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Biomedical subjects

H Kambic

Publications and source records attributed to H Kambic.

33 records · Page 2Linked to original sources
PubMed1983

Experimental results for chronic left ventricular assist and total artificial heart development.

After more than 20 years of research on the artificial heart, it is now accepted that the pneumatically actuated total artificial heart can maintain near-normal physiology in experimental animals for several months. Such systems are clinically acceptable for short-term application (a few months) in patients waiting for a suitable heart transplant. However, realistically, a cardiac prosthesis that has the capability of being totally implantable for over 2 years must be available. Based on this premise, our group initiated the development of a mechanically actuated total artificial heart, capable of coupling with either a thermal or electrical actuation system. Since 1977, under the National Institutes of Health chronic left ventricular assist program, we have used two different pusher-plate pumps and electrical systems. Taking advantage of technology generated in these programs, we began developing a prosthesis to replace the total cardiac function. This paper is a summary of both the chronic left ventricular assist and total artificial heart development progress in this laboratory.

Animals↗
PubMed1983

Sequential external counterpulsation (SECP) in China.

A new SECP was developed and is currently successfully used in more than 120 clinics in China. This sequenced counterpulsation device has the effect of milking more blood as pressure is applied on the extremities in succession (first distally then proximally) and in decreasing values (265 to 200 mm Hg). In comparison of the 4 types of counterpulsation, namely nonsequenced leg and 4 limb counterpulsation, and sequenced 4 limb and 4 limb with buttock balloons, the SECP with buttock balloons method raised the DA to appreciably higher levels with respect to DA amplitude and area. DA was raised 43.9% higher than that obtained with 4 limb SECP alone. From our experimental and clinical results, we conclude that SECP with buttock balloons is a far more effective method providing greater diastolic augmentation than previously reported in the literature. Two hundred angina and 52 AMI patients who had undergone the SECP treatment constitute the basis of this report. The present work represents an analysis of 6 yrs experience with studies on the design, development and clinical evaluation of the SECP method. Ninety-seven percent of the angina patients obtained long-term symptomatic relief. Relapse was minimal. In 95.7% of the AMI patients chest pain or shock symptoms were rapidly relieved. SECP with high DA appears to be very effective in improving myocardial blood supply and ventricular function. Moreover, the simplicity and advantages of this noninvasive sequenced counterpulsation method have been reported (1063 cases) from 31 clinics in China. This method is convenient, safe, and far more effective than conventional drug therapy for patients with acute and chronic ischemic myocardial disease.

Angina Pectoris↗
PubMed1978

Experimental bladder substitution using a biodegradable graft of natural tissue.

A controlled canine experimental study has been performed to test the application of a biodegradeable graft to vesical augmentation. The graft, after providing initial bladder enlargement, is progressively reabsorbed while serving as a foundation for the regeneration and healing of the layers of the bladder remnant. Follow-up studies at 1 year revealed no urinary infection, calculi, extravasation of urine, or rejection of the material. Normal bladder capacities were maintained throughout the study and the reconstructed bladders functioned normally. The biodegradable graft was equally successful when applied either to a histologically normal bladder remnant, or to a pathological bladder of intramural fibrosis. These results suggest that this material may be well suited to clinical bladder substitution in humans.

Animals↗
PubMed1976

Application of aldehyde treatments to cardiovascular devices.

Biolized natural and synthetic materials represent a new class of materials. Aldehyde treatment of natural tissue creates cross-links in the collagen molecules while retaining mechanical strength and collagen structure. Synthetic polymers can also be biolized by the addition of protein and aldehyde treatment. Cross-linked materials such as these are resistant to degradation by proteolytic enzymes. The procedure for the aldehyde treatment of natural tissue and protein polymer composites has been established, and in vivo and in vitro studies have demonstrated an improved blood compatibility. Long-term survival with TAH and LVAD implanted animals has shown the successful application of these materials without the use of anticoagulants. Pseudoneointima growth occurs on these surfaces, and results to date indicate growth stabilization within 2 wks of impalntation. Studies are currently underway to fully characterize the pseudoneointima formed on the biolized surfaces of cardiac prostheses.

Aldehydes↗
PubMed1975

A biological extracorporeal metabolic device for hepatic support.

The results from OCTOPUS-I indicate that combined metabolic activities could be maintained under the optimal conditions provided for a prolonged period of time, but most effectively up to 14 hrs. The results of OCTOPUS-II and -III are lower than those in OCTOPUS-I. However, the activity in these systems is still higher than those previously reported((18)), which had urea production of 0.47 mg/Gm of liver. As imposed by any mass transfer device rate limitation, 60% efficacy of OCTOPUS-I brought into OCTOPUS-II, calculated by urea level, is acceptable. What is required for further improvement is mainly oriented to device rather than procurement andpreparation stages. The obstacles in the OCTOPUS-II and -III were, 1) the long time consumed for mounting the slices and assembling the devices before initiation of incubation, 2) inadequate control of incubation media, particularly blood, for oxygenation and pH, which was only for a short period of time but in the critical early stage of operation, 3) possible inadequate flow geometry in the device resulting in mass transfer resistance between the medium and the slices, 4) decrease in effective surface area of the slices, especially in OCTOPUS-III in which only one side of the slice faced the blood, and 5) in OCTOPUS-II, sagging of the slices due to the vertical position of the frames, with eventual reduction of effective surface area. Could a hepatic assist device utilizing liver slices be practical? Daily excretion of urea in dogs is 0.3-0.5 Gm/Kg((31)). Should the urea productivity in OCTOPUS-I(7.2 mg/Gm of liver/24 hrs) be successfully incorporated in a system, 600 Gm of slices can produce the amount of urea equivalent to the daily excretion in a 15 Kg dog. This volume of slices should not be considered unrealistic. Even though it is realized that in the practical situation 60% efficiency is expected, substitution of liver functions does not appear impossible. Further exploration for optimal conditions and practical considerations for improvement of devices will bring the goal closer to reality.

Animals↗
PubMedDate not supplied

Compliance effect on patency of small diameter vascular grafts.

The compliance mismatch hypothesis as a cause of failure of small diameter grafts was investigated using 4 mm internal diameter, 5 cm long Biolized polyurethane grafts. The luminal surface of 0.5 mm thick Biomer sponge grafts was covered with 100 microns of crosslinked gelatin. Compliance matched, and noncompliant grafts had in vivo compliance values of 13.5 +/- 2.89 and 1.0 +/- 0.7 X 10(-2%) per mmHg, respectively. In vivo compliance defined as 2 X dD/dP X 1/Do was measured in situ using the ultrasonic Hokanson probe. Compliance values of compliant grafts equaled that of the canine carotid artery at 100 mmHg mean arterial pressure. Grafts were implanted using an end-to-end anastomosis in 14 dogs for 6 wk. Patency rates for compliant vs. noncompliant grafts were 64% (9/14) and 50% (7/14). Compliance values for compliant grafts decreased to a mean of 7.14 X 10(-2%) per mmHg. Anastomotic intimal hyperplasia at the proximal and distal ends of compliant and noncompliant grafts measured 239.9 +/- 128, 197 +/- 129 microns, 338.9 +/- 273.6, and 304.3 +/- 179.3 microns, respectively. There were no significant differences in localized anastomotic intimal hyperplasia at either graft end for either graft type. This study did not show any positive effects of graft compliance.

Anastomosis, Surgical↗
PubMedDate not supplied

Articular cartilage contact pressure after tibial tuberosity transfer. A cadaveric study.

Medial transfer of the tibial tuberosity has been commonly used for treatment of recurrent dislocation of the patella and patellofemoral malalignment. In this study, six fresh human cadaveric knees were used. Static intrajoint loads were recorded using Fuji Prescale pressure-sensitive film for contact pressure and contact area determination in a closed kinetic chain knee testing protocol. Peak pressures, average contact pressures, and contact areas of the patellofemoral and tibiofemoral joints were calculated on native intact knee specimens and after tibial tuberosity transfer. All native intact knee specimens had a normal Q angle. Medialization of the tibial tuberosity significantly increased the patellofemoral contact pressure. Medial displacement of the tibial tuberosity also significantly increased the average contact pressure of the medial tibiofemoral compartment and changed the balance of tibiofemoral joint loading. The results of our study suggest that caution should be used when transferring a patellar tendon in the face of a preexisting normal Q angle as this will result in abnormally high peak pressure within the tibiofemoral joint. Overmedialization of the tibial tuberosity should be avoided in the varus knee, the knee after medial meniscectomy, and the knee with preexisting degenerative arthritis of the medial compartment.

Adult↗
PubMedDate not supplied

Isolated sectioning of the medial and posteromedial capsular ligaments in the posterior cruciate ligament-deficient knee. Influence on posterior tibial translation.

This study was undertaken to determine the contribution of various structures in the posterior cruciate ligament-deficient knee in resisting posterior tibial translation. With "isolated" injuries to the posterior cruciate ligament, the amount of posterior translation will decrease with the posterior drawer test as the knee is taken from neutral to internal tibial rotation. The present study was performed to conclusively determine the anatomic structure responsible for this clinical observation. The TestStar device was used to perform single-plane posterior drawer tests in 14 cadaveric knee specimens. The tests were performed with the knee in neutral tibial rotation and in 20 degrees of internal tibial rotation. The intact knee was tested and then the knee was tested after sequential sectioning of the meniscofemoral ligaments, the posterior cruciate ligament, the posteromedial capsule, and the superficial medial collateral ligament. With the knee in neutral rotation, posterior translation continued to increase as each structure was sectioned. With the knee in internal tibial rotation, posterior displacement was significantly less than in neutral rotation for each state until the superficial medial collateral ligament was sectioned; posterior translation was increased after its sectioning. Our data demonstrate that the superficial medial collateral ligament is the structure responsible for a decrease in posterior tibial translation in the posterior cruciate ligament-deficient knee.

Anterior Cruciate Ligament↗