A Virtual Instrumentation (VI) based system to acquire physiological parameters during

Virtual Instrumentation
A typical virtual instrumentation (VI) system provides all functionalities of an instrumented test system
effectively reducing the cost of realization. Most of the components of a VI are versatile and reusable
providing the system designer the flexibility in the use of the same components for a variety of
applications, there by reducing the over all cost per deployment. The look and feel of any real
instrumented test and measuring equipment can be created using the software, and an extent of
standardization is also possible taking the ergonomics and human factors engineering requirements
into consideration. In the present solution under discussion, all the steps involved in recording and
processing of the physiological signals, from setting the gain of signal conditioning amplifiers to
digitizing, displaying, recording and post processing the data, were implemented using Virtual
Instruments (VIs) on a Microsoft Windows XP platform.
National Instrument products used:
PXI-8186 PCI compatibly system controller
PXI-1042 Chassis with universal power supply
PXI-6220 DAQ Module
SCXI-1000 SCXI Chassis
SCXI-1520 Signal Conditioning Module
SCXI-1314 Terminal Block
Lab VIEW 7.1 Express.
Problem
Preclinical animal trial is an important phase in the evaluation for any medical device, especially for an
implantable life saving device like an artificial heart valve. The data generated during these trials form a
critical component of the preclinical data for establishing the safety and efficacy of the product. An
instrumented test system is to be designed and developed for use during the preclinical evaluation of
an artificial tilting disc heart valve being developed at SCTIMST. Monitoring and recording physiological
parameters such as blood pressure, ECG and heart valve sounds provide inputs on the condition of the
animal during and subsequent to the implantation of the device and provides information on the safety
and performance of the device under evaluation. The challenge was to develop reliable instrumentation
that can be quickly set up and used in a typical surgical theatre environment.
Solution
The instrumentation system was developed using LabVIEW software platform and data acquisition and
signal conditioning using hardware from National Instruments, USA. The hardware of the system was
designed around the PXI modular data acquisition chassis. A set of transducers were identified,
validated and incorporated into the system for converting the physical signals to analog electrical
signals. The signal conditioning module SCXI 1520 was handy to provide excitation to the transducers
as well as conditioning of the signals from them prior to being fed to analog to digital converters. The
system could acquire and record data in real time with good signal quality, and also make it available
later for offline processing using VIs developed for the purpose.
Introduction
Artificial heart valves are devices used for replacing the diseased or damaged natural valves of the
heart. In vivo implantation studies using suitable animal models is mandatory during the development
of such devices. Primarily, for obtaining regulatory approvals, a series of animal experiments need to be
conducted as part of establishing the preclinical safety and efficacy of the device. International
standards like ISO 5840: Cardiovascular implants – cardiac valves [1] provide the details on the
selection of animal models, planning and conduct of the experiments and data collection requirements.
Another important reason for conducting animal experiments is to observe and analyze valve function in
vivo [2]. The influence of the presence of an artificial device on the heart function