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Biomedical subjects

D B Olsen

Publications and source records attributed to D B Olsen.

216 records · Page 12Linked to original sources
PubMedDate not supplied

In vivo evaluation of a peripheral vascular access axial flow blood pump.

More than 80 acute and chronic calf in vivo studies were utilized to develop a 3 L/min axial flow blood pump designed for intraarterial ventricular assist. The 7 mm diameter transvalvular inlet cannula of the cable driven pump receives blood from the left ventricle. The pump then discharges blood into the descending aorta. In the calf, the pump was introduced into the renal aorta. Safety and effectiveness of the device were demonstrated in three control and 21 implanted animals. Blood chemistry results showed an average plasma free hemoglobin of 3 mg/dl for control and 6.7 mg/dl for implanted animals. Platelets were 1.04 X 10(6) and 0.65 X 10(6), respectively, for control and implanted animals. Fibrinogen, BUN, creatinine, and bilirubin were essentially the same for both groups of animals. The hardware was typically free of deposits, and histopathologic examination revealed minimal injury to intracardiac structures, aortic valve leaflets, and aortic intima. The data indicates that the device may provide full support for a failing left ventricle with minimal trauma or risk.

Animals↗
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Cardiectomy for implantation of a total artificial heart: a modification.

The surgical implantation technique of a total artificial heart is important to improve its efficiency. The cardiectomy used for transplantation has been modified to leave different atrial remnants. The reasons, the advantages, and the technical modification are described.

Cardiac Surgical Procedures↗
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The role of cardiac valves in artificial heart performance.

The criteria for the design, selection of materials, and fabrication of a total artificial heart have evolved over several years. As these criteria have become more sophisticated and exact, they have optimized the performance of all components within the system. A pump with sufficient volume and pressure output that fits in the available anatomic space was a primary objective. Concomitantly, a nonthrombogenic, durable material that was nondegradable in body fluids was being developed. The most easily managed energy source selected to date has been pulsed, compressed air programmed for gentle but effective systole and diastole. The evolution of good cardiac valves has been of major importance to the artificial heart effort. The historical development of the artificial heart has often centered around existing prosthetic valves which are currently an integral component of the complete system. A detailed analysis of the performance of the total artificial heart clearly identifies the role of the cardiac valve.

Animals↗
PubMedDate not supplied

Adaptive full-ejection point detection for automatic control of the electrohydraulic total artificial heart.

An adaptive algorithm to detect full ejection points was developed for the automatic control of the electrohydraulic total artificial heart (EHTAH). To automatically control the EHTAH, systole in each ventricle is completed when a hyper-pressurization spike is detected on the oil side of that ventricle. A problem associated with the method of determining ventricular full ejection under variable afterload pressure is that a fixed level comparison method could fail to provide a normal full ejection condition. To increase system stability, safety, and efficiency, there is a definite need to vary the full ejection trigger level with changes in afterload. In this study, the full ejection trigger level for the current beat was changed based on the estimated afterload derived from the previous beat's pressure waveform. To increase this estimate's accuracy, an adaptive averaging window was used to determine which part of the previous pressure waveform would be used for the afterload estimation. With this enhanced control scheme, mock circulation tests with the EHTAH device demonstrated that estimated afterload tracked actual afterload. This scheme was also used successfully to control the EHTAH device implanted in three chronic calves.

Animals↗
PubMedDate not supplied

Adaptive responses of total artificial heart animals to treadmill exercise.

The hemodynamic and metabolic adaptations to exercise in five calves implanted with the Utah-100 total artificial heart (TAH) were investigated. The outputs of the left and right ventricles (LCO, RCO) were measured with a cardiac output monitoring and diagnostic unit (COMDU). Arterial and venous oxygen content (CaO2, CvO2) and blood lactate levels (Lac) were measured by blood gas analysis and enzymatic methods. Oxygen consumption (VO2), oxygen delivery (DO2), oxygen extraction rate (EO2), index of metabolic adequacy (IMA), and systemic and pulmonary vascular resistance (SVR, PVR) were calculated. The intensity of exercise was categorized into three horizontal grades: low speed (LS) 0.7-1.0 mph, medium speed (MS) 1.0-1.4 mph, and high speed (HS) 1.4-1.8 mph, each for 30 min. During LS, MS, and HS exercise, the LCO, RCO, LAP, RAP, VO2, DO2, and EO2 all increased, and the SVR and PVR decreased. During exercise, there was a positive correlation between DO2, EO2, and VO2. The blood pH, BE, SBE, and lactate levels were within normal ranges, and the IMA exceeded 1.5, denoting that tissue perfusion was adequate and anaerobic metabolism did not occur. This study implies that Utah-100 TAH animals could physiologically accommodate to exercise with an intensity of up to 1.8 mph for 30 min by increasing cardiac preload, cardiac output, oxygen delivery, and oxygen extraction rate, and by decreasing systemic and pulmonary vascular resistance without transition to anaerobic metabolism.

Animals↗
PubMedDate not supplied

Verification testing of the bearings used in the electrohydraulic total artificial heart.

This article reports the verification testing performed on the ball bearings used in the electrohydraulic total artificial heart (EHTAH) device. The bearings were tested for 70 days under conditions intended to simulate those actually experienced by the bearings in the EHTAH device. Vibration analysis to predict the condition of the bearings, as well as diagnosis of the wear experienced by the bearings, was included in this study. Examination of the bearings using light microscopy indicated the presence of wear, and in some instances the contact surfaces had undergone temper coloring, a warning sign that hardness of the bearing may have been impaired, and that the bearing has experienced a temperature excursion. Temper coloring can be caused by too thick a coating of grease or by insufficient hydrodynamic film thickness. In this investigation, the vibration amplitudes at specific frequencies that correlated with the bearing components were monitored for change. From analysis of the vibration spectra, it was found that the change in amplitude did not predict the damage incurred by the bearings. The type of damage experienced by the bearings is difficult to predict using spectral analysis.

Blood Flow Velocity↗
PubMedDate not supplied

Quantitative bacterial analysis of porous, fabric, and smooth non-blood contacting implant surfaces and their tissue interfaces in a 169 day pneumatic total artificial heart animal recipient.

All long-term total artificial heart (TAH) survivals are subject to sepsis. Survival can be prolonged, but the source of the infection cannot be eliminated with any known course of antibiotics or treatment regimen. Sambo, a U-100 pTAH calf, survived 169 days. At week 6, he became septic, growing a Pseudomonas species (Ps). Weekly blood cultures were intermittently positive until week 13 when they became continuously positive until his demise, from a ruptured left ventricular pumping diaphragm. Spatially specific porous silicone rubber (SSP) was used for surface modifications on the drive lines and as cuffs around the Dacron TAH graft to large vessel anastomoses. This gave an excellent opportunity to examine two types of porous implants surfaces (Dacron grafts and SSP) to the smooth Biomer ventricular surfaces with their respective adjoining tissue interfaces for bacterial colonization. Nine tissue samples and 13 implant surfaces were processed with Costerton's quantitative bacterial techniques. The largest numbers of bacteria (> 10(6)/cm2 Ps.) were grown from the smooth ventricular surface and in the cul-de-sac where the SSP delaminated from the driveline (two smooth implant surfaces in contact but without tissue apposition). The Dacron grafts were intermediate in bacterial concentrations and SSP surface modified drivelines and tissues were sterile. In this model, the more intimate biointegration found in the porous implants showed improved bacterial resistance in a chronically infected pTAH. The more completely biointegrated and neo-vascularized porosity SSP was the only implant surface and opposing implant tissue interface sampled to remain sterile.

Animals↗
PubMedDate not supplied

Development of a prototype magnetically suspended rotor ventricular assist device.

A continuous flow centrifugal blood pump with magnetically suspended impeller has been designed, constructed, and tested. The system can be functionally divided into three subsystem designs: 1) centrifugal pump and flow paths, 2) magnetic bearings, and 3) brushless DC motor. The centrifugal pump is a Francis vane type design with a designed operating point of 6 L/min flow and 100 mmHg pressure rise at 2,300 RPM. Peak hydraulic efficiency is over 50%. The magnetic bearing system is an all active design with five axes of control. Rotor position sensors were developed as part of the system to provide feedback to a proportional-integral-derivative controller. The motor is a sensorless brushless DC motor. Back electromotive force voltage generated by the motor is used to provide commutation for the motor. No slots are employed in the motor design in order to reduce the radial force that the bearings must generate. Tests pumping blood in vitro were very encouraging; an index of hemolysis of 0.0086 +/- 0.0012 was measured. Further design refinement is needed to reduce power dissipation and size of the device. The concept of using magnetic bearings in a blood pump shows promise in a long-term implantable blood pump.

Blood Volume↗