Excessive Negative Pressure Research Articles

Stress fields controlling the formation of nested and overlapping calderas: Implications for the understanding of caldera unrest

Commonly, the formation of a collapse caldera does not necessarily imply the end of the volcanic activity in the area. In many cases, successive calderas may form close to the previous collapse depression or intersecting it leading to overlapping collapse structures. Occasionally, subsequent caldera collapses may take place at the interior of the first caldera creating nested collapse structures. During the last years several authors have investigated numerically how the stress field around magma chambers may favour the formation of collapse calderas assuming that the host rock surrounding the magmatic reservoir behaves as a linear elastic homogeneous medium. The numerical models presented in this work study how a caldera collapse may modify the stress field of a volcanic area and hence the conditions for the formation of future collapse calderas. Our models take into account the effect of the collapse structure considering it as a mechanical discontinuity. We also investigate the mechanical influence of the intra- and extra-caldera deposits on the formation of new calderas. All the numerical models are two-dimensional assuming plane strain and considering that the surrounding crust behaves as a linear homogeneous elastic material. The computational domain corresponds to a cross-section of the upper crust (50 × 25 km) and magma chambers are modelled as sill-like cavities located at a certain depth below the Earth's surface. The existing collapse caldera depression is 8 km wide and 2.75 km deep, however we consider the caldera infill (i.e. intra-caldera material) to be 1.25 or 1.75 km thick. We assume as loading conditions an underpressure of 10 MPa imposed at the chamber walls, that is, negative excess pressure in the chamber. In some numerical runs we have considered the existence of a previous ring fault by introducing a thin and elongate vertical weak zone at the caldera margins. We find that the stress field around shallow-level magma chambers favouring the formation of either nested or overlapping caldera structures depend on: 1) the dimensions of the previous caldera collapse structure, 2) the size of the new magma chamber susceptible to generate the subsequent caldera-forming event, and 3) the mechanical properties of the surrounding host rock and the syn- and post-collapse materials. Moreover, results obtained in this paper may be relevant to the interpretation of unrest episodes in active caldera systems. Our numerical results confirm that the formation of multiple calderas (nested, overlapping, or separate) imply the development of new shallow magma chambers different from the one that lead to the first collapse caldera. In consequence, interpretation of magmatic unrest episodes in active collapse calderas should not be based on the assumption that the responsible for the current unrest is the same system that originated the caldera.

Conceptual and numerical models of ring-fault formation

Most ring faults of collapse calderas are primarily shear fractures the initiation and development of which depends on the state of stress in the host rock. The state of stress in a volcano is controlled by the loading conditions, such as magma-chamber geometry and pressure, but also by the mechanical properties of its rock units and structures (such as existing contacts, faults, and joints). Ring-fault formation is thus essentially a problem in rock physics. Field observations show that some ring faults are dip–slip, whereas others are partly faults (shear fractures) and partly ring dykes (extension fractures). Although slip on existing ring faults is much more common in basaltic edifices (shield volcanoes) than in true composite volcanoes, in both types of volcanoes most caldera unrest periods do not result in ring-fault slip. Here I present new conceptual and numerical models of caldera formation in volcanoes with shallow spherical (circular) or oblate ellipsoidal (sill-like) magma chambers. In the layered models, the host rock above the chamber is composed of 30 comparatively thin layers with stiffnesses (Young's moduli) alternating between 1 GPa and 100 GPa. The chamber itself is located in a single, thick layer. The crustal segment hosting the chamber is either 20 km or 40 km wide but has a constant thickness of 20 km. The loading conditions considered are: (1) a crustal segment subject to 5 MPa tension; (2) crustal segment subject to excess magmatic pressure of 10 MPa at the bottom (doming of the volcanic field containing the chamber); (3) a combination of tension and doming; and (4) chamber subject to underpressure (negative excess pressure) of 5 MPa. The main results are as follows: (1) Excess pressure and underpressure in a chamber normally favour dyke injection rather than ring-fault formation. (2) For doming or tension, a spherical magma chamber favours dyke injection except when the layer hosting the chamber is very soft (10 GPa) or one with recent dyke injections, in which case the surface stress field favours ring-fault formation. (3) For a sill-like chamber in a 20-km wide crustal segment, a ring-fault can be generated by either tension or tension and doming; for a 40-km wide segment, doming alone is sufficient to generate a ring fault. (4) Since individual layers in a volcano may develop different local stresses, stress-field homogenisation through all the layers between the chamber and the surface is a necessary condition for ring-fault formation. (5) Because the mechanical properties of the layers that constitute basaltic edifices are more uniform than those that constitute true composite volcanoes, it follows that stress-field homogenisation, and thus ring-fault formation or slip, is more commonly reached in basaltic edifices than in composite volcanoes. (6) Both for basaltic edifices and composite volcanoes, the stress fields most likely to initiate ring faults are those generated around sill-like chambers subject to tension, doming, or both.

Computer simulations of transient flow in a real city water distribution system

Several cases of computer simulation for transient flow have been conducted to demonstrate the transient effects in distribution system. Each case is simulated with specified scenarios. The results of computer model show that any changes of water demand can produce large pressure oscillation. If the change of demand is sudden, it will create many undesirable consequences such as backflow, excessive high pressure, or negative pulling pressure. The computer model utilized in this study has been found to be a promising simulation tool for the solution of transient flow in distribution system. Computer models have to be used for the design of distribution system subject to transient flow. Moreover, it can be used as an operational tool to protect the distribution system from the excessively high pressure, the column separation due to excessive negative pressure, or any undesirable incidents.

Management Of Unpredıcted Postoperatıve Negatıve Pressure Pulmonary Edema: A Report Of Two Cases

Negative pressure pulmonary edema is a potentially life-threatening complication especially during emergence in patients undergoing general anesthesia for a variety of surgical procedures. Laryngospasm-mediated upper airway obstruction leads to forced inspiration generating excessive negative intrathoracic pressure and causes negative pressure pulmonary edema. However the symptoms may also develop late in the postoperative period. We describe two young, strong men who developed this clinical picture at different times following routine uncomplicated surgical procedures. This paper not only reports the importance of early recognition of this potentially serious complication for anesthesiologists but also serves as a reminder to physicians caring for postanesthesia patients in the surgical ward to prevent the delay in diagnosis and significant morbidity.

The Jena universal perfusion system: a universal cardiopulmonary bypass circuit for cardiac surgery

Cardiopulmonary bypass (CPB) is a standard technique in cardiac surgery, which itself contributes to postoperative morbidity. Neurologic sequelae after CPB is caused by air embolism or systemic inflammatory response due to artificial surface and is closely related to the characteristics of the extracorporeal circuit. Minimized systems without a venous reservoir take these factors into account. They require a differentiated volume management to avoid excessive negative pressure in the venous line, which may lead to spontaneous formation of microbubbles and are said to cause air embolism. Perfusion technology also offers systems with closed soft-bag and open hard-shell reservoirs, that require individual setups with little flexibility. We developed an all-purpose perfusion system for application as cardiopulmonary bypass. The central part is a compound reservoir, consisting of a lower hard shell and an upper self-expanding shell, which is capable of actively increasing volume. It allows application of the circuit as closed or open system. Crossclamping the inflow turns the system into a minimized circuit, in which the reservoir compensates volume when backflow is low and safeguards against excessive subzero pressure. The system has been applied in pilot experiments. In cardiac surgery today patients present at higher ages and with complex comorbidities. Not all of them are suitable candidates for off-pump procedures and might profit from perfusion technology with reduced adverse effects. The Jena Universal Perfusion System (JUPS) may be applied as a minimized system with the option to compensate low venous backflow and allows flexible extension to a closed or open circuit anytime during the procedure.

Conductive Hearing Loss in Patients with Active Acromegaly

There have been rare conflicting results reported concerning possible higher frequency of hearing loss in acromegalic patients. Our goal was to determine whether there is higher frequency of conductive hearing loss in acromegalics and what may cause it if there is any. Prospective study. Tertiary referral center. Thirty previously untreated patients with acromegaly were compared with 20 age- and sex-matched healthy control subjects. In all subjects: Otomicroscopy, tuning fork tests, audiometry tympanometry, cochleostapedial reflex, otoacoustic emissions. In acromegalics: endocrinologic assessment, MRI and if necessary, epipharyngoscopy. We searched for: 1) Signs of ossicle fixation: absence of stapedial reflex in the presence of normal tympanogram, conductive hearing loss, and absence of or grossly disturbed OAE; 2) Disturbances of middle ear ventilation: excessive negative pressure (tympanogram type C), or middle ear effusion (tympanogram type B). The only statistically significant difference between untreated acromegalics and healthy subjects was the presence of middle ear ventilation problem: 7/30 acromegalics (23%) in comparison to none out of 20 healthy controls (0%), p = 0.033. The acromegalics with middle ear ventilation problem were significantly older, had longer duration of the disease, and lower mean growth hormone (GH) levels in comparison with acromegalics without this problem (51.6 +/- 1.7 vs. 44.4 +/- 2.5 years, 11.6 +/- 2.4 vs. 7.7 +/- 0.4 years, 21.68 +/- 4.89 vs. 49.98 +/- 12.54 microg/L respectively). Patients with active acromegaly have more frequent middle ear ventilation problem than normal population, especially those with longer duration of the disease. Possible causes are discussed.

Edema pulmonar por presión negativa: a propósito de 3 casos

Negative pressure pulmonary edema is a complication, described since 1977, caused by upper airway obstruction in both children and adults. Although its aetiopathogeny is multifactorial, especially outstanding is excessive negative intrathoracic pressure caused by the forced spontaneous inspiration of a patient against a closed glottis, that causes high arteriole and capillary fluid pressures that favor transudation into the alveolar space The resulting pulmonary edema can appear a few minutes after the obstruction of the airway or in a deferred way after several hours. The clinical manifestations are potentially serious, but normally respond well to treatment with supplemental oxygen, positive pressure mechanical ventilation and diuretics. Diagnostic suspicion is important for acting promptly. We report three clinical cases with acute negative pressure pulmonary edema.

MOCK CIRCULATORY SYSTEM FOR THE CONTINUOUS FLOW TOTAL ARTIFICIAL HEART

Purpose: A mock circulatory loop was designed to be used as a platform for testing feedback control strategies for the continuous flow total artificial heart (TAH). Methods: The mock circuit comprises both systemic and pulmonary circulations. The TAH consists of 2 axial flow pumps. The atria are flexible and collapse under excessive negative pressure. Pulmonary and systemic vascular resistances are adjusted to approximately 4 and 20 Wood units, respectively, using tubing clamps. The respective compliances are modeled with sealed cylinders containing air. During normal operation, approximately 80% of the fluid volume is in the systemic circulation. Pressure signals are filtered with anti-aliasing filters. Aortic and pulmonary arterial pressures, left and right atrial pressures, and flow rates are sampled at 1 kHz. Results: A wide range of hemodynamic conditions were simulated. Baseline aortic and pulmonary arterial pressures were maintained at 80 and 20 mm Hg, respectively, while atrial pressures were kept at approximately 0 mm Hg. Flow rate in the left pump was slightly higher than in the right due to the bronchial shunt. The mock circuit was successfully used for testing physiologic feedback control strategies for the dual-pump system. Conclusions: Normal and pathologic conditions, including atrial collapse, can be readily simulated in the mock circuit, making it a suitable platform for testing feedback control algorithms aimed at correcting hemodynamic abnormalities in patients with TAHs.

Thermodynamic nature of the glass transition interval

Quenching a glass-forming liquid as a kinetic factor, determines the formation of thermodynamic conditions that are characteristic of a solid glass and a system within the glass transition interval. In a glass-forming liquid, the excess volume is the reason for the existence of negative pressure that changes within the glass transition interval and becomes ‘frozen’ upon the transformation of a non-equilibrium liquid into a glass. Excess volume and negative pressure are the features of a glass transition that occurs either with quenching or with an increase in the external pressure. Negative pressure which is ‘frozen’ in solid glasses causes their anomalous thermal expansion in the vicinity of the absolute zero temperatures.

Advance in animal experiments with the undulation pump total artificial heart: 50 and 54 day survival periods with 1/R control.

The undulation pump total artificial heart (UPTAH) is a unique, implantable, total artificial heart (TAH) that uses undulation pumps. To achieve long-term survival in animals with physiologic hemodynamic conditions, a control method based on conductance and arterial pressure was applied to UPTAH. With this control method, called 1/R control, survival periods of 50 days (No. 0016, 49.6 kg) and 54 days (No. 0030, 42.5 kg) were obtained in adult female goats. In No. 0016, 1/R control was applied to the left pump, whereas in No. 0030, it was applied to the right pump. Another pump was used for left-right balance control. The control stability was better in No. 0030 than in No. 0016. The sucking effect of the left atrium was remarkable in No. 0016, possibly because of a time delay when left-right balance control was performed with the right pump. In No. 0016, the cause of death was probably a thrombus flown from a panus in the left atrium. It is possible that the left atrial suction effect influenced the thrombus and panus formation in the left atrium. In No. 0030, the cause of death was a small rupture of the membrane in the right pump. The rupture may have been caused by excessive negative pressure inside the pump. This pressure resulted from suction of the right atrium because of an unexpected control excursion, which was probably caused by a software bug. It will be necessary to redesign the undulation pump and improve the software to achieve longer survival periods for animals with physiologic hemodynamic conditions.

Cavitation and cavity‐free deformation of filled crystalline polymer systems

AbstractMain mechanisms of tough response of polymers are described. In heterogeneous polymer systems due to mechanical misfit between heterogeneities and the matrix a high negative pressure (tri‐axial stress) is generated. The excessive negative pressure is the main reason of material cavitation. Cavitation appears to be another mechanism of tough response of the material to loading. Cavitation is a massive phenomenon in crystalline polymers and in all filled polymers. Cavitation itself does not consume much energy but allows for further toughening by activating other mechanisms. Examples of polypropylene filled with chalk modified by liquid, rubber and mineral filled polypropylene and syndiotactic polypropylene filled with chalk are described. Modes of deformation with significant compressive component of stress prevents for cavitation. Materials deformed in a cavity‐free manner show much higher strength. It is pointed out that high polymer crystal anisotropy is necessary for the formation of a network of easy crystallographic slip in the unusual toughening of highly filled polymers observed recently. An example of syndiotactic polypropylene filled with submicro‐chalk particles is presented.

Development of disposable self-regulating blood pumps and automatically-controlled portable extracorporeal membrane oxygenation systems for neonatal extracorporeal membrane oxygenation.

For safer and simpler neonatal ECMO management, the authors have been developing an innovative, automatically-controlled ECMO machine using self-regulating blood pumps. The newest model is an air-driven, tube-type blood pump. A pair of blood pumps are placed in parallel and actuated alternately with compressed air. The pump flow is automatically regulated in accordance with hemodynamic changes of the body. The need for a venous reservoir is eliminated because the circuit does not generate excessive negative pressure when there are shortages of draining blood. Therefore, the priming volume of the circuit is only 85 ml. This ECMO apparatus has three driving modes, one of which is a "delay" mode. This enables the pump flow to easily be varied from 10 to 500 ml/min under automatic control, and it can be used when the pump flow is decreased for weaning. This newest ECMO apparatus was clinically used in 3 neonates with severe lung hypoplasia and persistent fetal circulation. The ECMO duration was 139 h to 168 h, and the maximum ECMO flow 71.3 to 109.0 ml/min/kg. Thanks to the self-regulation, intensive observation of the circuit was not necessary during ECMO. Damage to blood cells was less significant, and the use of blood products was only minimal (15.7 ml/kg/day) because a large volume of blood to stabilize the pump performance was not necessary. In conclusion, the automatically-controlled ECMO apparatus worked well without complications by changing the ECMO flow automatically in accordance with hemodynamic changes. This automatic ECMO system required fewer personnel expenditures and was also favorable in terms of hematological findings.

Ventilator Failure during Use of a New Anesthesia Machine

In Reply:—In their letter, Drs. Barahal and Sims describe a situation in which suction to the patient’s airway before bronchoscopy caused a problem with the Narkomed 6000 ventilator (Draeger Medical Inc., Telford, PA). Draeger Medical Inc. investigated this problem and would like to describe the findings and the results of the investigation.When the clinical circumstances of this event were recreated, it was determined that a negative pressure of −375 mmHg was applied to the airway through a 14-French suction catheter drawing a flow of 30 l/min through the catheter. When the same suction level was applied through the bronchoscope suction port, only 4.6 l/min of flow was drawn through the port, and the problem could not be recreated. Therefore, it seems that the initial airway suctioning was the inciting event, not the suction through the bronchoscope.The problem described by Drs. Barahal and Sims occurred when a relatively high negative pressure, resulting in a high degree of suction flow, was applied to the patient’s airway during ventilation. If the suction flow is high enough, it will exceed the capacity of the ventilator’s negative-pressure relief system. The resulting negative pressure in the breathing system holds the diaphragm control valves closed in such a way that gas cannot enter the breathing system and relieve the negative pressure. A similar situation was reported to Draeger Medical Inc. by another institution where a high degree of negative pressure was applied to the airway through a misplaced nasogastric tube.Typical clinical guidelines for suction applied to the adult airway recommend that suction pressure be set as low as possible to clear secretions effectively. Desirable suction levels in the range of −100 to −150 mmHg applied for up to 15 s have been cited. 1American Society for Testing and Materials standard F960 governing Medical and Surgical Suction and Drainage Systems offers a maximum static vacuum level of −160 mmHg for adult tracheal suctioning as a guideline. 2When the suction regulator used by Drs. Barahal and Sims was adjusted to −120 mmHg, 18 l/m of flow was drawn through the 14-French suction catheter, and the ventilator problem could not be made to occur.Draeger Medical has taken a number of steps to address this issue. Draeger recommends that regulated suction within the range of typical clinical guidelines be used either when applying suction to the airway or at the time of initial placement of a nasogastric tube before proper placement has been confirmed. We agree with Drs. Barahal and Sims that it is prudent to put the ventilator into “manual” mode and to fill the reservoir bag before applying suction to the airway (or to a gastric tube that may be in the airway). If the reservoir bag empties as suction is applied, suction should be stopped before the bag is completely empty to avoid exposing the breathing circuit to excessive negative pressure. Draeger has also incorporated a help feature into the Narkomed 6000, which appears automatically on the monitor display should this event occur. The help feature guides the user through the simple steps that must be taken to ensure the patient’s safety. Draeger has taken steps to enhance the training process to ensure that all users are made aware of the recommended degree of suction that should be applied to the airway. Finally, changes to the operator’s manual will more clearly describe this situation and the strategies for avoidance.

鼻すすりによりめまいを生じた耳管開放症例

Patulous eustachian tube syndrome has become rare and we report here a 33-year-old male diagnosed with a patulous eustachian tube in the right ear, resulting from severe weight loss. The patient reported that sniffing gave a transient improvement of his symptoms such as ear fullness and autophony, but the frequent sniffing seemed to induce vertigo. The fistula symptom was positive and the movement of the eardrum sympathized with breathing was observed under an operation microscope. Although the vertigo disappeared after the patient stopped sniffing, the fistula symptom and the movement of the eardrum remained. At the time of the exploratory tympanotomy, no perilymphatic fistula was observed in the mesotympanum. We reinforced the round window membrane using soft tissue, and in addition, injected atelocollagen around the pharyngeal orifice of the eustachian tube. After the operation, both the fistula symptom and the abnormal movement of the eardrum had disappeared. These results suggested that the excessive negative pressure to the mesotynpanum caused by sniffing may have affected the inner ear through the round window membrane.

Microbubble generation in roller and centrifugal pumps

In order to investigate the difference in microbubble generation between roller and centrifugal pumps, this quantitative bench study was conducted. Using a mock circuit and fresh bovine blood, a roller pump or a centrifugal pump was run with 51/min of flow and 350 mm Hg of total pressure head. Microbubbles were produced by inflow tube occlusion (3 or 5s). Blood temperature was maintained at 25° and 36°C. Using a Doppler microbubble detector, the maximum diameter of the bubbles was monitored every 0.1s for 60s (total, 600 samples) at the prearterial filter (pump outflow side) and the postarterial filter sites. The number of microbubbles larger than 32μm were counted. The roller pump generated significantly more large microbubbles than the centrifugal pump. Substantial numbers of large microbubbles were encountered at the postfilter site, particularly when the roller pump was used. The centrifugal pump does not create excessive negative pressure by inflow occlusion; microbubble generation was less than that of the roller pump. Furthermore, since the centrifugal pump has a pressure discrepancy in the pump, small bubbles tend to stay around the center of the pump. This study confirmed that the centrifugal pump generated fewer microbubbles than the roller pump during inflow obstruction. Therefore, the centrifugal pump is safer in terms of microbubble generation. Additional care should be taken to prevent air emboli while using the roller pump because substantial numbers of microbubbles may go through the arterial filter.

First clinical application of an automatic VA-ECMO system using artificial hearts as a blood pump

A new extracorporeal membrane oxygenation (ECMO) circuit using air-driven artificial hearts as a blood pump was first applied on a newborn with congenital diaphragmatic hernia. ECMO was continued for 67 hours 36 minutes with no mechanical trouble. Since the artificial hearts changed their output automatically in proportion to venous return and did not generate excessive negative and excessive positive pressure, the automatic ECMO circuit could be handled safely by a small number of less-skilled staff.

Comparison of a New Venous Control Device with a Bladder Box System for Use in ECMO

During extracorporeal membrane oxygenation (ECMO), forward pump flow must not be allowed to exceed the rate of blood drainage from the patient so that excessive negative pressure does not develop within the ECMO circuit or in the patient's right atrium. A distensible reservoir ("bladder") and mechanically actuated electronic switch ("bladder box"), has typically been used for this purpose. If the rate of blood flow from the patient to the pump is insufficient to support the perfusion rate desired and adjustments in volume status and catheter position do not increase blood drainage, the only recourse is to increase the siphon pressure by elevating the patient. At the author's institution, a novel venous control module (VCM), without a reservoir, that can provide increased venous drainage without elevating the patient is used. Using an in vitro model of neonatal ECMO, the authors' compared their VCM to a commercially available "bladder box" system. Pressures were monitored in a collapsible chamber inside a water bath (simulating the right atrium), at the gravitational high point of the ECMO circuit ("neck site") and at the low point of the circuit ("venous site") at flow rates of 100, 450, 900, and 1,300 cc/min. Pump shut-off characteristics for both systems were also measured with either sudden interruption of venous drainage ("cross-clamping") or restriction of venous inflow ("hypovolemia"). Under continuous flow conditions, higher flows could be achieved with the VCM. With acute venous catheter occlusion, instantaneous ("trough") pressures at the neck site were lower, and venous monitoring site pressures were higher with the bladder box system.(ABSTRACT TRUNCATED AT 250 WORDS)

Postoperative pulmonary edema in young, athletic adults

Pulmonary edema secondary to postextubation laryngospasm is a potentially life-threatening problem, demanding early diagnosis and prompt treatment. We believe that this problem has been grossly underestimated in its incidence, as only seven adults have been reported in the English literature, whereas seven adults have been observed at our institution in only a 24 month period. All were young, healthy, athletic adult males (average weight, 218 pounds) who underwent relatively minor, uncomplicated surgical procedures under general anesthesia. Five of these patients were collegiate and/or professional athletes and had meticulous medical records detailing their clinical course. Clinical laryngospasm was noted immediately following extubation and anesthesia by mask with subsequent pulmonary edema. The diagnoses were confirmed by clinical examination, arterial blood gas determinations or pulse oximetry, and chest roentgenogram. Four adults required reintubation. Six of the seven adults demonstrated very rapid resolution of the pulmonary edema with prompt diagnosis and institution of a therapeutic regimen including oxygen, diuretics, reintubation, and/or positive pressure ventilation. In one patient, the problem was not immediately recognized, and progressed to florid pulmonary edema requiring emergent intubation 14 hours later in the emergency room, and 3 days of mechanical ventilation. The etiology of pulmonary edema following upper airway obstruction represents an interplay between several factors: cardiogenic and neurogenic mechanisms, as well as hypoxia contribute. In this group, excessive negative intrathoracic pressure generated by forced inspiration against a closed glottis is the most likely, consistent, and logical explanation. This study suggests that young, healthy, athletic males may be at increased risk for this complication.(ABSTRACT TRUNCATED AT 250 WORDS)

Closed Tracheal Suction Systems: Effectiveness and Nursing Implications

Closed tracheal suction systems (CTSS) are currently being used to minimize complications associated with endotracheal suctioning. Advantages of CTSS include improved oxygenation, decreased clinical signs of hypoxemia, maintenance of positive end-expiratory pressure, infection control, convenience, cost, and reduced patient anxiety. Some concerns related to use of CTSS include autocontamination, decreased effectiveness, difficult to use, excess negative pressure, and airway trauma. Strategies for reducing these and other concerns are shared. Recommendations for nursing practice and nursing research are discussed.

Development of an implantable motor-driven assist pump system

A motor-driven artificial pump and its transcutaneous energy transmission (TET) system have been developed. The artificial pump consists of a high-speed dc brushless motor driving a ball screw and magnetic coupling mechanism between the blood pump and ball screw. The ball screw transfers high-speed rotary motion into low-speed rectilinear motion by a single component. Magnetic coupling enables active blood filling without applying an excess negative pressure to the pump. The transcutaneous transformer is formed from a pair of concave/convex ferrite cores. This design minimizes lateral motion of the external core. Information on motor voltage is transmitted through the skin by infrared pulses. The motor voltage is regulated by controlling the duty ratio of the square pulse supplied to the primary coil. Pump flow of 5.6 l/min was obtained with a mean outlet pressure of 100 mmHg at a drive rate of 100 bpm under preload of 15 mmHg. The performance of synchronous pumping has been very satisfactory. Continuous pumping was maintained by the backup battery in the case of interruption of TET. 24 W were transmitted by TET system with 78 percent of efficiency. Temperature rise of the internal core was 0.2 C. The developed system is promising as an implantable assist pump system.