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PV-WAVE®
A wide range and a large quantity of data are collected in the experiments. PV-WAVE software is used to analyze this data, with its powerful tools for the presentation and analysis of data and the ability to integrate into existing experimental environments. In addition to the general data collected to identify a test subject, there are data recorded on tape during the tests. These can be divided into three types of signal: analog, serial and parallel. The largest proportion of signals are analogue and consist of continuous trial data such as electrocardiograms, blood pressure impedance and breathing. Serial signals include blood pressure values that are sampled automatically. Parallel signals show switch states in the test structure. The recording of 16 data-collection channels with 16-bit resolution and a sampling rate of 500 Hertz generates around 58 MB of data each hour. To process this, a powerful computer-aided data system was developed in Aachen. First, heart-rate-related real-time signal processing is required throughout the trial, allowing signals that illustrate critical conditions to be visible and recognizable immediately. This processing is used for the monitoring of signals on a real-time basis, for experimental monitoring and control. Data compression and simplification of measurement results for later analysis also occur at this stage. A parallel-processing computer system is used for this research (Hyperflo® by PCM, USA). The Hyperflo computer is a VME bus data flow computer with a range of interfaces for communication with the outside world. It consists of four multiprocessor boards, each with four CISC processors (MC68020), and one signal processor board with three RISC processors of the TMS320C30 type. Using the data collected, researchers can carry out investigations after the battery of tests is completed. This requires a large amount of memory and a broad range of processing tools for the display and statistical evaluation of the data. At the same time, high data security, high performance in graphical presentation and the preparation of signal-processing tools and statistical routines are required This analysis is not intended to take place locally in the cardiovascular laboratory but on a decentralized basis on other systems. A network connection is therefore provided between the various specialized systems. A further basic requirement is an efficient, standardized data format for storage, archiving and preparation of scientific reports in the form of tables and graphs. The system uses the hierarchical data format (HDF) developed by the National Institute for Super Computer Applications (NSCA) in the USA. Consequently, the users do not need to worry about problems of different data formats while processing data on different hardware platforms (IBM® PC, UNIX®, Macintosh®). The system is freely extendible. The Hyperflo system is connected via Ethernet in a client server architecture with a Sun ® workstation, on which the programs are developed for online analysis and the data stored. 4GL tools for program development PV-WAVE, which supports HDF format, was chosen for off-line analysis and for the development of the real-time programs running on the data flow computer. PV-WAVE is an integrated scientific program development environment, which has powerful presentation functions, efficient signal-processing tools such as filters and FFTs, numerical methods and optimized algorithms for the processing of large data matrices and supports extensive univariate and multivariate statistics. Also, there are tools for the preparation of Graphical User Interfaces (GUIs). The basic functions of PV-WAVE can be extended almost at will by adding procedures. The program already offers many of the most popular facilities for presentation, plotter output and analysis. Additionally, PV-WAVE is an open system; users can include analysis modules, which can be written in C. Real-time presentation and off-line analysis In a typical trial arrangement, analogue data are fed from measurement devices via an A/D converter into the Hyperflo computer. The resultant digital data is filtered and then prepared for the processors, which generate the graphical displays for real-time monitoring and provide outputs on monitors. The data are transferred at the same time via an Ethernet LAN to the Sun workstation, which makes the data available for off-line analysis in the client server architecture, in which IBM PC and Apple Macintosh computers are used. If the user now wants to penetrate directly into the heart of the data, he or she starts the analysis session via the PV-WAVE GUI. First, the user selects the type of visual presentation and the desired data parameters. The program offers an almost inexhaustible range of presentation forms from a simple table through pie and bar charts to multicolored 3D presentations. Certain colors can be allocated to limit values, so that if any of these values are exceeded, this can be seen immediately in the graphical display. Interaction with the data for simulation A particular benefit of PV-WAVE is the ability to interact with the data. The user can experiment on the basis of the real event by adding or changing parameters. The behavior of test subjects can be simulated under conditions that are either not possible or not desirable in the current trial arrangement. The user can change the settings at any time, alter the type of graphic, zoom in on particular areas and rotate. It is possible to carry out analysis even at a very early stage, store results on an interim basis, extrapolate and make comparisons. The software package provides a range of mathematical routines for this purpose. The data can be printed in any form, ready for publication, or imported into other program packages in order to use them as part of a presentation. The concept described here, which was developed especially for the requirements of a cardiovascular laboratory for aviation and space travel medicine, can also be used in other areas in which large quantities of data must be presented on a real-time basis, prepared graphically and analyzed. This is possible as the result of the four basic pillars of parallel preprocessing on a parallel process computer, client-server architecture using Ethernet LANs, standard data format and the use of a powerful high-level programming language (PV-WAVE). The widest possible range of uses is available as the result of the openness of the PV-WAVE basic system, which can run on all major operating system environments and process all conceivable data formats. Use in the cardiovascular system laboratory demonstrates how meaningful information can be derived from data in a short time, leading to correct decisions.
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