QUICK FACTS
Researchers at RWTH in Aachen, Germany are using PV-WAVE to analyze cardiovascular data collected in experiments. The primary goal of conducting these tests is to understand the performance of human cardiovascular systems under the extreme conditions that occur in air and space travel. With PV-WAVE they have the ability to interact with data and the user can experiment on the basis of a real event by adding or changing parameters.

THE PROBLEM
The Cardiovascular Laboratory at RWTH Aachen, Germany, investigates the performance of human's cardiovascular systems under the extreme conditions that occur in air and space travel. Test subjects undergo a series of tests to establish whether they would survive the stresses that occur. In a typical test, the subject’s cardiovascular system dynamics are analyzed as the prospective pilots and astronauts are strapped to a table, which is then tipped from the horizontal to the vertical and back again. In other tests, they are spun around in a centrifuge to determine their body's reaction to conditions of simulated weightlessness. They are also exposed to various temperatures and pressures.

A wide range and a large quantity of data are collected in these 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 signals: analog, serial and parallel. The largest proportion of signals is analogue and consists 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 approximately 58 MB of data each hour. To process this information, 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.

THE SOLUTION
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, therefore, a network connection is provided between the various specialized systems.

Another 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). 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. It 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.

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.

Typically, analogue data are fed from measurement devices via an A/D converter. The resultant digital data is filtered and then prepared for the processors, which generate the graphical displays for real-time monitoring. The data are transferred at the same time via an Ethernet LAN to the Sun workstation, which makes the data available for offline analysis in the client server architecture, in which IBM PC and Apple Macintosh computers are used.

If users then want to view the heart of the data, they start 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 multi-colored 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.

RETURN ON INVESTMENT
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.

WORLD CLASS PRODUCTS, SERVICES, AND SUPPORT
Visual Numerics has provided technical software solutions for numerical analysis and visualization for over 30 years. The company's software products help users understand complex data from a variety of sources and build business-critical applications. Visual Numerics offers two product lines: the IMSL® Numerical Libraries for powerful mathematical and statistical analysis and the PV-WAVE® visual data analysis development environment. Visual Numerics also offers customized consulting services for applications that involve mathematical, statistical, or visual data analysis to meet today’s business analytical needs.