Motion-activated prevention of clogging and maintenance of patency of indwelling chest tubes.

OBJECTIVES: We designed a device that applies motion-activated energy (vibration) to prevent chest-tube clogging and maintain tube patency. We evaluated the efficacy of this device in vitro and in vivo. METHODS: The motion-activated system (MAS) device assembly comprises a direct current motor with an eccentric mass (3.2 g, centroid radius of 4.53 mm) affixed to its motor shaft. The device was tested in vitro using a model of an obstructed chest tube, with clots of bovine blood and human thrombin. The in vivo study (in nine healthy pigs, 46.0 ± 3.3 kg) involved a bilateral minithoracotomy and placement of 32-Fr chest tubes (with and without the device). Whole autologous blood (120 ml) was injected every 15 min into the right and left chest each over 120 min total. RESULTS: Chest-tube drainage over these 2 h using the MAS was significantly higher than that without the device (369 ± 113 ml vs 209 ± 115 ml; P = 0.027). CONCLUSIONS: Our results suggest that the motion-activation of the chest tubes may be an effective tool to maintain chest tubes patent. Further optimization of this technology is required to obtain more consistent prevention of clot deposition within or outside the chest tubes.

Short-term in vivo performance of the Cleveland clinic PediPump left ventricular assist device.

The PediPump was implanted in six healthy lambs (mean 25.6 ± 1.4 kg) between the left ventricular apex and the descending aorta to evaluate in vivo performance for up to 30 days. Anticoagulation was achieved by continuous heparin infusion. Three animals were euthanized prematurely, two because of respiratory dysfunction and one because of deteriorating pump performance resulting from thrombus formation inside the pump. Three lambs were electively sacrificed 30 days after implantation; all had stable hemodynamics and minimal hemolysis, as indicated by low plasma free hemoglobin (2.5 ± 3.1 mg/dL). Mean 30-day pump flow was 1.8 ± 0.1 L/min at a pump speed of 12 200 ± 400 rpm. Neither activated clotting time nor activated partial thromboplastin time followed the changes in heparin dose. At necropsy, depositions were observed at the front (n = 1) and rear rotor axial positioning stops (n = 4); improved polishing techniques on the stationary stop surfaces and the addition of a hard-carbon, thin-film coating on the rotating stop of the pumps used for the last two experiments addressed the deposition seen earlier. In conclusion, the PediPump showed excellent hydraulic performance and minimal hemolysis during support for up to 30 days. Depositions observed at the axial positioning stops in earlier experiments were addressed by design and material refinements. We continue to focus on developing effective anticoagulation management in the lamb model as well as on further evaluating and demonstrating pump biocompatibility.

The PediPump: a versatile, implantable pediatric ventricular assist device--update IV.

Cleveland Clinic's PediPump (Cleveland, OH, USA) is a ventricular assist device designed for the support of pediatric patients. The PediPump is a mixed-flow ventricular assist device with a magnetically suspended impeller measuring 10.5 mm in diameter by 64.5 mm in length. Progress and achievements for the PediPump program are considered according to the development project's three primary objectives: Basic engineering: along with size reductions, substantial design improvements have been incorporated in each design iteration including the motor, magnetic bearings, axial touch points, and heat transfer path; Anatomic modeling and device fitting studies: Techniques based on computed tomography and magnetic resonance imaging have been developed to create three-dimensional anatomic-modeling and device-fitting tools to facilitate device implantation and to assist in preoperative planning. For in vivo testing, to date, six acute (6-h duration) and nine chronic (30-day target duration) implantations have been performed in sheep; the implantation of the PediPump appears to be relatively easy with excellent hemodynamic performance and minimal hemolysis during support. Cleveland Clinic's PediPump program supported by the National Heart, Lung and Blood Institute's Pediatric Circulatory Support Program has led to the development of a pediatric ventricular assist device that has satisfactory performance in preclinical evaluation and appears to be ready to support a program of clinical testing.

The PediPump: a versatile, implantable pediatric ventricular assist device-update III.

The PediPump is a passive magnetic bearing, mixed flow, rotary ventricular assist device designed to provide support for the entire range of patient sizes encountered in pediatrics. Blood enters axially at the inlet and is accelerated and turned in the impeller to exit the pump at an intermediate angle. The size of the PediPump facilitates standard cannulation strategies with substantially downsized components. The program pursues three specific objectives: 1) System engineering: Progress within the last year has focused on the assembly and testing of PediPump prototypes. Initial in vitro hydraulic performance and hemolysis testing were judged satisfactory. 2) Anatomic fitting studies: As part of the PediPump program, three-dimensional modeling techniques based on routine, clinically obtained computerized tomography (CT) scans have been developed. During 2006, the same techniques developed for clinical scans were applied to CT scans obtained from sheep to guide the presurgical planning. 3) Animal studies: Animal implantation of PediPump prototypes commenced in July 2006. A total of four 6 hour acute studies were performed throughout the remainder of the year. In vivo performance was satisfactory and compared well with the in vitro results. Hemolysis levels were low.

Initial acute in vivo performance of the Cleveland Clinic PediPump left ventricular assist device.

The PediPump is a small ventricular assist device (VAD) with a hydraulic output range designed to support children from newborns to adolescents. The present report describes our initial evaluation of the PediPump as a left VAD in an acute sheep model. The PediPump was implanted in two sheep (50.8 and 62.7 kg). Pump speed was adjusted to achieve a flow of 2 L/min with the naturally occurring preload and afterload conditions to evaluate pump performance under a steady hemodynamic state for 4 hours. Upon completion, pump performance was evaluated under various blood pressure and heart rate conditions. During steady-state evaluations, the ascending aortic flow and pump speed varied slightly depending on systemic arterial pressure variations. During the hemodynamic manipulation studies, flows ranged between 0.5 and 3.2 L/min with pump speeds of 5,200-16,200 rpm and motor current of 0.06-0.75 A. The PediPump demonstrated good initial hemodynamic performance for use as an implantable left VAD. However, some depositions were detected at the time of explanation, mainly at the rear of the pump. We are continuing with further acute studies to evaluate pump performance in anticipation of beginning chronic studies to evaluate long-term biocompatibility.

The PediPump: development status of a new pediatric ventricular assist device: update II.

The PediPump is a new ventricular assist device with a hydraulic output range designed for children from newborn infants to adolescents. The design is based on a mixed-flow rotary pump; the rotating assembly consists of a front impeller, front and rear radial magnetic bearings, and a central motor magnet. Two different implantable pumps were designed initially: an intravascular pump measuring 7 x 75 mm and an extravascular pump measuring 14 x 85 mm. Current prototypes are substantially smaller: The current intravascular version measures 4.5 x 55 mm, whereas the current extravascular version measures 11 x 70 mm. Both devices provide pressure and flows capable of supporting adults, far exceeding the initially defined physiologic requirements for children weighing 2 to 25 kg. This basic pump design may be used in acute or chronic clinical settings to provide right ventricular, left ventricular, or biventricular support. There are three objectives for the PediPump development program: 1) determination of basic engineering requirements for hardware and control logic including design analysis for system sizing, evaluation of control concepts, and bench testing of prototypes; 2) performance of preclinical anatomic fitting studies using CT-based 3D modeling; and 3) animal studies to provide characterization and reliability testing of the device.

The pedipump: development status of a new pediatric ventricular assist device.

The PediPump is a new rotary dynamic ventricular assist device designed specifically for pediatric applications. Although it is capable of providing support for adults, the small size of the PediPump makes it suitable for newborn circulatory support while retaining excellent hemodynamics. Current and future development plans include: (1) determination of the basic engineering requirements for hardware and control logic, including design analysis for system sizing, evaluation of control concepts and bench testing of prototypes; (2) performance of preclinical anatomical fitting studies using computed tomography-based three-dimensional modeling; and, (3) evaluation with animal studies to provide characterization and reliability testing of the device.