A single pass ventricular lead with a dual chamber electrode system (atrial bipolar sensing electrode displaced along the lead axis 11cm and 12cm from distal tip in the CCS group; 11cm and 14cm in the Medico group) was implanted in 47 patients (40 cases in the CCS group and 7 cases in the Medico group) for symptomatic high degree AV block and normal sinus node function from December 1989 to July 1994. There was no significant difference between the two groups with regard to age, height and weight. Lead insertion and pacemaker implantation was the same as with the VVI system. At implant P wave amplitude was 1.86±1.02mV in the CCS group whereas it was 0.70±0.66mV in the Medico group. However, there was a significant difference in the two groups (P<0.05). In the CCS group post-operative complications included a pneumothorax and a pocket hematoma. Four late deaths occurred. One patient's pacemaker failed to function in the VDD mode. Lead fracture was noticed in one patient. Two patients had frequent atrial arrhymias several months post-operatively. The remaining 32 patients had no significant trouble while in the VDD mode. In the Medico group two patients experienced at atrial sensing failure. Activity levels improved significantly and their preoperative CTR decreased significantly in both groups. Over-curving leads were observed carefully in both groups. Under the conventional VVI technique, the single-lead VDD system can achieve physiological pacing; therefore, this system must be recognized as the advantageous therapeutic choice for selected patients.

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Seven VT/VF patients were safely implanted the 3rd generation implantable cardioverter defibrillator (I CD: Ventak PRxII) with the single lead (SL) system. 2 patients were used subcutaneous leads (array lead: AL) together. The mean defibrillation threshold was 15.0+/-3.5 J in the group using only SL and was not significantly different from that of the group using AL together (22.5+/-3.5J). However, the mean impedance at each defibrillation testing in the AL group was apparently lower (30.1+/-6.9ohms) than that of the SL group (46.9+/-4.0ohms)(p<0.05). We concluded that the AL using with the SL was useful to prevent a loss of defibrillation energy.

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The second generation impl antabl e cardioverter defibrillator (ICD: Ventak P Model 1600) was implanted to 6 patients (pts) with life-threatening ventricular tachycardia(VT)/ventricular fibrillation(VF). However, one patient with severe left ventricular dysfunction died due to LOS 8 months postoperatively, 5 pts were alive. Five pts had inappropriate shocks during sinus tachyarrhythmia, paroxismal supraventricular tachycardia or after termination of VT/VF. Four out of 6 pts needed generator exchange at mean 3.2 years after operation. This clinical experience indicated that Ventak P 1600 implantation for the life-threatening VT/VF is effective and safe in preventing sudden cardiac death.

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Diastolic mitral regurgitation(MR) during ventricular pacing was studied in 15 patients (70.7±11.8‹SD› years old) with complete AV block. Cardiac index (CI) and pulmonary capillary wedge pressure (PCP) were measured by Swan-Ganz catheter. Trans-mitral flow was recorded by pulsed Doppler echocardiography. When the ventricular pacing was switched to AV sequential pacing, CI increased (2.1±0.4 to 2.7±0.4 1/min/m² p<0.01), and PCMP decreased (9.5±3.8 to 6.4±3.1mmHg, p<0.01). Left ventricular ejection fraction was 29-79%. Diastolic MR was observed in as the patients during ventricular pacing, and was prevented by AV sequential pacing. In conclusion, diastolic MR is a common fining in patients with AV block even if the heart rate is normalized by ventricular pacing.

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Consecutive 8 patients involving true or dissecting aneurysms of the thoracic descending aorta or thoracoabdominal aorta were operated upon under the partial cardiopulmonary bypass using the antithrombotic coated device. The system is consisted of Maxima membrane oxygenator, Bio-Medicus centrifugal pump, and Medtronic percutaneous thin wall cannulae. These were all coated with Carmeda Bioactive Surace. Polyvinyl tube was coated with Biomate. The administration of systemic heparin was determined by ACT of around 200 seconds. All patients were tolerated operations well and alive. No thromboembolic accident, bleeding tendency, nor organ failure including renal failure were observed postoperatively in all patients. The analysis of blood platelets, coagulation, and fibrinolysis system revealed minimal fluctuation of the values. In conclusion, this system of anti thrombotic circuit is safe and preferable for thoracic descending or thoraco-abdominal aneurysm operations.

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Haematological effects of an antithrombin agent, argatroban was evaluated in left heart bypass (LHB) with a centrifugal pump (CFP) . From 1991 to 1994, 12 patients with thoracic or thoracoabdominal aortic disease underwent surgical treatment with a use of LHB. Patients were divided into two groups. In group A (n=6), low dose of heparin (1mg/kg, IV bolus) was administered just prior to LHB in the beginning. In Group B (n=6), argatoroban (2.5μg/kg/min) intravenously infused during LHB. Platelet count was significantly preserved after LHB in group B. β-TG and PF4 increased during LHB in the both groups, however these increases were significantly suppressed in group B. There were no significant difference in parameters of thrombogenesis between the two groups. there were no evidence of systemic thromboembolism in all patients after surgery. Platelet was effectively preserved during LHB with CFP by the use of intravenous argatroban.

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We used occlusion balloon catheter and retrograde perfusion for repair of aortic arch aneurysm. Retrograde perfusion through the femoral artery, however, is difficult, if the patient has severe atheroscrelosis obriterance of femoral artery or abdominal aortic aneurysm with mural thrombus. For convenient and safe procedure to perfuse through descending aorta during repair of aortic arch, we devised a aortic occlusion balloon catheter with perfusion lumen, which was supported with stainless steel wire that realized insertion into the descending aorta antegradely through the incision in the aortic arch aneurysm and fixation at favorite position. This catheter has 20Fr. size in diameterinchiding 14Fr.perfusion lumen. In mock circulation test, it showed 128mmHg pressure loss at 21/min of flow. This catheter was able to perfuse to the lower body antegradely, in patient with poor renal function, combined with selective cerebral perfusion. We used this catheter for repair of aortic arch aneurysm of 69y.o. man . During 58min. antegrade perfusion with this catheter, the blood pressure of lower extremity was from 32mmHg to 43mmHg, urine output was maintained over 40ml/hr and rectal temperature was lowered by 5.6°C. We concluded that this catheter is easy and safe to handle, and very convenient to perfuse patient who has difficulties in retrograde perfusion through the femoral artery.

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To clarify the hemodynamics in a bidirectional arterial perfusion, experimental circuit was provided with two arterial cannulation sites and one drainage cannula with pump-oxygenator. The glass window method and electro-magnetic flow meter were used to define the colliding portion of the bidirectional blood flow in just distal aorta to left subclavian artery under the total cardiopulmonary bypass. Under the normothermia, the blood flow of the femoral artery and axillary artery were in the ratio of 63% to 37%, and changed 41% to 59% at the 25°C. On the contrary, the ratio returned to the normothermic level, during the early rewarming phase. The systemic vascular resistance of the upper and lower part of the body, changed significantly during cooling and rewarming phase.

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We have undertaken the experimental protocol of 120 minutes of RCP followed by antegrade reperfusion. Eighteen mongrel dogs were used. Animals were divided into three groups as follow: in group I, no treatment was received; in group II, mannitol (2g/kg) was administered; and in group III, nicaraven 1, 2-bis(nicotmamido)-propanwas administered (1mg/kg/min). Our experimental results suggested that brain edema developed during the reperfusion period after RCP, and mannitol or nicaraven might prevent it. During the period from January 1991 to July 1994, 21 patients underwent operations of the thoracic aorta with the use of deep hypothermic retrograde cerebral perfusion(RCP). Four patients died before the adequate assessment of their neurolgic function. One patient had a cerebral infarction probably due to the dissection of the left common carotid artery. The remaining 16 cases showed clear consciousness and had no serious neurologic complications postoperatively. Blood gas analysis of the returned blood sampled from branches of the aortic arch and the ophthalmosco is findings demonstrated the insufficiency of blood supply to the brain during RCP. The supply of oxygen by RCP was not enough to maintain sufficient cerebral metabolism. Therefore, pharmacological brain protection should be recommended to prevent neurological complications during and after RCP.

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Five patients underwent coronary artery bypass grafting with normothermic cardiopulmpnary bypass (CPB) with CAPIOXSX. In those cases, blood temperature were kept warmer than 35t and perfusion rates greater than 2.61/min/m².The patients required high doses of α-agonist to maintain CPB pressures greater than 80mmHgJn postoperative course, no complications occurred.During CPB, SaO₂ were kept 99.9%, and SvO₂ more than 80%. At 1 hour after CPB started, oxygen consumption was 203±55ml/min, which was greater than that of the hypothermic CPB with UNNOX (90±22ml/min), There was no difference of β-TG change 1 hour after CPB between the normothermic CPB with CAPIOX-SX and the hypothermic CPB with UNIVOXHowever, PF-4 change was less and platelet count was greater 1 hour after CPB in the normothermic CPB with CAPIOXSX as compared to the hypothemlic CPB with UNIVOX. It suggested that CAPIOX-SX had sufficient oxygenetive capacity even in normothermic CPB, and normothermic CPB appeared to have a beneficial effect on blood coagulation system.

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To evaluate the influence of cardioplegia on systemic circulation during cardiopulmonary bypass(CPB), consecutive 179 cases were reviewed. Patients were divided in three groups: Group-I (n=79) were applied intermittent antegrade crystalloid cardioplegia, in Group-II (n=48) ante-and retrograde blood cardioplegia was applied intermittently and in Group-III (n=52) continuously. In Group-III, high potassium level crystalloid fluid was infused significantly much more than in other two groups and resulted over-hemodilution and hyperkalemia, and then more fluid removal by ECUM and more administration of NaHCO₃ were necessiated. Intermittent blood cardioplegia seemed to be more simple and preferable rather than continuous blood cardioplegia to maintain adequate systemic circulation during CPB.

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Heparin bonding of an extracorporeal circuit for cardiopulmonary bypass (CPB) improves the biocompatibility and reduces the activation of complements. We evaluated biocompatibility of heparin-bonded Carmeda MAXIMA membrane oxygenator and circuit in clinical cases undergoing CABG or valve replacement. In group NC (n=10), whole CPB circuit was non-heparin bonded. In group PC (n=10), only oxygenator of CPB circuit was heparin-bonded. In group FC (n-B), whole CPB circuit including oxygenator was heparin boded. The reduction of fibrinogen in group PC and FC was less than group NC. C3a and hemolysis were less in group PC and FC than group NC. However there was not significant differences between group PC and FC. We conclude that heparin-bonded Carmeda oxygenator improves biocompatibility as well as fully bonded CPB circuit in clinical use.

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We studied the bio-compatibility of heparin-coated cardiopulmonary bypass circuits compared with non-coated circuits. We performed a study on 33 patients undergoingcoronary artery bypass surgery who were randomly perfused with an u.ncoated (control) or a heparin-coated circuit (Duraflo-II). The concentrations of C3a, C5a, ATIII, fibrinogen, FDP, free Hb, and total blood cell countswere measured. The use of heparin-coated circuits resulted in a reduction of C3a generation, and a reduction of fibrinogen consumption. These obsarbations suggest that heparin-coated cardiopulmonary bypass circuit indicates a substantial improvement of bio-compatibility.

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We compared heparion-coated cardiopulmonary bypass circuit with non-coated circuit in terms of biocompatibility in 36 patients undergoing coronary bypass surgery. Two types of heparin-coated circuit were prepared; one was Carmeda MAXIMA with covalent heparin bonding (n=12) and the other was Duraflo II with ionic heparin bonding (n=12). Non-coated circuit was UNIVOX IC (n=12). We examined TAT, PIC, D-dimer, C3a, C4a, platelet count and ACT during bypass, and Respiratory Index after surgery. Concentration of C3a during the bypass was higher in the non-coated group than in the coated groups. Reduction of platelet count during bypass was significantly greater in the non-coated group than in the coated groups. There were no significant differences in the remaining parameters among the three groups. We concluded that heparin-coated cardiopulmonary bypass circuit improved biocompatibility by reducing complement activation and platelet consumption.

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Biosurfaced cardiopulmonary bypass (CPB) circuits (B) may reduce blood-foreign body surface reactions and decrease activation of coagulation systems compared with non-bosurfaced circuits (A). We performed an in vitro study using fresh human blood and a clinical study. CPB was performed using a roller pump for four hours in eight sets of each group. Bradykinin showed lower levels in group B (260±60: 520±120pg/ml). Thrombin-antithrombin III complex, fibrinopeptideA, beta-thromboglobulin, complement factors (C3a, C4a) and granulocyte elastase were lower in groupB. Platelet count were higher in group B (5.3±1.3:3.7±0.8×10⁴). Scanning electron micrography showed less blood cellular adhesion to CPB circuit in group B. In clinical study only C3a and C4a showed significantly lower levels in group B. Biosurfaced circuit reduces blood-foreign body surface reactions and diminishes platelet adhesion to the surface of CPB circuit.

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A good oxygenator is extremely importantt component in the cardiopulmonary circuit. Therefore, a comparison study of three different oxygenators on 33 adult open heart surgery patients was completed. Twelve of the patients had the newly developed AL-6000 (MENOX) a non-microporous polyolefin hollow fiber, mine patients hadi newly developed LH-760 a silicone hollow fiber and twelve patients had Sarns-16310 a microporous polyopropylyne hollow fiber. All three oxygenators showed no statistical defferences in the total protein levels after CPB. AL-6000 and LH-760 had a lower free-Hb/CPBT and higher platelet preservation than that the Sarns-16310 group. All of the oxygenators had good oxygenation and carbon dioxide elimination, however, the AL-6000 had the best oxygen reserve capacity. These results suggests that the AL-6000 and LH-760 had the highest performance of gas exchange with the least trauma to the blood cells. And these oxygenators are expected to be utilised for long term usage.

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We studied clinical availability ofCAPIOX SX in comparison with UNIVOX and MENOX AL6000 in relation to gas exchange performance. One hundred and nine patients who underwent various cardiac operations with CPB were derived into 3 groups, CAPIOX SX group (group C; 58 patients), UNIVOX group (group U; 29 patients) and MENOX group (group M; 22 patients). There were no significant diffemces among the 3 groups in regard to age, sex, weight, BSA, CPB time, aortic clamping time and minimum rectal temperature. Carbon dioxide elimination capacity of group C was almost equal to that of group U and better than that of group M. Effective lung blood flow ratio (QP/QT) showed an enough oxygene uptake capacity in all groups. An initial priming volume was significatly lower in group C than that of the other two groups. We concluded that CAPIOX SX is one of the usefull oxygenator for clinical application from the standpoint of the gas exchange performance.

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“AVECOR AFFINITY” is new extracapillary blood flow type hollow fiber oxygenator. We clinically evaluated “AVECOR AFFINITY” in comparison with “MENOXAL-6000”. Fifteen patient who underwent elective coronary artery bypass grafting were dividedinto two groups, “AVECOR AFFINITY” group (groupA: 8patients) and “MENOXAL-6000” group(groupM:7patients). In this study, age, sex, weight, body surface area (BSA), cardiopulmonary bypass (CPB) time and aortic clamping time were analyzed and these were not significantly differrent between the two groups. Blood samples were collected 5minutes before and after the initiation of CPB, then every 30 minutes during CPB. V/Q and FiO₂ 30minutes after sting rewarming were not significantly different between two groups. PaO₂ in groupA 30minutes after starting rewarming was significantly higher than that in groupM. Corrected platelet count(mathmatically corrected for hemodilution) and free serum hemoglobin were not significantly different between two groups. “AVECOR AFFINITY” has good oxygenation capacity.

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We have used the newly developed hollow fiber type membrane oxygenator “CAPIOX-SX” in 12 cases. Gas exchange performance, changes of base excess and the mean additional volume of HaHCO₃ were evaluated, respectively. Furthermore, postoperative surface conditions of hollow fibers were investigated by electron microscpoe. Capiox-SX has an excellent gas exchange performance and operability. Changes of the mean value of base excess was negative value all the time and mean added volume of NaHCO₃ was 126±67.5ml. There was no echinocyte and the surface of hollow fiber was clear and smooth, which probably explained why flow was smooth and gas exchange performance was excellent, even though there were small accumulations of red blood cells in the lower part of the fibers.

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We have evaluated anticoagulant activity of heparin immobilized onto hollow fiber oxygenators using a new heparin bonding method. The in vitro and ex vivo recirculation experiments have be done using bovine blood demonstrated that the heparin bioactivity as measured by the FXa assay maintained the initial bioactivity over the experimental period of up to 24 hrs. Both intra and extracapillary type oxygenators were then evaluated in an ex vivo chronic sheep model for extended periods under minimal systemic heparinization. The results showed excellent blood compatibility with minimal intra-device thrombus formation and minimal changes of coagulation parameters while maintaining the gas transfer capability throughout the experiment. Based on these results, the new heparin bonding method appears to be a reliable and effective method in the application to prolonged extracorporeal circulation system under minimal systemic heparinization.

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The liver ischemia is appeared at the begining of the CPB.And the lactate is metabolized at the liver.So we considered that the lactate administration at the CPB was unbeneficial to the liver. In order to assess the lactate effects of the liver, we compared the acetate Ringer's solution with the lactate Ringer's solution as the priming fluid of the CPB circuit. We used the arterial ketone body ratio (AKBR) for the redox state of the liver. The lactate's concentration increased in time dependent manner. But acetate was metabolized easily at the CPB.The arterial ketone boy ratio (AKBR)in acetate positive group was higher than that in lactate positive group.The base excess at CPB in the acetat positive group was higer than in the lactate positive group. So amount of the base was less in the acetate posiyive group than in the lactate positive group. .There was no difference in the systemic blood pressure and systemic vascular resistance between two groups.We conclude that the lactate loads more work on the liver at the CPB. So the acetate Ringer's solution is better priming fluid than the lactate Ringer's solution at the CPB.

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Plasma free hemoglobin were measured by means of ELISA method in 15 adult patients autologous stored blood(ASB) during cardiopulmonary bypass(CPB). Plasma hemoglobin value of ASB was 12.2±9.3mg/dl and plasama haptoglobin was 30.5±32.7mg/dl. After completion of CPB, we returned all ASB and perfustates of CPB. Plasma hemoglobin value was 61.3±31.3mg/dl, plasa ma haptoglobin was 17.6±19.6mg/dl, and plasma free hemoglobin was 38.1±13.3mg/dl. From these results, we concluded our ASB had no problem for hemolysis during CPB.

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A new hemoconcentrator (LH-840 P: JMS) was employed to control plasma volume during open heart surgery with cardiopulmonary bypass. LH-840P is made of polyethersulfone membrane. We clinically evaluated LH-840P in comparison with HC-100M: MERA. Twenty patients who undergoing elective valvular surgery were divided into two groups: LH-840P group (group L: 10 patients) and HC-100M(group H: 10 patients). Age, body weight, cardiopulmonary bypass time were not significantly different between the two groups. The ul trafiltration ratio of HC-100M was significantly higher than that of LH-840P. The sieving coefficient of LH-840P to albumin, direct-bilirubin, free-hemoglobin were significantiy lower than those of HC-100M. However, serum free-hemoglobin just after CPB showed no significant difference between the two groups. We speculated that this was caused by the adsorption of bilirubin to the hollow fiber of LH-840P which has been demonstrated in in vitro analysis. The new hemoconcentrator (LH-840P) was effective and safe in non-hemic primed extracorporeal circulation.

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Continuous veno-venous henofiltration(CVVH) and intermittent hemodialysis(HD) was instituted in 13 chronic dialysis patients duringperioperative period. Generally, HD was done within 48 hours prior to the operation, during extracorporeal circulation and the first postoperative day, and gradually recovered to the former HD program Henndynamic state was almost stable in every patient because low grade ultrafiltration was made by CVVH just after operation and there was no need for water reduction by HD. The operative time and blood loss are greater than those of non-dialysis patients, but there was no statistic difference in extracorporeal circulation time, aortic crossclarrp tine, annunt of transfused blood All patient were alive, but five had pericardial and/or pleural effusion and two had gastrointestinal henorrhage. The corrbination of CVVH and HD appears to be a safe and useful procedure for dialysis patient in the postoperative henndynamically unstable period.

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Between March in 1987 and July in 1994, estracorporeal ultrafiltration method (ECUM) and or hemodialysis (HD) during cardiopulmonary bypass (CPB) was applied dueto preoperative renal failure in 18 patients (valvular disease in 8 and ishcemie heart desease in 5, vascular disease in 3, valvular disease associatedd with ishcemic heart disease in 2). They were divided into the following three groups according to thier preoperative renal function: Group I (6 patients), the level of creatinine (Cr)≤3.0mg/dl; Group II (5 patients), 3.1≤Cr≤5.0mg/dl, Group III (7 patients, including preoperative HD in 6), Cr≥5.1mg/dl. The operation was performed with CPB under moderate hypothermia and HD and/or ECUM was installed parallel to the CPB. The results as follows: 1) The more preoperative renal function impaired, the more postoperative renal damage prolonged. 2) The postoperative dialysis for renal dy sfunction was not requiredin the patients with a preoperative Cr level less than 5.0mg/dl. It seemed to be quite effective for cardiovascular operation of patients with severe renal dysfunction to use ECUM and HD during CPB because perioherative elevation of the ler ets of serum BUN, Cr, and potassium was less than that in patients with ECUM alone.

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In consecutive 207 patients, we applied “Low-vacuum suction method”, in which sucking and venting the blood during cardiopulmonary bypass are performed using the hard shell venous reservoir with a low negative pressure. A little unstability of negative pressure in the reservoir, which was sometimes found during running of cardiopulmonary bypass, scarcely affects holding blood level in it. The blood level in the reservoir immediately responded to the blood volume with the short suction circuit, which makes it easy to handle cardiopulmonary bypass. In the case of using several suction circuits concurrently, suction tubes should be turned on and off in the operating field. A roller pump suction method was employed in the control group. Serum hemoglobin, haptoglobin, platelet count, platelet aggregation were measured in each group. Increase of serum hemoglobin and haptoglobin in the group with “Low-vacuum suction method” were significantly smaller than those in the control group. Platelet count and platelet aggregation did not show significant difference. It was concluded that “Lowvacuum suction method” can reduce hemolysis during CPB.

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In open heart surgery for infants, we studied clinical applicability of the newly developed membrane oxygenator M-16 in comparison with the MINIMAX and the MENOX AL-2000. The M-16 has a special structure of rigid metal plates covered with silicone membranes and showed an excellent O₂ and CO₂ transfer performance compared with the other oxygenators. There were no statistical differences in hemocompatibility among the three types of oxygenator in terms of plasma free hemoglobin and platelet preservation ratio. But it was very difficult and complex to evacuate the air :frgm the :M-16 during the priming period, and the static priming volume (200ml) of this model is iativeyly miidh for infants.

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We have developed artificial placenta which contains a mem bran oxygenator and a roller pump. Fetal blood collected from the umbirical arteries is oxygenated by the membrane oxygenator (Menox 2000), and returned to the umbirical vein. Seven goat fetues obtained by Cesarian incision. Using this system, 4 goat fetues were incubated for 43 hours(3-70hours). Three of them were dead from cardiac failure caused by ductus arteriosus constriction. The other case was lost from a tube trouble. Prostagrandin E1(PGE1) were given from the right ventricle in another three cases for the purpose of dilatation of ductus arteriosus. In two cases PGE 1 was infused in dose of 0.1μg/kg/min for 30 minutes. After infusion of PGE 1, constricted ductus arteriosus(DA) were dilatated. PGE1 was given by continuous infusion from beginning of ECMO perfusion in another of them. In this case, echocardiography showed that DA was opened continuously for 90 hours during ECMO. This finding suggsted that PGE 1 prevented the constriction of DA and permitted long support of fetal circulation by artificial placenta.

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To improve the ease of driving a centrifugal pump which is afterload dependent, we have developed an automatic flow control system for the Terumo Capiox centrifugal pump system. This system consists of an autoflow “cruise” control system with a safety cutoff. In the usual manual mode, the motor speed knob works as a pump speed control, and in the autof low mode, the same knob works as a blood flow rate control. In the autof low mode, the computer compares the desired flow rate with the actual flow measured by an ultrasonic Doppler flowmeter, and adjusts the motor rotational speed accordingly. During both in-vivo and in vitro testing, this autof low mode was able to return the changed flow which was disrupted by either clamping and declamping of the tubing, or by the bolus injection of a vasomotor drug, to the selected flow rate within 10 seconds wihout any significant fluctuation. In conclusion, the newly developed computer controlled autof low system was able to produce a reliable and effective flow regulation for a centrifugal pump. We believe that we may be ultimately able to establish a novel of terl oad independent centrifugal pump with further development of this autof low mode.

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We created a small-sized peristaltic type pump driven by an electric battery.This pump consists of a disposable infusion set that has a cassette type pump unit (58×12×5.5mm) with diaphragms moved by low pneumatic pressure and a control unit (70×58×22.5mm) with a pneumatic driver.This pump has several advantages as follows: (1) It is possible to control a little flow and to maintain a constant flow for long time. (2) It is possible to suppress the abnormal pressure at the occlusion of flow channel by using pneumatic pressure as driving source. (3) The flow rate is controlled by the driven frequency of the diaphragms. The performance of this pump is 6-30mL/hour in flow rate and 1.7-5kPa in occlusion pressure at 1-5Hz in driving frequency.

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To improve efficiency of heat exchanger in membrane oxygenator, we have investigated the possibility of common usage of hollow fiber for gas exchange with heat exchanger. With using hollow fiber instead of stainless or plastic pipe, we can easily increase the effective surface area of heat exchanger significantly. The efficiency of heat exchange of the hollow fiber used in blood outside perfusion system (Senko Medical Instruments Manufacturing HP-1, effective surface area; 2.08m²) was 0.96 with a flow rate of 4L/min and 0.88 with a flow rate of 6L/min. The pressure drop inside of the hollow fiber was 357mmHg with a flow rate of 4L/min 614mmHg with a flow rate of 6L/min. We believe that we can decrease this relatively high pressure drop with decreasing the length of the hollow fiber, and adjusting the necessary surface area and flow rate of the water for heat exchange. In addition to excellent efficiency, we may be able to eliminate the heat exchanger and decrease the priming volume of the membrane oxygenator with common usage of single hollow fiber for both oxygenation and heat exchange, .

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In order to simplify the extracorporeal blood circuit and to facilitate handling of cardiopulmonary bypass, we have combined ahollow fiber unit for gas exchange and that for hemofiltration in one component and developed a new membrane oxygenator with a function of hemoconcentrator. The cylindrical device is consisted of a hollow fiber for hemofiltration with another fiber for gas exchange provided outside. Both of them adopt the blood outside perfusion system. Blood flows from around the center core towards the hollow fiber around it, first hemoconcentrator and then oxygenator, in radial direction. By applying this flow mode, even distribution of blood flow to the entire fiber was realized and the performance of the device was improved. Oxygen transfer rate was 336ml/min at a flow rate of 6L/min, and ultrafiltration rate was 7L/ hour with a flow rate of 4L/min with a hematocrit of 25%. Pressure drop of the whole unit was only 60mmHg with a flow rate of 6L/min. The combined structure of the two units has not caused any adverse effects. In conclusion, by combining an oxygenator and a hemoconcentrator, excellent and simplified hemoconcentration is made available as the blood outside flow mode is adopted.

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