Abstract:
A respiratory monitor measures expiratory carbon dioxide. A display has a measurement indicator combined with a color indicator. The measurement indicator corresponds to a measured value of carbon dioxide. The color indicator corresponds to a predetermined range of carbon dioxide values including the measured value so as to provide a readily recognized visual cue that carbon dioxide is in a normal range or an abnormal range.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application claims priority benefit under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application Ser. No. 60/811,524, filed Jun. 6, 2006, entitled “Respiratory Monitor Display,” incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     Respiratory carbon dioxide (CO 2 ) is an important parameter that provides valuable patient status information to a healthcare provider. A typical carbon dioxide monitor, or capnometer, analyzes carbon dioxide from respiratory airflow, either mainstream or sidestream, from an intubated or non-intubated patient. Mainstream monitors insert a sample chamber within the patient&#39;s gas flow, whereas sidestream monitors deliver a sample of gas flow to a remote sample chamber. Capnometers utilize, for example, optical means (infrared spectra analysis) or chemical means (pH analysis) for carbon dioxide measurements. Carbon dioxide is conventionally measured at “end-tidal” or the completion of the exhalation cycle. This end-tidal carbon dioxide measurement (ETCO 2 ) is a partial pressure expressed as millimeters of mercury (mmHg or Torr), a percentage of normal atmospheric pressure (760 mmHg at an ambient temperature of 25° C.), where 1%=0.01×760 mmHg=76 mmHg, or in kilo Pascals (kPa), where 1 kPa=7.5 mmHg. ETCO 2  is a non invasive measurement that approximates the partial pressure of carbon dioxide in the arterial blood (PaCO 2 ), where the normal gradient between the two measurements is about 5 to 6 mmHg. Normal ETCO 2  is in a range of about 35 to 45 mmHg or roughly 5% to 6% CO 2 .  
       SUMMARY OF THE INVENTION  
       [0003]     Capnography has become a standard of care in surgical departments for airway and ventilation assessment. As examples, the absence of ETCO 2  may indicate esophageal intubation, accidental tracheal extubation, disconnection of the breathing circuit or complete obstruction of the endotracheal tube. In addition, capnography provides feedback for adjusting ventilator settings.  
         [0004]     It is crucial for a monitor to quickly alert a practitioner of abnormal CO 2  measurements and allow ready determination of normal CO 2  measurements. A respiratory monitor display advantageously provides an ETCO 2  measurement in combination with a ETCO 2  range indicator. The range indicator allows quick visual recognition of a normal or abnormal ETCO 2  measurement. In an embodiment, the ETCO 2  range indicator is a color cue, such as green for normocarbia, and yellow or red for increasing degrees of hypocarbia or hypercarbia.  
         [0005]     One aspect of a respiratory monitor display is a numerical indicator corresponding to a person&#39;s measured value of respiratory carbon dioxide and a color indicator also corresponding to the measured value of respiratory carbon dioxide. The color indicator is configured to display colors corresponding to each of a normal range of expiratory carbon dioxide and an abnormal range of respiratory carbon dioxide. In an embodiment, the numerical indicator is a number digit and the color indicator is a color applied to the digit itself or to the digit&#39;s background. In an embodiment, respiratory carbon dioxide is indicated with a bar graph. The numerical indicator is a printed number at the end of the bar. The color indicator is a color applied to the bar, where the bar may be continuous or a series of discrete LEDs. In an embodiment, the color indicator has a first color, such as a shade of green, for a normal range of ETCO 2 , a second color, such as a shade of yellow, for a moderately abnormal range of ETCO 2 , and a third color, such as a shade of red, for a significantly abnormal range of ETCO 2 .  
         [0006]     Another aspect of a respiratory monitor display comprises measuring respiratory carbon dioxide of a patient and displaying an end tidal carbon dioxide (ETCO 2 ) value from the measurement. A range of ETCO 2  is indicated in association with the displayed value. The range indication has at least a first color corresponding to a normal range of ETCO 2  and at least a second color corresponding to an abnormal range of ETCO 2 . In an embodiment, a waveform of respiratory carbon dioxide versus time is displayed and coloring of at least a portion of the waveform indicates the ETCO 2  range. For example, the waveform plateau may be colored a shade of green when ETCO 2  is within a normal range of between about 35 mmHg and about 45 mmHg and colored a shade of from yellow to red when ETCO 2  is outside a normal range. In an embodiment, digits representing the ETCO 2  value are displayed and either the digits or the digit background are colored according a normal or abnormal ETCO 2  range. In another embodiment, a bar graph having a bar representing the ETCO 2  value is displayed and the bar is colored according to a normal or abnormal ETCO 2  range. The bar may be a continuous illumination or a series of discrete color indicators, such as LEDs, where at least one of the LEDs is illuminated in a color according to a normal or abnormal ETCO 2  range. In an embodiment, the bar is a shade of green when ETCO 2  is within a range of between about 35 mmHg and about 45 mmHg and a shade of from yellow to red when ETCO 2  is outside that normal range.  
         [0007]     A further aspect of a respiratory monitor display comprises a measurement indicating means and a color indicating means. The measurement indicating means convey a measured value of a person&#39;s respiratory carbon dioxide. The color indicating means corresponds to the measurement indicating means and provides an immediate visualization or cue of a range of the measured value of respiratory carbon dioxide. A combination means combines the measurement indicating means and the color indicating means. In an embodiment, the combination means comprises a bar means for indicating the measured value and a bar color means for indicating the range. In an embodiment, the combination means comprises a digit means for indicating the measured value and a digit color means for indicating the range. In an embodiment, the color indicating means comprises a safe color means for indicating a normal range of measured ETCO 2  and a caution color means for indicating an abnormal range of measured ETCO 2 .  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is an illustration of a respiratory monitor display combining a respiratory waveform and an ETCO 2  range indicator;  
         [0009]     FIGS.  2 A-C are illustrations of respiratory monitor displays combining a numerical ETCO 2  measurement and an ETCO 2  range indicator;  
         [0010]      FIG. 3  is an illustration of a respiratory monitor display combining a continuous ETCO 2  bar graph and an ETCO 2  range indicator; and  
         [0011]      FIG. 4  is an illustration of a respiratory monitor display combining a discrete ETCO 2  bar graph and an ETCO 2  range indicator. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0012]      FIG. 1  illustrates a respiratory monitor display  100  having a CO 2  axis  101 , a time axis  102  and a respiratory waveform  105 . The waveform  105  has four phases corresponding to a respiratory cycle. The first phase occurs during inspiration. The second phase is the onset of expiration, which results in a rapid increase in CO 2 . The third phase occurs as the CO 2  is exhaled from all the alveoli. The fourth phase is the onset of inspiration. These phases are delineated by an inspiratory baseline  110 , an expiratory upstroke  120 , an expiratory plateau  130  and an inspiratory downstroke  140 . The highest point  132  of the plateau  130  is the ETCO 2  measurement at the end of expiration. In an embodiment, the waveform  105  is displayed in a color associated with one of a predetermined set of ETCO 2  ranges  150 . In an embodiment, the respiratory waveform  105  is a green shade when ETCO 2  is in a normal range  152 , a yellow shade when ETCO 2  is moderately outside of a normal range  154  and a red shade when ETCO 2  is significantly outside a normal range  158 . In an embodiment, only portions of the waveform trace are colored according to a measured ETCO 2  range, such as the plateau  130 .  
         [0013]     FIGS.  2 A-C illustrate respiratory monitor displays  201 - 203  having numbers  210  representing an ETCO 2  measurement and associated color indicators  220  representing an ETCO 2  range.  FIG. 2A  shows a respiratory monitor display  201  embodiment having colored digits  205 , where the digits  210  represent the numerical value of an ETCO 2  measurement and the color of the digits  220  indicates an ETCO 2  range. In an embodiment, the colored digits  205  are a green shade when indicating a normal ETCO 2  range, a yellow shade when indicating a moderately abnormal ETCO 2  range and a red shade when indicating a significantly abnormal ETCO 2  range.  
         [0014]     As shown in  FIG. 2B , a respiratory monitor display  202  has digits  210  and a vertical bar graph  230 . As above, the digits  210  represent the numerical value of an ETCO 2  measurement. The height  235  of the bar graph  230  also corresponds to the numerical value of the ETCO 2  measurement. Further, the color  220  of the bar graph  230  to its measured height  235  indicates an ETCO 2  range. In an embodiment, the bar graph color  220  is a green shade when indicating a normal ETCO 2  range, a yellow shade when indicating a moderately abnormal ETCO 2  range and a red shade when indicating a significantly abnormal ETCO 2  range.  
         [0015]     As shown in  FIG. 2C , a respiratory monitor display  203  has digits  210  displayed over a colored background  220 . As above, the digits  210  represent the numerical value of an ETCO 2  measurement. The background color  220  indicates an ETCO 2  range. In an embodiment, the background is a green shade when ETCO 2  is in a normal range, a yellow shade when ETCO 2  is in a moderately abnormal ETCO 2  range and a red shade when ETCO 2  is in a significantly abnormal range.  
         [0016]      FIG. 3  illustrates a respiratory monitor display  300  having a continuous colored bar graph  310 . In an embodiment, the length of the colored bar  320  indicates an ETCO 2  measurement. In an embodiment, printed numbers  340  aligned with the bar end  330  designate an ETCO 2  measurement value. A color indicator  350  along the length of the bar  320  corresponds to one or more ETCO 2  ranges. In an embodiment, at least a portion of the bar is a green shade corresponding to a normal ETCO 2  range, a yellow shade corresponding to a moderately abnormal ETCO 2  range and a red shade corresponding to a significantly abnormal ETCO 2  range.  
         [0017]      FIG. 4  illustrates a respiratory monitor display  400  having a discrete colored bar graph  410  having an illuminated bar  420 , printed numbers  430  and color range indicators  440 . In an embodiment, the bar is composed of multiple LEDs (light emitting diodes), where a single LED is illuminated corresponding to a particular ETCO 2  measurement and corresponding printed number. In an embodiment, multiple LEDs are illuminated along the bar length  420 , the last of which corresponds to a particular ETCO 2  measurement. In an embodiment, the LEDs emit light having a color corresponding to an ETCO 2  range. For example, the bar is composed of green (G) LEDs corresponding to a normal ETCO 2  range, yellow (Y) LEDs corresponding to a moderately abnormal ETCO 2  range and red (R) LEDs corresponding to a significantly abnormal ETCO 2  range, as shown.  
         [0018]     In various embodiments described above, the colors green, yellow and red, and shades thereof, are used to represent normal, moderately abnormal and significantly abnormal ETCO 2  range intervals, respectively. For example, green is a color cue that something is “safe,” and yellow or red is a color cue for “caution.” In each of those embodiments, colors other than green, yellow and red may be used to represent those range intervals; different range intervals may be designated by these colors; more range intervals may be represented by additional colors; colors representing hypocarbia range intervals may be different than colors representing hypercarbia range intervals; color combinations may be used to represent each interval; and multiple colors displayed simultaneously may represent particular range intervals, such as a bar graph that has progressively red, yellow, green, yellow and red sections displayed as ETCO 2  increases.  
         [0019]     In various embodiments described above, a normal ETCO 2  range is considered to be between about 35 to 45 mmHg, a moderately abnormal ETCO 2  range is considered to be between about 25 to 35 mmHg or between about 45 to 55 mmHg, and a significantly abnormal ETCO 2  range is considered to be below about 25 mmHg or above about 55 mmHg. In various embodiments described above, a significantly abnormal ETCO 2  range is considered to be below about 15 mmHg and above about 65 mmHg, an abnormal ETCO 2  range is considered to be between about 15 mmHg to 25 mmHg and between about 55 mmHg to 65 mmHg, and a normal ETCO 2  range is considered to be between about 35 to 45 mmHg. Other embodiments may include different range intervals and more range intervals or both. In an embodiment, instead of LEDs, the bar of a bar graph is composed of chemical indicators that display a color in response to the pH of the respiratory gas flow.  
         [0020]     In various embodiments described above, ETCO 2  range intervals are indicated by an associated color indicator. Other embodiments may include an audible range indicator in lieu of or in addition to a color range indicator. An audible range indicator may be one or more tones, sound volumes or sound patterns, or absence of one or more tones, volumes or patterns, which are triggered within various ETCO 2  range intervals so as to promptly alert a practitioner of an ETCO 2  measurement.  
         [0021]     A respiratory monitor display 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 art will appreciate many variations and modifications.