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Biomedical subjects

B G Min

Publications and source records attributed to B G Min.

14 recordsLinked to original sources
PubMed1992

Surface characteristics and blood compatibility of polyurethanes grafted by perfluoroalkyl chains.

Polyurethane (PU) surface was chemically modified by grafting of perfluorodecanoic acid (PFDA) to produce a highly hydrophobic surface to compare the blood compatability with hydrophilic poly(ethylene oxide) (PEO) grafted PUs. The advancing contact angle of modified PU-PFDA was increased up to 115 deg, while that of untreated PU was 86 deg. The PFDA grafted PU exhibited less adhesion and shape change of platelets than untreated PU, and the activated partial thromboplastin time (APTT) of PU-PFDA was considerably extended. The ex vivo occlusion time of untreated PU was only 50 min, but that of PFDA grafted PU was extended to 130 min, indicating that this hydrophobic surface is significantly blood compatible. It is interesting to find that the enhanced blood compatibility of very hydrophobic PU-PFDA was equivalent to hydrophilic PU-PEO.

Biocompatible Materials↗
PubMed1991

Negative cilia concept for thromboresistance: synergistic effect of PEO and sulfonate groups grafted onto polyurethanes.

In order to investigate the interaction between various sulfonated polyurethanes (PUs) and blood, a commercial PU surface was chemically modified by poly(ethylene oxide) (PEO), dodecanediol(DDO), and propane sultone to give hydrophilic, hydrophobic, and negative sulfonated surfaces, respectively. The blood compatibility of modified PUs was evaluated by an in vitro platelet adhesion test, activated partial thromboplastin time (APTT), and prothrombin time (PT) measurements as well as an ex vivo rabbit A-A shunt method. In the platelet adhesion test, the hydrophilic PEO grafted PUs showed less platelet adhesion than untreated PU and hydrophobic DDO grafted PU. Sulfonated PU-PEO exhibited a lower degree of adhesion and shape change of platelet. The APTT and PT, especially APTT, of the sulfonated PUs were extended, whereas those of PU-PEO and PU-DDO did not show any significant change compared with untreated PU. Meanwhile, in the ex vivo experiment, hydrophilic PEO grafted PUs showed longer occlusion times than untreated PU or hydrophobic DDO grafted PU. In addition, the incorporation of SO3 groups at the end of PU-DDO and PU-PEO, particularly PU-PEO-SO3, exhibited an enormous prolongation in occlusion time, indicating a synergistic effect of the hydrophilic PEO and the negative SO3 groups on thromboresistance. These occlusion times corresponded well to in vitro evaluation results: the less adhesion and shape change of platelet and the longer APTT and PT, the more extended the ex vivo occlusion time.

Animals↗
PubMed1978

A microcomputer-based data acquisition and analysis system for CO2 rebreathing studies.

A real-time microcomputer-based data acquisition and analysis system has been developed to automate the measurement of the ventilatory response to CO2 by the rebreathing method. Previous systems acquire the data on-line and then analyze and display the results off-line. The system described here performs all processing on-line and displays experimental results in real-time. The results of 5 min of data acquisition are available for display only 1.5 sec after completion of the experiment. Immediate interpretation of the results of each experiment enable a series of related studies to be performed on the same patient in a short time period. The microcomputer is Digital Equipment Corporation's LSI-11, a low cost 16 bit machine with the basic instruction set of a PDP-11/40. The system has 16 kbytes of memory, a CRT for data display, and a paper tape reader for program loading. Due to the time constraints of real-time processing and the memory constraints of a small system, the software is written entirely in assembler language. The software includes routines for numeric and character input, line and graphical output, linear curve fitting, start of rise detection and floating point computations.

Carbon Dioxide↗
PubMedDate not supplied

Image restoration of digital radiography using dual sensor Wiener filter.

A dual sensor Wiener filter (DSWF) technique was used to improve the image quality of a scanning type digital radiographic system. In a digital radiographic system, image quality is evaluated by resolution and SNR (signal-to-noise ratio), which are two important parameters representing the objective performance of the system. In this method, when two images are acquired in the same region using two sensors with different characteristics of resolution and SNR, they are processed simultaneously using DSWF, which is the extended concept of a Wiener filter to two dimensions. DSWF uses the cross power spectrum between dual sensor outputs of the same chest radiographic image in the design of filter parameters. It has been implemented with fast algorithm using FFT (fast Fourier transform). The performance of the proposed method is compared with that of conventional methods (Wiener filter and parametric projection filter). In simulation studies, it is shown in 12 cases that this new method has SNR improvement of 1-2 dB better than conventional methods.

Humans↗
PubMedDate not supplied

Cardiac output regulation in the moving actuator total artificial heart without a compliance chamber.

A new cardiac output regulation method for the moving actuator total artificial heart (TAH) has been developed without using an extra compliance chamber or any transducer. The left and right ventricular sacs are alternately pumped by the pendulous moving actuator, with the left sac attached to the actuator and a free right ventricle. Preload sensitive cardiac output response is achieved by adjusting heart rate just below the level needed to generate atrial collapse, while maintaining full-fill and full-ejection conditions. The motor current waveform analysis detects mild atrial suction related to the amount of venous return. In addition, the structural characteristic of the pendulous moving actuator allows for manipulation of the left and right ventricular output difference by adjusting the asymmetry of stroke angle to either the left or right. In mock circulatory system tests, cardiac output increased from 5 to 9 L/min, with left atrial pressure (LAP) maintained at approximately 5 mmHg higher than right atrial pressure (RAP) over a physiologic range of preload (0-12 mmHg of RAP) and afterload [80-120 mmHg of aortic pressure (AoP)].

Algorithms↗
PubMedDate not supplied

Development of a totally implantable total artificial heart controller.

Using a one chip microcontroller, 87C196 (One chip EPROM), and an erasable and programmable logic device (EPLD), an implantable control system to drive a pendulum type electromechanical total artificial heart was developed. This control system consists of four parts: a main management system, a motor driver with power regulator, a state monitoring system, and a communication portion. The main system has a speed detector, proportional and integral (PI) control, pulse width modulation (PWM) generation, serial communication, and an analog data processor. Two kinds of power system are used, separated by eight photocoupler arrays to improve system stability. When the performance of each compartment was compared with that of the previously used Z80 microprocessor based control system, good correspondence was shown. Logic power consumption was reduced to one third that of the previous controller. Using mock circulation tests, the overall performance of the control system was evaluated.

Blood Flow Velocity↗