WO1999039633A1 - Systeme d'affichage de schemas de processus medicaux - Google Patents

Systeme d'affichage de schemas de processus medicaux Download PDF

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Publication number
WO1999039633A1
WO1999039633A1 PCT/US1999/002798 US9902798W WO9939633A1 WO 1999039633 A1 WO1999039633 A1 WO 1999039633A1 US 9902798 W US9902798 W US 9902798W WO 9939633 A1 WO9939633 A1 WO 9939633A1
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WIPO (PCT)
Prior art keywords
patient
oxygen
data
blood
area
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PCT/US1999/002798
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English (en)
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WO1999039633A9 (fr
Inventor
George T. Blike
Nicholas Simon Faithfull
Glenn Rhoades
Original Assignee
Alliance Pharmaceutical Corp.
The Hitchcock Clinic
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US09/020,472 external-priority patent/US6234963B1/en
Application filed by Alliance Pharmaceutical Corp., The Hitchcock Clinic filed Critical Alliance Pharmaceutical Corp.
Priority to EP99906848A priority Critical patent/EP1054617A1/fr
Priority to JP2001507268A priority patent/JP2003503125A/ja
Priority to CA002321227A priority patent/CA2321227A1/fr
Priority to AU26667/99A priority patent/AU2666799A/en
Publication of WO1999039633A1 publication Critical patent/WO1999039633A1/fr
Publication of WO1999039633A9 publication Critical patent/WO1999039633A9/fr

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
    • A61B5/1455—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters
    • A61B5/14551—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters for measuring blood gases
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/41—Detecting, measuring or recording for evaluating the immune or lymphatic systems
    • A61B5/412—Detecting or monitoring sepsis

Definitions

  • This invention relates to display systems. More specifically, this invention relates to systems for displaying graphical information, particularly in a medical setting. Background of the Invention
  • Medical display systems provide information to doctors in a clinical setting.
  • Typical display systems provide data in the form of numbers and one-dimensional signal waveforms that must be assessed, in real time, by the attending physician.
  • Alarms are sometimes included with such systems to warn the physician of an unsafe condition, e.g., a number exceeds a recommended value, in the field of anesthesiology, for example, the anesthesiologist must monitor the patient's condition and at the same time (i) recognize problems, (ii) identify the cause of the problems, and (iii) take corrective action during the administration of the anesthesia. An error in judgment can be fatal.
  • AIMS Australian incident Monitoring Study
  • Cole, et. al. has developed a set of objects to display the respiratory physiology of intensive care unit (ICU) patients on ventilators.
  • This set of displays integrates information from the patient, the ventilator, rate of breathing, volume of breathing, and percent oxygen inspired.
  • ICU physicians made faster and more accurate interpretations of data than when they used alphanumeric displays.
  • Cole published one study that compared how physicians performed data interpretation using tabular data vs. printed graphical data.
  • Cole's work did not involve a system for receiving analog data channels and driving a real-time graphical display on a medical monitor.
  • Ohmeda a company that makes anesthesia machines, manufacturers the Modulus CD machine which has an option for displaying data in a graphical way.
  • the display has been referred to as a glyph.
  • Physiologic data is mapped onto the shape of a hexagon.
  • Six data channels generate the six sides of the hexagon.
  • this display is graphical, the alphanumeric information of the display predominates.
  • the physiologic data is assigned a side of the hexagon.
  • symmetric changes to the different signs of this geometric shape are very hard for individuals to differentiate.
  • Hematocrit is typically defined as the percentage by volume of packed red blood cells following centrifugation of a blood sample. If the hemoglobin level per deciliter of blood in the patient is high, the physician can infer that the patient has sufficient capacity to carry oxygen to the tissue. During an operation this value is often used as a trigger; i.e. if the value falls below a certain point, additional blood is given to the patient. While these parameters provide an indication of the arterial oxygen content of the blood, they provide no information on the total amount of oxygen transported (or “offered”) to the tissues, or on the oxygen content of blood coming from the tissues.
  • Cardiac output or CO is defined as the volume of blood ejected by the left ventricle of the heart into the aorta per unit of time (ml/min) and can be measured with thermodilution techniques. For example, if a patient has internal bleeding, the concentration of hemoglobin in the blood might be normal, but the total volume of blood will be low. Accordingly, simply measuring the amount of hemoglobin in the blood without measuring other parameters such as cardiac output is not always sufficient for estimating the actual oxygenation state of the patient.
  • the oxygenation status of the tissues is reflected by the oxygen supply/demand relationship of those tissues i.e., the relationship of total oxygen transport (D0 2 ) to total oxygen consumption (V0 2 ).
  • Hemoglobin is oxygenated to oxyhemoglobin in the pulmonary capillaries and then carried by the cardiac output to the tissues, where the oxygen is consumed.
  • the partial pressure of oxygen (P0 2 ) decreases until sufficient oxygen has been released to meet the oxygen consumption (V0 2 ).
  • pulmonary artery catheterization To fully assess whole body oxygen transport and delivery, one catheter (a flow directed pulmonary artery [PA] catheter) is placed in the patient's pulmonary artery and another in a peripheral artery. Blood samples are then drawn from each catheter to determine the pulmonary artery and arterial blood oxygen levels. As previously discussed, cardiac output may also be determined using the PA catheter. The physician then infers how well the patient's tissue is oxygenated directly from the measured oxygen content of the blood samples.
  • PA flow directed pulmonary artery
  • Partial pressure of oxygen in the mixed venous blood or mixed venous blood oxygen tension is another important parameter that may be determined using a PA catheter. Because of the equilibrium that exists between the partial pressure of oxygen (P0 2 ) in the venous blood and tissue, a physician can infer the tissue oxygenation state of the patient. More specifically, as arterial blood passes through the tissues, a partial pressure gradient exists between the P0 2 of the blood in the arteriole passing through the tissue and the tissue itself. Due to this oxygen pressure gradient, oxygen is released from hemoglobin in the red blood cells and also from solution in the plasma; the released 0 2 then diffuses into the tissue. The P0 2 of the blood issuing from the venous end of the capillary cylinder (Pv0 2 ) will generally be a close reflection of the P0 2 at the distal (venous) end of the tissue through which the capillary passes.
  • dD0 2 is the amount of the oxygen transported to the tissues (D0 2 ) that is able to be delivered to the tissues (i.e. consumed by the tissues) before the Pv0 2 (and by implication the global tissue oxygen tension) falls below a certain value.
  • dD0 2 (40) is the amount of oxygen that can be delivered to the tissues (consumed by the tissues) before Pv0 2 is 40 mm Hg while dD0 2 (35) is the amount consumed before the Pv0 2 falls to 35 mm Hg.)
  • V0 2 whole body oxygen consumption
  • Cardiac output may also be non-invasively inferred by measuring arterial blood pressure instead of relying on thermodilution catheters.
  • Kraiden et al. U.S. Patent No. 5,183,051, incorporated herein by reference
  • a Pv0 2 value of 35 mm Hg or more may be considered to indicate that overall tissue oxygen supply is adequate, but this is implicit on the assumption of an intact and functioning vasomotor system.
  • the accurate determination of D0 2 depends on an intact circulatory system.
  • a transfusion trigger (whether D0 2 , Pv0 2 , Sv0 2 or some derivation thereof) at which the patient is obviously in good condition as far as oxygen dynamics are concerned.
  • a transfusion trigger whether D0 2 , Pv0 2 , Sv0 2 or some derivation thereof
  • Embodiments of the invention provide for the determination and display of one or more values that accurately reflect the physiological condition of a patient.
  • Preferred values include the global oxygenation and cardiovascular status of the patient.
  • Each of these values can be displayed as intuitive medical process diagrams to assist the physician in understanding the medical condition of their patient.
  • many of the displayed values can be advantageously determined without invasive procedures on the patient.
  • the display system and methods discussed herein may be used to safely and intuitively monitor the physiological condition of patients and adjust therapeutic parameters based on the displayed values.
  • the present invention provides for the determination and real-time display of physiologically important oxygenation parameters indicative of a patient's tissue oxygenation status such as, for example, total oxygen transport (D0 2 ), deliverable oxygen transport (dD0 2 ), mixed venous blood oxyhemoglobin saturation (Sv0 2 ) and mixed venous blood oxygen tension (Pv0 2 ).
  • the invention may also be used to provide a supply/demand ratio (dD0 2 /V0 2 ), another oxygenation parameter, that allows a physician to accurately monitor and adjust the oxygen status of a patient using a single numerical value.
  • the derived oxygenation parameters may be used alone or, more preferably, in combination to provide an indication as to global tissue oxygenation levels.
  • the invention may be used as an uncomplicated, realtime intervention trigger in clinical settings without the risks associated with conventional invasive monitoring equipment.
  • the attending physician is provided with a simple trigger point where intervention is indicated.
  • a physician may determine that the Pv0 2 of a patient should not be below 35 mm Hg or that the D0 2 should remain above 600 ml/min in order to provide adequate oxygenation.
  • the clinician will have access to each of the oxygenation parameters and can display one or more values as desired.
  • the system will provide a supply/demand ratio (dD0 2 /V0 2 ) for a selected Pv0 2 thereby allowing the physician to address the needs of the patient based on a single value.
  • a value of one or greater indicates the Pv0 2 (and hence global tissue oxygenation) is higher than the established trigger point.
  • Particularly preferred embodiments provide a continuous (beat-to-beat) measurement of cardiac output (CO), using inputs from an indwelling catheter placed in a peripheral artery.
  • CO cardiac output
  • an apparatus such as the Modelflow * system (TNO-Biomedical Instrumentation, Amsterdam), can optionally be used in conjunction with the present invention to provide the CO measurement continuously in real-time.
  • Cardiac output may be computed using an algorithm that simulates the behavior of the human aorta and arterial system via a three-element, nonlinear model of aortic input impedance. Cardiac output computed using this model has been validated against cardiac output determined by thermodilution.
  • Embodiments of the invention also determine the arterial oxygen content (Ca0 2 ) of the patient for use in deriving the desired values. Specifically, in determining the arterial oxygen content (Ca0 2 ), one or more numerical values may be used corresponding to the patient's hemoglobin concentration, arterial oxygen tension (Pa0 2 ), arterial carbon dioxide tension (PaC0 2 ), arterial pH and body temperature. These numerical values may be obtained from a blood chemistry monitor or entered manually. Particularly preferred embodiments employ a blood chemistry monitor to obtain the desired values contemporaneously with the measurement of the cardiac output values. Additionally, the oxygen consumption of the patient (V0 2 ) is determined, preferably by gas analysis or metabolic rate determination.
  • the embodiments of the invention further provide methods and apparatus that may be used to monitor the tissue oxygenation status of a patient using a supply/demand ratio. Accordingly, one embodiment of the invention is directed to a relatively non-invasive method for monitoring, in real-time, tissue oxygenation status of a patient comprising the determination of a supply/demand ratio (dD0 2 /V0 2 ). Similarly, another embodiment is directed to a relatively non-invasive apparatus for determining, in real-time, tissue oxygenation status of a patient. The apparatus may include instructions for determining a supply/demand ratio (dD0 2 /V0 2 ). The calculations, values and equipment necessary to provide the desired ratios are as described throughout the present specification.
  • oxygenation constants are numerical values primarily related to the physical characteristics of oxygen carriers or to the physiological characteristics of the patient. Such oxygenation constants include, but are not limited to, blood volume, oxygen solubility in plasma and the oxygen content of a desired unit of saturated oxyhemoglobin. Preferably, one or more oxygenation constants is used in the present invention to derive the selected oxygenation parameters.
  • Cv0 2 mixed venous blood oxygen content
  • Sv0 2 can be calculated and the Pv0 2 can be readily be derived using algorithms for calculating the position of the oxyhemoglobin disassociation curve such as the Kelman equations (Kelman, J. Appl. Phvsiol, 1966, 21(4): 1375-1376; incorporated herein by reference).
  • other parameters such as D0 2 , dD0 2 and dD0 2 /V0 2 may be derived from the obtained values.
  • an anesthesiologist could continuously receive real-time data (i.e., the oxygenation parameters discussed above), thereby revealing a complete picture of the patient's global oxygenation status. Should any of the selected parameters approach the established trigger points, appropriate actions such as pharmacological intervention, fluid loading, blood transfusion or adjustment of the ventilation profile could be undertaken in plenty of time to stabilize the subject. Thus, this continuous flow of data would allow the physician to more readily determine the etiology of the oxygenation decrease (such as, but not limited to, anemia, decreased cardiac output or hypoxia) and tailor the response appropriately.
  • aspects of the invention focus on the graphical display of data to users in high-risk environments (such as medicine) to reduce possible human error, in particular, the systems and displays of the invention serve to map the operator's cognitive needs into the graphical elements of the display. In certain aspects, therefore, the invention mimics body physiology so that display data better represents patient data and body function.
  • the invention utilizes task-analysis methodology to transform data into information and display oxygen-transport physiological data.
  • the physician is able to see information (not raw data) to interpret this data - with fewer errors as compared to like interpretation of data generated by other systems - to diagnose pathological states and to take appropriate corrective action.
  • the invention thus generates a set of informative object displays from one, two or more sensors collecting data from the patient. These object displays can show, for example, (1) the relationships of data relative to other data; (2) data in context; (3) a frame of reference for the data; (4) the rate of change of information for the data; and/or (5) event information.
  • a system constructed according to the invention is thus particularly advantageous in presenting oxygen-transport physiology to doctors.
  • the system utilizes data acquisition hardware (e.g., patient probes), a computer, and object display algorithms and software.
  • the software and algorithms use digital representations of analog data channels (derived, for example, from patient monitoring signals and probes) to construct a set of object displays representing oxygen-transport physiology.
  • analog data channels derived, for example, from patient monitoring signals and probes
  • object displays representing oxygen-transport physiology.
  • aspects of the invention related to the intuitive medical process diagrams of oxygen-transport physiology do not require any particular monitoring equipment. Any type of well-known patient monitoring devices could be used for gathering data that is thereafter displayed as an intuitive medical process diagram.
  • the invention provides several advantages over the prior art. By way of example, data displays of the invention map patient information into meaningful mental models.
  • One suitable oxygen-transport physiology model of the invention thus includes: (1) the loading of fuel in the form of oxygen onto red blood cells at the lungs; (2) the pumping of oxygenated blood by the heart to organs and tissues; (3) the unloading of oxygen from red blood cells to tissues; and (4) the utilization of the oxygen by organs and tissues.
  • the software of the invention can be installed on medical devices currently used in data acquisition, particularly those used in connection with oxygen-transport physiology or cardiodynamics.
  • the invention can also be used to monitor oxygen-transport physiology for veterinary medicine, or to monitor oxygen-transport physiology in animal laboratories.
  • the invention can be a module which interacts with other displays of physiology, such as respiratory physiology. It can also be used to implement research protocols which allow better execution of complex control tasks. Further use can include an interface for analyzing large data sets of oxygen-transport information.
  • One embodiment of the invention is a method for displaying physiologic data from a patient.
  • data is measured by way of a probe or other device from an organ in a patient.
  • the measured data is then used to determine a physiologic quantity relating to the data, such as the blood oxygenation level or cardiodynamic values in the patient.
  • the physiologic quantity is then displayed as an object, wherein the shape of the displayed object reflects the structure of the organ.
  • Another embodiment of the invention is a method for displaying physiologic data from a patient.
  • the blood oxygenation levels of a patient are first measured by conventional means.
  • a circular shape is then displayed, wherein the circular shape is shaded to represent the percentage of the patient's blood that is oxygenated.
  • Yet another aspect of the invention is a method for displaying physiologic data from a patient, wherein the blood oxygenation levels in a patient are first measured through conventional methods.
  • a plurality of shapes are then displayed on a monitor, wherein each of the plurality of shapes represents the structure of an organ in the human body.
  • One additional embodiment of the invention is a method for displaying physiologic data from a patient, wherein analog gauges, such as dials or needles are used to represent the physiologic data.
  • Another aspect of the invention is a display system for representing physiologic data from a patient.
  • the display system includes a set of display objects, with each object representing a different, but related measurement taken from the patient.
  • An integrated display may be formed from a set of four objects. The first object represents the patient's cardiac output, the second object represents the patient's arterial blood oxygenation levels, the third object represents the patient's venous blood oxygenation levels, and the fourth object represents the tone of the patient's arteries, capillaries and veins.
  • FIGURE 1 is a schematic diagram illustrating one system constructed according to embodiments of the invention for collecting, processing and displaying oxygen transport physiology.
  • FIGURE 2 is a schematic diagram of a computer system that may be used to run the present invention.
  • FIGURE 3 is a flowchart detailing a preferred software scheme that may be used to run the present invention.
  • FIGURE 4 is a schematic diagram of data input and calculations as performed in selected embodiments of the present invention.
  • FIGURE 5 illustrates one embodiment of a red blood cell object.
  • FIGURE 6 is a flowchart illustrating one method for updating a display of the red blood cell object from Figure 5.
  • FIGURE 8 is a flowchart illustrating one method for updating a display of the heart pump object from Figure 7.
  • FIGURE 9 illustrates one embodiment of a vascular resistor object.
  • FIGURE 11 illustrates one embodiment of a metabolism object.
  • FIGURE 12 is a flowchart illustrating one method tor updating a display of the metabolism object from Figure 11.
  • FIGURE 13 illustrates a display representing a circuit for displaying physiological data.
  • the display includes a heart pump object, vascular resistor object, red blood cell object and metabolism object.
  • FIGURE 14 illustrates one embodiment of the circuit during anaphylaxis or sepsis.
  • FIGURE 15 illustrates one embodiment of the circuit during cellular acidosis.
  • FIGURE 16 illustrates one embodiment of the circuit during a pulmonary embolism.
  • FIGURE 17 illustrates selected object displays and elements that are compatible with the present invention. More particularly, Fig. 17A shows an alveolar-arterial partial pressure oxygen gradient object. Fig. 17B shows a data box graphical element and Fig. 17C shows an acid-base graph object.
  • the present invention relates to methods and systems for obtaining medical information from patients and then displaying that information in an intuitive format to a physician.
  • the intuitive format may be termed a medical process diagram because physicians reading the displayed information can quickly perceive the importance of changing patient values.
  • Medical process diagrams have been developed by others in non-anesthesia domains to take advantage of advancements in cognitive research.
  • the set of display objects was developed to illustrate: 1 ) the relationships of data to other data; 2) data in context; 3) a frame of reference for the data; 4) the rate of change information for the data; and 5) event information.
  • a system was developed for presenting oxygen-transport physiology to doctors.
  • the system uses data acquisition hardware, a computer, oxygen transport calculation software and object display software.
  • the object display software uses data provided by oxygen transport calculation software to construct a set of four objects representing oxygen-transport physiology.
  • the display system described below utilizes visual memory cues and perceptual diagrams to map complex data graphically. These data maps are then displayed to match the mental model physicians use to interpret oxygen-transport physiology. Because the system receives analog signals from the patient and thereafter calculates several physiological quantities, patient data is used to drive the display in real-time.
  • the present invention may be used or associated with a variety of medical instruments including ventilators, anesthesia machines, partial or total liquid ventilation systems, cardiodynamic monitors and heart- lung machines. More generally, the present invention may be used in concert with any computerized laboratory information system such as may be found in an operating room or intensive care unit.
  • the parameters or values to be displayed will be derived by one or more instruments and communicated to a centralized display (i.e., a video monitor).
  • a centralized display i.e., a video monitor
  • the devices may operate as stand alone systems with a built in display. Either way, the operator will preferably be able to manipulate the display parameters so as to optimize the presentation of the desired data. It will then be appreciated that the operator can adjust the appropriate devices based on the displayed data.
  • the displays are compatible with several systems in current use. Either volume regulated, time-cycled respirators or pressure-limited time-cycled respirators are suitable. As previously alluded to, conventional ventilators such as these may be used with the present invention in conjunction with traditional gas ventilation or with partial liquid ventilation. Similarly, the present invention may be used in conjunction with a wide variety of commercially available cardiopulmonary bypass machines or blood oxygen and hemoglobin monitoring equipment (i.e. pulmonary catheters, EKGs, etc.). In other preferred embodiments the displays of the present invention may be driven by commercially available integrated anesthesia delivery and monitoring units.
  • the graphical displays may be used in concert with closed-circuit liquid ventilation systems such as those described in WO 97/1971 which is incorporated herein in its entirety.
  • closed-circuit liquid ventilation systems such as those described in WO 97/1971 which is incorporated herein in its entirety.
  • the present invention allows for the intuitive display of the relevant parameters.
  • the displays of the present invention are compatible with several types of medical instrumentation.
  • the following discussion will examine the display of oxygenation parameters in conjunction with a novel real-time oxygenation analyzer.
  • the present invention discloses only exemplary embodiments thereof, it is to be understood that other variations are contemplated as being within the scope of the present invention. Accordingly, the present invention is not limited to the particular embodiments which are described in detail below.
  • FIG. 1 illustrates a system 10 constructed according to an embodiment of the invention directed to the determination of oxygenation parameters.
  • a series of probes 12 are connected to various monitoring activities associated with the patient 14, e.g., a heart rate probe 12a. These probes are well known and typically generate analog signals 16 representative of the monitored activity.
  • the signals 16 are converted through well-known A/D devices 18 in a data conversion module 20 to generate digital data corresponding to the analog signals 16. This data is made available on a data bus 22.
  • a processing module 24 processes data on the bus 22 to generate usable quantitative measures of patient activity as well as to compare and create object displays that, for example, (1) relate certain data relative to other data; (2) present data in context; (3) relate data to a frame of reference; (4) determine the rate of change information in the data; and/or (5) to present event information.
  • One embodiment of the module 24 thus includes a plurality of data processing sections 26 that analyze and/or quantify the data being input from the probe 12.
  • one section 26a connected in the data chain to probe 12a, processes data on the bus 22 to provide a representation of heart rate in the form of a digital word. As the patient's heart rate changes, so does the digital word.
  • a memory module 28 is used to store selected data, such as the digital word corresponding to heart rate, so that the module 24 contains a record and a current value of the patient's heart rate activity.
  • the memory 28 also stores information, such as nominal values from which to compare data to a frame of reference, or such as extreme values representative of desired patient thresholds.
  • the display driver section 30, connected to the sections 26, can thus command the display of the heart rate data in context on the display 32, and/or relative to frame of reference data within the memory 28.
  • the data from the sections 26 can also be compared to other data or related to stored thresholds within the assessment module 34.
  • data corresponding to probe 12a can be compared relative to probe 12b through a process of digital division within the module 34.
  • the driver 30 can in turn command the display of this related data on the display 32.
  • the assessment module 34 can compare other data to stored data within the memory 28; and a warning event can be displayed on the display 32 if the comparison exceed a set threshold.
  • certain probes 12 may have self-contained A/D conversion capability and data manipulation. Furthermore, such probes can easily be connected directly to the assessment module 34 and memory 28 by known techniques.
  • the system 10 is controlled by inputs at a user interface 36, such as a keyboard, and the display driver 30 formats data into various object formats 40 on the display 32. Accordingly, by commanding selected processes within the assessment module 34 - such as comparison of certain data with other data - such data can be automatically displayed on the display 32 in the desired object format.
  • the particular object formats, according to the invention, are described below. Preferably, these objects are displayed simultaneously on the same display so as to provide a comprehensive data profile to the operator.
  • Figure 2 shows a representative computer system 155 that may be used in conjunction with the system 10 of Figure
  • System 155 can be operated in a stand-alone configuration or as part of a network of computer systems.
  • the system 1 5 is an integrated system that collects data from the patient and presents processed data to a display for viewing by a physician.
  • the computer system 155 includes blood-monitoring software executed in conjunction with an operating system, for instance Windows 95 available from Microsoft Corporation, on a computer 160. Other embodiments may use a different operational environment or a different computer or both.
  • the computer 160 can be connected via a wide area network (WAN) connection to other physicians or hospitals.
  • WAN wide area network
  • a WAN connection to other medical institutions enables a real-time review of the patient's progress during surgery or in the intensive care unit.
  • one embodiment of the computer 160 includes an Intel Pentium or similar microprocessor running at 300 MHz and 32 Megabytes (Mb) of RAM memory (not shown).
  • the system 155 includes a storage device 165, such as a hard disk drive connected to the processor 170.
  • the hard drive 165 is optional in a network configuration, i.e., the workstation uses a hard disk or other storage device in a file server. If the computer 160 is used in the stand-alone configuration, the hard drive 165 is preferably 100 Mb or more.
  • the system is not limited to particular types of computer equipment. Any computer equipment that can run the display system described herein is anticipated to function within the scope of this invention.
  • the computer 160 is integrated with a group of computer peripherals, and is connected to a VGA (video graphics array) display standard, or better, color video monitor, which provides the display output of the system 155.
  • the display 175 may be a 17 inch monitor running at 1024 x 768 pixels with 65,536 colors.
  • a keyboard 180 that is compatible with IBM AT type computers may be connected to the computer 160.
  • a pointing device 185 such as a two or three button mouse can also connect to the computer 160. Reference to use of the mouse is not meant to preclude use of another type of pointing device.
  • a printer 190 may be connected to provide a way to produce hard-copy output, such as printouts for file records.
  • programming languages such as Labview, C + +, Basic, Cobol, Fortran or Modula-2 can be used to integrate the features of the present invention into one software package.
  • An alternative method of illustrating the software of the present invention is to use a spreadsheet program to collect and determine the Pv0 2 of a patient in real-time. This method is described in detail below.
  • the systems and methods of the present invention collect data from a patient and determine various tissue oxygenation parameters of a patient in real-time. Software is used to direct this process. Those skilled in the art will appreciate that the desired parameters may be derived and displayed using various software structures written in any one of a number of languages. Figure 3 illustrates one possible software scheme that could be used in conjunction with the disclosed methods and systems.
  • the start signal can be a keystroke of mouse command that initiates the software to begin collecting data.
  • arterial pressure data is collected from a patient at state 202.
  • Arterial pressure data may be collected by hooking a patient up to an arterial pressure monitor as is well known.
  • a "data in range” decision is made at decision state 204.
  • the software compares the data collected at state 202 with known appropriate ranges for arterial pressure values. Appropriate ranges for arterial pressure data are, for example, between 70/40 and 250/140.
  • the software pointer moves to process state 208 that contains instructions for collecting arterial data.
  • the collected data will include patient temperature, arterial pH, hemoglobin levels, Pa0 2 and PaC0 2 .
  • the data is preferably generated by an attached blood chemistry monitor which may provide information on the patient's blood gas levels, acid-base status and hematology status.
  • the data is collected by receiving data streams via the serial connection from the blood chemistry monitor into the computer.
  • the relevant values may be obtained from accessing data that is manually input from the keyboard.
  • the blood chemistry monitor continually samples arterial blood from the patient preferably determining several properties of the patient's blood from each sample. Data corresponding to each of the properties taken from the blood chemistry monitor at process state 208 are checked so that they are in range at decision state 210.
  • An appropriate range for the pH is 7.15 to 7.65.
  • An appropriate range for the hemoglobin level is from 0 to 16 g/dL.
  • An appropriate range for the Pa0 2 is from 50 mm Hg to 650 mm Hg while an appropriate range for the PC0 2 is from 15 mm Hg to 75 mm Hg.
  • an error/exception handling routine at state 212 is begun.
  • the error/exception handling routine at state 212 independently analyzes variables collected at state 208 to determine whether it is in range. If selected variables collected at state 208 are not within the appropriate range, the error/exception handling routine 212 loops a software pointer back to state 208 so that accurate data can be collected. If the selected data are in range at decision box 210, the software then derives the Ca0 2 value along with the cardiac output (CO) from the previously obtained arterial pressure data at state 214.
  • CO cardiac output
  • cardiac output can be derived from arterial pressure measurements by any number of methods.
  • the Modelflow system from TNO Biomedical can derive a cardiac output value in real-time from an arterial pressure signal.
  • Other methods could also be used at process step 214 to determine cardiac output.
  • the patient's total oxygen transport (D0 2 ) may be derived at process step 215.
  • the total oxygen transport is the product of the cardiac output and the arterial blood oxygen content. This parameter may optionally be displayed and, as indicated by decision state 217, the program terminated if the software has received a stop command.
  • process state 216 relates to the measurement or input of the patient's V0 2 .
  • the patient's V0 2 can be calculated using the methods previously described measured by hooking the patient up to a suitable ventilator and measuring his oxygen uptake through a system such as the Physioflex discussed above or using a number of other devices such as systems manufactured by Sensormedics and Puritan Bennett. By determining the amount of oxygen inspired and expired, the ventilator may be used to calculate the total amount of oxygen absorbed by the patient. After the patient's V0 2 value has been determined at process step 216, these variables are applied to the Fick equation at state 218 to provide a real time Cv0 2 . The Fick equation is provided above.
  • mixed venous oxyhemoglobin saturation (Sv0 2 ) and the mixed venous oxygen tension (Pv0 2 ) can be derived at state 220.
  • values for mixed venous pH and PC0 2 are assumed to have a constant (but alterable) relation to arterial pH and PaC0 2 respectively and these are used, along with other variables, in the Kelman equations to define the position of the oxyhemoglobin dissociation curve.
  • algorithms can be derived to calculate these values. Knowing the Hb concentration, a Pv0 2 is derived that then provides a total Cv0 2 (which includes contributions from Hb, plasma and PFC) equal to the Cv0 2 determined from the Fick equation. If the Cv0 2 value will not "fit" the Fick equation, another Pv0 2 value is chosen. This process is repeated until the Fick equation balances and the true Pv0 2 is known.
  • Sv0 2 is closely related to Pv0 2 and may easily be derived from the oxygen-hemoglobin dissociation curve using conventional techniques. It will further be appreciated that, as with Pv0 2 , Sv0 2 may be used to monitor the patient's oxygenation state and as an intervention trigger if so desired by the clinician. As discussed above, mixed venous blood oxyhemoglobin saturation may be used alone in this capacity or, more preferably, in concert with the other derived parameters.
  • the value or values may be displayed on the computer display at step 222. If the software has not received a keyboard or mouse input to stop collecting data at decision state 224, a pointer loops the program back to process state 202 to begin collecting arterial pressure data again. In this manner, a real-time data loop continues so that the patient's mixed venous blood oxygen tension (Pv0 2 ) or saturation (Sv0 2 ) is constantly updated and displayed on the computer at state 222. If the software has received a stop command from a keyboard or mouse input at decision state 224, then a finish routine 226 is begun.
  • Pv0 2 mixed venous blood oxygen tension
  • Sv0 2 saturation
  • the following system utilizes a large Microsoft EXCEL® spreadsheet to collect information from the patient and display the desired parameters including Pv0 2 , Sv0 2 and D0 2 .
  • a number of oxygenation constants may be entered into the system. These constants preferably include the patient's estimated blood volume, oxygen solubility in plasma and the oxygen content of 1 g of saturated oxyhemoglobin. The oxygenation constants are then stored in the computer's memory for use in later calculations.
  • TABLE 1 shows commands from part of a Microsoft EXCEL® spreadsheet that collects a patient's data and derives the value of the desired oxygenation parameters.
  • the program is initialized by assigning names to various oxygenation constants that are to be used throughout the software.
  • oxygenation constants corresponding to blood volume (BV), oxygen solubility in a perfluorocarbon emulsion (02S0L), specific gravity of any perfluorocarbon emulsion (SGPFOB), intravascular half-life of a perfluorocarbon emulsion (HL), weight/volume of a perfluorocarbon emulsion (CONC), barometric pressure at sea level (BARO), milliliters oxygen per gram of saturated hemoglobin (HbO) and milliiiters of oxygen per 100ml plasma per 100mm of mercury (PIO) are all entered.
  • the constants relating to perfluorocarbons would be entered in the event that fiuorocarbon blood substitutes were going to be administered to the patient.
  • Kelman constants An example of starting values for Kelman constants, a subset of the oxygenation constants, is also shown in TABLE 1. These starting values are used in later calculations to derive the patient's mixed venous oxygenation state or other desired parameters such as mixed venous blood oxyhemoglobin saturation. As with the other oxygenation constants the Kelman constants are also assigned names as shown in TABLE 1.
  • real time inputs from the arterial pressure lines and blood chemistry monitor may be initialized and begin providing data.
  • the system depicted in this embodiment derives or receives data relating to the arterial oxyhemoglobin saturation percentage (Sa0 2 ).
  • saturation percentages are derived from arterial data for oxygen tension (Pa0 2 ), pH (pHa), carbon dioxide tension (PaC0 ) and body temperature (TEMP).
  • the present invention provides for the real-time display of Sv0 2 values (as derived from calculated Pv0 2 , pHv, PvC0 2 and temperature) to be used for the monitoring of the patient's tissue oxygenation status.
  • Cardiac Output (l/mm) -CO ((14 - Hemoglobin (gm/dl) * 1 CO Response to 1 gram of Hb Depletion) +5
  • the program calculates oxygenation parameters such as Pv0 2 and Sv0 2 in real time, as shown in TABLE 2. These values are then fed into the display system described below to generate perceptual diagrams. These diagrams are then used by the physician to determine, for example, when to give the patient a blood transfusion or alter the patient's clinical management. Significantly, the displayed values may be used to monitor the physiological effects of blood substitutes, including those based on hemoglobin or perfluorochemicals following their administration.
  • TABLE 3 and TABLE 4 show additional information that may be provided by the instant invention further demonstrating its utility and adaptability. More specifically, TABLE 3 provides various oxygenation values that may be calculated using the methods disclosed herein while TABLE 4 provides other indices of oxygen consumption and oxygen delivery that are useful in optimizing patient treatment.
  • TABLE 3 provides calculations that give the arterial or venous oxygen content of circulating hemoglobin, plasma and fluorochemical respectively.
  • TABLE 4 illustrates that the present invention may also be used to provide real-time information regarding oxygen consumption and delivery.
  • Hb or Hct measurements are not a suitable reflection of tissue oxygenation. This is mainly because they only give an indication of the potential arterial 0 2 content (Ca0 2 ), without providing information about the total oxygen transport (D0 2 ) to the tissues where it is to be used.
  • the instant invention solves this problem by providing on line oxygen transport information which is derived based on Ca0 2 and cardiac output (CO).
  • Ca0 2 ([Hb] X
  • the present invention combines the continuous cardiac output algorithm with the Kelman equations to provide the position of the oxygen hemoglobin dissociation curve.
  • the present invention is able to trend D0 2 on a continuous basis.
  • the factors used to determine D0 2 are displayed along with their product; thus, the etiology of a decrease in D0 2 (inadequate cardiac output, anemia, or hypoxia) would be readily apparent to the physician, decisions regarding the appropriate interventions could be made expeditiously, and the results of treatment would be evident and easily followed.
  • preferred embodiments of the invention may be used to provide and display real-time D0 2 , arterial blood gases, hemoglobin concentration and CO (and all other hemodynamic data already discussed such as BP, heart rate, systemic vascular resistance, rate pressure product and cardiac work). As shown in TABLE 3, such embodiments can also provide separate readouts of contributions of Hb, plasma and PFC (if in circulation) to D0 2 . That is, the oxygen contributions of each component may be accurately monitored and adjusted throughout any therapeutic regimen. Such data would be particularly useful in both the OR and ICU for providing a safety cushion with respect to the oxygenation of the patient.
  • D0 2 the maximum 0 2 consumption (V0 2 ) that could be supported for a certain chosen (and alterable) Pv0 2 .
  • V0 2 the maximum 0 2 consumption
  • Pv0 2 deliverable oxygen
  • a Pv0 2 of 36 mm Hg might be chosen for a healthy 25 year old patient, where as a Pv0 2 of 42 mm Hg or higher might be needed for an older patient with widespread arteriosclerosis or evidence of coronary atheroma or myocardial ischemia.
  • Oxygen consumption under anesthesia is variable, but almost always lies in the range of 1.5 to 2.5 ml/kg/min. If the supportable V0 2 , at the chosen Pv0 2 , was well above this range all would be well and no intervention would be necessary. The closer the supportable V0 2 to the normal V0 2 range the earlier intervention could be considered.
  • This relationship could be used to provide a single value, based on deliverable oxygen (dD0 2 ) vs. oxygen consumption
  • V0 2 V0 2
  • dD0 2 is the amount of oxygen transported to the tissue that is able to be delivered before the partial venous oxygen pressure (Pv0 2 ) and, by implication, tissue oxygenation tension falls below a defined level.
  • Pv0 2 partial venous oxygen pressure
  • the supply/demand ratio (dD0 2 /V0 2 ) for a selected Pv0 2 can be used to provide a single value showing that the amount of oxygen being administered is sufficient to maintain the desired oxygenation state.
  • the supply/demand ratio is 300 ml/min 200 ml/min or 1.5.
  • a supply/demand ratio of 1 would imply that the Pv0 2 (or other selected parameter i.e. Sv0 2 ) was at the selected trigger value (here 40 mm Hg).
  • the ratio is 0.66 and the patient is not receiving sufficient oxygen (i.e., the Pv0 2 will be less than 40). Continuous monitoring and display of this ratio will allow the clinician to observe the value approaching unity and intervene appropriately.
  • the computer system 155 of Figure 2 includes software and systems for displaying medical process diagrams relating the values calculated above.
  • the display system collects the oxygen transport values and creates display objects that are presented to the physician. Although some of the data may be derived by reading raw analog or digital data from a patient monitor, many of the values may be read from calculated data such as shown in TABLES 1-4 above.
  • the system might sample the data at 200 times per second, and update the display every 2 seconds. However, the system may be capable of higher sampling and display updates to provide the most up to date data to the physician.
  • the perceptual diagrams comprise a series of data objects representing physiological processes in the body.
  • these data objects include a red blood cell object, a heart pump object, a vascular resistor object, an alveolar-arterial object, an acid-base object and a metabolism object.
  • This graphical display object contains information regarding the quantity of red cells (as the hemoglobin), the oxygen loading of the red cells (as the percent oxygen saturation) and the oxygen content (using an accepted formula).
  • the size of a circle correlates with the hemoglobin.
  • the portion of the circle filled black from the bottom up correlates with the oxygen saturation.
  • the product of the hemoglobin and the oxygen saturation correlates with the oxygen content
  • a red blood cell object 300 displays information relating to the amount of hemoglobin in a patient's blood, the amount of oxygen which is loaded onto the red blood cells, the effect of temperature on blood viscosity, and the oxygen content of the blood.
  • Arterial Oxygen Content (Arterial Oxygen Saturation) x ( Hemoglobin) x (1.34).
  • Oxygen Saturation is labeled “Sa0 2 "
  • hemoglobin is labeled as “HB”
  • Arterial Oxygen Content is labeled as “Ca0 2 ".
  • red-blood cell related values are then converted to a perceptual diagram (e.g., on a computer display 32, Figure 1 ) in the form of a pair of nonconcentric circle sets 310a, 310b.
  • a perceptual diagram e.g., on a computer display 32, Figure 1
  • the patient's Ca0 2 value is indicated by a diamond 320 and is mapped to the Y-axis.
  • the patient's hemoglobin level, the volume percentage of erythrocytes in whole blood, is mapped to the X-axis, in the venous portion 316, the patient's Cv0 2 is indicated by a diamond 330 and is mapped to the Y-axis.
  • the hemoglobin level is mapped to the X-axis.
  • the nonconcentric circles 310a,b are created by using a Y-axis to define a tangential line along the left-most point 340a,b of the nonconcentric circles 310a,b.
  • Each nonconcentric circle includes the same left-most point 340a,b along the Y-axis.
  • a horizontal oxygen extraction line 350 indicates the level of arterial oxygenation by defining the upper boundary of a shaded area 360 in the arterial red-cell shaped object 310a.
  • the red cell objects 310a,b can be partially or completely shaded, as illustrated in Figure 5 to show the percent filled with oxygen of the patient's red blood cells (e.g., when half shaded, the cell is only half filled with oxygen).
  • Hb hemoglobin
  • the Cv0 2 diamond 330 moves up and down along its Y-axis. As the Cv0 2 diamond 330 moves up and down, the amount of shading 370 within the venous red-cell shaped object 310b changes.
  • the oxygenation on the venous side of the vascular circuit is readily illustrated to the physician.
  • the arterial and venous oxygen contents are compared by looking at the relative shading 360 (arterial side) and 362 (venous side), a rapid, perceptual understanding of oxygen extraction is made evident.
  • Oxygen Extraction (Arterial Oxygen Content) - (Venous Oxygen Content).
  • the oxygen extraction line 350 is extended from the arterial blood cell 310a to an oxygen extraction sliding scale 364.
  • the oxygen extraction sliding scale 364 maintains the Cv0 2 diamond 330 as its lower boundary.
  • the oxygen extraction sliding scale 364 increases.
  • the oxygen extraction sliding scale 364 also increases. This makes sense since the amount of oxygen extraction is expected to increase with rising arterial oxygen pressure or with decreasing venous oxygen pressure. A physician can thereby look to the oxygen extraction sliding scale 364 as a quick measure of the amount of oxygen extraction taking place in the patient.
  • the manner in which the red-cell object 300 mimics the in vivo action of actual red blood cells makes the red-cell object 300 very intuitive to a physician.
  • a process 370 of updating the red cell object 300 begins at a start state 372.
  • the process 370 then moves to a state 374 wherein the Ca0 2 value for the patient is read. As discussed above, this value can be read from a data table or from any type of memory storage in the computer system.
  • the process 370 moves to a decision state 376 to determine if the Ca0 2 value has changed from the last sampling. If the Ca0 2 value has changed, the process 370 moves to a decision state 378 to determine whether the Ca0 2 value has increased or decreased. If the Ca0 2 value has increased, the Ca0 2 indicator 320 and oxygen extraction line 350 are moved up vertically along the Y-axis at a state 382.
  • the process 370 moves to a state 380 wherein the Ca0 2 indicator 320 and oxygen extraction line 350 are moved downward along the Y-axis.
  • the process 370 then moves to a state 384 wherein the Cv0 2 value is read.
  • the process 370 then moves to a decision state 392 to determine whether the hemoglobin value has changed since the last sampling. If a determination is made that the hemoglobin level has changed, the process 370 moves to a decision state 394 wherein a determination is made whether the hemoglobin value has increased or decreased. If the hemoglobin level has increased, the process 370 moves to a state 397 wherein the shaded area 360 is increased in size to indicate a larger quantity of red blood cells in the patient's blood. However, if a determination is made at the decision state 394 that the hemoglobin level has decreased, the process 370 moves to a state 395 wherein the shaded areas, 360- 362 are reduced in circumference. The process 370 then terminates at an end state 399.
  • This graphical display object contains information regarding blood flow (as cardiac output), pulse rate (as derived from an arterial transducer) and stroke volume (using an accepted formula).
  • the resulting rectangle (defined by the pulse rate and the stroke volume) is filled black during the diastolic phase of the cardiac cycle.
  • the rectangle empties from the top down at a rate defined by correlates of cardiac contractility (such as dP/dt).
  • the rectangle 410 is divided into a right ventricular (RV) metaphor 440 and left ventricular (LV) metaphor 450 by dividing the size of the rectangle 410 in half along the X-axis.
  • RV right ventricular
  • LV left ventricular
  • the shape of a low Stroke Volume ventricle would be reflected by a rectangle 410 that is short and wide, while the shape of a bradycardic ventricle with a normal SV would be indicated by a rectangle 410 that is tall and thin.
  • the filling pressure or volume information, or contractility of the heart chambers is presented in the form of a central venous pressure (CVP) analog gauge 452 and Pulmonary Artery Capillary Wedge Pressure (WP) analog gauge 454 located on the X-axis.
  • CVP central venous pressure
  • WP Pulmonary Artery Capillary Wedge Pressure
  • the 12 o'clock position is defined as normal.
  • the rectangle 410 has squared sides.
  • the CVP analog meter 452 scribes an arc along the X-axis, if a CVP reading is not normal, the left side 456 of the rectangle 410 will bow in or out.
  • the left side 456 bows outward due to a high CVP, it represents a distended, overfilled left ventricle. Similarly, when the left side 456 bows inward due to a low CVP, it indicates an empty, under-filled left ventricle. As can be imagined, the bulging shape of the left side 456 of the rectangle 410 readily conjures up images of the in vivo heart being over-filled with blood.
  • the WP analog meter 454 scribes an arc along a right side 480 of the rectangle 410. As the WP increases, the right side 458 bulges outward indicating a swollen, overfilled right ventricle in the patient. In addition, as the WP decreases, the WP analog meter 454 scribes a scalloped arc along the right side 458 so that the right ventricle is illustrated as an empty, unfilled ventricle.
  • the right side 458 and left side 456 correspond with the image of the heart seen with a long-axis four chamber view using transesophageal echo-cardiography.
  • the process 460 moves to a state 468 wherein the stroke volume indicator 420 is moved downward along the Y-axis. As illustrated in Figure 7, as the stroke volume indicator 420 is moved downward along the Y-axis, the shaded rectangle 410 is reduced in height. If a determination is made at the decision state 466 that the stroke volume has increased, the process 460 moves to a state 469 wherein the stroke volume indicator 420 is moved upward along the Y-axis. This, in turn, increases the height of the shaded rectangle 410. The process 460 then moves to a state 470 wherein the patient's heart rate is read. A determination is then made at a decision state 471 whether the heart rate has changed from the last reading.
  • the process 460 then moves to a state 477 wherein the central venous pressure (CVP) value is read. A determination is then made at a decision state 478 whether the CVP has changed since the last reading. If the CVP has changed, a determination is made at a decision state 479 whether the CVP has increased or decreased. If the CVP has decreased, the process 460 moves to a state 480 wherein the analog CVP gauge 452 is moved to the right along its predetermined arc. As discussed above, as the CVP analog gauge 452 is moved to the right along its arc, the shape of the right ventricular metaphor 440 is altered to indicate a less filled heart chamber.
  • CVP central venous pressure
  • the process 460 moves to a state 482 wherein the CVP analog gauge 452 is moved to the left along its arc, the left side 456 of the right ventricular metaphor 440 begins bulging outward to indicate a swollen heart chamber.
  • the process 460 then moves to a state 483 wherein the wedge pressure (WP) value is read.
  • WP wedge pressure
  • the process 460 then moves to a decision state 485 to determine whether the wedge pressure has changed since the last reading. If the wedge pressure has changed, a determination is made at a decision state 486 whether the value of the wedge pressure has increased or decreased. If the value of the wedge pressure has decreased, the process 460 moves to a state 488 wherein the wedge pressure analog gauge 454 is moved to the left along its predetermined arc.
  • the side 458 of the left ventricular metaphor 450 becomes more concave indicating a less-filled heart chamber.
  • HR heart rate
  • the WP analog gauge is slide left to right along the X-axis.
  • HR heart rate
  • the process 460 moves to a state 490 wherein the wedge pressure gauge 454 is moved to the right along its predetermined arc.
  • the edge 458 of the left ventricular metaphor 450 is curved outward indicating a bulging or swollen heart chamber.
  • the process 460 then ends at an end state 492.
  • the blood flow is shown on the right pressure scale and is defined by the cardiac output pointer (CO).
  • CO cardiac output pointer
  • the perfusion pressure and cardiac output are centered and connected to each other using a meter showing the systemic vascular resistance (SVR) such that a tube is formed which appears "dilated” when the SVR is low and appears “constricted” when the SVR is high.
  • SVR systemic vascular resistance
  • vascular resistor object 500 is used to display the blood flow equivalent of Ohm's Law.
  • Output) x Systemic Vascular Resistance
  • the data is displayed in the object 500 such that the shape of a "pipe” emerges with flow from left to right.
  • Two lineal scales relating to the pressure gradient for blood flow and the actual cardiac output in liters per minute are shown as a function of the systemic vascular resistance (SVR) such that a "pipe” metaphor emerges.
  • SVR systemic vascular resistance
  • the flow of blood is reduced, as indicated by a constricted pipe.
  • the flow of blood is increased, as indicated by a more open pipe.
  • the MAP indicator 510 can also affect the model, since an increasing MAP widens the inflow so more overall blood flow is found.
  • the vascular resistor object 500 closely reflects the actual physiology of the patient. It is thus an intuitive object for deciphering complex situations in a patient.
  • the process 535 moves to a state 546 wherein the MAP indicator 510 is moved upwards along the X- axis. As can be seen upon review of Figure 9, as the MAP indicator 510 moves up and down along the X-axis the area 520 becomes larger or smaller, respectively.
  • the process 535 then moves to a state 548 wherein the central venous pressure of the patient is read.
  • a determination is then made at a decision state 550 whether the CVP has changed since the last reading. If the CVP has changed, the process 535 moves to a state 552 to determine whether the CVP has increased or decreased.
  • the process 535 moves to a state 554 wherein the CVP indicator 515 is moved down. If a determination is made at the decision state 552 that the CVP has increased, then the process 535 moves to a state 556 wherein the CVP indicator 515 is moved up. The process 535 then moves to a state 558 wherein the cardiac output (CO) is read.
  • CO cardiac output
  • SVR systemic vascular resistance
  • the metabolic factory graphical display object contains information regarding oxygen delivery (D02) to cellular factories (in aggregate), aerobic (oxygen burning) metabolic activity (oxygen utilization or V02), and anaerobic metabolic activity (using correlates suggestive of lactate production, in this case the Base Deficit).
  • the data scales are arranged to allow the oxygen supply to be compared to the indicators of utilization and cellular well being.
  • a metabolism object 600 is illustrated.
  • V0 2 oxygen Utilization
  • a fulcrum or pivot 610 is used to illustrate the balance between an oxygen supply (D0 2 ) indicator 620 and oxygen demand (V0 2 ) indicator 630.
  • a lever or balance line 640 runs between the D0 2 indicator 620 and V0 2 indicator 630 and balanced on the pivot 640.
  • the slope of the D0 2 to V0 2 is used to indicate the "balance" or relationship between D0 2 and V0 2 more readily apparent to the physician .
  • anaerobic metabolism and its associated acidosis cause the scale to tip in the wrong direction to indicate that although oxygen is being supplied, the cells are not using it.
  • the process 650 begins at a start state 652 and then moves to a state 654 where the oxygen supply of the patient's blood is read. The process 650 then moves to a decision state 656 to determine whether the oxygen supply value (D0 2 ) has changed since the last reading. If the oxygen supply value has changed, the process 650 moves to a decision state 658 to determine whether the oxygen supply has increased or decreased in the patient's blood. If the value of the oxygen supply has decreased, the process 650 moves to a state 660 wherein the oxygen supply indicator 620 ( Figure 11) is moved downward along its Y-axis.
  • the process 650 moves to a state 662 wherein the oxygen supply indicator 620 is moved upward along its Y-axis.
  • the process 650 then moves to a state 664 to read the oxygen demand value (V0 2 ) in the patient.
  • the process 650 moves to a state 666 to determine whether the oxygen demand value has changed since the last reading. If the oxygen demand value has changed, the process 650 moves to a decision state 668 to determine whether the oxygen demand value has increased or decreased. If the oxygen demand value has decreased, the process 650 moves to state 670 wherein the oxygen demand indicator 630 ( Figure 11 ) is moved downward along its Y-axis. However, if a determination is made at the decision state 668 that the oxygen demand has increased, the process 650 moves to a state 672 wherein the oxygen demand indicator 630 is moved upwards. The process 650 then terminates at an end state 674
  • this graphical data display object 800 contains an outline 802 suggestive of a lung unit on the left, an outline 804 suggestive of an artery on the right, and a scale 806 in-between which represents the barrier to oxygen diffusion from lung to blood.
  • a pointer 808 on the left, inside the "lung” depicts partial pressure of Alveolar oxygen using the Ideal Alveolar Gas Equation.
  • a pointer 810 on the right, inside the "artery” depicts partial pressure of arterial oxygen.
  • Trending is shown to the left.
  • the normal gradient shown on the scale as a green region, is based on accepted formulas (normal arterial oxygen is a function of the fraction of inspired oxygen).
  • the line connecting the pointers represents the gradient.
  • data boxes may have three sub-boxes: a numeric box 902, an alarm box 906 and a trend box 904.
  • the numeric box contains the data value, the data label and the data units.
  • the alarm box has a reference scale, a value pointer, color encoded (typically green on green) normal zones representing the upper and lower alarm limits (here 34 and 15). Warning zones clinicians can set, are represented triangular regions.
  • the pointer and numeric box may change color (i.e. to red) in a graded fashion as the value moves through the warning zone.
  • Confidence intervals for the data are represented by linking the thickness of the pointer tip to the precision of the measured variable.
  • the trend box shows the recorded value of the parameter over a selected period of time. It will be appreciated that multiple data boxes may be used in a single display to represent several relevant parameters.
  • FIG 17C shows an exemplary acid-base object 950.
  • the acid-base object represents the metabolic and respiratory components of the Henderson-Hasselback relationship on an x, y graph 952.
  • Diagonal pH lines 954 are shown on the reference grid. Colored markings are used to encode normal zones 958, 956 and 960 for bicarbonate, partial pressure carbon-dioxide and pH respectively. Using bicarbonate and carbon-dioxide allows clinicians to see the two major components of the acid-base system that they can treat (with IV Sodium Bicarbonate and Ventilation changes respectively).
  • Figure 13 illustrates one embodiment of a display having each of the data objects 300, 400, 500 and 600.
  • the data objects are arranged in the pattern shown to create a circuit illustrating that oxygen is carried from the left ventricle of the heart pump object 400, into an arterial blood cell 310a, through the vascular resistor 500 (e.g. capillary cells) where oxygen is unloaded at the tissue cells (object 600) and returns to through a venous blood cell 310b to the right ventricle 440.
  • the vascular resistor 500 e.g. capillary cells
  • All of the scales used to map values to indicators and gauges preferably have normal and abnormal zones (which can be and preferably are colored).
  • the indicators can change colors when a patient is entering an abnormal zone.
  • the alert zones are selectable so that the physician can make the warnings more or less stringent based on the physiology of the particular patient. In this manner, the user sets the value above or below the critical thresholds at the point she wishes to be alerted.
  • an indicator begins to change color, or start flashing in a graded manner such that the brighter the red color of the indicator, the closer the value is to the threshold.
  • the indicators could change in many different ways to alert the physician that an abnormal zone has been entered. This invention should not be construed to be limited by any particular notification method.
  • the pointer tip is preferably centered on the appropriate value but will have a thickness which touches the scale and which covers the know error associated with that datum. This creates a pointer which changes color and which enters danger zones based on worse case scenarios.
  • the trend information for example, includes a set of "cards" on a z-axis or on a time scale on the X-axis. The values over a time interval selected by the user are displayed and the resolution of the data (sampling rate) is made visible.
  • a "normal" SVR setting for the SVR object 550 of Figure 9 can default to 1000 at the 3 o'clock position. However, if a patient normally has a SVR of 2000, this function can reset the normal 3 o'clock position of the SVR analog gauge to 2000.
  • Popup windows next to the data pointers are thus available, similar to the trend windows, to detect noise or artifact information.
  • the pop-up windows are activated by, for example, clicking on a data pointer.
  • the data regarding disease states can be saved, if desired, to reset boundary defaults. For example, hypertension shifts the autoregulatory curve to the right such that most doctors keep the blood pressure in a higher range than usual.
  • Figure 14 illustrates one embodiment of the circuit display during anaphylaxis or sepsis.
  • Figure 15 illustrates one embodiment of the circuit display during cellular acidosis.
  • Figure 16 illustrates one embodiment of the circuit display during a pulmonary embolism.
  • the data sets were used to generate twenty "flash cards" (one set standard display cards and one set of graphical display cards).
  • Figure 14 is an example of one flash card from the study indicating a ⁇ aphylaxis.
  • Hardware consisted of a computer workstation with a 21 inch touch-screen monitor.
  • the study test was a software application written in LabView. The application "shuffles" the cards to randomize the order in which they are presented to the study subject.
  • a screen with a "next” button hides the upcoming display.
  • the study subject touches this button the first display picture appears and the subject must choose from five buttons (No Problem, Anaphylaxis, Bradycardia, Hypovoiemia, Ischemia, and Pulmonary Embolus).
  • the "next" button screen then appears and touching the button advances the next card. This is done for all twenty cards.
  • the internal clock in the computer is used to measure problem (shock) recognition speed, accuracy and pattern recognition (etiology) speed and accuracy. Study subjects completed surveys pre- and post-testing. We discovered that the residents were able to recognize problems 30 percent faster in comparison to previous displays, in addition, the residents were able to identify patient patterns 25% faster than with previous displays. We found that there was no difference in accuracy. The total training time was approximately 30 minutes.
  • the system receives analog signals which drives the display real-time. Alarm conditions can be set by the physician and are visible at all times.
  • the danger zones which create shades of red in the data pointer are easy for physicians to understand (physicians are accustomed to using fuzzy logic for interpreting data).
  • the way that data elements have been constructed and displayed produces perceptual diagrams.

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Abstract

La présente invention concerne un système non invasif permettant de mesurer et d'afficher graphiquement l'état d'oxygénation d'un patient en temps réel, et de fournir de manière intuitive des informations au médecin. L'invention se rapporte à plusieurs objets d'affichage qui illustrent les valeurs d'oxygénation de sortie. Les objets d'affichage reflètent la physiologie in vivo qu'ils mesurent et rendent par conséquent l'interprétation des valeurs mesurées très intuitive.
PCT/US1999/002798 1998-02-09 1999-02-09 Systeme d'affichage de schemas de processus medicaux WO1999039633A1 (fr)

Priority Applications (4)

Application Number Priority Date Filing Date Title
EP99906848A EP1054617A1 (fr) 1998-02-09 1999-02-09 Systeme d'affichage de schemas de processus medicaux
JP2001507268A JP2003503125A (ja) 1998-02-09 1999-02-09 医学的プロセスダイアグラムをディスプレイするシステム
CA002321227A CA2321227A1 (fr) 1998-02-09 1999-02-09 Systeme d'affichage de schemas de processus medicaux
AU26667/99A AU2666799A (en) 1998-02-09 1999-02-09 System for displaying medical process diagrams

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US09/020,472 1998-02-09
US09/020,472 US6234963B1 (en) 1996-12-11 1998-02-09 System and method for displaying medical process diagrams
US22631299A 1999-01-07 1999-01-07
US09/226,312 1999-01-07

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EP2502555A1 (fr) * 2011-03-22 2012-09-26 Bmeye B.V. Système de mesure de distribution d'oxygène non invasive et procédé
CA3123011A1 (fr) * 2018-12-13 2020-06-18 Nxt Biomedical, Llc Procedes et dispositifs de traitement de l'oxygenation dans le sang

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EP1054617A1 (fr) 2000-11-29
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JP2003503125A (ja) 2003-01-28
AU2666799A (en) 1999-08-23

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