A QRS PreprocessorBased on DigitalDifferentiation

Digital preprocessors caneasetheincreasing data collection demandsplaced onreal-time computers inpatient moni- toring. Thispaperdescribes apreprocessor thatdetects inreal time anelectrocardiogram QRScomplex andcomputes theR-Rinterval. Detection isperformed using multiple digital differentiation, which isencouraging asanultrareliable meansforlocating theQRS.In- herent inthetechnique isadependable control thatcanautomati- cally compensate forsignal-level variations. Clinical datademon- strate thatdetection isinsensitive tolow-andhigh-frequency noise, frombaseline drift tomuscle artifact andcautery bursts. Thedevice canbeconnected directly toapatient, whosesafety isguaranteed by optoelectronic isolation andinterelectrode current limiting. Pre- processor operation hasbeenhuman-engineered toasimple on/off procedure. SIGNALPROCESSING C URRENT trends inmedical research include the detailed studyofphysiologic parameters during varied disease states. Thisenormoustaskis usually attacked withsomeformofdatalogging and analysis equipment, whichquite frequently isadigital computer. Real-time computers will, however, soonbe- comesaturated astheir workloadincreases duetothe continual addition ofanalytic procedures. A practical solution, without restricting thegrowthofanalytical procedures, isdatacompression, whichcanreducethe rawdataburdens thattaxacomputer's efficiency. One technique, called preprocessing, isdesigned toextract themostpertinent characteristics frombioelectric sig- nalsandperform routine buttime-consuming data manipulations external toacomputer. Functioning in multiple-bed environments, thetechnique isexpected togreatly facilitate patient monitoring andreal-time analyses. Preprocessing mustoccurinrealtimesothatthe computer system cancollect otherreal-time datathat maybetime-locked tothepreprocessing results. Ap- plied tocardiovascular monitoring, dataacquisition can besynchronized withtheoccurrence oftheelectro- cardiogram QRScomplex. Several QRS detectors re- ported (I)- (31 donotfulfill therequirements forapre- processor withrigidly defined detection criteria. This paperdescribes a digital instrument thatlocates the QRS inrealtime, computes theR-R interval, and validates thepresence orabsence ofventricular con- tractions.