Patent GB-1382527-A (GB)
Title: Electro -cardiographic patient monitoring and morphology recognition and method
IPC: G06F17/00
Filed: 1972-10-24
Abstract: 1382527 Electro-medical apparatus AMERICAN OPTICAL CORP 24 Oct 1972 [26 Oct 1971] 48999/72 Heading G1N The invention relates to operating a digital computer to monitor cardiographic waveforms from a plurality of patients, including a characteristic learning period for each patient. Monitoring depends broadly on the times peaks of (a) the waveform and the (b) differential of the waveform exceed certain threshold levels, and the relative timing of these peaks determines the patients characteristic. The threshold levels are continuously updated from a running average, and the results of current tests are compared with the learned characteristic in the computer. The ECG signals are fed through an analoguemultiplexer and A/D converter to the computer which scans the input under the control of a 1 KHz clock. Fig. 1 shows the OVERALL SYSTEM for monitoring 8 patients whose ECG's are fed to the multiplexer which is controlled by the 3-bit patient number appearing on line 24 to connect one of the eight inputs to the A/D converter providing an 8-bit output to eight gates 32 (only one shown). The patients number is fed to gates 34 which are "enabled" as each clockpulse triggers a flip-flop 60 and feeds the number to the computer. In a few micro-seconds the computer sends back the "done" signal to reset the flip-flop 60 "disabling" gate 34, and gate 32 is "enabled" to send a digital sample of the patients ECG to the computer. i.e. with eight patients, each ECG is sampled at 8-millisecond intervals. (As described octal code is used with the numbers 000-167 for positive data values and 200-337 for negative values with 170-177 reserved for patients numbers. Thus 170 is added to the patients number at adder 26). When the computer senses a non-characteristic waveform it actuates one of the eight recorders 14-0.. 14-7, which are fed through two-second delay-lines 12-0.. 12-7 to record the offending signal. It may also provide a "print-out". MONITORING PROCESS Although the processing is carried out in digital form with 8-millisecond sampling, it is explained more simply with reference to continuous curves in Fig. 2 with an ECG wave labelled FDP (having two VPB's at the end). Pulses A and B show the times during which the peaks exceed + and - threshold limits. The thresholds are a function of the average of the maximum signals. The DIFSUM signal is a trace of the differential of the ECG wave comparable to the digital DIFSUM signals developed in the computer and pulses D and C show the duration of peaks in excess of the thresholds. The codes below such as AD, C AD, BC show by their content and order of occurrence eight different  characteristic wave types. Computer print-outs are made especially for:- (a) deviations greater than 11% of the time between waves - routine RRP. (b) ENLRGD when the integral (area) of the wave is 25% greater than average - routine ARPI.  (c) UNLRND for waveform not previously learned - routine MRP. (d) MULTIPLE after detecting two premature beats - routine MPV. (d) FREQUENT for a large number of VPB's in one minute - routine FVP. (f) MULTIFORM for different forms of VPB - routine MFP. Fig. 3 (not shown) illustrates the order in which routines are carried out and their timing, and flow charts are provided for each sub-routine and the "Executive" programme, Figs. 4..25 (not shown). Specification 1304460 is referred to, as performing somewhat similar tests with individual monitoring apparatus for each patient.