Abstract:
A method and apparatus for acquiring and displaying physiological patient data wherein the amplitude of the data is represented in color.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a method and apparatus for displaying physiological patient data, and particularly, to a method and apparatus for displaying physiological patient data in a colorized waterfall format. 
     Medical patient monitors are typically employed by physicians and other health care providers to monitor the physiological data of patients in operating rooms, intensive care units and emergency rooms, and for conducting long-term trend monitoring such as Holter monitoring or stress testing. 
     An array of sensors (also commonly called transducers) are typically connected to the patient to acquire the various physiological data. These data are then displayed on the screen of a monitor either in graphical or numerical form. These data may also be recorded or displayed on analog or digital strip chart recorders, spreadsheets and plotting programs. 
     In prior patient monitoring systems, and particularly in Holter and stress testing systems, it was found to be advantageous to take a series of successive periods of physiological patient data and cascade the periods in a quasi-three-dimensional display format to render visually obvious the abnormalities attendant to certain physiological conditions. However, this kind of data presentation can become cluttered if too many waveform samples are displayed at any one time. Moreover, some users of the equipment find such a display presentation visually unappealing, notwithstanding the clinical importance of the display technique. 
     SUMMARY OF THE INVENTION 
     Accordingly, the invention provides a method of displaying physiological and/or pathological patient data (hereinafter, the terms “physiological data” or “physiological patient data” shall be broadly defined as including pathological data, or any other type of patient information that is capable of being displayed using the invention). The method includes acquiring the physiological patient data, storing the physiological patient data in a waveform array, and displaying the physiological patient data on a monitor having a first (for example an “X”) coordinate axis, a second (for example a “Y”) coordinate axis, and a color component. In one form of the invention, the step of displaying the physiological patient data includes dividing the waveform array into a series of successive waveforms such that each successive waveform is plotted at a successive Y coordinate, and dividing each waveform into a series of successive data points such that each data point is plotted at a successive X coordinate and assigned a color according to the amplitude of the data point. The waveform array may be physiological data that represents individual physiological cycles such as heart beats, or the waveform array may be data that has been aggregated in some fashion such as averaging or filtering, or reduction to median complex. 
     The invention also provides an apparatus for acquiring and displaying physiological patient data. The apparatus includes a sensor or a transducer for acquiring physiological patient data from a patient, a processor for receiving the physiological patient data and for generating a waveform display on a monitor having an X coordinate axis, a Y coordinate axis and a plurality of color pixels such that the physiological patient data is stored in a waveform array. The processor divides the waveform array into a series of successive waveforms, and assigns each successive waveform a respective Y coordinate. The processor also divides each waveform into a series of successive data points and assigns each data point a respective X coordinate. Next, the processor assigns a color (which may be a shade of gray in the case of a black and white monitor, or a variation in intensity in the case of a monochrome monitor) according to the amplitude of the data point and plots the data point on the display monitor so that the pixel at the respective X and Y coordinate is energized using that color. 
     It is an advantage of the invention to provide a method and apparatus of displaying amplitude differences of physiological patient data using a gray scale or color display presentation. 
     Other features and advantages of the invention are set forth in the following drawings, detailed description and claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The file of this patent contains at least one drawing executed in color. Copies of this patent with color drawing(s) will be provided by the Patent and Trademark Office upon request and payment of the necessary fee. 
     FIG. 1 is a block diagram illustrating a patient monitoring system according to the invention. 
     FIG. 2 is a flow chart illustrating the method of the invention. 
     FIG. 3 is a color illustration showing a comparison of two waterfall displays of the prior art versus corresponding waterfall displays according to the invention. 
    
    
     Before one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of the construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates the patient monitoring system  10  of the invention. The patient monitoring system  10  acquires and displays physiological patient data. While the monitoring system  10  can be used in connection with any kind of clinical environment, in the preferred embodiment, the monitoring system  10  is for conducting long-term trend monitoring such as in Holter monitoring or stress testing. Monitoring system  10  is coupled to the patient  14  by an array of sensors or transducers which may include, for example, electrodes  18  mounted on the patient&#39;s chest for determining electrocardiogram and heart rate, an oximetry sensor  22  mounted on the patient&#39;s finger for measuring hemoglobin oxygen saturation, a catheter  26  for measuring hemoglobin oxygen saturation in the vena cava in the central venus pressure, an arterial canula  30  for measuring arterial systolic and diastolic pressures, flow meter  34  and a pressure sensor  38  in the endotrachial tube  42  for measuring trachial gas flow, and airway pressure, respectively, and sensors  46  in the patient&#39;s mask  50  for measuring the volume percentage of oxygen and CO 2  in the patient&#39;s mouth. Hereinafter, the terms “sensor” and “transducer” will be used synonymously, and each term will be defined as including the subject matter of the other term. 
     The signals derived from the sensors are converted from analog form to digital form by the analog to digital converter  54  and are then provided to a processor  58  that prepares the data for display on display monitor  62 . The monitor is a conventional computer-style display monitor having a generally rectangular cathode ray tube or CRT (not shown). The CRT includes a plurality of pixels. The vertical location of the pixels is defined by a Y coordinate and the horizontal location is defined by an x coordinate. As is known in the art, each pixel is capable of being energized electronically so that the pixel emits light visible to the user of the monitoring system. 
     In the preferred form of the invention, the display monitor  12  is capable of displaying full color pixels, i.e., the display monitor is an RGB color monitor capable of displaying 256 colors or more. In other embodiments however, a black and white display capable of showing black, white and a plurality of gray shades (preferably no less than 64) in between is acceptable. The term “color” as used in this application is used to indicate either true color or shades of gray as described above unless the context indicates otherwise. Also, while any physiological patient data may be displayed in the format of the preferred embodiment, the invention will be discussed in the context of displaying long-term electrocardiogram (“ECG”) data. 
     FIG. 2 illustrates a flow chart of the process of the invention. The waveforms are stored in a waveform array. The processor sets the current waveform count to the first waveform in the waveform array. The processor then initializes the Y-axis pixel coordinate value to begin at the bottom of the CRT, sets the sample pointer to the first data sample in the current waveform and initializes the X-axis pixel coordinate value to begin at the left of the CRT. The processor then retrieves the current data point from the current waveform, determines a pixel color for the data point based on the amplitude of the waveform data point, and plots that data point at the respective X and Y coordinate using the selected color. In the preferred form of the invention, the color scheme of the monitoring system  10  is fully configurable. That is, the user can select any color to represent a given amplitude. Alternatively, the monitoring system  10  is programmed to provide the user with a set of manufacturer defined color schemes. In the preferred form of the invention, there would be graphical and numerical information generated on the display to indicate the corresponding voltage level of displacement for each color used. 
     The processor then increments the X coordinate and repeats the process for each data point in the current waveform until all data points in that waveform have been plotted. Once all data points in that waveform are plotted, then the processor increments the Y coordinate in order to retrieve the next waveform in the waveform array. This process is repeated until all of the waveforms in the waveform array are plotted. The results are displays such as those shown in FIG.  3 . 
     Alternatively, the waveforms may be displayed by starting at the top of the screen and incrementing the Y coordinate downward for successive waveforms, or waveforms may be drawn by starting at an X and Y coordinate on the left side of the screen. First, an individual data point is plotted, then the processor increments the Y coordinate and the next data point is plotted until all data points for a waveform are plotted. Then, the X coordinate is incremented and the next waveform is plotted in the same manner. 
     FIG. 3 illustrates two waterfall displays of the prior art plotted above the same waveform data displayed using the method of the invention. The data labelled “Median Waveforms” in FIG. 3 is displayed so that the waveforms are stacked in a quasi-three-dimensional display presentation that allows some observation of long-term trends for a given set of physiological data. However, subtle trends that may exist in the data are difficult to observe. For example, in the uppermost Median Waveform of FIG. 3, there appears to be an amplitude shift in the waveform data just after 240 ms mark. It is difficult, however, to discern the meaning of this amplitude shift. The same waveform data is represented in FIG. 3 directly below the uppermost Median Waveform using the method of the invention and is labelled Median Intensity MAP. As shown in the uppermost Median Intensity MAP of FIG. 3, the long-term waveform amplitude shift is easily indicated by a change in color extending vertically at approximately the 240 ms mark. Moreover, variations in the amount of time between events (as shown on the X-axis) are also more easily detected. Again referring to the uppermost Median Waveform of FIG. 3, there is a slight change in amplitude that occurs between 480 ms and 720 ms. As shown in the corresponding Median Intensity MAP, the change in amplitude between waveform  1  and waveform  12 , shifts to the left (i.e., from near the 720 ms mark in waveform  1  to nearer the 480 ms mark in waveforms  9 ,  10  and  11 ), thereby indicating a long-term shift in the timing of the event. 
     It is obvious from the contrasting views, that the physiological patient data colorized waterfall display is much more effective than the traditional prior art waterfall display in indicating subtle long-term trends and changes in physiological patient data. 
     Various other features and advantages of the invention are set forth in the following claims.