Biomedical subjects

B A Weber

Publications and source records attributed to B A Weber.

42 records · Page 3Linked to original sources

PubMedDate not supplied

The composite Corethane/Dacron vascular prosthesis. Canine in vivo evaluation of 4 mm diameter grafts with 1 year follow-up.

Polyurethane vascular prostheses offer the potential of superior thromboresistance and reduced anastomotic hyperplasia compared to existing Dacron and ePTFE alternatives, but have suffered from susceptibility to biodegradation, with resulting mechanical failure. To address this problem, the authors have developed and evaluated a composite prosthesis comprised of: 1) an inner blood interfacing elastomeric porous membrane made from Corethane, a proprietary Shore 80A polyurethane like material substantially devoid of ether/ester linkages, with superior biostability over conventional polyether urethanes, spun into a nonwoven structure with fiber diameters 10-15 microns and pore sizes 30-60 microns filled with gelatin +/- heparin; and 2) an outer soft, tissue interfacing, warp knitted Dacron mesh bonded to the inner layer to assure long-term dimensional stability. Twenty 4 mm ID x 5 cm L composite prostheses, half with heparinized gelatin (the remainder nonheparinized) were implanted as femoral interposition grafts in 10 dogs. Four of the 10 nonheparinized grafts occluded. All 10 with heparin remained widely patent, with two explanted at 6 months showing vascularized connective tissue growth through the graft, in contrast to the giant cell inflammatory response to the Dacron mesh, with a substantially endothelialized neointima and no Corethane biodegradation. Of the 10 patent grafts at 1 year follow-up, none showed aneurysm formation. This vascular prosthesis provides compliance superior to ePTFE and Dacron alternatives, with excellent suture retention and good kink resistance, while combining the superior thromboresistance and tissue ingrowth properties of polyurethanes with the proven biostability of Dacron.

Animals↗

PubMedDate not supplied

Effects of increased stimulus rate on brainstem electric response (BER) audiometry as a function of age.

The purpose of this investigation was to describe the effects of rate of stimulus presentation on the brainstem electric response in groups selected as models for such brainstem disorders as demyelinating diseases and focal lesions. Two groups, infants and geriatric adults, were chosen as models because of their known neurological differences from a normal young adult population. Three groups of eight subjects each; infants, geriatric adults, and young adults were tested using routine brainstem electric response techniques with four rates of click presentations. Using the wave V latency at the slow rate (13/sec) as base line, three latency shift scores were obtained for each of the three fast rates (33/sec), 50/sec, 67/sec). Analysis of the data revealed greater shifts for infants and geriatric adults than were present for the young adults. The experimenters concluded that the imposition of a fast rate of click presentation offers a promise as a clinical tool for the discovery of brainstem differences.

Adolescent↗

PubMedDate not supplied

A compliant Corethane/Dacron composite vascular prosthesis. Comparison with 4-mm ePTFE grafts in a canine model.

We have developed a composite vascular prosthesis with the inner blood interfacing layer made of a porous elastomeric membrane of spun Corethane fibers (10-15 microns in diameter, pore size 30-60 microns) impregnated with a gelatin-heparin complex and an outer soft tissue interfacing warp knitted Dacron sheath. Forty-eight Corethane/Dacron composite (CDC) vascular grafts, 4 mm in diameter and 5 cm in length, and 48 expanded polytetrafluoroethylene (ePTFE) vascular grafts of similar size were implanted bilaterally as end to end interposition grafts on opposite sides in the carotid and femoral arteries in dogs on low dose (162 mg/day) aspirin. Patency at 3 months was 37/48 (77%) for the ePTFE grafts and 44/48 (91.7%) for the CDC grafts. Fisher's exact test (two-tailed comparison) indicates the probability of superior CDC graft patency to be 95.5%. In the seven pairs of grafts in which one graft was occluded and the contralateral graft of another type was patent, the CDC graft was patent and the ePTFE graft was occluded in every instance. Explant histology and scanning electron microscopy showed greater collagenization, less residual platelet-fibrin and red blood cell deposits, and more frequent mid-graft endothelialization in the CDC grafts than in the ePTFE grafts.

Animals↗

PubMedDate not supplied

Brainstem wave V latencies to tone pip stimuli.

The present study was undertaken to examine the feasibility of using tone pip stimuli rather than conventional clicks in brainstem evoked response (BER) audiometry. Trains of 2000-Hz tone pips, 4000-HZ tone pips or clicks were presented at seven intensity levels to six normal young adults. Results demonstrated that BERs can be readily elicited by tone pips. This latter finding may be attributable to the differences in stimulus rise times. Tone pips appear to introduce greater frequency specificity to BER audiometry without a marked loss in the ability to elicit the response.

Acoustic Stimulation↗

PubMedDate not supplied

A Corethane/polyester composite vascular prosthesis for vascular access. Comparison with expanded polytetrafluoroethylene grafts in a canine model.

An important need in hemodialysis is a self-sealing prosthesis for vascular access with at least equivalent patency and biostability to expanded polytetrafluoroethylene (ePTFE) alternatives. The authors have developed a Corethane/polyester composite (CPC) graft with an inner blood interfacing layer of spun Corethane fibers (10-15 microns diameter; pore size 30-60 microns) impregnated with a gelatin-heparin complex and an outer soft tissue interfacing warp-knitted polyester sheath. Twenty-six CPC grafts (6 mm internal diameter; 25-30 cm length) and eight Gore-Tex ePTFE grafts (same dimensions) were implanted as femoral artery-to-vein shunts in dogs on low dose (162 mg/day) aspirin, and subjected to weekly dialysis needle punctures for up to 52 weeks. Patency was 73% (19/26 with 15 at 52 weeks) for the CPC grafts and 63% (5/8 at 52 weeks) for the ePTFE controls, with more favorable healing (e.g., less extensive mural thrombi) of the CPC grafts. The hemostasis time per needle pair after removal (3.1 min mean for CPC versus 21.2 min mean for ePTFE) and the blood loss in achieving hemostasis (5.7 g mean for CPC versus 47.9 g for ePTFE) documented the significant (p < 0.0001) performance advantages of the CPC prosthesis.

Animals↗

PubMedDate not supplied

Brainstem evoked response (BER) audiometry at various stimulus presentation rates.

The utilization of the latency of the brainstem auditory evoked response to estimate the status of high frequency hearing is rapidly becoming a part of the audiologist's clinical armamentarium. Because it is important to utilize the most efficient rate of stimulus presentation, the present investigation was undertaken to provide some initial latency information for three commonly used stimulus rates. Brainstem auditory evoked responses were recorded from 22 adults for three click rates (13.3/sec, 33.3/sec, and 67/sec) at seven intensity levels (10 to 60 dB sensation level). It was shown that rate of click presentation markedly affects the intensity-latency functions for wave V. In clinical use, norms must be established for each stimulus rate used to maximize the accuracy of the test results.

Acoustic Stimulation↗