Impacts of the COVID-19 pandemic on access to HIV and reproductive health care among women living with HIV (WLHIV) in Western Kenya: A mixed methods analysis.

Introduction: The COVID-19 pandemic has impacted access to health services. Our objective was to understand the pandemic's impact on access to HIV, pregnancy, and family planning (FP) care among women living with HIV (WLHIV). Methods: Data were collected after June 2020, when questions about the pandemic were added to two ongoing mixed methods studies using telephone surveys and in-depth interviews among WLHIV in western Kenya. The Chaguo Langu (CL) study includes primarily non-pregnant WLHIV receiving HIV care at 55 facilities supported by AMPATH and the Opt4Mamas study includes pregnant WLHIV receiving antenatal care at five facilities supported by FACES. Our outcomes were self-reported increased difficulty refilling medication, accessing care, and managing FP during the pandemic. We summarized descriptive data and utilized multivariable logistic regression to evaluate predictors of difficulty refilling medication and accessing care. We qualitatively analyzed the interviews using inductive coding with thematic analysis. Results: We analyzed 1,402 surveys and 15 in-depth interviews. Many (32%) CL participants reported greater difficulty refilling medications and a minority (14%) reported greater difficulty accessing HIV care during the pandemic. Most (99%) Opt4Mamas participants reported no difficulty refilling medications or accessing HIV/pregnancy care. Among the CL participants, older women were less likely (aOR = 0.95, 95% CI: 0.92-0.98) and women with more children were more likely (aOR = 1.13, 95% CI: 1.00-1.28) to report difficulty refilling medications. Only 2% of CL participants reported greater difficulty managing FP and most (95%) reported no change in likelihood of using FP or desire to get pregnant. Qualitative analysis revealed three major themes: (1) adverse organizational/economic implications of the pandemic, (2) increased importance of pregnancy prevention during the pandemic, and (3) fear of contracting COVID-19. Discussion: The two unique participant groups included in our study encountered overlapping problems during the COVID-19 epidemic. Access to HIV services and antiretrovirals was interrupted for a large proportion of non-pregnant WLHIV in western Kenya, but access to pregnancy/family planning care was less affected in our cohort. Innovative solutions are needed to ensure HIV and reproductive health outcomes do not worsen during the ongoing pandemic.

[Study on the effect of simple incision of ventral tunica albuginea on the correction of penile curvature in hypospadias].

Objective: To investigate the therapeutic effect of simple tunica albugineaincision and ventral penile lengthening surgery on the correction of penile curvature due to asymmetry of the cavernous bodies in hypospadias. Methods: A retrospective analysis was performed in 39 children with hypospadias who underwent simple tunica albuginea incision and ventral penile lengthening surgery for correcting asymmetry of the cavernous bodies from January 2016 to December 2018(36 of them were from Department of Pediatric Urology surgery, The Children's Hospital, Zhejiang University School of Medicine, and 3 from Department of Urology surgery, Affiliated Hospital ofJiaxing University), all of whom aged from 0.5 to 5, with a median age of 1.1 years. During the first stage of the operation, firstly penile skin and sarcoma was released by completely degloving the skin and fascia of penis, secondly the factor of short urethral plate was solved by transection of urethral plate, and then the dorsal length of penis (A), the ventral length of the penis before and after straightening by incision of tunica albuginea (B and C) were measured and recorded; onto the second stage of the operation, an artificial erection test was performed to observe the curvature of the penis, the dorsal and ventral length of the penis (D and E) were measured. The dorsal and ventral length of the penis before and after straightening were compared. Results: The dorsal length of penis (A) was 33-39(35.6±3.2) mm, the length of ventral length of penis before straightening (B) was 28-35 (29.8±2.8) mm and the length of ventral length of penis after straightening (C) was 32-38 (34.3±2.1) mm, which were measured during the first stage of operation, and the difference between B and C was statistically significant (P<0.05), while the difference between A and C was not statistically significant (P>0.05). The dorsal length of penis (D) was34-41 (36.4±2.5) mm and the ventral length of penis (E) was 33-40 (35.7±3.6) mm, which were measured during the second stage of operation, and there was no significant difference between D and E (P>0.05). The degree of penile curvature at the time of erection was less than 15° by measuring with the side photos in all patients during 0.5 to 2.5 years of follow-ups with an average of 1.7 years. Conclusions: Penile curvature due to the asymmetry of the cavernous bodies could be effectively corrected by simple incision of ventral tunica albuginea, which showed a good result of early follow-up. The effect of this surgery on ventral penile straightening could be verified by measuring and comparing the ventral and dorsal length of penis during surgery.

Lipophilic organic pollutants induce changes in phospholipid and membrane protein composition leading to Vero cell morphological change.

Membrane damage related to morphological change in Vero cells is a sensitive index of the composite biotoxicity of trace lipophilic chemicals. However, judging whether the morphological change in Vero cells happens and its ratio are difficult because it is not a quantitative characteristic. To find biomarkers of cell morphological change for quantitatively representing the ratio of morphological changed cell, the mechanism of cell membrane damage driven by typical lipophilic chemicals, such as trichlorophenol (TCP) and perfluorooctanesulphonate (PFOS), was explored. The ratio of morphologically changed cells generally increased with increased TCP or PFOS concentrations, and the level of four major components of phospholipids varied with concentrations of TCP or PFOS, but only the ratio of phosphatidylcholine (PC)/phosphatidylethanolamine (PE) decreased regularly as TCP or PFOS concentrations increased. Analysis of membrane proteins showed that the level of vimentin in normal cell membranes is high, while it decreases or vanishes after TCP exposure. These variations in phospholipid and membrane protein components may result in membrane leakage and variation in rigid structure, which leads to changes in cell morphology. Therefore, the ratio of PC/PE and amount of vimentin may be potential biomarkers for representing the ratio of morphological changed Vero cell introduced by trace lipophilic compounds, thus their composite bio-toxicity.

Mycoplasmas in the urine of HIV-1 infected men.

The aim of this study was determine the prevalence of Mycoplasma hominis, M. genitalium, M. fermentans, M. pirum, M. penetrans and Ureaplasma urealyticum in HIV-infected patients. Culture and PCR were used to detect six species of Mycoplasma in first-void urine of HIV-1 infected men. A total of 497 HIV/AIDS patients (age range 5-75 years, mean 37 years) were screened in the study. All presented positive for at least one kind of mycoplasma, especially U. urealyticum and M. hominis. Six mycoplasmas were significant in the homosexual contact and heterosexual contact groups. The distribution of M. hominis, M. penetrans, and M. pirum were significantly different in this four-transmission category. CD4+ cell count levels were lower in the AIDS-associated Mycoplasma-positive group than in the Mycoplasma-negative group (P<0.01). This study indicates that U. urealyticum, M. hominis and M. fermentans are prevalent in HIV-1-infected male patients. This may be an indication of whether mycoplasmas are co-factors in the progression of HIV disease.

Propidium iodide staining method for testing the cytotoxicity of 2,4,6-trichlorophenol and perfluorooctane sulfonate at low concentrations with Vero cells.

In this article, the feasibility of propidium iodide (PI) staining based on cell membrane damage as a sensitive and quantitative method to test the cytotoxicity of typical lipophilic compounds including 2,4,6-trichlorophenol (TCP) and perfluorooctane sulfonate (PFOS) was examined. The sensitivity of PI staining was compared to that of the methylthiazol-2-yl-2,5-diphenyl tetrazolium bromide (MTT) assay. We found a good correlation between PI uptake and increasing concentrations of TCP (10-50 µM) and PFOS (20-50 µM) at lower concentrations than those between growth inhibition ratio determined by the MTT assay and increasing concentrations of TCP (150-400 µM) and PFOS (100-500 µM). These findings indicated that the PI staining was more sensitive than the MTT assay. Furthermore, both the amount of PI uptake and the ratio of morphologically changed cells increased with increasing TCP concentrations, suggesting that PI staining may be a suitable quantitative substitute for the original method based on the observation of morphological changes in Vero cells. Our data also suggest that it is possible that the cell membrane damage that resulted in increased PI uptake may be due to variations in the phospholipid and protein content of the membrane, which are affected by interactions between the lipophilic compounds and components of the cell membrane.

PIV pictures of stream field predict haemolysis index of centrifugal pump with streamlined impeller.

Previously it has been found by pump haemolysis testing that the flow rate has a remarkable effect on index of haemolysis (IH), while pressure head does not affect IH. Recent investigation with particle image velocimetry (PIV) technology has demonstrated that IH is directly related to the flow pattern of stream field in impeller vane channels. PIV is a visible approach showing the real flow status in the pump. The different positions of a tracer particle in two PIV pictures taken at 20 micros intervals decide the velocity value and direction. The velocity vectors of many particles draw the flow pattern of the stream field. The same pictures are taken at 2, 4 and 6 l min(-1) flow rates while the pressure head is kept unchanged at 100 mmHg; then the pictures are taken at 4 l min(-1) flow with different pressure heads of 80, 100 and 120 mmHg. Results reveal that the flow rate of 4 l min(-1) (IH = 0.030) has the best stream field, and neither turbulence nor separation can be seen. In other flow rates (IH: 0.048 - 0.082), there is obviously second flow. Meanwhile, no significant difference can be seen among the PIV pictures of different pressure heads pumped, which agrees with the results of haemolysis testing showing that pressure has no effect on pump haemolysis. It may be concluded that the haemolysis property of a centrifugal pump can be assessed approximately by PIV pictures, which are much easier to take than haemolysis tests.

An improved design of axially driven permanent maglev centrifugal pump with streamlined impeller.

BACKGROUND: In 1839, Earnshaw proved theoretically that it is impossible to achieve a stable equilibrium with a pure permanent maglev. Furthermore, in 1939, Braunbeck deduced that it is only possible to stabilize a super conductive or an electric maglev. In 2000, however, the present authors discovered that stable levitation is achievable by a combination of permanent magnetic and nonmagnetic forces, and its stability can be maintained even with mere passive magnetic forces by use of the gyro-effect. DESIGN CONCEPTS: An improved design of permanent maglev impeller pump has been developed. Passive magnetic (PM) bearings support the rotor radially; on its right side, an impeller is fixed and on its left side a motor magnets-assemble is mounted. Unlike a previous prototype design, in which the rotor magnets were driven by a motor via magnetic coupling, a motor coil is installed opposite to the motor magnets disc, producing a rotating magnetic field. At standstill or if the rotating speed is lower than 4000 rpm, the rotor has one axial point contact with the motor coil. The contact point is located at the centre of the rotor. As the rotating speed increases gradually to higher than 4000 rpm, the rotor will be drawn off from the contact point by the hydrodynamic force of the fluid. Then the rotor becomes fully suspended. KEY POINTS OF STABILIZATION: For radial and peripheral stabilization, a gyro-effect is important, which is realized by designing the motor magnets disc to have large diameter, short length and high rotating speed; for axial stability, an axial rehabilitating force is necessary, which is produced by PM bearings. RESULTS: The rotor demonstrated a full levitation by rotation over 4000 rpm. As a left ventricular assist device, the rotation of the pump has a speed range from 5000 to 8000 rpm. The relation between pressure head and flow rate indicates that there is neither mechanical friction nor hydrodynamic turbulence inside the pump; the former is due to the frictionless maglev and the latter is a result of the streamlined design of the impeller.

World-smallest LVAD with 27 g weight, 21 mm OD and 5 l min-1 flow with 50 mmHg pressure increase.

To investigate the feasibility of a long-term left ventricular assist device (LVAD) placed in the aortic valve annulus, an implantable aortic valve pump (21 mm outer diameter, weighing 27 g) was developed. The device consists of a central rotor and a stator. The rotor assembly incorporates driven magnets and an impeller. The stator assembly has a motor coil with an iron core and outflow guide vanes. The device is to be implanted identically to an aortic valve replacement, occupying no additional anatomic space. The pump delivers the blood directly from left ventricle to the aortic root, like a natural ventricle, therefore causing less physiologic disturbance to the natural circulation. Neither connecting conduits nor 'bypass' circuits are necessary. The pump is designed to cycle between a peak flow and zero net flow to approximate systole and diastole. Bench testing indicates that the pump can produce a blood flow of 5 l min(-1) with 50 mmHg pressure increase at 17,500 rpm. At zero net flow rate, the pump can maintain a diastole aortic pressure against 80 mmHg at the same rotating speed.

Novel totally implantable trans-ventricular and cross-valvular cannular pump with rolling bearings and purge system for recovery therapy.

In the early 1990s, Yamazaki et al. developed a partly intra-ventricular pump, which was inserted into the left ventricle via the apex and then into the aorta through the aortic valve. The pump delivered blood flow directly from the left ventricle to the aorta, like a natural heart, and needed no inflow and outflow connecting tubes; it could be weaned off after the left ventricle had been recovered. The shortcomings were that the driving DC motor remained outside of the ventricle, causing an anatomic space problem, and the sealing and bearing were not appropriate for a durable device. Recently, a totally implantable trans-ventricular pump has been developed in the authors' laboratory. The device has a motor and a pump entirely contained within one cannula. The motor has a motor coil with iron core and a rotor with four-pole magnet; the pump has an impeller and an outflow guide vane. The motor part is 60 mm in length and 13 mm in diameter; the pump part is 55 mm in length and 11 mm in diameter. The total length of the device is therefore 115 mm. The total weight of the device is 53 g. The motor uses rolling bearing with eight needles on each side of the rotor magnets. A special purge system is devised for the infusion of saline mixed with heparin through bearing to the pump inlet (30 - 50 cc per hour). Thus neither mechanical wear nor thrombus formation along the bearing will occur. In haemodynamic testing, the pump can produce a flow of 4 l min-1 with 60 mmHg pressure increase, at a pump rotating speed of 12,500 rpm. At zero flow rate, corresponding to the diastolic period of the heart, the pump can maintain aortic blood pressure over 80 mmHg at the same rotating speed. This novel pump can be quickly inserted in an emergency and easily removed after recovery of natural heart. It will be useful for patients with acute left ventricular failure.

Computational fluid dynamics verified the advantages of streamlined impeller design in improving flow patterns and anti-haemolysis properties of centrifugal pump.

Computational fluid dynamics (CFD) technology was applied to predict the flow patterns in the authors' streamlined blood pump and an American bio-pump with straight vanes and shroud, respectively. Meanwhile, haemolysis comparative tests of the two pumps were performed to verify the theoretical analysis. The results revealed that the flow patterns in the streamlined impeller are coincident with its logarithmic vanes and parabolic shroud, and there is neither separate flow nor impact in the authors' pump. In the bio-pump, the main flow has the form of logarithmic spiral in vertical section and parabola in cross section, thus there are both stagnation and swirl between the main flow and the straight vanes and shroud. Haemolysis comparative tests demonstrated that the authors' pump has an index of haemolysis of 0.030, less than that of the bio-pump (0.065).

Study on stable equilibrium of levitated impeller in rotary pump with passive magnetic bearings.

It is widely acknowledged that the permanent maglev cannot achieve stable equilibrium; the authors have developed, however, a stable permanent maglev centrifugal blood pump. Permanent maglev needs no position detection and feedback control of the rotor, nevertheless the eccentric distance (ED) and vibration amplitude (VA) of the levitator have been measured to demonstrate the levitation and to investigate the factors affecting levitation. Permanent maglev centrifugal impeller pump has a rotor and a stator. The rotor is driven by stator coil and levitated by two passive magnetic bearings. The rotor position is measured by four Hall sensors, which are distributed evenly and peripherally on the end of the stator against the magnetic ring of the bearing on the rotor. The voltage differences of the sensors due to different distances between the sensors and the magnetic ring are converted into ED. The results verify that the rotor can be disaffiliated from the stator if the rotating speed and the flow rate of the pump are large enough, that is, the maximal ED will reduce to about half of the gap between the rotor and the stator. In addition, the gap between rotor and stator and the viscosity of the fluid to be pumped also affect levitation. The former has an optimal value of approximately 2% of the radius of the rotor. For the latter, levitation stability is better with higher viscosity, meaning smaller ED and VA. The pressure to be pumped has no effect on levitation.

New concepts and new design of permanent maglev rotary artificial heart blood pumps.

According to tradition, permanent maglev cannot achieve stable equilibrium. The authors have developed, to the contrary, two stable permanent maglev impeller blood pumps. The first pump is an axially driven uni-ventricular assist pump, in which the rotor with impeller is radially supported by two passive magnetic bearings, but has one point contact with the stator axially at standstill. As the pump raises its rotating speed, the increasing hydrodynamic force of fluid acting on the impeller will make the rotor taking off from contacting point and disaffiliate from the stator. Then the rotor becomes fully suspended. The second pump is a radially driven bi-ventricular assist pump, i.e., an impeller total artificial heart. Its rotor with two impellers on both ends is supported by two passive magnetic bearings, which counteract the attractive force between rotor magnets and stator coil iron core. The rotor is affiliated to the stator radially at standstill and becomes levitated during rotation. Therefore, the rotor keeps concentric with stator during rotation but eccentric at standstill, as is confirmed by rotor position detection with Honeywell sensors. It concludes that the permanent maglev needs action of a non-magnetic force to achieve stability but a rotating magnetic levitator with high speed and large inertia can maintain its stability merely with passive magnetic bearings.

World-first implantable aortic valvo-pump (IAVP) with sufficient haemodynamic capacity.

For better anatomic and physiologic fitting, a novel implantable aortic valvo-pump (IAVP) has been developed. A valvo-pump is a micro axial flow impeller pump, which has the same dimensions and function, as well as the same location, of a valve. Therefore, IAVP needs no inlet and outlet tubes, no additional anatomic occupation, and has less physiologic disturbance to natural circulation compared with the traditional bypass left ventricular assist device (LVAD). The device has a stator and a rotor. The stator consists of a motor coil with an iron core and an outflow guide vane; the rotor includes driven magnets and impeller. There is neither bearing nor strut in both the pump and the motor. In order to reduce the attractive force between the rotor and the stator, so as to enhance the durability of the performance, the rotor magnets were minimized without reducing the driving torque and efficiency of the motor. The impeller vane was designed according to a three-dimensional and analytical method, for preventing stasis and turbulence. The largest outer diameter is 24.7 mm and the length at this point is 12.4 mm. The total weight is 40 g (including the rotor of 11 g). The consumed power is 7 W (14 V x 0.5 A) at 15 000 rpm. This rotating speed stays unchanged during haemodynamic testing together with a pulsatile centrifugal pump, which imitates a failing ventricle. The maximal flow cross IAVP reaches over 10 l min(-1) and the pressure head at 0 l min(-1) can be as large as 80 mmHg. At flow rate of 4 - 8 l min(-1), IAVP enlarges the flow c. 1 l min(-1) and meanwhile increases the pressure about 10 mmHg. The pressure pulsatility generated by the pulsatile centrifugal pump remains 40 mmHg after passing IAVP. By first animal experimental trial the device was sewed in aortic position of an 80 kg pig without harm to adjacent tissue and organs. IAVP promises to be a viable alternative to natural donor heart for heart transplantation in the future.

A novel permanent maglev rotary LVAD with passive magnetic bearings.

It has been widely acknowledged that permanent maglev cannot achieve stability; however, the authors have discovered that stable permanent maglev is possible under the effect of a combination of passive magnetic and nonmagnetic forces. In addition, a rotary left ventricular assist device (LVAD) with passive magnetic bearings has been developed. It is a radially driven impeller pump, having a rotor and a stator. The rotor consists of driven magnets and impeller; the motor coil and pump housing form the stator. Two passive magnetic bearings counteract the attractive force between motor coil iron core and rotor magnets; the rotor thereafter can be disaffiliated from the stator and become levitated under the action of passive magnetic and haemodynamic forces. Because of the pressure difference between the outlet and the inlet of the pump, there is a small flow passing through the gap of rotor and stator, and then entering the lower pressure area along the central hole of the rotor. This small flow comes to a full washout of all blood contacting surfaces in the motor. Moreover, a decreased Bernoulli force in the larger gap with faster flow produces a centring force that leads to stable levitation of the rotor. Resultantly, neither mechanical wear nor thrombosis will occur in the pump. The rotor position detection reveals that the precondition of levitation is a high rotating speed (over 3250 rpm) and a high flow rate (over 1 l min(-1)). Haemodynamic tests with porcine blood indicate that the device as a LVAD requires a rotating speed between 3500 and 4000 rpm for producing a blood flow of 4 - 6 l min(-1) against 100 mmHg mean pressure head. The egg-sized device has a weight of 200 g and an O.D. of 40 mm at its largest point.

A novel permanent maglev impeller TAH: most requirements on blood pumps have been satisfied.

Based on the development of an impeller total artificial heart (TAH) (1987) and a permanent maglev (magnetic levitation) impeller pump (2002), as well as a patented magnetic bearing and magnetic spring (1996), a novel permanent maglev impeller TAH has been developed. The device consists of a rotor and a stator. The rotor is driven radially. Two impellers with different dimensions are fixed at both the ends of the rotor. The levitation of the rotor is achieved by using two permanent magnetic bearings, which have double function: radial bearing and axial spring. As the rotor rotates at a periodic changing speed, two pumps deliver the pulsatile flow synchronously. The volume balance between the two pumps is realized due to self-modulation property of the impeller pumps, without need for detection and control. Because the hemo-dynamic force acting on the left impeller is larger than that on the right impeller, and this force during systole is larger than that during diastole, the rotor reciprocates axially once a cycle. This is beneficial to prevent the thrombosis in the pump. Furthermore, a small flow via the gap between stator and rotor from left pump into right pump comes to a full washout in the motor and the pumps. Therefore, it seems neither mechanical wear nor thrombosis could occur. The previously developed prototype impeller TAH had demonstrated that it could operate in animal experiments indefinitely, if the bearing would not fail to work. Expectantly, this novel permanent magnetic levitation impeller TAH with simplicity, implantability, pulsatility, compatibility and durability has satisfied the most requirements on blood pumps and will have more extensive applications in experiments and clinics.

Experimental method to reveal the effect of rotor magnet size and air gap on artificial heart driving motor torque and efficiency.

To investigate experimentally the effect of rotor magnet design on artificial heart driving motor performance, seven rotors with different magnet lengths or thicknesses, as well as different peripheral angles, were manufactured and tested in the same motor stator with different rotating speeds. The input power (voltage and current) and output torque were measured and the motor efficiency was computed. The results demonstrated that the reduction of rotor magnet size and the enlargement of the air gap between the rotor magnets and the stator coil core have no significant effect on motor efficiency, but will reduce the torque value on which the motor achieves the highest efficiency; it could be remedied however by increasing the rotating speed, because the torque at the high efficiency point will increase along with the rotating speed. These results may provide a basis for developing small rotor magnets, large air gap and high efficiency motors for driving an artificial heart pump.

A novel impeller TAH using magnetic bearings for load reduction.

A novel impeller TAH (total artificial heart), i.e. bi-ventricular assist impeller pumps, has been developed. The device consists of a rotor with motor magnets and two impellers, a stator with motor coil and iron core, and two pump housings. In both sides of the rotor magnets, as well as the stator coil core, a pair of magnetic bearings was devised to partly counteract the attractive forces between the rotor magnets and the stator coil core. This means the magnetic bearings are used for load reduction. On hydrodynamic testing, the two pumps both produced a flow rate as high as 6 l min(-1) and the left pump had a pressure head of 150 mm Hg, and that of the right pump was 50 mm Hg. The highest efficiency of the device, including the motor, the two pumps and the controller, reached 14.7%. The device, weighing 250 g, had a length of 80 mm and a diameter of 40 mm at its largest point. Currently in the world, this is a unique TAH, which is electrically powered and driven by a single motor and has only one moving part, can produce either pulsatile or non-pulsatile flow, both pumps eject flow synchronistically by pulsatile mode, and the volume equilibrium of the two pumps can be achieved automatically without the need for control.

Axial reciprocation of rotating impeller: a novel approach to preventing thrombosis in centrifugal pump.

For long-term application, rotary pumps have to solve the problems of bearing wear and thrombosis along the bearing. Some investigators choose the magnetic bearing for zero friction and to provide no contact between the rotor and stator; the former avoids the mechanical wear and the latter eliminates the possibility of thrombus formation. The authors have tried and have found, however, that it is difficult to apply a magnetic bearing to the rotary pump without disturbing its simplicity, reliability, and implantability, and have therefore developed a much simpler approach to achieve the same results. Instead of using a sliding bearing, a rolling bearing has been devised, and its friction is about 1/15 that of the sliding bearing. Furthermore, a wearproof material of ultra high molecular weight polythene has been adopted to make the rollers, and its antiwear property is eight times better than metal. The service life of the bearing has thus been prolonged. To prevent thrombus formation along the bearing, the impeller reciprocates axially as the impeller changes its rotating speed periodically to produce a pulsatile flow. The reciprocation is the result of the effects of a magnetic force between the motor rotor and stator and a hydraulic force between the blood flow and the impeller. Similar to a piston pump, the oscillating impeller can make the blood flow in and out of the bearing, resulting in washout with fresh blood once a cycle. This obviously helps to prevent thrombosis along the bearing and in the pump. Endurance tests with saline of this novel pump demonstrated device durability, promising long-term assisted circulation.

Streamlined design of impeller and its effect on pump haemolysis.

To investigate the effect of impeller design on pump haemolysis, five impellers with different numbers of vanes or different vane angles were manufactured and tested in one pump for haemolysis comparison. The impellers had the same dimension and logarithmic spiral vane form that coincided with the stream surfaces in the pump, according to an analytical and three-dimensional design method developed by the authors. Consequently, an impeller with six vanes and a 30 degrees vane angle had the lowest haemolysis index. The result agrees with the theoretical analyses of other investigators searching for the optimal vane number and vane angle to achieve the highest efficiency of the pump.

Recent progress in developing durable and permanent impeller pump.

Since 1980s, the author's impeller pump has successively achieved the device implantability, blood compatibility and flow pulsatility. In order to realize a performance durability, the author has concentrated in past years on solving the bearing problems of the impeller pump. Recent progress has been obtained in developing durable and permanent impeller blood pumps. At first, a durable impeller pump with rolling bearing and purge system has been developed, in which the wear-less rollers made of super-high-molecular weight polythene make the pump to work for years without mechanical wear; and the purge system enables the bearing to work in saline and heparin, and no thrombus therefore could be formed. Secondly, a durable centrifugal pump with rolling bearing and axially reciprocating impeller has been developed, the axial reciprocation of rotating impeller makes the fresh blood in and out of the bearing and to wash the rollers once a circle; in such way, no thrombus could be formed and no fluid infusion is necessary, which may bring inconvenience and discomfort to the receptors. Finally, a permanent maglev impeller pump has been developed, its rotor is suspended and floating in the blood under the action of permanent magnetic force and nonmagnetic forces, without need for position measurement and feed-back control. In conclusion, an implantable, pulsatile, and blood compatible impeller pump with durability may have more extensive applications than ever before and could replace the donor heart for transplantation in the future.