CA1326553C - Combined pacemaker parameter and vital sign monitor - Google Patents

Abstract

ABSTRACT
A portable combined pacemaker parameter and vital sign monitor which acquires data relating to a patient's ECG wave form and pacemaker wave form by means of electrodes (20-23) and displays the derived wave forms on self contained display means (31). The monitor also stores data derived from the wave forms for subsequent recall and analysis. The monitor displays wave form information in such a way that the relationship in time between the ECG wave form and the pacemaker wave form is immediately clear to a user. The monitor is particularly useful for the portable measurement of ECG and/or pacemaker wave forms and for the ongoing analysis of the condition of a working pacemaker in vivo.

Description

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-` 132~

C~MBINED PACEklAKER PARAMEJER AND VITAL SIGN MONITOR
Field of ~he Invent~on The present lnvent~on relates to a hand held 1nstrument wh~ch comblnes a pacemaker monitor and an ECG mon~tor ~nto a single hand held unlt.
Background of the Invent~Qn Prlor art equlpment has measured pacemaker electr~cal pulse rate, the pulse wldth and ~n the case of dual-chamber pacemakers ~wh~ch have two sources of electrtcal pulses) the ~nterval between the two pulses 10 Stermed the A.V. lnterYal). These are typ~cally displayed as numeric informat~on w~th no accompany~ng ~nformat~on concerning the pat~ent s physiolog~cal state be~ng measured or d1splayed at the same t~me.
The most relevant of the prior art patents/patent applications known to the appllcant ls Austral~an Patent Appllcation AU-A 44712/85 to lS Purdue Research Foundatlon publ~shed on 16 January 1986. Thls c~tatlon clearly dlscloses a portable monltor wh~ch prov~des ECG wave form lnformation to a user by means of a hand held monltor which can be appl~ed dlrectly to the sk~n o~ the human thorax. The dev~ce of the citat10n, however, does not contemplate ~n any way the comblning of ECG
20 wave form display together w~th sens~ng and display of pacemaker wave form ~nformat~on.
- At least a preferred embodiment of the present inventlon seeks to comblne pacemaker parameter measurement and phys~ologlcal v~tal signs measurement ~nto a s~ngle portable un~t. It ~s a further ob~ect of the 25 preferred embod~ment to d~splay the shape of the paclng pulses which provlde the doctor with further valuable 1nformatlon about the performance of the pacemaker and may warn o~ problems wlth the pacemaker lead whlch connects the pacemaker to the heart since the pacemaker pulse shape normally varies with the lead lmpedance.
Summary o~ the Inventlon In accordance wlth one aspect o~ the present ~nvention there is d~sclosed a portable, hand held mon~tor for monitor~ng and d~splaying s~multaneously pacemaker parameter ~nformatlon and v~tal s~gn parameter informat~on~ sa~d mon~tor compr~s1ng:
a hous~ng of a s1ze and shape that can be easlly held ln a user s hand;
data ~cq~lsit10n means mountsd on the hous1ng for recelvlng electr~cal s~gnals from a sk~n contact regton o~ a pat~ent, the electr~cal slgnals belng representat~ve of pacemaker parameters lnclud~ng ama/0873E -~, ,~ ~J

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~32~3 pacemaker pulse waveform and at least one from parameters 1ncludlng pulse rate pulse wldth pulse ~nterval AV interval or Atr~al and Ventr~cular pulse d~scrimlnat~on and sa~d electrlcal slgnals further belng representatlve of vltal sign parameters lnclud~ng at least heart rate and ECG wave forms;
data process~ng means prov7ded wlthln the houslng and coupled to the data acquls1tlon means for process~ng sald electr~cal slgnals and producing pacemaker parameter ~nformat~on lncludlng at least pacemaker pulse t~m~ng markers and v1tal s~gn parameter ~nformatlon includlng ECG
waveform ~nformatlon and heart rate lnformatlon therefrom;
dlsplay means mounted wlth~n sa~d houslng and coupled to sald data processlng means for d7splaying sald pacemaker parameter lnformat~on and said vital slgn parameter informatlon slmultaneously; and further ~ncludlng means to superlmpose sald ECG waveform informatlon and sald t~ming markers on sa~d d~splay means so that.
relat~ve t1ming 1nformat~on can be observed by an observer of sald display means.
Brlef Descr~pt~on of the Drawlnqs The present lnventlon w~ll now be more fully descrlbed by way of example with reference to the drawlngs of whlch:
Flgure 1 ls a block diagram of the mon1tor of a flrst preferred embodlment;
Figures 2A and 2B show two dlsplay formats ava~lable from the monitor of the f1rst and second embodiments;
F~gure 3 shows a block d~agram arrangement of a second embodlment of the 1nvent~on;
F~gure 4 shows an exploded v1ew of the cas~ng ~or the second embod~ment;
Flgure 5 1s a block dlagram of the funct~o~al components comprlslng an analog block of a third embod~ment;
Flgure 6 shows ~n more detall the components compr~s1ng a third embodiment and the~r lnterconnection;
F~gure 7 ls a flow chart of the mode sw7tch interrupt servlce routlne of the thlrd embod1ment;
F~gure 8 ~s a flow chart of the maln routlne for ECG and heart rate d~splay of the th1rd embod7ment;
Fl~ure 9 ls the tlmer 1nterrupt serv~ce routine fcr the ECG and heart rate dl~play o~ the thlrd embod~ment;

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~. , ~, '. , F19ure 10 ls the flow chart of the QRS detectlon algor~thm for the ECG and heart rate display of the th~rd embodlment;
F~gure 11 ~s the flow chart of the maln rout~ne for the pacemaker pulse d~splay algorithm of the th~rd embodlment; and F~gure 12 ~s a flow chart of the pulse ~nterrupt serv~ce routine for the pacemaker pulse dlsplay of the thlrd embod~ment.
Detailed Descr1pt1On of the Preferrecl EmbQdiments The embod~ments of the present ~nventlon have as a common alm the productlon of a portable hand held monltor wh~ch allows the ln sltu 10 ~on~toring of both the ECG wave forms of a patient and the wave Forms produced by a pacemaker module wh~ch ls ~nstalled and operat~onal ln the patient s body. The mon1tor of the preferred embod~ments carr~es out these two complementary functlons in a non-~nvaslve manner and ~n real t~me.
Furthermore a predetermined amount of data derived by the ~onltor ls stored wlth~n the mon~tor for subsequent analys~s or transmisslon to remote data processlng means thereby enhanc~ng the utlltty of the portable monltor.
The devlce of the f~rst embodlment comblnes the features disclosed 20 ~n the devlce of copend~ng PCT Applicatlon No. AU88/00016 (Publ~catlon No ~088l5282 publlshed on 10 August 1988~ (i.e. the obtalning and display of ECG ~nformation heart sounds temperature and resp~rat~on by means of a hand held portab1e dev~ce wh~ch lncorporates multl-funct1Onal electrodes) together w1th the der~vlng and d~splay of pacemaker pulse 25 ~nformatton on the same d~splay the pacemaker pulse lnformat~on belng dertved from the same mult~-funct~onal electrodes. Information for dlsplay 1s derlved generally as shown ln the block dlagram of F~gure 1.
The d~splay essent~ally takes one of two ava11able formats at any one t~me: the two formats are shown ln Flgures 2A and 2B. It w~ll be noted 30 that the screen output labelled as dlsplay 1 ln Figure 2A shows a der~ved QRS wave form 3 havlng superlmposed thereon vertical bars or timing markers 4 these bars or t1m~ng markers showing the relat~ve poslt~on of the pacemaker pulses ~n tlme relative to the QRS wave form.
A~r~al ventr~cular and dual-chamber pacemakers are all able to be 35 monltored wlth accurate measurements of the pacemaker parameters clearly dlsplayed.
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, ' _ 4 _ ~ ~ ~ 6 ~ ~ 3 The ECG is also displayed on the clear hlgh resolutton screen to observe card~ac and pacemaker function and ensure that reliable heart capture ls occurrlng.
The pacing pulse waveforms S and 10 are also able to be dlsplayed as shown by Dlsplay 2 and Flgure 2B allow~ng observat~on of pulse shape to hlghllght any anomalles or gross changes ~n lead paclng ~mpedance.
Hard copy recordlngs of the pacemaker parameters ECG and paclng pulse waveforms can be made on an opt~onal paper strlp recorder.
The preferred embod~ment not only dlsplays physlolog~cal signals 10 but also dlsplays measurements and waveforms relat~ng to implanted pacemaker electr~cal act~v~ty. This ls performed by monitoring etectr~cal pulses on the skin whlch or~g~nate from the implanted pacemaker.
The flrst preferred embod1ment of the present ~nvent~on is encased 15 ~n s~mllar fashlon to the portable phys~ologlcal monltor d~sclosed ~n Australlan Speciflcat~on PH 09984 whlch has been subsequently published under PCT Appllcat~on No. AU88/00016 published under No. W088/05282 on 10 August 1988 to the present applicant.
Essentially electrlcal s19nals are derived from the skin of a 20 patient by means of a three electrode structure or equ~valent. Referrlng to Flgure 1 the slgnals from the senslng electrodes are fed to a signal conditloning unit thence converted to d~g~tal form and subsequently processed by the devlce accordlng to the general block diagram of Figure 1. The processed information ~s displayed as generally shown in 25 F~gures 2A and 2B.
Referring to Figure 2A ~nformation d1splayed on the output dlsplay shown as D~splay 1 is as follows:

A waveform display of the heart s electr~cal act~vlty 30 (electrocardlogram) 3 is shown wlth vertical bars 4 being added to show the pos~t~on of the pacemaker pulses 5 and 10 in relation to the ECG 3.
HEART RATE
Numeric lnformat~on 6 sho~ing the pat~ent s heart rate is dlsplayed on the screen 1 at the same t~me.
35 A.V. DELAY
In the case of a dual chamberl pacemaker ~hich has two sources of pac~ng pulse`s~ the delay between t~e pulse from one source to the pulse ama/0873E

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` - 5 - ~ ~ 2 ~ ~ ~ 3 from the other is known as the A.V. Delay and ls dlsplayed as numerlc ~nformatlon 7.
Referrlng to Flgure 2B lnformatlon ls d~splayed as on Dlsplay 2 ~s follows:
PACEMAKER PULS~ WAVEFORM
The actual shape of the pacemaker pulses 5 and 10 are dlsplayed to hlghl19ht any abnormalltles which may be due to a fault ln the pacemaker or pacemaker lead.
PACI~ RATE
The rate at whlch the pacemaker 15 emlttlng pulses to the heart can -; be displayed as numer k lnformatlon.
PULSE WIDTHS
The width 8 9 of the pacing pulses ls dlsplayed numerically typically ~n the range 0.25 to 1 m~ second. The atrlal pacing pulse w1dth 8 ~s d~splayed separately from the ventrlcular paclng pulse wldth 9.
An example of two typlcal d~splays ~s shown ln Flgures 2A and 2B.
The user can swltch between the two dlsplays by means of a mode control button (not shown) on the dev~ce.
Speclfically ln Flgure 2A dlsplay 1 a heart rate of 70 beats per minute 1s shown 6 and an AV lnterval of 160 ms ls shown 7. In dlsplay 2 of Flgure 2B an atrlal pacing pulse width of 0.50 ~s ~s shown 8 and a ventrlcular paclng pulse width of 0.75 ms 9 ls shown.
The devlce of the second embodlment ls constructed functlonally accord~ng to the block d~agram of F~gure 3. Four electrodes 20 21 22 23 rece1ve low level s1gnals ~rom a pat~ent. The slgnals are lnitlally processed by an analog block wh~ch block 24 separates out signals assoclated w~th the ECG wave form of the patlent and also (and separately~ those s~gnals assoc~ated wlth a cardlac pacemaker operatlonal wlthln the pat~ent s body. The analog block 24 then feeds the pacemaker pulse slgnal 64 and the ECG s~gnal 63 ~to an analog to dlgital converter 25). The d~s~tal pacemaker pulse s1gnal and the dlgital ECG slgnal are then passed to a d~g~tal process~ng block 26. The d1gltal processin~
block 26 processes the dlgital pace~aker pulse s1gnal and the digltal ECG
s~gnal and d~splays appropr1ate process informatlon on the front panel d~splay 27 ln con~unct10n w1th the operator s requ~rements as expressed by approprlate operat~on of the slde mounted swltches ~block 28 of Flgure 3).
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Figure 4 shows the arrangements of the cas~ng of the second preferred embodlment. ~ith part~cular referense to Flgure 4 the exploded vlew shows the cas~ng to comprlse a front cover 29 and a back cover 30 between wh~ch are sandw1ched a l~quld crystal d~splay panel 31 a back S light panel 32 and a pr~nted c~rcu~t board 33. A dlsplay w~ndow eover 34 ~s appl~ed to the front face of the front cover 29. The l~quld crystal display 31 ~s v~ewed through thls d~splay w~ndow 3~. The electrodes 20 21 22 and 23 (23 not shown~ are affixed to the back cover 30 and provlde the prlnclpal means of derlvlng ECG and pacemaker s~gnal ~nformatlon from the patient when the monitor~ts used 1n portable mode. Information can r~r~ also be 1nput to the device through ~he patlent cable connectlon 41.
,. i Primary controls for operat~ng the mon~tor comprlses on/off sw~tch 39 "hold" push button 36 "record" push button 37 and "mode" toggle push button 38. A battery cover 35 covers the batteries once they are ~laced withln the cas~ng. An ~nfrared l~nk 42 is used to commun~cate data derived by the ~on1tor to other data processlng means.
. The front cover ~s mated wlth the back cover 1n permanent fash~on by use of socket screws belng the same screws wh~ch hold the electrodes 21-23 to the back cover.
The LCD display used incorporates trapezoldal p~cture elements wlth a denser layout. The display sweep speed ~s 12.5 mm per second the viewing area 1s 38.1 by 50.8 mm. The trape~oldal p~cture elements are arranged ln a 120 x 480 matrix thereby compr~slng a total of 57 600 ! elements. The element ~tself ls a TN type l~quld crystal.
The electrodes 20-23 each compr~se a sect~on from a 16 mm dlameter sta~nless steel (AISI type 316 stalnless steel) rod. The work~ng thickness of the electrodes ls 3 mm.
The electronics of the devlce are pr1mar~1y 1ncorporated on the one printed c~rcu1t board 33. The board ~ncorporates the analog bloek 24 the analog to dlgital eonverter 25 the d~g~tal block 26 and an electronlc power supply.
A th~rd embod~ment of the devlce w~ll now be descr~bed w~th reference to Flgures 5 and 6 ln wh~ch the analog block 24 ls shown ln greater funct1Onal deta11. Funct1Onally F~gure 5 operates as follows:
T~e s~gnals LL and RR from the sk~n electrodes are a~pl1f~ed by a factor of 10 ~n the 1nstrumentat~on ampl~f~Pr 40. It ~s then flltered through an 0.5 Hz h~gh pass f~lter 40a to reduce base l~ne ~ovement on ~, :~

_ 7 _ ~ 3 the output screen. Then the slgnal ls spllt and fed to the ECG channel 45 and the pacemaker-pulse channel 52.
The f~rst s~gnal ~s amplif1ed by lO0 ln ampllf~ers 44 and 44 and filtered w1th a low pass filter ~LPF) 43 of lO0 Hz. Th~s output 1s taken to the A/D converter 25 (shown ln Figure 6 lntegral w~th~n CPU 57) and used as the ECG s~gnal 63.
The second channel signal wh~ch ls the pacemaker pulse s1gnal from the output of the high pass filter (HPF) 40a ~s d~vided by 4 ln divlder 46 and ~s filtered by high pass filter 47. A d~gltally galn-controlled amplifier 48 ls subsequently used to ampl~fy the pulses for slgnal processing. It ls controlled by the CPU 57 (shown ~n F~gure 6) by way of analog switch 51. The output of the amplifier prov~des an ~nput 52 to the second channel 54 of the A/D converter 25 and ~s later displayed on the LCD screen 31. A HPF 49 of 4 KHz ~s used to remove low frequency skin v~bratlons and detect pulse edges. A constant threshold 1s used to differentiate between no~se and pulses. A comparator 50 compares the threshold level w~th the pulse edges and produces a start and end of pulse t~mlng s~gnal. These allow the CPU to calculate the durat~on of the pulse. An lnterrupt is generated 3 ms after the beginn1ng of pulse to start the pulse processing rout1ne in the CPU 57.
The other major funct10nal component on the printed c1rcu1t board 33 is the d~g~tal block 26. Functlonally thls block is generally as shown ~n F~gure 6. Note that the analog to d~g~tal converter 25 trefer to Figure 3) ~s ~n fact on board the m~croproces~or (CPU 57) on ~he dig~tal block 26.
F~gure 6 also shows 1n greater detall the components of the ma~n printed c1rcu1t board 33 and the1r 1nterconnect10n.
The software for execut~on by the CPU 57 is shown ~n flow chart form ~n F~gures 7 through to 12 1nclus~ve.
- 30 F19ure 6 1s a block d1agram of the third em~odlment show1ng lts funct~onal construction.
The analog ctrcu1t 24 ls as descr~bed ~n F~gure 5. The outputs from the analog clrcu1t directly connect to a s~ngle-ch~p m~crocomputer (1n th~s embod~ment the Motorola MC68HCll) 57. The ECG slgnal 63 and pace~aker pulse s~gnal 64 are converted 1nto d1g1tal form by the analog to d1g~al converter 25. The Start and End slgnals from the analog c1rcu~t connect to lnput capture reglsters wh1ch capture the t1me at which these events occur to enable measurements of pac~ng pulse , ~ ~.. :. .

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- 8 - ~ ~2~3 parameters and generation of tlmlng markers on the ECT dlsplay. The lnterrupt slgnal ls used to generate an lnterrupt ln the mlcrocomputer and when a paclng pulse occurs to enable executlon of the approprlate software routlnes.
The lnfra-red llnk 42 allows transmlss~on of acqulred data and waveforms to a remote prlnter or computer for prlntout, storage or analysis. The lnfra-red llnk 1s eonnected to the Serlal Com~unlcations Interface (SCI) of the microcomputer and data ls tlansmitted uslng a digital serial protocol.
The m~crocomputer ls eonnected to the RAM, EEPROM and Graphlcs Controller Chlp by separate address and data buses.
The program code ~s stored ln the EEPROM. EEPROM ls used rather than ROM so that the so~tware can easlly be upgraded without needlng to remove the chlp from the board.
The RAM ls used to hold var~ables durlng program executlon, and ~s also used for storage o~ ECG and pacemaker pulse waveforms and pacemaker pulse parameters for later recall and dlsplay. The stored data may also be transmltted vla the lnfra-red llnk 42 to a prlnter or computer.
The Graphlc Controller generates the signals requlred to drive the display 27, 31. A b7t-map of the lmage to be dlsplayed ls stored ln the dlsplay RAM. The Graphlc Controller then per~odlcally wrltes th~s image-data to the d1splay to enable lt to be viewed. The types of lmages generated are shown ~n Flgures 2A and 2B. The Graphlcs Controller ls under control of the m1crocomputer 57.
The three control buttons for the devlce labelled HOLD, RECORD and MODE, are connected to lnput llnes of the mlcrocomputer. Button pushes are detected by the software, causlng the approprlate actlons to be performed.
As ment~oned above, the on-shlp A/D converter 25 and tlmer are used for sampl~ng ECG channel 63 and pacemaker channel 64. The three lnput capture reg~sters ~nternal to processor) are used for detecting pacemaker spikes. In response to a detected pacemaker splke, the monltor hardware generates t~o pulses at the f~rst and second lnput capture reglster lnputs to mark the start and end polnts of the pacemaker splke.
Timing ~nformat~on w~th regard to these events ls then automatlcally stored in the flrst and second ~nput capture reglsters. A 3 ms delayed ~nterrupt pulse followlng the end of pacemaker splke ls applled to the third lnput capture reglster lnput. Thls pulse sets the necessary ., .

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9 ~32~3 lnterrupt for the servlce routlne whlch then stops sampllng and calculatPs the pulse wldth as the tlme dlf~erence between f~rst and second 1nput capture reg1ster contents. The 3 ms delay ensures that the complete shape of the pacemaker pulse ls sampled and stored ln the buffer.
When the power ls first turned on ~by swltch 39) the program starts with the main ECG and heart rate dlsplay routine as shown ~n the softw~re flow charts. The mode switch 38 ls asslgned to the hlghdst prlority lnterrupt and when pressed toggles between ECG and pacemaker pulse modes. The ECG routine consists of a maln routlne ~or dlsplaylng graphlcs and an interrupt serv~ce routlne for sampllng fllterlng and QRS
wave form detect1On. The followlng routlnes are shown 1n the flow charts:
maln routlne interrupt servlce routine QRS detect10n algor'thm.
Slm~larly the pacemaker pulse d~splay conslsts of a maln routlne for cont~nuous sa~pllng the pacemaker channel and an lnterrupt serv~ce rout~ne to stop sampllng and dlsplay pulse lnformat~on and shape. These rout~nes are also shown ln the flow charts.
Figure 8 lllustrates the flow chart for the mode swltch lnterrupt servlce routlne. Thls routine ls activated when the mode swltch 38 ~Figure 4) ls depressed. In the first block 500 the switch ls checked to determine that 1t has been pressed long enough and a debounce rout1ne prevents multlple lnterrupts due to bounc~ng of the contacts of the switch.
In block 501 the mode ls toggled to between ECG and pacemaker pulse mode with each valld mode swltch acttvatlon.
If ECG mode ls selected then block 502 descrlbes the next actlon whlch 1s to go to the maln ECG and heart rate dlsplay rout~ne (Flgure 9).
If pacemaker pulse mode is selected then block 503 descrlbes the next actlon whlch ls to go to the maln pacemaker pulse dlsplay routlne (F1gure 12).
The maln routlne ~or ECG and heart rate dlsplay ls lllustrated ~y the flowchart Flgure 9. Th1s routlne lnlt1allzes the hardware and varlablès and then d~splays the ECG and heart rate on the LCD dlsplay as they are acqulred.
The routlne starts at block 600 where the graphlrs are lnit1alized; as are the varlables {block 602). The tlmer lnterrupt 1s then 1nlt1al1zed and enabled ~block 602) whlch results ln there belng a , .

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- lO- 132~3 per~odic lnterrupt to sample the ECG. The routlne for thls ls shown tn F~gure 10.
At block 603 the X axis dlsplay coordinate ~s set to zero and the d~splay polnter Is set to the value of the slgnal memory prlnter.
Next, the scan/hold flag ls checked (block 604) to determ~ne lf the hold switch 37 has been pushed. Hold and scan are selected alternately.
If hold ls selected, then at block 605 ~t ~s checked to determ~ne whether a prlnt of the ECG 1s required (determlned by switch 360). If not, then block 60~ 1s reentered. If a pr~nt of the ECG ~s requ~red, then at block 606 the ECG data ls output to the ~nfra-red link 42 for transm~sslon to a printer. Block 604 ts then reentered.
I, scan ls selected then at block 607 the d~splay printer ls checked to see ~ lt ~s equal to the slgnal memory printer. If not, then the Y ax1s display pr~nter ~s set to the value ~n the s~gnal memor~
indexed by the d~splay printer (block 608). Then the display printer ~s incremented by one (block 609). A prlnt ~s then wr~tten to the d~splay determined by the X and Y axis coord~nates ~block 610). The X ax~s coord~nate ls then ~ncremented by one ~block 611). At block 612 lt ~s checked ~f the screen boundary has been reached. If 1t has, then the heart rate is updated on the dlsplay (block 613) and the routlne continues at block 603. If the screen boundary has not been reached then the routlne cont~nues from block 604.
Flgure 10 ~s a flowchart 111ustrat~ng the tlmer lnterrupt serv~ce rout~ne for ECG and heart rate dlsplay. Th~s routlne is executed per~odically as determ~ned by a hardware t~me wh~ch causes an interrupt, typ~cally every three m~lltseconds.
The routlne starts at block 700. At block 701 the s1gnal memory printer ~s lncremented by one. Next the A/D converter ~s read (block 70Z) to sample the ECG. The acqu~red data ~s then flltered by a d1g~tal notch f~lter to remove the 50Hz and 60Hz ~a~ns supply lnterference ~block 703~. The data ~s then analyzed to detect the QRS waveform lf present for heart rate measurement (block 704). Th~s ~s further descrlbed ~n Figure -11.
If the measured s~gnal 1s outs~de the d~splay boundary then it ~s clamped.(block 705). The measured s~gnal ~s then saved 1n memory (block 706). Next the scan/hold swltch 37 ls checked and debounced ~block 707). If a valld sw~tth push 1s detected (btock 708) then th~ scan/hold flag is updated ~block 709) and then the 1nterrupt rout~ne ls term1nated .
, 32~3 (block 710). If no switch push ~s detected at block 708 then the interrupt rout~ne ls termlnated ~mmed~ately at block 710.
Flgure 11 ~s a flowchart ~llustrat~ng the QRS detectlon algor~thm for ECG and heart rate d~splay. The routlne starts at block ~00. If the QRS flag ls not set ~block 801), then ~t ls checked to determlne whether the refractory perlod is still set (block 802). lf not, the slope of the acquired ECG data ls measured (block 803), the polar1ty of t~.e slope determined (block 8040), and the slop ~s checked to see lf St l~es between two thresholds (block 805). If S09 the time durat~on for wh~ch the stope has met the other crit2rla 1s checked (block 806), and ~f this .; durat~on exceeds a certaln l~mit, the QRS flag is set (block 807), andthe thresholds are adjusted (block 808~. The routine then terminates at block 809.
If at block B02 the refractory perSod ~s still set, then the~
rout~ne term~nates lmmedlately at block 809.
If the threshold criteria at block 805 are not met, then the rout~ne also terminates im~edlately at block 809.
If the QRS flag is set at block 801, the heart rate calculatlon ls updated. The print inflection of the QRS waveform is checked at block 20 810. If 1t is found, then the R-peak has been detected (block 811). The time between success~ve R-peaks 1s then calculated and from thls the 4-beat runnlng average heart rate ls calculated ~block ~12). The QRS
flag is then eleared (block 813) and the routine terminates at block 809.
!-~ If, at block 810, the po~nt of ~nflect~on ~s not ~ound, then the routine terminates lmmedlately at block 809.
Flgure 12 7s a flowchart ~llustrating the main rsut~ne for pacemaker pulse display. This routlne runs continuously, sampl~ng the ~nput slgnals to capture the pacemaker pulse waveform ln memory for measurement and display.
The rout~ne starts at block 900 where the graph1cs are ~nit~al1zed, ~ollowed by block 901 where the var1ables are ~nltialized. Next the timer 1s set up (block 902) and the ~nput capture registers ICl, IC2 ~nd IC3 are.set up (block 903).
The A/D converter ~s then set up 1n block 304 to continuously 3S sample ~he ~ncom~ng signal. The hardware pulse ~nterrupt ls then enabled to enable the pacemaker pulse edges to be detected ~block gO5).
The AID converter ~s then read (block 906) and new A/D convers~on started imme~iately ~block 907). The data read from the AID converter is i ,.

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then saved ~n the pulse buffer (block 908) and the program then loops back to read the AID converter at block 906.
F~gure 13 ls a flowchart lllustrat~ng the pulse lnterrupt servlce rout~ne for pacemaker pulse d~splay. Th~s routlne is entered by a hardware lnterrupt caused by the detect~on of a pacemaker pulse edge.
The purpose of the rout~ne ~s to val~date the detectlon of a pacemaker pulse to measure the pacemaker pulse paraF.eters, belng the pulsew~dths, the AV ~nterval and pac~ng rate, and to dlsplay the pacemaker pulse waveform shape and the pacemaker pulse parameters.
The routine beg~ns at block 400 when a hardware pulse lnterrupt occurs to dlsable the ~nput capture reg~sters to prevent further interrupts. At block 401, the ICl and IC2 flags are checked to make sure they are both set. I~ so, the ICl and IC2 reg~ster values are saved (block 402). Next ICl ~s checked to see ~f ~t ls less than IC2 (bl~ck 403). If so, then the start tlme of the pulse ls the value of the ICl reg1ster (block 404) and the end t~me of the pulse ls the value of the IC2 reglster (block 405). If ICl ls not less than IC2 (at block 403) then the order ls reversed (blocks 40~ and 407).
The pulse width ls then calculated by subtractlng the IC2 reg~ster value from-the ICl reg~ster value (block 408).
The pulse w~dth ~s then checked to determine ~f lt ~s less than 3 ms Sblock 409). If 1t is not, then lt 1s determlned not to be a value pulse and the routine ends. If the pulse w1dth ls less than 3 ms, then the pulse w~dth ls saved ~block 410), as well as the pulse arrlval t~me (block 411).
At block 412 a check ~s made to determ~ne whether three consecut~ve pulses have been detected. If not, the routlne then ends. If so, then further pulse parameters can be measured.
By look1ng at the tim~ng of the three pulses a determlnat~on ls made whether the pacemaker ls a s~ngle or dual chamber pacemaker (block 413).
If ~t 1s a dual chamber pacemaker, then the AV 1nterval ~s calculated (block 4140, and the atr1al pulse wldth and pulse shape (block 415), th`e ventr~cular pulse wldth and pulse shape (block 416~ and the AY
1nterval (block 417) are all dlsplayed.
Pulse ~nterrupts are then reenabled by enabl~ng the lnput capture reg~sters ~block 419). The 1nterrupt service rout~ne ~s then termlnated ~block 420).~.
s~

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, " ' - 13 - 1 326~
If at block 413 ~t is determ~ned that there ~s s~ngle chamber pacing, only a s~ngle pulse wldth and pulse shape are dlsplayed ~block 418) before the routlne termlnates.
The performance character1stlcs of the monltor of the thlrd embod~ent are as follows:
3E~L_S~ARACTERISTICS
E~ lrcult Frequency Response: 0.5 - 100 Hz (-3dB max) CMMR: u 80 dB 0-100 Hz Isolatlon: Infrared external output Pacemaker Artifact: . Putse re-insert~on D~splav Sweep Speed: 12.5 mm/sec (for ECG) V~Pw~ng Area: 38.1 x 50.8 m~
lS No. of P~xels: 57,600.~120 x 480) D~splay Element: TN type LCD
Element Shape: Trapezo~dal Back Llght: Electrolum~nescent Measured Parameters Heart Rate (HR): 0-255 bpm (~ 1 bpm) Pacemaker Rate (PR): 0-255 bpm (~ 1 bpm) A-V Delay I~terval (AVI): 1-300 ms (+ 1 m5) Atr1al Pulse ~idth (AP~): 0.1-2.5 ms ~ 5 ms) Ventrlcular Pu7se ~ldth (VPW): 0.1-2.5 ms (~ S ms) D~splaved Parameters Atrlal Pulse Wave Form: ,Accuracy of ~ 5 ms Ventrlcular Pulse Wave Form: Accuracy of ~ 5 ms Cal~brat~on: lmV/cm square wave ECG wave form: Sweep speed 12.5 mm/sec Po~er Requ~rements Battery Type: 2 x AA A1kallne cells Battery L~e: u 4 hours cont~nuous use Phvs~cal Chara~terlstics ` Length: 13.4 cm ' ~ldth: 8.5 cm Th~ckness: 2.6 cm ~elght: 410 ~m - 14 - I 3 2 ~ ~ ~ 3 Env~ronmental ~haracter~st~cs 5.3.1 Temperature Operat~ng: 5 to 45C
Storage: -15~ to 55~C
5.3.2 Humidlty Operatlng: 10% to 95%
Storage: lOX to 80%
The functlonal behavlour of the mon~tor of the second embodlment with reference to the controls and dlsplay prevlously descr~bed are as follows:
~:, OPERATOR CONTRQLS
On/Off ~ h~n sw~tch 3g ls swltched to the ON poslt~on the ECG monitor mode is lnvoked. In the OFF posit~on all operatlon modes are powered down, with the exceptlon o~ the data ln memory which ls retained until the system ls reset manually or by output to a prlnter or computer.
Con~r~
A potentlometer 40 ls used to control the contrast level to the LCD
31.
Hold A momentary push button 36 that causes the current dlsplay to be frozen. No data update occurs at this tlme.
Record ~,~ A momentary push button 37 that lnltlates the record~n~ of the current dlsplayed data for a 10 second 1nterval. There are slx lntervals ava11able for recordlng. At the commencement of the record1ng a 1 mV
callbrat~on s1gnal ls d~splayed.
Mode A momentary push button 38 that toggles between the ECG/heart rate dlsplay and the pacemaker wave forms and data d~splay. (Refer ~lgures 2A
and 28.~
B~ , .
By depresslng MODE 38 and RECORD 37 buttons s1multaneously the record~ng memory ~s reset, clearlng all prev~ously recorded data.

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- 15 - ~ 32~
INDICATORS
Heart Rate (~) The heart rate ls indlcated on the LCD 6 (dlsplay 1 of Flgure 2A) and determ~ned by uslng a four beat runnlng average of the R to R
lnterval.
Pacemaker Ra~e ~B) The pacemaker rate is lndicated separately cn the LCD 31 and represents the actual pacing rate. Should there not be capture the paced rate as well as the heart rate ~111 be dlsplayed.
Atrlo-Ventrlcular Delav In~erval ~AVI) . The A-V delay ls measured ln mllllseconds and dlsplayed 7 on the pacemaker data screen.
Atrial Pulse Wldth ~AP~) The atrlal pulse wldth ls measured and dlsplayed æ when an ~trlal p~!lse ~s present. In additlon the atrlal wave form 5 ls dls~layed.
Ventr~cular Pulse W~dth (VPW~
. The ventr~cular pulse width ~s ~easured and d~splayed 9 when a ventrlcular pulse ls present. In addltlon the ventrlcular waveform ls displayed 10.
Low Batterv Should the operatlonal voltage drop below an optlmal level a contlnuous audlble tone ~s sounded for 1 second. At thls tlme the procedure should be co~pleted as soon as posslble and batterles replaced or re-charged.
Funçtlonal Test The monltor becomes operatlonal in the ECG monltor mode when the power switch ls turned ON. At thls t1me at test cycle of 1 second ls lnlt~ated to check the m1croprocessor functlon, memory lntegrlty, and dlsplay characterlst k s, wlth a separate battery voltage check. On -- 30 co~pletion of the test cycle a 1 second audlble tone ls sounded to indlcate correct functlonal operat~on.
Callbrate At the RECORD button be~ng depressed a 1 mV cal~bratlon pulse is lnserted lnitlally to allow accurate wave form analysls. .

STAl06~6E
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'`, - - 16 ~ 3 INPUT/OUTPUT CONNECTORS
Patie~t Cable Input The patlent cable ~nput ls a Lemo Sertes "OB" fixed socket connector. It has three inputs RA, LA and RL to obtain the ECG/pacemaker s~gnals.
Infrared Output_~nk The ~nfrared output 4Z ~5 a bi-directlonal commun~catlons llnk.
This output prov~des total electrlcal lsolation wh~n connected to external devices, such as printers, computers or ser~al commun~cat~ons links.
In summary, the monitor of the second:embod~ment behaves as previously descr~b~d wlthin the follow~ng llmits:
Pace~aker parameters are measured by detectlng the pacing pulse artifacts on the skin surface, then ampl~fylng and f~lterlng them ~nd convertlng them to d~gltal slgnals for analysls by the CPU 57 of the second embod1ment.
. The d~gltal hardware and software 15 capable of resolvlng paclng pulse wldths down to 1 us with a resolutlon of +l- 0.5 us. The AV delay and pac1ng rate can be resolved to ~ 128 us, though with software changes th~s can be reduced to ~l- 0.5 us.
The actual resolution of the paclng pulse widths is governed by the analog c~rcu~try. Two factors are 1mportant here. Slew rate llmltatlons of the amplifiers'mean that there may be an error vf 1 us. The second F~ factor is really one of the def~n~tlon of paclng pulse width. Pacemaker manufacturers may deflne the pulse w~dth at a dlfferent level on the pulse compared wlth the monitor of the second embodiment and may also measure them ~n v~tro. Dependlng on the characterlst~cs of the pulse, this may amount to an error of up to 5 us when fompared w1th the publlshed spec~flcat~on of the pacemaker.
Tak~ng all these factors lnto account, the monitor of the second embod~ment can satlsfactorlly measure pac1ng pulse w~dths down to 10 us lf requ~red w~th a resolution of +/- 1 U5, though measurement may var~ ln some cases by up to S us from pacemaker publ~shed data due to a dif~erence ~n measurement technique between the mon1tor and the pacemaker manufacturer. AV delays and pac~ng rates have a resolutlon of +J- 12~ us.
Importantly tc~ the onboard memory storage of the dev~ce comblned with the optlon to actually store data der~ved by the mon~tor ~thln the ~, STAtO656E

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' - 17 - ~ 32 6 5 ~J 3 monitor casing allows a medical practioner to take the monitor of either the f1rst or the second embodiment into the field and take "samples" of a patient's ECG and pacemakerwave form behavlour for subsequent analysis in the o~flce. Similarly a patient can be suppl~ed wlth a monltor and S lnstructed to take samples of the patient's own wave forms hlm or herself at predetermined times each day or durlng or following spec1flc l'events". The whole mon~tor can then be given to the practitioner at a later time at which time the practtt~oner can recal'l the stored data and anatyze ~t.
The above descr1bes three embod~ments of the present 1nvent~on and modi~ications obvious to those skllled ~n the art can be made thereto without departing from the scope and sp~r~t of the present ~nYent~on.
For example the lnfrared link 42 can be replaced by a RF radlo link or an ultrason k communications l~nk. In all cases the purpose of lS the l~nk ~s to provlde a wire ~ree means of commun~cating data derived by the mon~tor of the ~nvention to remote data processing and/or recording means and/or hard copy means to allow subsequent and/or concurrent display and analysis of a patient's ECG and pacemaker wave forms and most ~mportantly the interaction between those two wave forms.

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STAl0656E
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Claims (39)

1. A portable hand held monitor for monitoring and displaying simultaneously pacemaker parameter information and vital sign parameter information, said monitor comprising:
a housing of a size and shape that can be easily held in a user's hand;
data acquisition means mounted on the housing for receiving electrical signals from a skin contact region of a patient, the electrical signals being representative of pacemaker parameters including a pacemaker pulse waveform and at least one from parameters including pulse rate, pulse width, pulse interval, AV interval, or Atrial and Ventricular pulse discrimination and said electrical signals further being representative of vital sign parameters including at least heart rate and ECG wave forms;
data processing means provided within the housing and coupled to the data acquisition means for processing said electrical signals and producing pacemaker parameter information including at least pacemaker pulse timing markers and vital sign parameter information including ECG
waveform information and heart rate information therefrom;
display means mounted within said housing and coupled to said data processing means for displaying said pacemaker parameter information and said vital sign parameter information simultaneously; and further including means to superimpose said ECG waveform information and said timing markers on said display means so that relative timing information can be observed by an observer of said display means.

2. A as claimed in claim 1 wherein the data processing means further includes means to process the electrical signals representative of the pacemaker pulse waveform to produce pacemaker pulse waveform shapes, and the display means displays the waveform shapes.

3. A monitor as claimed in claim 1 wherein said data acquisition means comprises a plurality of electrodes for placing of said skin contact region for picking up said electrical signals representative of said pacemaker parameters.

4. A monitor as claimed in claim 1, further comprising memory means for storing data corresponding to said electrical signals, said vital sign parameter information and said pacemaker parameter information the stored data being available for subsequent recall and display or transmission to remote data processing means.

5. A monitor as claimed in claim 4 further comprising transmission means for transmitting any one or more of said stored data, said electrical signals, said vital sign parameter information and said pacemaker parameter information to remote data processing means.

6. A monitor as claimed in claim 5 wherein said transmission means comprises an infrared transmitter.

7. A monitor as claimed in claim 5 wherein said transmission means comprises a radio frequency transmitter.

8. A monitor as claimed in claim 5 wherein said transmission means comprises an ultrasonic transmitter.

9. A monitor as claimed in any one of claims 1 or 2 or 5 or 6 or 7 or 8, wherein said display means is an LCD display.

10. A method of monitoring and displaying simultaneously vital sign parameter information and pacemaker pulse parameter information on a single display means, said method comprising the steps of:
sensing electrical signals from a skin contact region of a patient in real time the electrical signals being representative of pacemaker parameters including pacemaker pulse waveform and at least one from parameters including pulse rate, pulse width, pulse interval, AV
pulse interval, or Atrial and Ventricular pulse discrimination of pacemaker heart stimulation pulses produced by a pacemaker operating with said patient and vital sign parameters including at least heart rate and ECG waveforms occurring in said patient;
processing said electrical signals representative of pacemaker parameters to produce pacemaker parameter information including at least pacemaker pulse timing markers therefrom;
processing said electrical signals representative of vital sign parameters to produce vital sign parameter information including ECG
waveform information and heart rate information therefrom; and displaying on said single display means at least said pacemaker pulse timing markers superimposed on the ECG waveform so that relative timing information can be observed by an observer of said display means.

11. The method of claim 10 further comprising the steps of:
processing the electrical signals representative of the pacemaker pulse waveform to reconstruct the pacemaker pulses; and displaying said reconstructed pacemaker pulses.

12. The method of claim 11, wherein the step of processing the electrical signals includes processing said signals so that said reconstructed pacemaker pulses are an approximation of the actual pulse shape of each of said pacemaker pulses.

13. A method as claimed in any one of claims 10, 11 or 12, wherein said display means is an LCD display.

14. A monitor as claimed in any one of claims 1 or 2 or 5 or 6 or 7 or 8, wherein said data processing means including means to differentiate between atrial pacemaker pulses and ventricular pacemaker pulses and to determine the interval therebetween, and the display means further includes means to display a measurement of the interval between the atrial and the ventricular pacemaker pulses.

15. A portable hand held monitor for monitoring and displaying simultaneously pacemaker parameter information and vital sign parameter information said monitor comprising:
a housing of a size and shape than can be easily held in a user's hand;
data acquisition means mounted on the housing for receiving electrical signals from a skin contact region of a patient, the electrical signals being representative of pacemakers including pacemaker pulse waveform and at least one from parameters including pulse rate, pulse width, pulse interval, AV interval, or Atrial and Ventricular pulse discrimination, said electrical signals further being representative of vital sign parameters including at least heart rate and ECG wave forms;
data processing means provided within the housing and coupled to the data acquisition means for processing said electrical signals and producing pacemaker parameter information including at least pacemaker pulse timing markers and vital sign parameter information including ECG
waveform information and heart rate information therefrom, said data processing means including a) amplifier means for receiving said electrical signals from said data acquisition means and producing an amplified data signal, b) first circuit means including low pass filter means responsive to said data signal for producing ECG signals corresponding to said ECG
waveforms, c) second circuit means including divider means and high pass filter means responsive to said data signal for producing pacemaker signals corresponding to said pacemaker pulse waveform, and d) third circuit means including a high pass filter and threshold comparator means for producing pulse timing markers, LCD display means mounted within said housing and coupled to said data processing means for displaying said pacemaker parameter information and said vital signal parameter information simultaneously; and graphic control means to supply said pulse tuning markers and said ECG waveform to said LCD display means so as to superimpose said ECG
waveform and said timing markers on said LCD display means so that relative timing information can be observed by an observer of said display means.

16. A monitor as claimed in claim 3, further comprising memory means for storing data corresponding to said electrical signals, said vital sign parameter information and said pacemaker parameter information, the stored data being available for subsequent recall and display or transmission to remote data processing means.

17. A monitor as claimed in claim 3, wherein said display means is an LCD display.

18. A monitor as claimed in claim 4, wherein said display means is an LCD display.

19. A monitor as claimed in claim 16, wherein said display means is an LCD display.

20. A monitor as claimed in claim 3, wherein said data processing means including means to differentiate between atrial pacemaker pulses and ventricular pacemaker pulses and to determine the interval therebetween, and the display means further includes means to display a measurement of the interval between the atrial and the ventricular pacemaker pulses.

21. A monitor as claimed in claim 4, wherein said data processing means including means to differentiate between atrial pacemaker pulses and ventricular pacemaker pulses and to determine the interval therebetween, and the display means further includes means to display a measurement of the interval between the atrial and the ventricular pacemaker pulses.

22. A monitor as claimed in any one of claims 1 or 2 or 5 or 6 or 7 or 8, wherein said display means is an LCD
display, and wherein said data processing means including means to differentiate between atrial pacemaker pulses and ventricular pacemaker pulses and to determine the interval therebetween, and the display means further includes means to display a measurement of the interval between the atrial and the ventricular pacemaker pulses.

23 A monitor as claimed in any one of claims 16 or 17 or 18 or 19, wherein said data processing means including means to differentiate between atrial pacemaker pulses and ventricular pacemaker pulses and to determine the interval therebetween and the display means further includes means to display a measurement of the interval between the atrial and the ventricular pacemaker pulses.

24. A monitor as claimed in claim 2 wherein said data acquisition means comprises a plurality of electrodes for placing on said skin contact region for picking up said electrical signals representative of said pacemaker parameters.

25. A monitor as claimed in claim 2, further comprising memory means for storing data corresponding to said electrical signals, said vital sign parameter information and said pacemaker parameter information, the stored data being available for subsequent recall and display or transmission to remote data processing means.

26. A monitor as claimed in claim 25 further comprising transmission means for transmitting any one or more of said stored data said electrical signals, said vital sign parameter information and said pacemaker parameter information to remote data processing means.

27. A monitor as claimed in claim 26 wherein said transmission means comprises an infrared transmitter.

28. A monitor as claimed in claim 26 wherein said transmission means comprises a radio frequency transmitter.

29. A monitor as claimed in claim 26 wherein said transmission means comprises an ultrasonic transmitter.

30. A monitor as claimed in any one of claims 26 or 27 or 28 or 29, wherein said display means is an LCD
display.

31. A monitor as claimed in any one of claims 26 or 27 or 28 or 29, wherein said data processing means including means to differentiate between atrial pacemaker pulses and ventricular pacemaker pulses and to determine the interval therebetween, and the display means further includes means to display a measurement of the interval between the atrial and the ventricular pacemaker pulses.

32. A monitor as claimed in claim 24, further comprising memory means for storing data corresponding to said electrical signals, said vital sign parameter information and said pacemaker parameter information, the stored data being available for subsequent recall and display or transmission to remote data processing means.

33. A monitor as claimed in claim 24, wherein said display means is an LCD display.

34. A monitor as claimed in claim 25, wherein said display means is an LCD display.

35. A monitor as claimed in claim 32, wherein said display means is an LCD display.

36. A monitor as claimed in claim 24, wherein said data processing means including means to differentiate between atrial pacemaker pulses and ventricular pacemaker pulses and to determine the interval therebetween, and the display means further includes means to display a measurement of the interval between the atrial and the ventricular pacemaker pulses.

37. A monitor as claimed in claim 25, wherein said data processing means including means to differentiate between atrial pacemaker pulses and ventricular pacemaker pulses and to determine the interval therebetween, and the display means further includes means to display a measurement of the interval between the atrial and the ventricular pacemaker pulses.

38. A monitor as claimed in any one of claims 26 or 27 or 28 or 29, wherein said display means is an LCD
display, and wherein said data processing means including means to differentiate between atrial pacemaker pulses and ventricular pacemaker pulses and to determine the interval therebetween, and the display means further includes means to display a measurement of the interval between the atrial and the ventricular pacemaker pulses.

39. A monitor as claimed in any one of claims 32 or 33 or 34 or 35, wherein said data processing means including means to differentiate between atrial pacemaker pulses and ventricular pacemaker pulses and to determine the interval therebetween, and the display means further includes means to display a measurement of the interval between the atrial and the ventricular pacemaker pulses.