Abstract:
In one aspect, the invention is a method for processing pulse oxymetry data signals. The method includes recording pulse oxymetry data signals. The pulse oxymetry data signals have a plurality of oxymetry waveforms. The method also includes determining a correlation coefficient between sequential oxymetry waveforms and identifying a valid pulse oxymetry waveform.

Description:
[0001]    The present invention relates in general to electrocardiographic (ECG) and oxygen saturation signal recording and more particularly concerns a novel technique for processing the ECG and oxygen saturation signals.  
         BACKGROUND OF THE INVENTION  
         [0002]    For background on ECG and oxygen saturation signal recording reference is made to U.S. Pat. No. 6,125,296.  
           [0003]    A typical prior art approach for measuring oxygen saturation uses either a large nonportable bedside unit or a portable unit with recording capability.  
           [0004]    An object of this invention is to provide an automatic mechanism for identifying those portions of the recorded pulse oxymetry data signals that are invalid.  
           [0005]    Another object of the invention is to use pulse oxymetry data signals, which this invention determines as valid, and identify those segments of the data signals that are valid desaturation signals.  
         BRIEF SUMMARY OF THE INVENTION  
         [0006]    In one aspect, the invention is a method for processing pulse oxymetry data signals. The method includes recording pulse oxymetry data signals. The pulse oxymetry data signals have a plurality of oxymetry waveforms. The pulse oxymetry data signals correspond to oxygen saturation data signals. The method also includes determining a correlation coefficient between sequential oxymetry waveforms and identifying a valid pulse oxymetry waveform.  
           [0007]    This aspect of the invention may have one or more of the following features. Determining the correlation coefficient includes storing a first pulse oxymetry waveform segment having a first length in a first buffer, copying the first pulse oxymetry waveform segment from the first buffer to a second buffer, copying a second pulse oxymetry waveform segment having a second length to the first buffer, comparing the first length, the second length and a predetermined value, and determining a correlation length related to the first and second lengths and the predetermined value. Determining a correlation length includes taking the minimum of the first length, the second length, and the predetermined value. Determining a correlation coefficient includes determining a correlation coefficient from the first pulse oxymetry waveform segment and the second pulse oxymetry waveform segment, comparing the correlation coefficient to a threshold value, and filtering out an invalid pulse oxymetry waveform segment that has a correlation coefficient below the threshold value. Filtering out the invalid pulse oxymetry waveform segment includes eliminating pulse oxymetry waveform segments if 75% of the correlation coefficients for the last 6 seconds are above the threshold value of 0.9. The method also includes determining valid oxygen desaturation data signals. Determining valid desaturation signals comprises labeling oxygen saturation signals below a threshold value for a predetermined time as valid desaturation data. The threshold value is 88% and the predetermined time is 300 seconds. Determining valid desaturation signals comprises eliminating artifacts. Determining valid desaturation signals comprises ignoring desaturation signals below the threshold value that do not reach a peak value.  
           [0008]    In another aspect, the invention is an apparatus for processing pulse oxymetry data signals. The apparatus includes a memory that stores executable instruction data signals and a processor. The processor executes the instruction data signals to record the pulse oxymetry data. The pulse oxymetry data has a plurality of oxymetry waveforms. The pulse oxymetry data signals correspond to oxygen saturation data signals. The processor also executes the instruction data signals to determine a correlation coefficient between sequential oxymetry waveforms and to identify invalid pulse oxymetry waveforms.  
           [0009]    This aspect of the invention may have one or more of the following features. Determining the correlation coefficient includes storing a first pulse oxymetry waveform segment having a first length in a first buffer, copying the first pulse oxymetry waveform segment from the first buffer to a second buffer, copying a second pulse oxymetry waveform segment having a second length to the first buffer, comparing the first length, the second length and a predetermined value, and determining a correlation length related to the first and second lengths and the predetermined value. Determining a correlation length includes taking the minimum of the first length, the second length, and the predetermined value. Determining a correlation coefficient includes determining a correlation coefficient from the first pulse oxymetry waveform segment and the second pulse oxymetry waveform segment, comparing the correlation coefficient to a threshold value, and filtering out an invalid pulse oxymetry waveform segment that has a correlation coefficient below the threshold value. Filtering out the invalid pulse oxymetry waveform segment includes eliminating pulse oxymetry waveform segments if 75% of the correlation coefficients for the last 6 seconds are above the threshold value of 0.9. The processor also executes the instruction data signals to determine valid oxygen desaturation data signals. Determining valid desaturation signals comprises labeling oxygen saturation signals below a threshold value for a predetermined time as valid desaturation data. The threshold value is 88% and the predetermined time is 300 seconds. Determining valid desaturation signals comprises eliminating artifacts. Determining valid desaturation signals comprises ignoring desaturation signals below the threshold value that do not reach a peak value.  
           [0010]    In still another aspect, the invention is an article that includes a machine-readable medium that stores executable instruction signals for processing pulse oxymetry data signals. The instruction signals cause a machine to record the pulse oxymetry data signals. The pulse oxymetry data signals have a plurality of oxymetry waveforms. The pulse oxymetry data signals correspond to oxygen saturation data signals. The instructions also cause a machine to determine a correlation coefficient between sequential oxymetry waveforms and to identify invalid pulse oxymetry waveforms.  
           [0011]    This aspect of the invention may have one or more of the following features. Determining the correlation coefficient includes storing a first pulse oxymetry waveform segment having a first length in a first buffer, copying the first pulse oxymetry waveform segment from the first buffer to a second buffer, copying a second pulse oxymetry waveform segment having a second length to the first buffer, comparing the first length, the second length and a predetermined value, and determining a correlation length related to the first and second lengths and the predetermined value. Determining a correlation length includes taking the minimum of the first length, the second length, and the predetermined value. Determining a correlation coefficient includes determining a correlation coefficient from the first pulse oxymetry waveform segment and the second pulse oxymetry waveform segment, comparing the correlation coefficient to a threshold value, and filtering out an invalid pulse oxymetry waveform segment that has a correlation coefficient below the threshold value. Filtering out the invalid pulse oxymetry waveform segment includes eliminating pulse oxymetry waveform segments if 75% of the correlation coefficients for the last 6 seconds are above the threshold value of 0.9. The instructions also cause a machine to determine valid oxygen desaturation data signals. Determining valid desaturation signals comprises labeling oxygen saturation signals below a threshold value for a predetermined time as valid desaturation data. The threshold value is 88% and the predetermined time is 300 seconds. Determining valid desaturation signals comprises eliminating artifacts. Determining valid desaturation signals comprises ignoring desaturation signals below the threshold value that do not reach a peak value.  
           [0012]    Some or all of the aspects of the invention described above may have some or all of the following advantages. The invention makes it impossible to automatically differentiate valid oxymetry data signals from invalid oxymetry data signals. The invention also automatically determines true desaturation signals from invalid desaturation signals.  
           [0013]    Other features, objects and advantages will become apparent from the following detailed description when read in connection with the accompanying drawing in which: 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0014]    [0014]FIG. 1 is a flowchart of a process for processing pulse oxymetry data signals;  
         [0015]    [0015]FIG. 2 is a graph of a pulse signal and a corresponding pulse oxymetry signal;  
         [0016]    [0016]FIG. 3 is a graph showing normal recorded pulse oxymetry data signals;  
         [0017]    [0017]FIG. 4 is a graph showing invalid recorded pulse oxymetry data signals;  
         [0018]    [0018]FIG. 5 is a flowchart of a process of detecting invalid pulse oxymetry data signals;  
         [0019]    [0019]FIG. 6 is a graph showing valid recorded desaturation data signals;  
         [0020]    [0020]FIG. 7 is a graph showing invalid recorded desaturation data signals;  
         [0021]    [0021]FIG. 8 is a flowchart of a process for detecting desaturation signals; and  
         [0022]    [0022]FIG. 9 is a block diagram of a computer system on which the process of FIG. 1 may be implemented. 
     
    
     DETAILED DESCRIPTION  
       [0023]    Typically, an oxygen sensor is used to record pulse oxymetry signals. The oxygen sensor provides a signal representative of oxygen saturation. The oxygen sensor is applied to a finger or ear lobe. However, pulse oxymetry measurements are sensitive to patient movement. Small movements of the sensor can produce invalid data signals, which is difficult and time consuming for a user to discern.  
         [0024]    It is especially difficult for the user to identify periods of desaturation in the data from false desaturation data. Desaturation periods are marked by low values of blood oxygen saturation. Desaturation can be caused by emphysema, blockages of the airways (e.g., snoring), etc. In many cases, it is difficult or impossible to differentiate a true desaturation from the invalid data signals by looking at the oxygen saturation data signals alone.  
         [0025]    Referring to FIGS. 1 and 2, a process  10  automatically (i.e., without user intervention) determines invalid oxymetry data signals recorded from an electrocardiographic and oxygen saturation signal. Process  10  determines a cross-correlation coefficient between two adjacent pulse oxymetry waveforms and compares it to a predetermined value. Every pulse oxymetry waveform corresponds to a pulse wave having a series of R-waves  24  (e.g., first R-wave  24   a  and second R-wave  24   b ). R-waves  24  are a depolarization of the apex of the heart whereby most of the ventricle is activated. R-waves  24  are represented by an upward deflection on a pulse signal  26 . R-waves  24  are used to identify the beginning of a pulse oxymetry waveform  28  (e.g., first pulse oxymetry waveform  28   a  and second pulse oxymetry waveform  28   b ) in the pulse oxymetry data signal  30 . For example, first R-wave  24   a  corresponds to first pulse oxymetry waveform  28   a  and second R-wave  24   b  corresponds to second pulse oxymetry waveform  28   b . Process  10  keeps those successive oxymetry waveforms that have a cross-correlation coefficient above the predetermined value. The valid oxymetry data signals are further reviewed to determine if the oxygen desaturation signal values are also valid. By automatically filtering-out erroneous and invalid oxymetry data signal, a physician has a better understanding of the condition of a patient to make a better diagnosis faster than having the physician sift through the recorded oxymetry data signals looking for false recorded data signals.  
         [0026]    Referring to FIGS.  3 - 4 , a pulse signal  32  (e.g., pulse signal  32   a  and pulse signal  32   b ) corresponds to a pulse oxymetry signal  34  (e.g., pulse oxymetry signal  34   a  and pulse oxymetry signal  34   b ). In box  36 , pulse oxymetry waveform  34   a  is valid because successive oxymetry waveforms are correlated. In box  38 , successive oxymetry waveforms are not correlated.  
         [0027]    Process  10  records ( 12 ) the ECG and saturation data signals. In this embodiment an apparatus to record the signals is described in U.S. Pat. No. 6,125,296 (“&#39;296” patent) and incorporated herein. Process  10  stores ( 14 ) the data signals in a removable memory (see &#39;296 patent). Process  10  reads ( 16 ) the stored data signals from the removable memory. In this embodiment, the removable memory is a memory card that is placed in a memory card reader and subsequently read.  
         [0028]    Referring to FIG. 5, process  10  determines ( 18 ) a correlation between successive pulse oxymetry waveforms by using a process  40 . Process  40  uses a correlation coefficient to filter out invalid data signals. Process  40  receives the present R-wave, R n , and determines ( 42 ) if the last R-wave has been received. If the last R-wave has been received, process  40  returns ( 44 ) to process  10  for further processing to determine the valid oxygen desaturation data signals ( 20 ). If more R-waves are present, process  40  copies ( 46 ) a previous segment of a pulse oxymetry waveform corresponding to the previous R-wave, R n−1 , and the R-wave previous to R n−1 , R n−2 , and a correlation length, L n−1 , from a new buffer to an old buffer. For each R-wave that is detected and is associated with a normal beat of sinus origin, process  40  copies ( 48 ) a segment of pulse oxymetry waveform corresponding to the present R-wave, R n , and the previous R-wave, R n−1 , to the new buffer. Process  40  determines ( 50 ) a correlation length of the present segment, L n , by comparing the pulse oxymetry waveforms in the new buffer to the old buffer. L n  is determined by taking the smallest of: the time between R n  and R n−1 , R n−1  and R n−2 , and a constant equal to 0.4 times a sampling rate of 180 or a constant of 72. Process  40  stores L n  in the new buffer. Process  40  determines ( 52 ) the cross correlation coefficient, C n , as:  
           C   n =Σ(( BUFN   m )( BUFO   m ))/((Σ( BUFN   m ) 2 )(Σ( BUFO   m ) 2 )) 1/2    
         [0029]    for m=0, . . . LEN n−1  where BUFN are the pulse oxymetry waveform segment values in the new buffer, BUFO are the pulse oxymetry waveform segment values in the old buffer, and LEN n−1  is the correlation length of the previous pulse oxymetry waveform segment. Process determines ( 54 ) the validity by comparing the cross correlation coefficient to the predetermined value. If more than a fraction of the correlation coefficients of normal beats, FRAC, in the last NS seconds of data have the C n  less than a threshold value, C th , then oxymetry data signals from R n  to R n−1  are invalid. In this embodiment, if more than 75% of the coefficients of normal beats in the last 6 seconds of data signals have the C n  less than 0.9, then the oxymetry signals from R n  to R n−1  are invalid. The values of FRAC, NS, and C th  are determined by the user. Again, process  40  determines if the last R-wave has been received ( 42 ).  
         [0030]    Referring to FIGS.  6 - 7 , an ECG pulse signal  52  (e.g., ECG pulse signal  52   a  and ECG pulse signal  52   b ) is compared to an oxygen saturation signal  34  (i.e., oxygen saturation signal  54   a  and oxygen saturation signal  54   b ). In box  56 , a valid oxygen saturation signal is shown because oxygen saturation signal  54   a  is correlated with ECG pulse signal  52   a . In box  58 , an invalid oxygen saturation data signal is shown because oxygen saturation signal  54   a  is not correlated with ECG pulse signal  52   b.    
         [0031]    Referring to FIG. 8, process  80  determines from the valid data signals the true desaturation data signals. Process  80  finds those points in an oxygen saturation signals that are below a certain threshold, desat_max_value, for a minimum amount time, desat_min_length. However, process  80  allows for some values to be above desat_max_value. For example, a patient has desaturation signals for fifteen minutes but every minute there was an oxygen saturation signal above desat_max_value for a few seconds. The patient would still be considered physiologically in a desaturation mode for the entire 15 minutes. Process  80  uses a time artifact value, desat_max_artifact, to disregard these occurrences. Desat_max_artifact is the maximum amount of time that during desaturation process  80  will ignore values above desat_max_value. Process  80  also uses a desat_max_peak value to ignore values below desat_max_value that never reach desat_max_peak. Process  80  also uses a desat_min_separation value. The desat_min_separation value is the minimum time that is allowed between periods where the saturation value is above desat_max_value. Process  80  measures values from 0 to the last_saturation_value. In this embodiment, desat_max_value is 88%, desat_min_length is 300 seconds, desat_max_peak is 85%, desat_max_artifact is 30 seconds, and desat_min_separation is 120 seconds. In this embodiment, the values in process  80  can be set by a user.  
         [0032]    One embodiment of the invention is realized in the following software code:  
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         1.   if(open_file(&amp;oxy_handle,“oxymin”,OPEN_READ_NO_MESSAGE) &amp;&amp;       2.   filelength(oxy_handle) &amp;&amp;       3.   open_file(&amp;oxy_pulse,“oxypulse.dat”,OPEN_RANDOM) &amp;&amp;       4.   filelength(oxy_pulse) &amp;&amp;       5.   open_file(&amp;beatstream, “beatstr”,OPEN_READ)       6.   )       7.   {       8.   MEM_BEAT_STREAM_FILE_FORMAT bt{0,0,0},lbt;       9.   #define MAX_OXY_BUF ((SAMP_RATE*4)/10)       10.   #define OXY_BEATS_CHECKED (OXYMINUTE_5::SecPerOxy*5)       11.   struct            12.   {       13.   long offset;            14.   int artifact_detected;   //!=0 if aftifact detected            15.   }det_buf[OXY_BEATS_CHECKED];            16.   short mk[4]={80,80,−80,−80};       17.   short oxy_buf[MAX_OXY_BUF+4],last_oxy_buf [MAX_OXY_BUF+4];       18.   int sb,sc,coll_len;       19.   int oxymin_records;       20.   double sumx,sumy,sumxy,coll;       21.   OXYMINUTE_5 *ox_min_buf;       22.   int beat_cnt;       23.   memset(oxy_buf,0,sizeof(oxy_buf));       24.   beat_cnt=0;       25.   close(oxy_handle);            26.//   Printf(“\n process oxy ”);            27.   open_file(&amp;oxy_handle, “oxymin”,OPEN_RANDOM);       28.   oxymin_records=filelength(oxy_handle)/sizeof(OXYMINUTE_5);       29.   ox_min_buf=new OXYMINUTE_5[oxymin_records];       30.   lseek(oxy_handle,0,SEEK_SET);       31.   for (lb=0;lb&lt;oxymin_records;lb++)            32.   {            33.read(oxy_handle, (char*)&amp;ox_min_buf [lb],       sizeof(OXYMINUTE_5));            34.   ox_min _buf[lb].status&amp;=˜ (0x200 | 0x100);       35.   }            36.   while (!eof(beatstream))            37.   {       38.   lbt=bt;       39.   read(beatstream,&amp;bt,sizeof(bt));            40.lseek(oxy_pulse, (lbt.offset+(SAMP_RATE/10)−4)*2,SEEK_SET);            41.   read(oxy_pulse,oxy_buf,MAX_OXY_BUF*2+8);       42.   coll_len=MIN(MAX_OXY_BUF,bt.offset-lbt.offset);       43.   sumx=0.0;       44.   sumy=0.0;       45.   sumxy=0.0;       46.   for (ia=4;ia&lt;coll_len+4;ia++)            47.   {       48.   sb=oxy_buf[ia]-oxy_buf [4];       49.   sc=last_oxy_buf[ia]-last_oxy_buf[4];       50.   sumx+=sb*sb;       51.   sumy+=sc*sc;       52.   sumxy+=sb*sc;       53.   last_oxy_buf[ia]=oxy_buf [ia];       54.   }            55.   if (sumx * sumy &gt;0.0)            56.   coll=sumxy/sqrt(sumx*sumy);            57.   else            58.   coll=0;            59.det_buf[beat_cnt%OXY_BEATS_CHECKED].offset=lbt.offset;       60.det_buf[beat_cnt%OXY_BEATS_CHECKED].artifact_detected=(coll       &lt;0.9) &amp;&amp; lbt.beat_label==BEAT_LABEL_NORMAL;            61.   sb=0;       62.   sc=0;       63.   for (ia=0;ia&lt;OXY_BEATS_CHECKED;ia++)            64.   }       65.   if (det_buf[ia].offset&gt;lbt.offset-            (SAMP_RATE*OXYMINUTE_5::SecPerOxy))            66.   {           67.   sb++;   //total count            68.   sc+=det_buf[ia].artifact_detected;            69.   }            70.   }            71.   ia=lbt.offset/(SAMP_RATE*OXYMINUTE_5::SecPerOxy);            72.   lb=0;       73.   if (sc*4&gt;sb*3 &amp;&amp; ia&gt;=0 &amp;&amp; ia&lt;oxymin_records)            74.   {       75.   ox_min_buf[ia].status|=0x200;       76.//   Printf(“ ARTIFACT %5d sc %2d sb %2d”,ia,sc,sb);       77.   lb=1;       78.   }       79.#if 0            80.lseek(oxy_pulse,(lbt.offset+(SAMP_RATE/10)−4)*2,SEEK_SET);            81.   if (lb)           82.       sb=oxy_buf[0]−100;       83.   else       84.       if (coll&gt;0.9)            85.   sb=oxy_buf[0]+100;            86.   else            87.   sb=oxy_buf[0]+50;            88.   oxy_buf[1]=sb;       89.   oxy_buf[2]=sb;       90.   oxy_buf[3]=sb;       91.   write(oxy_pulse,oxy_buf,8);       92.   if (DEBUG_ART_DESAT)            93.   if ((beat_cnt%100)==0)            94.   for (ia=0;ia&lt;coll_len;ia++)            95.   Printf(“ %3d”,oxy_buf [ia]);       96. #endif            97.   beat_cnt++;       98.   }            99.if (DEBUG_ART_DESAT)            100.   Printf(“\n look for desats for %d records thresh            %d %d %d %d ”,oxymin_records,            101.   c_i.desat_spo2_thresh,       102.   c_i.artifact_desat_skip,       103.   c_i.desat_spo2_min _thresh,            104.   c_i.desat_min length);            105.   for (ia=0;ia&lt;oxymin_records;ia++)            106.   {            107.   if (DEBUG_ART_DESAT)       108.   if (ia&lt;400)Printf(“ %d”,ox_min _buf[ia].spo2_max);            109.   if ((ia&amp;15)==0)            110.   StatusPrintf(“Oxy            %s”,time_to string(ia*OXYMINUTE_5::SecPerOxy*SAMP_RATE));            111.   if (DEBUG_ART_DESAT)            112.   Printf(“\n at %3d %s %2d %2d %d %d”,            113.   ia,            114.   time_to_string(ia*OXYMINUTE_5::            SecPerOxy*SAMP_RATE+c_i.base_time),            115.   ox_min _buf[ia].spo2_min,       116.   ox_min _buf[ia].spo2_max,       117.   ox_min buf[ia].OxyArtifact(),       118.   (ox_min _buf[ia].status&amp;0x100) !=0)            119.   if (ox_min_buf[ia].spo2_max&lt;=c_i.desat_spo2_thresh)            120.   {       121.   if (DEBUG_ART_DESAT)            122.   Printf(“ start desat ”);            123.   int term_loop;       124.   for            (lb=ia, lc=0, ld=0, le=0,term_loop=0;lb&lt;oxymin_records   &amp;&amp;            (lc&lt;(c_i.artifact_desat_skip/OXYMINUTE_5::SecPerOxy))   &amp;&amp;       !term_loop;lb++)            125.   {       126.   if (ox_min _buf[lb].OxyArtifact() | |            ox_min_buf[lb].spo2_max&gt;c_i.desat_spo2_thresh)            127.   {       128.   if            (le&lt;=c_i.artifact_desat_min separation/OXYMINUTE_5::SecFerOxy       &amp;&amp; !lc)            129.   term_loop=1;            130.   lc++;       131.   le=0;       132.   }            133.   else            134.   {       135.   lc=0;       136.       137.   le++;            138.   if (ox_min_buf[lb].spo2_min&lt;=c_i.desat_spo2_min thresh)            139.   ld++;            140.   }            141.   lb−=lc;       142.   if (DEBUG_ART_DESAT)            143.   Printf(“ check lb-ia %d ld %d lc %d            le %d term %d”,lb-ia,ld,lc,le,term_loop);            144.   if (((ib-            ia)&gt;(c_i.desat_min _length/OXYMINUTE_5::SecPerOxy)) &amp;&amp; ld)            145.   {       146.   if (DEBUG_ART_DESAT)            147.   Printf(“ DESAT IT ”);            148.   for (lc=ia; lc&lt;lb; lc++)            149.   ox_min_buf[lc].status|=0x100;   }            150.   }            151.    }       152.   lseek(oxy_handle,0,SEEK SET);       153.   for (lb=0;lb&lt;oxyminn_records;lb++)            154.   write(oxy_handle, (char*)&amp;ox_min _buf[lb],            sizeof(OXYMINUTE_5));            155.   delete [ ](ox_min_buf);       156.   close (beatstream);       157.   close(oxy_pulse);       158.   close(oxy_handle);            159.   if (((la=(clock( )-start_clock)) &gt;0) &amp;&amp; start_clock)            160.   Printf(“ time at end of oxy art %g”,la/CLK_TCK);       161.   }                  
 
         [0033]    Referring to FIG. 9, a computer  70  includes a processor  72  for processing oxymetry data signals stored on a memory card (not shown) and read by memory card reader  73 . Computer  70  also includes a memory  74 , and a storage medium  56  (e.g., hard disk). Storage medium  76  stores operating system  81 , data signals  82 , and computer instruction signals  78  which are executed by processor  72  out of memory  74  to perform process  10 . In this embodiment, the memory card is a Personal Computer Memory Card (International Association) (PCMCIA) which is compatible with the Advanced Technology Attachment (ATA) interface standard, and memory reader  73  is manufactured by Sandisk of Sunnyvale, Calif. In one embodiment, computer instructions include executable instruction signals.  
         [0034]    Process  10  is not limited to use with the hardware and software of FIG. 9; process  10  may find applicability in any computing or processing environment and with any type of machine that is capable of running a computer program. Process  10  may be implemented in hardware, firmware, software, or a combination of two or more. Process  10  may be implemented in computer programs executed on programmable computers/machines that each include a processor, a storage medium/article of manufacture readable by the processor (including volatile and non-volatile memory and/or storage elements), at least one input device, and one or more output devices. Program code may be applied to data entered using an input device to perform process  10  and to generate output information.  
         [0035]    Each such program may be implemented in a high level procedural or objected-oriented programming language to communicate with a computer system. However, the programs can be implemented in assembly or machine language. The language may be a compiled or an interpreted language. Each computer program may be stored on a storage medium (article) or device (e.g., CD-ROM, hard disk, read only memory (ROM) integrated circuit, or magnetic diskette) that is readable by a general or special purpose programmable computer for configuring and operating the computer when the storage medium or device is read by the computer to perform process  10 . Process  10  may also be implemented as a machine-readable storage medium, configured with a computer program, where upon execution, instructions in the computer program cause the computer to operate in accordance with process  10 .  
         [0036]    In other embodiments, process  10  can be performed using a processor located on a patient. In still other embodiments, the recorder can perform process  10 . The invention is not limited to a specific location. Process  10  can be performed by a device connected to the patent, at the recorder, or anywhere external to the patient.  
         [0037]    The invention is not limited to the specific embodiments described herein. The invention is not limited to the specific processing order of FIGS. 1, 5, and  8 . Rather, the blocks of FIGS. 1, 5, and  8  may be re-ordered, as necessary, to achieve the results set forth above.  
         [0038]    Other embodiments not described here are also within the scope of the following claims.