12-Lead ECG modulator and demodulator equipment for telephony transmission

12 -LEAD ECG MODULATOR AND DEMODULATOR EQUIPMENT FOR TELEPHONY TRANSMISSION SL. To a l, B. La a Az n al; JM. Que o and L.G. F anquelo Depa men o Elec onic Eng inee ing, Un i e si y o Se ille A da. Camino de los Descub imien os, 41092, Se ille, Spain E-ma il: [email p o ec ed] T no: +34 954487371 Fax: +34 954487373 ABSTRA CT This pape desc ibes a eleassis en cy sys em ha consis s o a modula o equipmen o he acquisi ion. s o age and FM ansmission o he ypic al 12 lead ECG signals and a demodulalO equipmen o eco e ing he o iginal sig- nals in a medical ceme . Swi ched elephone ne wo k and GSM ne wo k can be used o ansmi he audio e- quency modula ed signal ca ying E CG In o ma ion. This p ojec h as been de eloped in collabo a ion wi h Teleasis- cencia Ca dio es . S.L. 1. INTRODUC T IO N Consume s a e dema nding mo e access o heal h in o - I na ion and mo e con enien hea l h ca e se ice. Pa ic- ula ly, people li ing in u al o emo e a eas la ck he ac- cess on u gen and special medical ca e . In hese cases, heal h insu a nce companies mus p o ide a medical as- sis ance wi hin a minimum dis ance . Besides, consume sa is ac ion in all e lemedicine p og am e alua ions has been e y high, Gi en he choice be ween con enience o elemedicine and a eling o see he consul an in pe - son. hey o e whelmingly choose elemedicine. I n his pape . we p opose a modula o and demodula - o equipmen o ECG ansmissIon . The link be ween he pa ien and he specialis is es ablished using a e- quency modula ed audiO signal ansmi ed by he ele- phone ne wo k. Figu e I shows he basic now o in o ma- ion. The emo e po i n (a pa ien , a non specialis doc o ) ca n connec wi h a medical cen e o ansmi he p e i- ously s o ed ECG signal using he ECG modulalO . The ECG demodula o o he hos cen e can eco e he o ig- inal ECG signal and hen a specialis can diagnose any hea dis unc ion. ". -a - 10 ---::---:-10 ... - REMOTE POINT MEDICAL CENTER Figu e I: Block diag am o ECG sys em The 12 -lead ECG equipmen is ac ually an expansion module o he basic equ ipmen desc ibed in {II. In nex 722 wo seClions. we explain he ha dwa e and so wa e o he ECC modula o and demodula o . Sec ion III shows he inal p olO ype and some esu l s, and inally conclusions will be poin ed ou in sec ion IV 2. 12·L EA D MOD U LATOR The 12 lead modula o eqUipmen mus op imize se e al es i c ions: a ea . powe consump ion and simul a neous acquisi ion. I mus be aken in o a cco um ha ECG signals mus be sensed and ampli ied by a ac o o 1000. Elec oca dio- g aphic signals ma y be co up ed by a ious kind o noise (21 . Typical examples a e : • Powe line In e e ence. I is he main sou ce o noise, because o he cables a ached o he 10 elec- odes. • Elec ode co n a c noise. I is a ansien in e e ence cause by he loss o con ac be ween he elec ode and he skin. • Mo ion a i ac s. I consis s o ansien baseline c hanges caused by chang es in he elec ode-skin impedance because o mo emen s o h e pa ien . • O he noise sou ces. The e a e se e al o he noise sou ces due o muscle co n a c ion. espi a ion o a- dio equency in e e en ces. To eco d an ECG an elec ic ci cui be ween he hea and he elec oca diog aph mus be comple ed. Fo his pu pose, elec odes a e placed on di e en pa s o he body su ace. Ten elec odes a e connec ed o he mod- u la o equipmen by means o cables: nine o hem a e Mexplo ing- elec odes while he las one is he e e ence placed on he igh leg. Depending on he posi ion o elec odes and he measu ed ec o s, we can di s inguish h ee g oups o ECG signals 131. • Bipola s anda d leads. Elec odes placed on he igh a m (RA), le a m (LA) and l e leg (LL) a e used o pi ck up he po en ial a ia ions on hese ex- emiCies. Bipola leads named dl. dIl and dIl l a e ob ained by eco ding espec i ely he po en ial di - e ences be ween LA and RA. LL and RA, and LL and LA. • Unipola ex emi y leads. Unipola ex emi y leads a e ob ained by eco ding he di e ences be ween RA. LA a nd LL a nd a poin n amed Wilson's cen al e minal. This poin is g i en by he s um o he po- en ials om RA. LA and LL. These leads a e known as aVR. a VL and aVF. • Unipo la p e co dial leads. The unip ola p eco dial ECG is ob ained by placing he explo ing el ec ode on hl:: classical six loca ions o he an e i o and le po ions o he ches . U nipola p eco dial l eads a e ob ained a~ h e di e ence be ween h ese six posi- ions and h e Wllson's cen al e minal. They a e p e ixed by he le e ~V~ o ll owed by numbe s 1 h ough 6. which indica e he co espo ndin g ches si es . The acquisi ion s age is pel o med by a low powe in- s um e n a ion ampli ie w i h a p og ammab le gain ac- O . ECG in e e ences a e e a ed in h e ollowing way: ,Jowe line in e e en ces a e a enua ed ha nk s o com- mon mode ejec ion a io (CMRR) o he ampli ie ; be- sides. a 50 Hz no ch il e is di gi a ll y jmplemen ed in he mi c op ocesso c hip . Inpu signals a e high pass il e ed o elimin a e ba se line c han ges. Finally, elec odes co n sis s o pa ch es wi h a conduc o gel ha gua an ees a good c on a c wj h he body su ace. I is a eq ui em en o h e p ojec ha h e 12 l eads mus be acqui ed simul aneousl y in en seconds. Tha m ea ns ha he inpu signals mu s be mul iplexed o he 8-bi analog o digi al con e e o he mic o-co m olle . Fi gu e 2 shows a bl oc k diag am o h e modula o equip- men . Using he ypical 10 elec odes, he 1 2- l ead ECG signals a e acqui ed in pa allel and hem mul iplexed o h e analog o digi al con e sion. Sa mpling equency is 100 Hz . The mic o-con olle (MC6 8L II om Mo o ola 141) s o es h e ECG signals usin g h e analog o dig i al co n- e e (10 seconds o each lead) In he R EG po si ion o h e eqU ipmen and sends h e modula ed ECG sig nals o he speake in he PLAY posi ion, showing he co espo nding ECG l ea d in a o u digi s alphanume ic dis pl ay . ~ ~-. - -, ~ ~ '-- --' "- u Figu e 2: Block di ag a m o he 12 -lead ECG modul a o 3. DEMODULATOR Figu e 3 Is a block diag am o h e demodula o equi p- men . The audio signal is ac qui ed and p eampli ied. Figu e 3: Block diag am o he ECG demodula o Then a equency- ol age con e e eco e he o iginal SignaL A e a il e s a ge. he ECG signal is digi ally co n- ened using he analog o digi al co n e e o h e mlc o- co n olle c i c ui . Finally. h e digi al signal is ansmi ed o a hos PC using a se ial RS-232 link o a in a ed link (l DA). The equipmen can wo k w i h ba e i es o a DC powe s up pl y. 4. PROTOTYPE AND R ESULTS The modula o equip men h as been di ided in an analog boa d and a digi al boa d. Figu e 4 is a pic u e o h e anal og boa d ( op iew). I includes he acquisi ion o he 12-1 ea d Signals. SMT co mp one n s allow o achie e size es ic ions. The e is a po en iome e o eac h Signal o se h e ze o alu e. Figu e 4: Modula o : analog boa d Figu e 5 shows he digi al boa d. I is based on h e mic o-con olle ci cui ha con ols he analog mul i - plexe s. he ou digi alphanume ic display and a low ba e y ci cui de ec o . Figu e 5: Modula o : digi al boa d Finally. igu e 6 is a pic u e o he demodula o equip- men . The boa d includes a DC powe supply (on he igh bo om pa o he pic u e) he p eampli ie and he e- quency o ol age con e e (on he le bo om) and he se ial connec o and he I DA Jed on he op o h e piC- u e. The mic o-con olle and he d i e o he se ial link a e placed on he o he la ye o he boa d. Figu e 6: Demodula o boa d An example he demodula ed signals a e shown in ig. u es 7 and 8. Pa Ucuia iy. ig. 7 shows he bipola and unipola ex emi ies leads, and ig. 8 shows unipola p e- co dJal leads. Ve ical axis is he cap u ed digi al alue ansmi ed o he PC. 5. CONCLUSIONS A el easis ency sys em o ECG signals has been de el- oped in collabo a ion wi h a medical cen e . The sys em co nsis s o a po able 12 l ead modula o equipmen , used by he pa ien o a non specialis doc o , and a demodula- o loca ed in his medical cen e . The main es ic ions a e ela ed w i h he modula o because i will be used by he pa ien . I mus be o educed size. wi h he maximum au onomy and use iendly. This equipmen can be use ul in emo e a eas wi hou a ca diology specialis and in manda o y mecl caJ e isions in ac o ies whe e hund eds o ECC mus be done. Simul- aneous acquisi ion o he 12 lead allows a eco d ime o en seconds o each e ision. 6. REFERENCES 111 S.L. To aI. J.M. Que o. M. Ele na P ez . L.G. F anquelo. Sl T Bo a d o Ac quisi ion o El ec oca diog aph Sig - nals and CSM T ansmission. P oc. DCIS·2000 .. Mon pellie . pp. 805- 814. No . 2000. 121 G.M. F iesen . T.C. Janne . M.A. Jadallah. S.L. Ya es. S.R. Quin and H.T. Nagle. A Compa ison o Noise Sensi iey o Nine QRS Decec ion Algo i hms. IEEE T ans . Biomed. Eng .. ol. 37. no. I. pp. 85-98. Aug. 1990. 131 J. W. Hu s and RC. Schlan . The Hea . McG aw- Hill. Heal h P o esions Di ision. 71h edi ion. 1990. 141 Mo o ola In c.. MC68HCll Re e ence Manual . Mo· o ola. Re . 3. 199 1. 724 " '" ~II "" ' 2SO "" ,- 200 -200 200 'SO • 'SO J I 'SO '00 -'00 '00 SO - SO SO " " " 2 2 .VR oVL ,VF 2SO • 2SO 2SO 200 -200 2bo 'so - 'SO I .I '" , oon, ' ' 00 ' 00 SO - SO SO " " , , , 2 , 2 ime ($) ime (5) MIe(s) Figu e 7: 12 lead EC G: bipola and unipola ex emi ies leads V. V2 V3 2SO - 2SO "" 200 200 200 'so - 'SO 'SO ' 00 -'00 '00 50 SO SO " , " 2 , , , 2 W V, V6 2SO 2SO 200 200 '50 'so ' SO '00 - "Xl '00 I SO - SO SO " , " , " , ime (5) ime (I) lime ($) Fi gu e 8: 12 lead ECC: unipola p eco dial leads 71'