Abstract:
A data capture system utilizes a sensor with emitters adapted to transmit light into a fleshy medium and a detector adapted to generate intensity signals in response to receiving light after absorption by the fleshy medium. A monitor is configured to input the intensity signals, generate digitized signals from the intensity signals at a sampling rate and compute at least one physiological parameter responsive to magnitudes of the digitized signals. A data storage device is integrated with the monitor and is adapted to record data derived from the digitized signals on a removable storage media at the sampling rate.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application relates to and claims the benefit of prior U.S. Provisional Patent Application No. 60/518,051 entitled Pulse Oximetry Trend Data Storage System, filed Nov. 7, 2003 and incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     Pulse oximeters have gained rapid acceptance in a wide variety of medical applications, including surgical wards, intensive care units, general wards and home care by providing early detection of decreases in the arterial oxygen supply, reducing the risk of accidental death and injury.  FIG. 1  illustrates a pulse oximetry system  100  having a sensor  110  applied to a patient, a monitor  120 , and a patient cable  130  connecting the sensor  110  and the monitor  120 . The sensor  110  has emitters (not shown) and a detector (not shown) and is attached to a patient at a selected fleshy medium site, such as a fingertip  10  as shown or an ear lobe. The emitters are positioned to project light of at least two wavelengths through the blood vessels and capillaries of the fleshy medium. The detector is positioned so as to detect the emitted light after absorption by the fleshy medium, including hemoglobin and other constituents of pulsatile blood flowing within the fleshy medium, generating at least first and second intensity signals in response. A pulse oximetry sensor is described in U.S. Pat. No. 6,256,523 entitled Low Noise Optical Probes, and a pulse oximetry monitor is described in U.S. Pat. No. 6,745,060 entitled Signal Processing Apparatus, both assigned to Masimo Corporation, Irvine, Calif. and both incorporated by reference herein. 
     The monitor  120 , which may be a standalone device or may be incorporated as a module or built-in portion of a multiparameter patient monitoring system, computes at least one physiological parameter responsive to magnitudes of the intensity signals. A monitor  120  typically provides a numerical readout of the patient&#39;s oxygen saturation  122 , a numerical readout of pulse rate  124 , and a display of the patient&#39;s plethysmograph  126 , which provides a visual display of the patient&#39;s pulse contour and pulse rate. 
     In one embodiment, the pulse oximetry system  100  has a portable instrument  210  and a docking station  220 , such as described in U.S. Pat. No. 6,584,336 entitled Universal/Upgrading Pulse Oximeter, assigned to Masimo Corporation, Irvine, Calif. and incorporated by reference herein. The portable  210  is a battery operated, fully functional, stand-alone pulse oximeter monitor, as described above, which can be installed into the docking station  220  to expand its functionality. 
       FIG. 2  illustrates data communications for the portable  210  and docking station  220 . The portable  210  has bi-directional serial data communications with the docking station  220  using universal asynchronous receive, Rx 0 , and transmit, Tx 0 , (UART) signals, and the docking station  220  has bi-directional serial data communications with an external device  230  using Tx 1  and Rx 1  UART signals. 
     SUMMARY OF THE INVENTION 
     A conventional pulse oximeter may store trend data that consists of, for example, oxygen saturation and pulse rate. This data is recorded at a low rate, such as 1 Hz. Although the resolution afforded by a low data rate is fine for many patient diagnostic purposes, it is desirable to store the plethysmograph waveform, other pulse oximeter parameters and various internal data at a high rate, such as the sensor signal sampling rate. The resulting high resolution data advantageously assists and/or improves patient condition evaluation, pulse oximetry exception diagnosis and algorithm development. Further, pulse oximetry data is conventionally stored using an external computer or a laptop, which may not always be available or is otherwise cumbersome. 
     A pulse oximetry data capture system advantageously replaces an external computer with a small data storage device that utilizes removable storage media to hold many hours of high resolution data. In one embodiment, the data storage device is integrated into a docking station for a portable instrument. The removable storage media, having been written with data, can be easily shipped off-site from where the data is collected for later analysis. 
     One aspect of a pulse oximetry data capture system is a sensor having emitters adapted to transmit light of at least first and second wavelengths into a fleshy medium. A detector is adapted to generate at least first and second intensity signals in response to receiving light after absorption by constituents of pulsatile blood flowing within the fleshy medium. A monitor is configured to input the intensity signals, generate digitized signals from the intensity signals at a sampling rate and compute at least one physiological parameter responsive to magnitudes of the digitized signals. A data storage device is integrated with the monitor and is adapted to record data derived from the digitized signals on a removable storage media at the sampling rate. 
     Another aspect of a pulse oximetry data capture system is a method having the steps of emitting light of at least first and second wavelengths and detecting the light after absorption by a fleshy tissue site so as to generate a corresponding sensor signal. Additional steps are digitizing at a sampling rate, demodulating the sensor signal so as to generate a plethysmograph, and calculating at least oxygen saturation and pulse rate from the plethysmograph. A further step is writing data to the removable media. The data comprises the plethysmograph at the sampling frequency along with the oxygen saturation and the pulse rate at a sub-sampling frequency. 
     A further aspect of a data capture system has a sensor adapted to generate an intensity signal responsive to light absorption by constituents of pulsatile blood flowing within a fleshy medium. A digitizer inputs the intensity signal and generates a digital plethysmograph signal at a sampling rate. A signal processor inputs the plethysmograph and calculates an oxygen saturation and pulse rate. A storage media is configured to removably load into a data storage device. The data storage device inputs the plethysmograph, oxygen saturation and pulse rate and writes the plethymograph to the storage media at the sampling rate, along with the oxygen saturation and the pulse rate at a sub-sampling rate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a prior art pulse oximetry system having a portable pulse oximeter and a docking station; 
         FIG. 2  is a block diagram of portable and docking station data communications; 
         FIG. 3  is a general block diagram of a pulse oximetry data capture system; 
         FIG. 4  is a block diagram of a pulse oximetry docking station incorporating a data capture system; 
         FIGS. 5A-E  are front, front perspective, back, side and internal top views, respectively, of a pulse oximetry docking station incorporating a data capture system; 
         FIG. 6  is a program flow diagram for a pulse oximetry data capture system; and 
         FIG. 7  is a table illustrating a multiple byte message package. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 3  illustrates a pulse oximetry data capture system  300  having a digitizer  310 , signal processor  320 , a data storage device  330 , a removable media  340  and a data port interface  350 . The digitizer  310  samples the sensor signal  301  based upon a predetermined sampling frequency  302  and performs an analog-to-digital conversion of the sampled signal to generate a digitized sensor signal  312 . The signal processor  320  demodulates the red (RD) and IR components of the digitized sensor signal  312  into RD and IR plethysmograph signals and operates on those plethysmograph signals so as to calculate oxygen saturation and pulse rate. A pulse oximetry demodulator is described in U.S. Pat. No. 6,643,530 entitled Method and Apparatus for Demodulating Signals in a Pulse Oximetry System, assigned to Masimo Corporation, Irvine, Calif. and incorporated by reference herein. As a result, the signal processor  320  generates a data stream  322  comprising plethysmograph, oxygen saturation and pulse rate values among other data. The data storage device  330  inputs the data stream  322 , which is recorded on the removable media  340 . The data stream  322  may also be provided to an external device via the data port interface  350 . In various embodiments, the data storage device  330  may transparently “pass-through” the data stream  322  to other system components, such as the data port interface  350 , or it may otherwise tap the data stream  322  as it is utilized elsewhere in the system  300 . Alternatively, the signal processor  320  or other system components may provide the data storage device  330  with a dedicated data stream used solely for data recording purposes. 
     In one embodiment, the data stream  322  comprises raw, filtered and/or scaled plethysmograph waveform data; computed output data such as oxygen saturation, pulse rate, signal strength and signal quality; and other system data such as sensor status, monitor status, monitor settings, alarms, and internal algorithm parameters and variables. Pulse oximetry signal strength and signal quality or confidence data are described in U.S. Pat. No. 6,463,311 entitled Plethysmograph Pulse Recognition Processor and U.S. Pat. No. 6,684,090 entitled Pulse Oximetry Data Confidence Indicator, both assigned to Masimo Corporation, Irvine, Calif. and both incorporated by reference herein. Sensor status, monitor status and settings and alarms are described in U.S. Pat. No. 6,658,276 entitled Pulse Oximeter User Interface, also assigned to Masimo Corporation and incorporated by reference herein. 
       FIG. 4  illustrates a docking station embodiment  400  of a data capture system  300  ( FIG. 3 ). A docking station  401  has a CPU  410 , a data storage device  420  and an associated removable storage media  430 . The docking station communicates with a portable pulse oximeter via input UART signals  402  and with an external device via output UART signals  403 . The docking station CPU  410  communicates with the data storage device  420  using internal UART signals  412 . The CPU  410  receives pulse oximetry and related data from the portable via the input UART signals  402  and may generate additional data in response. The received portable data and/or the CPU generated data is transmitted to the data storage device  420  via the internal UART signals  412  and recorded on the removable media  430  accordingly, as described in further detail below. 
       FIGS. 5A-E  illustrate a particular docking station embodiment  500  of a pulse oximetry data capture system  400  ( FIG. 4 ). The data storage device  520  ( FIG. 5E ) is a Flashcore-B available from TERN, Inc., Davis, Calif., and the removable storage media  530  ( FIG. 5E ) is a 256 MB Compact Flash card. The data storage device  520  is installed internally to the docking station  510  adjacent a circuit board  540  ( FIG. 5E ) and proximate the docking station bottom  501 . The docking station  510  supplies power to the data storage device  520 . The data storage device  520  transparently passes-through the internal UART signals  412  ( FIG. 4 ) to the output UART signals  403  ( FIG. 4 ). A slot  550  is created in the bottom of the docking station  510 , which allows insertion and removal of the storage media  530  into and out of the storage device  520 . One of ordinary skill will recognize that the data storage device  520  and associated removable media  530  can utilize various data storage technologies other than Compact Flash, such as Memory Stick, SmartMedia, Secure Digital Card, USB Flash Disk and MicroDrive to name just a few. 
       FIG. 6  illustrates program flow  600  for the docking station CPU to control and write data to the data storage device  520  ( FIG. 5E ). To start, a flash card  530  ( FIG. 5E ) is validated and initialized  610 . If a valid flash card is in the data storage device, then the card capacity is checked  620 . If the card capacity is sufficient, then a file is opened  630  and data writing begins  640 . Data is advantageously written to the data storage device in multiple byte message packets at up to the IR and red signal sampling rate, as described with respect to  FIG. 7 , below. The writing time is checked  650 . After one hour of data is recorded, the card capacity is rechecked  620  and, if sufficient, another file is opened  630  and recording continues. If an error occurs in opening a file, an LED indicator is flashed  660 . If no valid flash card is detected, data is passed through to the external device signal lines and the LED indicator is turned on  670 . If there is insufficient flash card capacity, the oldest file is deleted  680 . 
       FIG. 7  illustrates a multiple byte message packet having start of message (SOM)  710 , end of message (EOM)  720 , sequence (seq)  730  and check sum (CSUM) 770 bytes and one or more data segments d 1 -d 2   740 , w 0 -w 7   750  and x 0 -xm  760 . The SOM  710  and EOM  720  are fixed-value bytes that delineate each message packet. The seq 730 byte identifies specific message packets in a cyclical group of message packets, as described below. The data segments  740 - 760  are formatted so as to allow storage of the data stream  322  ( FIG. 3 ) described above. The check sum  770  is for communications error detection and is the sum of the data bytes  740 - 760  modulo  256 . The message packets  700  are transmitted to the data storage device  420  ( FIG. 4 ) and stored on the removable storage media  430  ( FIG. 4 ) at about the IR and red (RD) signal sampling rate. In this manner, sufficient information with sufficient resolution is stored on the removable storage media for a thorough external data analysis. 
     In one embodiment, 32-bit IR waveform data can be stored in w 0 -w 3   750 ,  32 -bit RD waveform data can be stored in w 4 -w 7   750 , and various 16-bit output data, such as oxygen saturation and pulse rate can be stored in d 1 -d 2   740  as identified by the sequence byte  730 . In a particular embodiment, the sampling rate is 62.5 Hz, and  62  messages packets are stored in a specific sequence per second. The sequence byte (seq)  730  increments from 1 to 62 with each successive message packet  700  and then resets to 1, repeating so as to identify the specific data in, say, d 1 -d 2   740 . For example, plethysmograph waveform data is stored in w 0 -w 7   750  at a 62 Hz rate and oxygen saturation, corresponding to seq=1 and pulse rate, corresponding to seq=2, are stored in d 1 -d 2   740  at a sub-sampling rate of 1 Hz. 
     A pulse oximetry data capture system has been disclosed in detail in connection with various embodiments. These embodiments are disclosed by way of examples only and are not to limit the scope of the claims that follow. One of ordinary skill in the art will appreciate many variations and modifications.