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    • 专利摘要:
    A non invasive method and apparatus determines continuously the volume of oxygen delivered to the tissues using several infrared sensors. The various sensors are programmed to determine the haemoglobin level, the oxygen saturation of the blood, and the cardiac output. The product of these three factors with the known carrying capacity of haemoglobin gives the volume of oxygen delivered to the tissues in a unit time, with a microcomputer providing the necessary calculations. Other important cardiac factors are derived and all the results displayed on a screen. Non invasive blood pressure measurements, arterial haemoglobin and oxygen saturation levels are all obtained by methods which are known and are commercially available. Determination of cardiac output and other cardiac factors are described in PCT/AU2012/000854. Wave timing Cont ctility Rat Mean Arterial Pressure. Time Constant. Com liance 103 114 101 100 102 104 ave T. ontrac Rate M.A.P. Time C. Comp. ECG [ 11 11 Cardiac Output. Vascular Resist. Pre Ejection Ejection Period Period. 114 Hb Rate of change 112 110 111 [a] of pressure. Srk 1.r [b] of volume Volume Cardiac Index. en Delivery
    公开号:AU2013205767A1
    申请号:U2013205767
    申请日:2013-04-15
    公开日:2014-11-06
    发明作者:Duncan Islay CAMPBELL
    申请人:DUNCAN CAMPBELL INVEST Pty Ltd；
    IPC主号:A61B5-145
    专利说明:
    I CONTINUOUS NON-INVASIVE OPTICAL MEASUREMENT OF TISSUE OXYGEN DELIVERY Patent of addition to AU2012318248 TECHNICAL FIELD [0001] The present disclosure relates generally to medical devices and, more particularly, to medical devices for measurement of tissue oxygen delivery. BACKGROUND [0002] Human life depends on a continuous adequate oxygen supply to the tissues. The measurement of this factor is valuable, particularly in poor risk patients for determining the safety margin, and if low, identifying the system at fault so that appropriate treatment can be given. The systems involved are respiratory, cardiovascular and haematological systems. Partial defects in one system may be compensated by the other two. [0003] Various monitoring systems are currently in use. Blood pressure monitoring is important, but alone, gives little indication of the volume of oxygen being delivered to the tissues. For example, the blood pressure may be high, but intense vasoconstriction may result in low tissue perfusion with inadequate oxygen delivery to the tissues. Pulse oximetry is an important monitoring system indicating the percentage oxygen saturation of the blood, but even when combined with blood pressure monitoring, poor oxygen delivery to the tissues may not be recognised if cardiac output is low. Cardiac output monitoring alone may not indicate oxygen delivery to the tissues, even if combined with blood pressure monitoring, so for 8641812 2 example poor ventilation, presence of arterio venous shunts, and anaemia may all result in inadequate oxygen delivery to the tissues in spite of an apparently satisfactory cardiac output, and even with the addition of pulse oximetry, reduced haemoglobin levels may result in unrecognised inadequate oxygen delivery to the tissues. DETAILED DESCRIPTION [0004] Aspects of the present disclosure provide method and apparatus for the measurement of oxygen supplied to tissues in millilitres of oxygen each minute, together with various cardiovascular factors displayed continuously on a screen. The method is non invasive, and deriving the cardiovascular factors makes use of the method and apparatus described in AU2012318248. [0005] The main areas of use of the presently disclosed method and apparatus is in emergency and accident units, intensive care units and monitoring during surgical operations. In all these areas life threatening situations may occur rapidly and immediate recognition and appropriate treatment is essential. [0006] The presently disclosed arrangements use the patient's haemoglobin value, the known oxygen carrying capacity of haemoglobin, the oxygen saturation percentage of the patient's haemoglobin, and the patient's cardiac output. Multiplication together of all these factors gives the volume of oxygen delivered to the tissues in a unit time, and all these together with other derived factors are displayed continuously on a screen and updated at about fifteen second intervals. 8641812 3 [0007] Haemoglobin measurements are routine standard investigations for all hospital patients, so that the value in grams per litre will be documented and available for patients monitored according to the present disclosure. Non invasive continuous haemoglobin monitoring is preferable, especially in situations where sudden changes may occur, and the Masimo Corporation of Irvine, California, manufacture optical haemoglobin monitors which are currently used in major surgery, and are of use where considerable blood loss may occur and enable rapid assessment and adequate blood replacement. The oxygen carrying capacity of haemoglobin is a known standard of 1.34ml of oxygen per gram of haemoglobin and the percentage saturation is determined from the pulse oximeter. Pulse oximeters have been commercially available for many years and are supplied by many companies including the Masimo Corporation. The sensor unit consists of an infrared photocell system which is applied to a digit and continually monitors the oxygen saturation level of the blood in the digit, and so indicates problems with ventilation or de-saturation from other causes. Some models also indicate carboxyhaemoglobin and methaemoglobin levels and thus provide immediate information on the presence of carbon monoxide and other poisons. The cardiac output monitor is also an infrared sensor system which is preferably incorporated in the oximeter sensor to avoid duplication. The cardiac output monitoring method is of great importance as other factors displayed by this system are necessary for the diagnosis of the many problems of tissue oxygen delivery. Examples include mean arterial pressure, systemic vascular resistance, ejection time, and many others, as described in AU2012318248. 8641812 4 [0008] A main feature of the presently disclosed apparatus for measuring tissue oxygen delivery is that it is a completely non-invasive optical based system which runs continuously from sensors which do not require holding by hand. Further, cardiac output, pulse oximetry and haemoglobin monitoring are all integrated within the one system with waveform analysis performed without the use of pressure transducers. [0009] Death is unlikely to occur in the presence of a normal volume of oxygen delivered to the tissues so that continuous monitoring will enable the operator to rapidly correct and treat any problems. Major surgery is increasingly performed on poor risk patients with cardiovascular and respiratory problems, who have borderline margins of safety for oxygen delivery to the tissues, and also with surgery involving considerable blood loss. This new monitor is for use for all ages from neonates to old age and is likely to save lives in the operating theatre, recovery rooms, intensive care areas, and also in the accident and emergency units where rapid assessment and treatment are essential. [0010] There are a few circumstances where a high tissue demand for oxygen exists. Examples are severe sepsis, malignant hyperpyrexia, and thyroid crisis. These conditions will be revealed on the monitor by a high cardiac output with low blood oxygen saturation. There is also a high body temperature. There are also conditions where the tissues are unable to utilise oxygen, and examples are cyanide poisoning and other poisons which may arise from exogenous or endogenous sources. This new method will provide comprehensive monitoring and so enable optimal 8641812 5 conditions to be maintained while diagnosing and treating all such conditions. [0011] No disposable items are used during monitoring, so that there are no ongoing costs as occur with invasive procedures. This absence of financial restraints will allow wider use and possibly result in its routine use during major surgery. [0012] The method used for measuring cardiac output is by non invasive infrared sensors which give a continuous display of cardiac output and other cardiovascular parameters. The sensors do not require hand holding in position and are therefore suitable for prolonged use in the operating theatre, emergency and accident units and intensive care areas. The method and apparatus is fully described in AU2012318248. [0013] The optical sensor which delivers the pulse waveform that replicates the intra-arterial pressure is attached to the patient's finger or thumb of either hand. This may be incorporated in the pulse oximeter sensor but if separate sensors are used, they will be attached to separate digits. If a continuous running haemoglobin sensor is used, this will also be attached to a digit although in the future it is possible that these three sensors may all be incorporated in one unit so that only one digit is used. If a haemoglobin sensor is not used and reliance is placed on previous laboratory results, this value must be entered into the computer. One optical sensor is attached to an ear lobe and one optical sensor is attached to any convenient toe. A non invasive blood pressure system (NIBP equipment such as Omron) is connected to the patient with the cuff 8641812 6 preferably applied to the upper arm on the body side which does not have the finger sensors. These units are all connected through a control module and computer so that all the required factors are displayed on a screen. The sensor from the finger provides the waveform which is scaled and calibrated from the NIBP systolic and diastolic pressure, and also the waveform for measuring the time constant. The ear and toe sensors only provide the pulse delay measurements and so do not require scaling. The compliance value derived from these two sensors may remain stable with no requirement for frequent upgrading. If less accuracy of compliance is acceptable, and it is more convenient, the toe sensor may be eliminated and the ear to finger pathway used for pulse delay measurements to derive compliance. It is preferable to use the finger trace for scaling and time constant measurements as some distortion may occur with the clip pressure on the ear lobe reducing tissue flow at the diastolic pressure levels, whereas in the finger the bony structure prevents this from occurring. The optical trace from the toe is of inferior quality to the finger trace. With both the ear and the toe, pulse timing remains unaffected by the above problem. It may occasionally be desirable to wrap sensors in disposable sheaths to avoid cross infection. This is particularly important if using the sensors in regions exposed to body secretions such as lips, tongue or nose. In these regions disposable sensors would be preferable, but such occasions are rare as good signals are normally available from the ear and the digits. The cardiac output value is calculated by the computer and with the pulse oximeter and haemoglobin values, calculates the volume of oxygen delivered to the tissues, and all are displayed on a screen. 8641812 7 [0014] Other sensors may be used and may be desirable, so that for instance in the operating theatre, if an electrocardiograph is in use, the signal from this might be preferred over the ear lobe sensor for pulse wave timing. Although the invention is non-invasive, on occasions when an arterial line is already in place, it might be preferable to have the flexibility of using the systolic and diastolic output from this source rather than duplicating measurements by applying a NIBP apparatus to the patient. Ultrasonic Doppler probes and microphones may also be used. [0015] For continuous monitoring under stable conditions checking compliance every hour is satisfactory, but reduced to quarter hourly or every minute in unstable situations. Similarly, electronic blood pressure readings may be taken at half hourly intervals but reduced to five minutes or even every minute if cardiac output is unstable. With continuous monitoring the time constant and pulse rate are continually monitored with averaging for about fifteen seconds before computing the various parameters and updating the information. Cardiac output corrections will be necessary for absent limbs or during surgical procedures when tourniquets are applied or major vessels clamped, as these conditions alter total arterial compliance. The operator must also be aware that if the aortic valve is incompetent, the percentage reflux will reduce the effective cardiac output by that amount. An Ultrasonic Doppler probe can be used to diagnose the existence and degree of incompetence. [0016] Using these determinants of mean arterial pressure, compliance, and the time constant, cardiac output is derived using the equation described in patent AU2012318248. The volume of oxygen delivered to 8641812 8 the tissues is the cardiac output times the haemoglobin level, times the oxygen carrying capacity of haemoglobin, times the oxygen saturation. This and further calculations are rapidly effected and displayed on a visual display screen attached to a programmed computer, as the analogue signals from the sensors are converted to digital format. The PICO system (picotech.com) is an example of a method for programming a computer, displaying the traces as with an oscilloscope, performing mathematical functions and displaying results in digital format. [0017] Any microcontroller or microcomputer well known to the technician in the field of electronics or medical electronics can be used as a programmable device to measure and calculate the above stated factors. The hardware and software components are well known in the art and it is within the skill of a person of average ability in the art to construct a device to determine these parameters or write software to operate the microcontroller or microprocessor to perform these functions. [0018] For example as shown in figure 1 a typical apparatus involves a computer 50, having an input 52 from sensors 51, 54, 56, 58, corresponding respectively to an electronic sphygmomanometer or other arterial pressure measuring device, the several infra red optical sensors, one or more Doppler probes and one or more electrocardiographic leads. The computer 50 involves a processing unit 53 operated under software control in RAM 55 or ROM 57 which performs a series of software steps such as set forth in figure 2. The output of these software steps provides values which can be displayed as tables 61, 63, 65, 67, in an output device 60 such as a visual display unit, a meter or similar device, a printer 59 or 8641812 9 may be input into a further communication device 62 for transmission to a remote location either over a phone line or wireless link 69 including radio, optical fibre, microwave link or the like. A meter may be an electromechanical device or may be a light emitting diode display or liquid crystal display. [0019] Referring to figure 2, the series of software steps perform the following operations. The pulse wave trace is input through the input device as discussed above. The trace is converted from an analogue form to a digital form for processing by the computer. Once the trace has been converted to a digital form it is scaled, calibrated and sampled over a period of typically 15 seconds to provide the mean arterial pressure (step 100). The time constant is calculated by analysing the slope of the pulse wave below the dicrotic notch and extrapolating a tangent on the curve to zero to obtain the time constant (stepI 02). Several such measurements can be taken on each curve and averaged for example over 15 pulse waves. A programmed computer may also derive the time constant by timing the fall from a given point to a percentage drop from that point. (With an exponential fall, one time constant gives a fall to 36.8% of the initial value). The computer may further have available a table of compliances to use for the best match for the trace for example stored in ROM device 57. [0020] The time constant is divided by the compliance (Step 104) to determine the total peripheral resistance (step-106). The total peripheral resistance can then be used with the mean arterial pressure to determine the cardiac output (step 108). The cardiac output can then be used to determine the volume of oxygen delivered to the tissues when combined 8641812 10 with the haemoglobin (Hb) and oxygen saturation values (02 Sat) (step 111). A variety of other values including the cardiac index (stepI 10) and the stroke volume (step 112) can also be determined. [0021] From the optically derived pulse wave, the maximum slope of the rising wave reflects cardiac contractility (step 114) which can be expressed as rate of change of pressure or rate of change of volume. [0022] Measuring the period from the start of the upswing of the pulse trace to the dicrotic notch provides the ejection period (stepI 16). The pre ejection period is measured in conjunction with an electrocardiogram (stepI 18) and preferably using a Doppler signal from the ascending aorta for precise timing. [0023] The outputs from the calculations or steps can then be displayed in a tabular or numerical or histogram form 120 for interpretation, while the pulse waveform is displayed as an analogue trace 122. The display of output values 120 will show the volume of oxygen delivered to the tissues in ml/minute and may for example include the values of systolic pressure, diastolic pressure, heart rate, mean arterial pressure, compliance, systemic vascular resistance, cardiac output, cardiac index, stroke volume, maximum contractility (expressed as volume and/or pressure change), ejection period, systolic pre ejection period, and as well the haemoglobin value and the oxygen saturation value derived from the pulse oximeter. 8641812 11 [0024] Alternatively, these values may be transmitted to a remote location through a telecommunication link (69) for evaluation by a specialist, for example in a road side emergency or a home care environment. [0025] It is not considered necessary to include the exact sequence of steps for calculating the various values in the flow diagram shown with respect to figure 2 as this is within the skill of an average programmer or workman in the field. Examples of oxygen delivery measurement [0026] An adult patient has a haemoglobin (Hb) value of 140 grams per litre of blood. The monitor shows a saturation of 98% with a cardiac output of 6litres per minute. The calculation is: (Hb x 1.34) x (%saturation of Hb) x (Cardiac Output in Litres/minute) Which is: (140 x 1.34) x (98/100) x (6) ml/min. Oxygen delivery. This is: 1,1 03ml/minute oxygen delivery to the tissues, which is satisfactory. If the Cardiac Output of this patient falls to 5 litres per minute with the haemoglobin and oxygen saturation unchanged: Oxygen delivery falls to 919ml/min., which is borderline safe. If blood loss occurs with this patient, resulting in a fall in haemoglobin to 90 grams per litre of blood but the cardiac output remains at 5litres/min., and the oxygen saturation unchanged: Oxygen delivery will now fall to 590ml/min. This is a dangerously low level for an adult and will require immediate correction. 8641812 12 [0027] Most cardiovascular values are converted to relate to body surface area in square metres by using a standard formula relating weight and height of the patient. 600ml/min of oxygen per square metre body surface area is regarded as the lowest safe limit. [0028] All the above calculations are performed by the programmed computer in the system, and displayed on a screen under the control of the operator. [0029] Although the invention has been herein shown and described in what is conceived to be the most practical and preferred embodiments, it is recognized that departures can be made within the scope of the invention, which are not to be limited to the details described herein but are to be accorded the full scope of the appended claims so as to embrace any of the equivalent assemblies, devices, apparatus articles, compositions, methods, processes and techniques. [Next page is page 14] 8641812
    权利要求:
    Claims (14)
    [1] 6. An apparatus for deriving continuously the volume of oxygen delivered to the tissues in a patient as claimed in claim 2 wherein said means for displaying includes means for displaying said haemoglobin, oxygen saturation, cardiac output, and said volume of oxygen delivered to the tissues remotely.
    [2] 7. An apparatus for deriving continuously the volume of oxygen delivered to the tissues in a patient as claimed in claim 2, wherein means for portable operation is provided by the inclusion of an electrical battery. 8641812 16
    [3] 8. A method for measuring the volume of oxygen delivered to the tissues of a patient, the method comprising: receiving a haemoglobin value of the patient; determining the oxygen saturation percentage of the haemoglobin of the patient; determining the cardiac output of the patient; and determining the volume of oxygen delivered to the tissues based on the haemoglobin value, the oxygen saturation percentage of the haemoglobin and the cardiac output.
    [4] 9. The method of claim 8, wherein receiving the haemoglobin value comprises: obtaining the haemoglobin value from a haemoglobin sensor attached to the patient; or obtaining the haemoglobin value from a memory.
    [5] 10. The method of claim 8, wherein determining the oxygen saturation percentage comprising sensing the oxygen saturation percentage through a pulse oximeter.
    [6] 11. The method of claim 8, wherein determining the cardiac output comprises: obtaining a (first) continuous waveform corresponding to an arterial pressure waveform at a first site on the patient using a (first) non-invasive sensor in contact with the patient; measuring systolic and diastolic arterial pressures using a non invasive pressure system in contact with the patient; 8641812 17 scaling and calibrating the first continuous waveform based on the measured systolic and diastolic arterial pressures; determining mean arterial pressure and an arterial time constant from the scaled and calibrated continuous waveform; deriving vascular compliance based on a pulse wave delay between two continuous waveforms corresponding to the arterial pressure waveform at different sites on the patient; and calculating the cardiac output as a function of the mean arterial pressure, the vascular compliance, and the arterial time constant.
    [7] 12. The method of claim 8, wherein determining the volume of oxygen delivered to the tissues comprises multiplying the haemoglobin value with known oxygen carrying capacity of haemoglobin, the oxygen saturation percentage and the cardiac output.
    [8] 13. A system for measuring the volume of oxygen delivered to the tissues of a patient, the system comprising: an input unit configured to receive a haemoglobin value of the patient and an oxygen saturation percentage of the haemoglobin of the patient; a processing unit configured to: determine a cardiac output of the patient; and determine the volume of oxygen delivered to the tissues based on the haemoglobin value, the oxygen saturation percentage of the haemoglobin and the cardiac output; and an output device configured to present the determined volume of oxygen delivered to the tissues. 8641812 18
    [9] 14. The system of claim 13, wherein the processing unit is further configured to multiply known oxygen carrying capacity of the haemoglobin with the measured haemoglobin value, the oxygen saturation percentage of the haemoglobin and the cardiac output to determine the volume of xygen delivered to the tissues.
    [10] 15. The system of claim 13, wherein the input unit is operatively coupled to one or more sensors configured to measure the haemoglobin value and the oxygen saturation percentage of the haemoglobin.
    [11] 16. The system of claim 13, wherein the output device is at least one of a display unit, a meter, a printer, or a communication device.
    [12] 17. The system of claim 13, wherein the processing unit is further configured to: obtain a first continuous waveform corresponding to an arterial pressure waveform at a first site on the patient using a first non-invasive sensor in contact with the patient; measure systolic and diastolic arterial pressures using a non-invasive pressure system in contact with the patient; scale and calibrating the first continuous waveform based on the measured systolic and diastolic arterial pressures; determine mean arterial pressure and an arterial time constant from the scaled and calibrated continuous waveform; derive vascular compliance based on a pulse wave delay between two continuous waveforms corresponding to the arterial pressure waveform at different sites on the patient; and 8641812 19 calculate the cardiac output as a function of the mean arterial pressure, the vascular compliance, and the arterial time constant.
    [13] 18. The system of claim 16, wherein the processing unit is further configured to: divide the arterial time constant with the vascular compliance to determine total peripheral resistance; and divide the mean arterial pressure by the total peripheral resistance to calculate the cardiac output.
    [14] 19. The method of claim 1, wherein determining the cardiac output is based on claim 1 of AU2012318248. Duncan Campbell Investments Pty Ltd Patent Attorneys for the Applicant SPRUSON & FERGUSON 8641812
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    同族专利:
    公开号 | 公开日
    AU2013205767B2|2015-05-07|
    AU2013205767A9|2015-02-05|
    AU2013205767A2|2015-03-05|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US6309360B1|1997-03-17|2001-10-30|James R. Mault|Respiratory calorimeter|
    EP2502555A1|2011-03-22|2012-09-26|Bmeye B.V.|Non-invasive oxygen delivery measurement system and method|
    WO2013113055A1|2012-01-30|2013-08-08|Campbell Duncan Islay|Method and apparatus for non-invasive determination of cardiac output|
    法律状态:
    2014-10-02| DA3| Amendments made section 104|Free format text: THE NATURE OF THE AMENDMENT IS: AMEND THE PRIORITY DETAILS TO READ REMOVE PRIORITY 2012318248 |
    2015-02-05| SREP| Specification republished|
    2015-03-05| DA3| Amendments made section 104|Free format text: THE NATURE OF THE AMENDMENT IS AS SHOWN IN THE STATEMENT(S) FILED 08 MAY 2014 |
    2015-09-03| FGA| Letters patent sealed or granted (standard patent)|
    优先权:
    申请号 | 申请日 | 专利标题
    AU2013205767A|AU2013205767B2|2013-04-15|2013-04-15|Continuous non-invasive optical measurement of tissue oxygen delivery|AU2013205767A| AU2013205767B2|2013-04-15|2013-04-15|Continuous non-invasive optical measurement of tissue oxygen delivery|
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