ISSN:0363-8855    

出版商:OVID    

年代:1989

数据来源: OVID

ISSN:0363-8855    

出版商:OVID    

年代:1989

数据来源: OVID

ISSN:0363-8855    

出版商:OVID    

年代:1989

数据来源: OVID

ISSN:0363-8855    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

This paper reviews the in-vitro engineering testing of prosthetic heart valves. Although final assessment of prosthetic heart valve performance must come from the results of long-term clinical implantations, the initial in-vitro evaluation of a new design can be obtained from appropriate, well-designed laboratory tests. In-vitro testing can reveal valuable information for both the cardiac surgeon and the valve designer, and can also indicate weaknesses in basic design, functionality and materials. In-vitro engineering testing may be categorized in three basic steps: (1) steady-state flow studies; (2) pulsatile flow condition studies; and, (3) fatigue life studies. All three test steps are discussed here, as are the test fluid and test chambers.The essential characteristics of an ideal prosthetic valve are described and the basic advantages and disadvantages of mechanical and biological valves are presented. Criteria for the design of an adequate pulse simulator system are discussed, as are criteria for accelerated valve fatigue testing for durability. It is noted that while the data from in-vitro tests cannot necessarily be extrapolated to predict in-vivo performance, the test results are nevertheless essential to prosthetic valve development.

ISSN:0363-8855    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

This paper describes a system for the diagnosis, monitoring and prediction of perinatal conditions built around the fetal topogram. An ergonomic display is presented, which is a new method for rapid display of the information contained in the fetal heart rate (FHR) and maternal uterine pressure (UP) signals. The additional use of diagnostic algorithms can allow both interpretation of the response to individual contractions and prediction of the child's Apgar rating if born within half an hour. This prediction is estimated on the basis of the dip sentence (the sequence of FHR responses to the UP), and a correction for antenatal and perinatal risk factors. A primary objective of the design was to interface efficiently with the clinician. The display comprises two separate screen layouts, one summarizing information on the current contraction and the other presenting the course of labor since the commencement of monitoring.

ISSN:0363-8855    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Impedance pulse sensors, suitable for long-term implantation, were developed and tested for diagnostic applications. This report describes the application of these sensors to the determination of systemic blood pressure in dogs. These periarterial, impedancesensing electrodes virtually eliminate the problems of blood sepsis, hemorrhage, and fibrosis or thrombosis formation with embolization. Over short periods of time (several minutes to a few hours), the relationship between blood pressure and the reciprocal of pulse transit time is linearly proportional to diastolic pressure in the physiologic range. However, usefulness for beat-to-beat determination of blood pressure is limited by the need for frequent calibration due to changes in slope of the regression relationship between pressure and the reciprocal of pulse transit time in an artery.

ISSN:0363-8855    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

This paper describes a computerized system for clinical investigations in cardiac electrophysiology. The following instrumentation sections are outlined: the interface between the instrumentation and an Intel System 310, the stimulator, and the amplifiers. This system provides a maximum of eight measurement and stimulation channels. Each channel amplifier is essentially composed of one preamplifying and two amplifying stages. Real-time controls are provided for the amplitude of the signal from the two amplifiers. In addition, control and correction of the offset at the output of the amplifier and the preamplifier are provided.

ISSN:0363-8855    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

In this brief paper, the author analyzes the nationwide 1985Journal of Clinical Engineeringdepartment survey data and 1988 Pennsylvania data in relationship to clinical or biomedical department staffing. The 1988 Pennsylvania data yield a relationship between the total facility engineering department staffing and the hospital bed count. The 1985 journal survey data provide relationships between the smaller clinical/biomedical staffing and bed count, number of devices, and budgets. While the linear correlation coefficients were higher for the Pennsylvania total facility engineering department data, none of the relationships presented here should be considered to be absolute predictors. Departments differ in their responsibilities, work load, and types of equipment serviced. These differences make absolute analysis or prediction of staffing problematic. The results presented here may be useful, however, as general indicators when applied with caution.

ISSN:0363-8855    

出版商:OVID    

年代:1989

数据来源: OVID

ISSN:0363-8855    

出版商:OVID    

年代:1989

数据来源: OVID