ECG Acquisition in a Computer - ECG Acquisition and Automated Remote Processing - page 74

FM Modulator 1

Hardware
acquisition
Module

Telephone link

FM Modulator 1

FM Modulator 1

Patient

Demodulator 1

Analog
MUX

Comm.
interface

ADC

Demodulator 2

Modem

Demodulator 3

Receiving end computer Sampling pulses

from controller

Fig. 4.1 Block schematic of an analog ECG communication system

Tele-ECG applications can be broadly classified based on certain factors, viz.,
distance of transmission, mobility of the patient and doctor, continuous or inter-
mittent monitoring etc. For short-range communication like patient monitoring in
hospitals, embedded systems and low-range radio transmitters are used for real-
time ECG transmission. A typical tele-ECG setup consists of three basic functional
modules, viz., patient data collector, communication interface, and communicating
device at the transmit end. A similar structure with corresponding complement
functional blocks at the receiving end completes a computerized acquisition. The
patient ECG is collected through a hardware acquisition module (HAM), which
consists of lead connectors, ECG amplifiers, filters, isolation circuits followed by a
DSP-based microcontroller unit (MCU). Its function is to condition the low-
amplitude ECG signal, digitize it and then supply the samples to the communi-
cating device using a suitable protocol. The communicating device may be a
mobile phone, PDA, or computer. It applies a data compression algorithm, encodes
the compressed data, and finally transmits. Sometimes, the MCU of the HAM
performs the compression and source encoding function and directly feeds the data
stream to the transmitter module. Works on such prototype system using portable
stand-alone embedded systems and low-power commercial FM transmitters are
available in the literature. Like, in [ 5 - 7 ], the authors report an 8051 MCU using
with FM/FSK transmitter for ECG transmission. In similar applications [ 8 ], NI
DAQ cards are used for direct acquisition of received data in a laptop or PC along
with some processing [ 9 ] capability.