Search PubMed⌕ Search

Biomedical subjects

W Smith

Publications and source records attributed to W Smith.

401 records · Page 23Linked to original sources
PubMedDate not supplied

Nonpulsatile ventricular assist bridging to transplantation.

Six patients accepted into a cardiac transplantation program have been supported with a Biomedicus LVAD. Five of the six patients deteriorated while awaiting a donor organ; the sixth was being supported with a device following mitral valve surgery and showed no recovery of ventricular function. In all cases the device was used only after all other therapeutic modalities had failed. The periods of support ranged from 2.5 to 31 days, mean of 10 days. Three patients underwent cardiac transplantation and all three have been discharged and are well. The three survivors were supported for 2.5, 3, and 31 days. Three deaths occurred in the patients supported for 5, 9, and 15 days, the causes being sepsis, massive cerebral embolism, and respiratory failure. Patients were for the most part maintained with some degree of heparinization, and hemolysis was a significant problem in only one patient and associated with a very small arterial return cannula. Flows were routinely maintained above 2.4 L/min/m2, and all showed recovery of other organ functions while being supported. The patient supported for 31 days was capable of limited mobilization by use of the removable drive system. The Biomedicus LVAD represents a relatively inexpensive support modality for patients awaiting cardiac transplantation.

Adult↗
PubMedDate not supplied

Hemolysis. A comparative study of four nonpulsatile pumps.

Hemolysis is one of the important performance parameters of blood pumps. However, comparisons of published data are compromised by the different test methods used. This article reports the results obtained when testing four nonpulsatile blood pumps (Roller pump, Biopump Model 600, Biopump BP-80, Hemadyne pump) in the identical test circuit under the same hemodynamic conditions. A closed test circuit was composed of a flexible bag reservoir and two short tubes for connection to the pump head. The priming volume was 1 L, and the total surface area was 950 cm2. Fresh blood from a fasted calf was directly primed into the circuit and maintained at 37 degrees C. It was pumped at 6 L/min for 12 hr against a 100 mmHg afterload. The hemolysis index (HI), defined as grams of hemoglobin released per 100 L pumped, was calculated from a curve fit to the hourly data. Each pump was tested five times. The mean HI obtained ranged from 0.0467 for the roller pump to 0.0076 for the Biopump BP-80. There was no statistically significant difference among the three centrifugal pumps tested.

Animals↗
PubMedDate not supplied

Comparison of retention and release periods for implant overdenture attachments.

The aim of this study was to compare the retention and release periods of the Nobel Biocare bar and clip (NBC), Nobel Biocare ball (NB), Zest anchor (ZA), Zest magnet (ZM), and Sterngold ERA (SE) attachments on an implant-retained overdenture model. The attachments were tested using two permanently placed Brånemark implants on a test model that was attached to an Instron machine (cross-head speed 50.8 mm/minute). Each attachment had one part embedded in a denture-like housing, and the other part screwed into the implants. Dislodging tensile forces were applied to the housings in two directions simulating function: vertical and oblique. Eight tests were done in two directions with three samples of each attachment. The dislodging forces generated measurements of the peak load, break load, and displacement at peak load and break load. Release periods were calculated using displacements between the peak load and break load and the cross-head speed. Results showed the NBC to be significantly most retentive for the break load when subjected to vertical and oblique forces with mean values and standard deviations of 2104.5 +/- 506.7 g and 1958.1 +/- 165.4 g, respectively. Next most retentive was the SE, followed by the ZA and NB. The ZM was significantly least retentive (127.8 +/- 7.0 g and 143.5 +/- 19.7 g). For the release period, results showed the NBC to have significantly the fastest release period for vertical and oblique forces (1.86 x 10(-3) and 7.35 x 10(-4) minutes). The ZM significantly had the slowest release period for those forces (3.02 x 10(-2) and 2.35 x 10(-2) minutes). The data suggested that the NBC could be selected when a higher degree of retention and fast release period are desired. The next most retentive was the SE; ZM was the least retentive and had the slowest release period.

Dental Abutments↗
PubMedDate not supplied

Condition monitoring of rotary blood pumps.

Long-term, trouble-free operation of ventricular assist devices (VADs) is critical to the patient. A catastrophic failure of the VAD could cost the patient's life, thus defeating the purpose of the device. The targeted 90% 5 year reliability also implies that the average device life would exceed the 5 year limit. Time based explantation of the device after the fifth year will replace many devices with significant additional life, subject the patient to unnecessary surgical risk, and increase costs. To preclude the need for time based replacements and prevent catastrophic failures, a condition monitor is proposed in this article for early detection of faults in VADs. To develop this monitor, the effectiveness of various sensing and monitoring methods for determining the VAD condition is investigated. A Hemadyne pump was instrumented with a set of eight sensors, and a series of experiments were performed to record and analyze signals from the normal and abnormal pumps with five different faults. Statistical, spectral, envelope, and ensemble averaging analyses were performed to characterize changes in sensor signals due to faults. Experimental results indicate that statistical and frequency information from the acceleration and dynamic pressure signals can clearly detect and identify various VAD faults.

Biomedical Engineering↗