplicate with 5 min intervals; recordings were made at baseline and the trial end-point. Each participant's lipid profile was assessed before and after intervention.RESULTS: Assessment at the weeks 6 intervention showed a significant reduction from baseline in total cholesterol levels and total cholesterol to high-density lipoprotein cholesterol(HDL-C) ratio in the intervention group(179.01 ± 31.86 to 165.9 ± 32.4 mg/L; P = 0.00 and 3.9 ± 0.88 to 3.6 ± 0.082 mg/L; P = 0.00 respectively), but the change was not significantly different between the two groups(P = 0.07, P = 0.29 respectively). Systolic blood pressure levels were significantly reduced from baseline in both the FDS and placebo drink groups(129.95 ± 14.9 to 114.3 ± 27.5 mm Hg; P = 0.02 and 127.6 ± 15.6 to 122.9 ± 14.47 mm Hg; P = 0.00 respectively), but the reduction was not significantly different between the two groups. Diastolic blood pressure was significantly reduced post-intervention in the FDS drink group compared to placebo group(78.7 ± 7.2 vs 84.4 ± 5.8; P = 0.01), the reduction was also significant within the FDS drink group(84.2 ± 8.03 to 78.7 ± 7.2; P = 0.00). Triglycerides, HDL-C concentrations and anthropometric indices showed no significant differences between or within groups. CONCLUSION: Short-term FDS supplementation improved selected cardiovascular risk factors in subjects with T2 D. Long-term effects on other metabolic biomarkers need to be investigated in future trials.     

Morphologic quantitation of pseudointima and effects of antiplatelet drugs on vascular prostheses in goats

The natural process of endothelialization, pseudointimal formation, and connective tissue incorporation of the expanded PTFE grafts in the goat was documented through histologic examination of specimens harvested at 2, 4, 6, and 8 weeks. The goats demonstrated a progressive increase in pseudointimal pannus ingrowth from the anastomoses at a rate of 11.3 mm over a 12 week period. Histologic changes according to time of vascular graft incorporation in the goat model were found to be comparable to those of the dog, pig, and calf models reported in the literature. Platelet-inhibiting drugs, aspirin, dipyridamole, nifedipine, and ibuprofen were administered to goats after replacement of their infrarenal aorta with 5 cm of 8 mm diameter expanded PTFE grafts. The effects of the drugs on graft endothelialization and anastomotic pseudointimal formation was compared with those in the untreated control group after 12 weeks. Aspirin and dipyridamole had no detrimental effect on the healing process compared with the untreated control group. Studies with nifedipine and ibuprofen did not demonstrate a decrease in pseudointimal hyperplasia. Antiplatelet treatment resulted in no significant change in the rate of endothelialization of expanded PTFE grafts.     

Cartilage degeneration in post-collapse cases of osteonecrosis of the human femoral head: altered mechanical properties in tension, compression, and shear.

Osteonecrosis, or avascular necrosis, is a painful and debilitating condition characterized by progressive joint degeneration subsequent to collapse of necrotic regions of trabecular bone. A clear understanding of the mechanism of cartilage degeneration in osteonecrosis is critical to the development of treatment strategies aimed at sparing the femoral head. An analysis of 13 post-collapse osteonecrotic (ON) human femoral heads was performed relative to 24 non-ON controls to determine quantitatively the biomechanical and histological properties of post-collapse osteonecrotic cartilage. Cartilage mechanical properties were measured in tension, compression, and shear at different sites on the femoral head and correlated to histologic measures of cartilage degeneration using a semi-quantitative grading scale. Decreasing cartilage tensile strength correlated with histologic evidence of degeneration in the ON group; however, less correlation was noted with shear and compressive properties. After statistical correction for the more severe histologic degeneration in the ON group, the non-ON samples were found to exhibit significantly smaller loss angles during shear testing, while samples from the ON group were found to have greater tensile strength. Similarly, the ON group was found to exhibit significantly greater proteoglycan loss while the non-ON group showed significantly increased surface fibrillation. This study provides evidence that the changes occurring in post-collapse cases of osteonecrosis may involve mechanisms other than those typically attributed to osteoarthritic degeneration. One potential explanation is that decreased loading of cartilage overlying collapsed ON lesions leads to proteoglycan loss similar to that occurring with cartilage disuse. Unlike degenerative changes, some articular cartilage changes caused by disuse may be reversible. The presence of reversible changes would likely increase the chances of success of head sparing treatment strategies that rely on the viability and mechanical integrity of the articular cartilage.     

Short-term effects of obestatin on hexose uptake and triacylglycerol breakdown in human subcutaneous adipocytes

AIM To study complete dose-dependent effects of obestatin on lipolytic and glucose transport activities in human adipocyte preparations highly responsive to insulin.METHODS Adipocytes were prepared by liberase digestion from subcutaneous abdominal adipose tissue obtained from overweight subjects undergoing plastic surgery. The index of lipolytic activity was the glycerol released in the incubation medium, while glucose transport was assessed by [~3H]-2-deoxyglucose uptake assay.RESULTS When tested from 0.1 nmol/L to 1 μmol/L, obestatin did not stimulate glycerol release; it did not inhibit the lipolytic effect of isoprenaline and did not alter the insulin antilipolytic effect. Obestatin hardly activated glucose transport at 1 μmol/L only. Moreover, the obestatin stimulation effect was clearly lower than the threefold increase induced by insulin 100 nmol/L.CONCLUSION Low doses of obestatin cannot directly influence lipolysis and glucose uptake in human fat cells.     

胃转流术对GK大鼠肝脏脂代谢的影响及其意义

目的:探讨胃转流术对自发性糖尿病Goto-Kakizaki(GK)大鼠肝脏脂代谢的影响及其意义。方法:40只雄性GK大鼠随机均分为实验组与对照组。实验组行Roux-en-Y胃转流术,对照组行胃窦十二指肠离断原位吻合术。分别于术前、术后1,2,4周检测两组大鼠空腹血糖、口服葡萄糖耐量试验2 h(OGTT 2 h)的血糖;并于术前及术后4周测定大鼠血液中空腹游离脂肪酸(FFA),胆固醇(Tch),甘油三酯(TG)。此外,于术中及术后第4周获取大鼠肝脏组织行免疫组化油红O染色,观察肝脏TG沉积情况。结果:与术前比较,实验组大鼠术后空腹及OGTT 2 h血糖值均呈下降趋势,两者在术后2,4周时明显降低(均P<0.05);术后第4周,实验组大鼠血液中FFA明显降低(P<0.05),而TG及Tch无明显变化(均P>0.05),肝脏组织切片内TG沉积现象明显减少。对照组以上所有指标手术前后均无明显改变(均P>0.05)。结论:胃转流术降低GK大鼠血糖的机制可能与改善肝脏脂质代谢,降低FFA含量,使胰岛素抵抗得以缓解有关。     

Alterations in red blood cell volume and hemoglobin concentration, viscoelastic properties, and mechanical fragility caused by continuous flow pumping in calves

In this study, we have analyzed the changes in mean corpuscular volume (MCV), mean corpuscular hemoglobin concentration (MCHC), and the dynamic deformability and mechanical fragility of red blood cells (RBCs) in five male Holstein calves (body weight: 95.6 ± 10.8 kg) whose circulation was partially supported with a novel magnetically levitated extracorporeal centrifugal blood pump MedTech Dispo. One hour after the pumping has started, the MCV increased and the MCHC decreased by 1.064 ± 0.006 and 0.906 ± 0.050 times, respectively, as compared with those of the prepumped blood (P < 0.05). The deformability index L/W, where L and W are the long and short axes of the two-dimensional RBC images, respectively, sheared by a cyclically reversing shear flow increased indicating that the RBCs pumped for 1 h exhibited more elastic characteristics (P < 0.05). In addition, when the pumped blood cells were sheared for 30 min with a uniform shear stress of 25.38 Pa, the hemolysis level decreased dramatically as compared with the control blood, as more fragile RBCs were destroyed by pumping, leaving behind less fragile RBCs. All these characteristics of the RBCs exposed to continuous flow resemble those of young RBCs having larger MCV, lower MCHC, higher elasticity, and lower fragility. In conclusion, during continuous flow pumping, the RBCs having relatively lower threshold for hemolysis to mechanical shear stress generated by continuous flow blood pump (CFBP) are destroyed first and removed from circulation in the early stage of application of CFBP, thus leaving behind less fragile and stronger RBCs.