Interfacing the IBM-PC to Medical Equipment: The Art of Serial Communications

RWD Nickalls and R Ramasubramanian


Reviewed by:
D. John Doyle, MD, PhD, FRCPC
The Toronto Hospital

Introduction

modified from the authors' preface

Most of the monitoring equipment used in hospital medicine has a serial interface, and thus data can be accessed directly by a personal computer (PC), processed, and stored on disk. Conversely, many items of medical equipment can also be controlled directly by a PC via the serial interface.

The range of such equipment is growing each year, and currently includes pulse oximeters, non-invasive blood pressure machines, syringe drivers, infusion pumps, spirometers, ventilators, and anesthesia monitors.

Although most of these devices are used extensively in the fields of anesthesia, intensive care, and respiratory medicine, there is an increasing use of many of them in other fields. For example, pulse oximeters are now widely used to monitor patients on both medical and surgical wards; they are also appearing in dental clinics using sedation. In addition, non-invasive blood pressure monitors and spirometers are appearing increasingly in general practitioner clinics.

However, serial interfacing to such equipment tends to be under used and very poorly documented. Furthermore, information regarding the serial interface is widely dispersed throughout a myriad of texts and published articles as well as in unpublished coprorate technical notes and on electronic bulletin board systems.

This book represents an attempt to bring together both the details of serial communication as they relate to IBM-compatible PCs, and the challenges of interfacing to specific items of medical equipment.

Part I of the book addresses the serial interface, including the RS-232 Standard, transmission of data, and an introduction to serial-interface programming using Microsoft QuickBASIC.

Part II addresses a number of related topics, such as electrical safety, analysis of data, and the use of Kermit serial communications protocol.

Part III considers the practical aspects of interfacing an IBM-compatible PC to a range of equipment found principally in medicine and physiology, and includes example programs for collecting data, and in some cases, for controlling the equipment directly.

The Appendix includes a glossary, as well as sections on binary and hexadecimal notation, the ASCII code, pin-outs of serial connectors, programming information, key codes, the null modem, and a note on using the freeware package GNUPLOT.


THE PROGRAMS

All programming examples have been written in QuickBASIC 4.5 since not only is it one of the most popular compiled BASICs, but it is also particularly well suited for measurement and control applications involving the serial interface. In addition, since QuickBASIC is very similar to the interpreted QBASIC which comes as standard with MS-DOS 5.0 or greater, most of the example programs will also run using QBASIC. Furthermore, a QuickBASIC program can be modified for use with Visual Basic. (n.b. A recommended tutorial for users new to QuickBASIC is Using QuickBASIC 4.5, Second Edition, by Don Inman and Bob Albrecht. The book is published by Osborne McGraw-Hill.)

Although an elementary grounding in BASIC programming will be an advantage when reading this book, prior experience with QuickBASIC or QBASIC is not strictly necessary. However, newcomers to programming will need to have a QuickBASIC manual near by.

All the example programmes have been written with the beginner in mind and are fairly simple; they are not meant to be comprehensive `all singing, all dancing' programmes. They are simply meant to illustrate one way of either accessing the data, or controlling the device, and the reader is expected to modify and expand the programs as necessary to suit his or her particular requirements. For example, while an item of equipment may output several groups of data, the example program may well only demonstrate how to access one particular group of data.


ASSESSMENT

This is a remarkable book that will serve as a "goldmine" for anyone who wants to interface medical equipment to their PC. It will have special appeal to researchers or clinicians wanting to explore new methods of on-line data analysis or to simplify the collection of data for clinical trials.

Not suprisingly, the book has a distinct British flavor. For example interfacing to the Ohmeda 9000 syringe pump is covered in detail, but this particular unit is not generally available in North America. Similarly, Abbott volumetric pumps, popular in North America, but less so elsewhere, are not covered at all. The programs appear to be well-structured, with appropriate use of indenting and other techniques to provide clarity, and are well-commented throughout.

As valuable as this book is, it will appeal only to a minority of clinicians; those that think that a "bus driver" is what takes their children to school each morning may have some extra reading to do to take full advantage of this book. While I would not recommend this book to be in every anesthesiologist's library, it clearly should be in every university library and every biomedical engineering departmental library.


RWD Nickalls and R Ramasubramanian: Interfacing the IBM-PC to Medical Equipment: The Art of Serial Communications. London: Cambridge University Press, 1995, ISBN 0-521-46280-0 hardback; 402 pages.