Improved method for converting venous blood gas value into arterial blood gas value

Abstract

A computer-implemented method, system, and decision support system adapted to provide arterial venous blood gas values without providing arterial oxygenation saturation values or arterial blood gas values. The method includes providing arterial blood gas values from a subject for which only venous blood gas values are provided by providing a mathematical model adapted to convert the venous blood gas values with provided predefined default arterial oxygenation values to output arterial blood gas values of the subject. Thus, the present invention provides a method for providing arterial blood gas values from a particular subject without the need for providing an arterial blood sample by painful arterial blood drawing, and also without the need for the subject's arterial oxygenation saturation values, thereby reducing the patient's pain and reducing the task of related health care personnel.

Description

Technical Field

[0001] The present invention relates to an improved method for converting venous blood gas values ​​from a subject into arterial blood gas values ​​of the subject and a corresponding computer program product for executing the method on a computer system. The present invention also relates to a corresponding decision support system (DSS), preferably a portable data processing system, and a corresponding computer program product. Background Art

[0002] The assessment of emergency patients is a complicated process, involving the assessment of the patient's numerous physiological systems (e.g., lungs, metabolism, kidneys and circulatory system). Most of the information necessary for this assessment comes from the analysis of the patient's blood. Blood samples can be collected from both arteries and veins. Arterial blood can be sampled by placing an arterial catheter or cannula in the patient or by performing arterial puncture with a needle. Venous blood can be sampled from cannula or venous puncture at the periphery (peripheral venous blood), from the catheter sampled (central venous blood) placed in the vena cava or right atrium, or from the pulmonary artery catheter sampled (mixed venous blood) placed in the pulmonary artery.

[0003] Placement of venous and arterial catheters is an invasive procedure and is generally limited to specialized / high-dependency departments. In addition, catheterization, cannulation, or puncture of an artery rather than a vein increases the risk of complications (such as bleeding, hemorrhage, thrombosis, embolism, nerve damage, or pseudoaneurysm formation). The collection of arterial blood by arterial puncture is generally considered to be a more difficult procedure than the collection of venous blood by venipuncture. Therefore, routine sampling of arterial blood is generally limited to specialized / high-dependency settings. Routine sampling of peripheral venous blood is most common in other wards where patients are severely neglected (e.g., cardiology, abdominal surgery, thoracic surgery, and internal medicine).

[0004] Many measurements collected from blood and used to assess the patient's status are similar in venous and arterial blood samples. These measurements include electrolytes and metabolites, such as sodium (Na), potassium (K) and blood glucose. However, regardless of the sampling site, the acid-base status of arterial and venous blood is not the same. Acid-base status generally refers to the following measurements in blood: pH, oxygen partial pressure (pO2), carbon dioxide partial pressure (pCO2), bicarbonate concentration (HCO3), hemoglobin concentration (Hb) and abnormal forms of hemoglobin (e.g., carboxyhemoglobin (COHb), methylhemoglobin (MetHb), hemoglobin oxygen saturation (SO2), concentration of base concentration (base excess (BE)) above reference conditions, and bicarbonate concentration (standard bicarbonate SBC) under reference pCO2. The change in acid-base status between arterial and venous blood is due to the removal of oxygen in the blood and the addition of carbon dioxide caused by metabolism at the tissue. In addition, in patients with circulatory or metabolic abnormalities, the production of strong acids at the tissue due to anaerobic metabolism may also change the acid-base status.

[0005] The acid-base status of arterial blood is used to assess the patient's pulmonary and metabolic status. It has been argued (Adrogue et al., 1989a, 1989b; Brandi et al., 1995; Radiometer 1997) and is largely clinically accepted that venous blood samples are inadequate for assessing a patient's acid / base and respiratory status. This is considered particularly true for peripheral venous samples, which "are not recommended for blood gas analysis because they provide little or no information about the patient's general status" (Radiometer 1997).

[0006] In intensive care units, placement of an arterial catheter is routine, and an assessment of the acid-base status can be obtained from arterial blood. In some other hospital departments (e.g., pulmonary or renal departments), arterial blood gases are also measured. However, in other wards that admit critically ill patients (e.g., cardiology, abdominal surgery, thoracic surgery, and internal medicine), arterial samples are not usually collected. Peripheral venous samples are usually collected and analyzed in a central laboratory. Samples are usually collected under aerobic conditions, i.e., no attempt is made to ensure that pO2 and pCO2 remain constant during the sampling process. Only a small amount of information about the patient's acid-base status is measured in such samples, i.e., standard bicarbonate, SBCv, and hemoglobin Hbv. Other acid-base parameters pHv, carbon dioxide pressure (pCO2v), base excess (BEv), oxygen saturation (SO2v), and oxygen pressure (pO2v) are not measured, and considering the aerobic nature of the sample, if measured, it may not reflect the true value of the venous blood in such a sample.

[0007] In recent years, methods for converting venous blood gas values ​​into arterial blood gas values ​​have been demonstrated. Over the years, several initiatives have been taken to reduce the need for arterial puncture, such as the method for converting venous blood values ​​into arterial blood values ​​disclosed in international patent application WO 2004 / 010861 (granted to OBI Medical Aps, Denmark). The advantage of this method is that it does not require the collection of arterial blood samples and eliminates the disadvantages of collecting arterial blood samples compared to venous blood samples. The method is basically based on three steps, namely, a first step, for example, to measure arterial oxygenation saturation by pulse oximetry; a second step, preferably by anaerobic sampling to measure and estimate the values ​​of venous blood acid / base state and oxygenation state of a venous blood sample (including peripheral venous blood (PVBG) or central venous blood (CVBG))); and a third step, by applying a mathematical model that derives the acid-base state and oxygenation state of the blood, the venous blood value is converted into the desired estimated arterial blood value, i.e., one or more values ​​of the acid-base state in the arterial blood. The method generally described in WO 2004 / 010861 is now available from OBI (a Roche company) under the trade name v-TAC TM Commercially available, see web page https: / / diagnostics.roche.com / global / en / products / instruments / v-tac-standalone-ins-6779.html for more information.

[0008] As described above, current methods require providing a venous blood sample from a subject and a measured or estimated arterial oxygen saturation value (SpO2), such as provided by a pulse oximeter. The v-TAC algorithm then processes the venous blood gas value, the arterial oxygen saturation value and provides an arterial blood gas value. In some cases, an arterial oxygenation value is not present, may be subject to measurement error, or incorrect readings from a healthcare provider reading and entering the arterial oxygenation value from the pulse oximeter.

[0009] Hence, an improved method of converting venous blood values ​​to arterial blood values ​​would be advantageous, and in particular a more efficient and / or reliable method would be advantageous.

[0010] Purpose of the Invention

[0011] Another object of the present invention is to provide an alternative to the prior art.

[0012] In particular, one object of the present invention may be seen as providing a method of providing arterial blood gas values ​​converted from venous blood values ​​without providing a measured or estimated arterial oxygen saturation value (SpO2), which method solves the above mentioned problems of the prior art. Summary of the invention

[0013] Therefore, in a first aspect of the present invention, the above and several other objects are achieved by providing a computer-implemented method for converting a venous blood gas value of a subject to an arterial blood gas value when a measured or estimated arterial oxygen saturation value (SpO2) for the subject is not available, the method comprising:

[0014] a. Provide a predefined default arterial oxygen saturation value as an alternative value I,

[0015] b. optionally adjusting the replacement value I by input from the user,

[0016] c. providing a venous blood gas value of a provided venous blood sample from the subject,

[0017] d. Applying mathematical models to venous blood gas values ​​and surrogate values ​​I, and

[0018] e. Providing an estimated arterial blood gas value based on mathematical modelling applied to the value provided in step c and the replacement value I.

[0019] The present invention is particularly, but not exclusively, advantageous in providing a method for converting venous blood gas values ​​to arterial blood gas values ​​in the absence of a measured or estimated arterial oxygen saturation value (SpO2). Thus, the present invention eliminates the prerequisite of providing an estimated or measured arterial oxygen saturation value for the conversion, thereby simplifying the task of converting arterial blood gas values ​​from venous blood gas values, and further ensuring that, assuming that venous blood gas values ​​(such as pH, pCO2, pO2, sO2 and Hb) are available, even if a measured or estimated arterial oxygen saturation value is not available, at least arterial values ​​(including but not limited to pH, pCO2, BE, HCO3, tO2 and tCO2) can be estimated.

[0020] It will be appreciated that venous blood gas values ​​may be derived from a peripheral venous blood sample.

[0021] It will further be appreciated that the present invention is capable of providing estimated arterial blood gas values ​​even in situations where neither measured nor estimated arterial oxygenation values ​​are provided.

[0022] Even further, it should be appreciated that the mathematical model may be, at least in part, a version of the v-TAC algorithm as described in the cited prior art.

[0023] Another advantage of the present invention is that the chance of measurement error is reduced because the step of providing an arterial oxygen saturation value has been eliminated from the method of converting arterial blood gas values ​​from venous blood gas values.

[0024] Yet another advantage of the present invention is that the chance of reading or input errors is reduced when a health care provider converts or transmits estimated or measured arterial oxygen saturation values ​​(such as from a pulse oximeter) to the input of a conversion device or computer program product suitable for converting venous blood gas values ​​and arterial oxygen saturation values ​​to arterial blood gas values, because the step of providing an arterial oxygen saturation value has been eliminated from the method of converting arterial blood gas values ​​from venous blood gas values.

[0025] Thus, the present invention provides a computer-implemented method for providing arterial blood gas values ​​from a subject (such as a patient) to a user (such as a physician or other health care provider) without providing an arterial oxygen saturation value and an arterial blood sample or an arterial blood gas value. By reducing the need for the above-mentioned arterial oxygen saturation value and arterial blood sample, the patient's suffering and pain, the complexity of patient care for any involved personnel, and the risk of error are greatly reduced.

[0026] In the context of the present invention, the method is provided for a specific subject, wherein an arterial oxygen saturation value is not available for the specific subject.

[0027] Furthermore, in the context of the present invention, a predefined default value is to be understood as a value that is not based on any previously estimated, measured or otherwise assessed information about a particular subject.

[0028] In the context of the present invention, it should be understood that providing a blood value from a blood sample does not necessarily include a specific step of collecting or extracting a blood sample from a patient, and thus the measurement result may be obtained, transmitted, communicated, etc. from another entity or individual (e.g., a nurse who has performed a blood measurement or draw).

[0029] In an embodiment of the invention, the estimated arterial blood gas values ​​provided in step e do not include arterial pO2, since no measured or estimated arterial oxygen saturation value is provided.

[0030] In a preferred embodiment of the present invention, the venous blood gas value of step c is at least one of a venous acid / base parameter and a venous oxygenation parameter.

[0031] In another preferred embodiment, the estimated arterial blood gas value of step e is at least one of an arterial oxygenation parameter and an arterial acid-base status parameter.

[0032] In an embodiment of the present invention, the replacement value I of step a is based on clinical / medical guidelines, such as global health guidelines, national health guidelines, regional guidelines, hospital guidelines or physician guidelines.

[0033] In an advantageous embodiment of the invention, the user input of optional step b is based on whether the subject is currently being treated with supplemental oxygen and / or one or more of the subject's physical parameters. The physical parameters may include one or more of the following: age, pathology / disease, gender, weight, and user-estimated fat percentage.

[0034] In the context of the present invention, the relevant pathology / disease may be one or more of the following but is not limited to: chronic obstructive pulmonary disease (COPD), such as interstitial lung disease (ILD), such as cystic fibrosis (CF), such as pulmonary hypertension, such as patients with neuromuscular or chest wall disorders or such as patients with advanced heart failure.

[0035] Furthermore, in the context of the present invention, user estimated fat percentage is to be understood as a visual assessment or other estimate made by a healthcare professional during the provision of input according to optional step b. of the present invention.

[0036] In embodiments of the invention where the subject is receiving supplemental oxygen therapy, the user input of step b may be based on whether the subject has been receiving long-term oxygen therapy or acute oxygen therapy.

[0037] In the context of the present invention, long-term oxygen therapy is understood to be oxygen therapy of at least 12 hours per day for more than 30 days. It is also understood that acute oxygen therapy may be an acute treatment for a patient associated with a trauma or sudden onset of a condition requiring urgent care. It should be noted that a person skilled in the art will know the difference between acute oxygen therapy and long-term oxygen therapy.

[0038] In another advantageous embodiment of the present invention, step c further comprises providing a hemoglobin value of the provided venous blood sample from the subject, and step d further comprises:

[0039] - applying a mathematical model to the provided haemoglobin value, and wherein the estimated arterial acid-base status value and the blood gas value provided in step e are further based on the mathematical modelling of the haemoglobin value.

[0040] In a preferred embodiment of the present invention, the mathematical model in step d is further applied as follows: the true value of the respiratory quotient (RQ) can only vary between 0.7 and 1.0, which is 0.7 for aerobic metabolism of fat and 1.0 for aerobic metabolism of carbohydrates.

[0041] In another preferred embodiment of the present invention, the mathematical model in step d is further mathematically applied as follows:

[0042] - by setting a constant respiratory quotient (RQ) within the physiologically possible range of 0.7 to 1.0

[0043] The determined ratio, such as adding O2 and removing CO2 from venous blood at a fraction of the RQ set at 0.82, and

[0044] - The simulation is performed until the estimated arterial blood gas value is correlated with the provided venous blood gas value and the replacement value I of step a or step b.

[0045] In an advantageous embodiment of the invention, the method further comprises providing a machine learning algorithm, and the following further steps after step e:

[0046] f: provides the subject's measured arterial oxygenation value,

[0047] g: comparing the surrogate value I from step a and / or step b with the measured arterial oxygenation value, and

[0048] h: The subsequent substitute value I of step a is adjusted based at least on the comparison performed by the learning algorithm in step g.

[0049] This embodiment is particularly useful for continuously improving the method of converting venous blood gas values ​​into arterial blood gas values ​​based on empirical data.

[0050] In an embodiment of the present invention, the replacement value I of step a is an arterial oxygen saturation fraction between 0.85 and 1.00.

[0051] In the context of the present invention, fractions are understood to be decimal fractions, where 1.00 represents 100% arterial oxygen saturation, and where 0.85 represents 85% arterial oxygen saturation of the subject. It should be noted that a person skilled in the art will know how to convert these values.

[0052] In a second aspect, the present invention provides a system adapted to convert a venous blood gas value of a subject to an arterial blood gas value when a measured or estimated arterial oxygen saturation value is not available for the subject, the system comprising:

[0053] - a user interface, such as a touch screen, configured to provide information to a user and receive input from the user,

[0054] - an input / output device configured to receive data from a peripheral device such as a blood gas analysis system or device,

[0055] - a processor configured to process the data and apply an algorithm, a mathematical blood gas model or a simulation, preferably wherein the processor is configured to apply a mathematical model according to claim 1,

[0056] Wherein the system is configured to provide estimated arterial blood gas values ​​to the user when the system is provided with:

[0058] - venous blood gas values ​​from a venous blood sample taken from the subject, and

[0059] - an alternative value I, where I is a predefined default oxygen saturation value, or

[0060] - The user input represents an alternative value I for the oxygen saturation value.

[0061] In the context of the present invention, a user interface should be understood as any device configured to display a user interface and configured to receive input from a user, the input to be received in a digital device (such as a computer with a screen, keyboard and mouse, or a smartphone, tablet or other suitable device). In a preferred embodiment, the digital device or system further comprises a memory configured to store data and / or one or more computer program products.

[0062] In the context of the present invention, a processor should be understood as any suitable type of logic circuit (such as a CPU in a computer configured to execute a computer program product) that responds to and processes basic instructions and data provided to the processor (in particular, such as a computer-implemented method according to the first aspect of the present invention).

[0063] In the context of the present invention, an input / output device should be understood as any suitable device adapted to receive / send input, output or other processed data between the system and a peripheral device (such as a blood gas analyzer). The device may be further adapted to acquire corresponding media data to send as input to a computer or to send computer data as storage output to a storage medium. The input / output device may be wired or wireless, such as being configured to receive / send data via a wired connection (such as a data cable) or wirelessly (such as via a radio signal).

[0064] In a preferred embodiment of the invention, the system is a decision support system that is configured to provide a user with decision support regarding a subject, such as decision support regarding the flow of oxygen from a supplemental oxygen device to a patient. This embodiment is particularly advantageous for obtaining decision support when adjusting the flow of oxygen from a supplemental oxygen device to a patient. The decision support can help a health care provider, such as a nurse or physician, achieve a patient's desired oxygen level with fewer than usual adjustments to the flow of oxygen. Fewer than usual adjustments save the health care provider's time and also reduce the time the patient is uncomfortable.

[0065] In a third aspect, the present invention relates to a computer program product adapted to enable a computer system (preferably a portable computer system) to include at least one computer having data storage means connected thereto and comprising instructions which, when the program is executed by the computer, cause the computer to perform the computer-implemented method of the first aspect of the invention.

[0066] This aspect of the invention is particularly, but not exclusively, advantageous because the invention may be implemented by a computer program product which, when downloaded or uploaded to a computer system, enables the computer system to perform the operations of the computer-implemented method of the first aspect of the invention. Such a computer program product may be provided on any kind of computer-readable medium or over a network.

[0067] In a fourth aspect, the invention relates to the use of a system according to the second aspect of the invention, such as where a user adjusts the flow of supplemental oxygen to a patient based on estimated blood gas values ​​provided by the system.

[0068] In another embodiment of the invention, the use of the system relates to use of a decision support system according to the second aspect of the invention, such as wherein a user adjusts the supplemental oxygen flow to a patient based on decision support provided by the system based on the patient's estimated arterial blood gas values.

[0069] Each aspect of the invention may be combined with any of the other aspects. These and other aspects of the invention will be apparent from the following description, with reference to the described embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] The computer implemented method, system and computer program product according to the present invention will now be described in more detail with reference to the accompanying drawings. The drawings illustrate one way of implementing the present invention and should not be construed as limiting other possible embodiments falling within the scope of the appended claim set.

[0071] Figure 1 is a schematic diagram of a method according to an embodiment of the present invention.

[0072] Figure 2 is another schematic diagram of a method according to an embodiment of the present invention.

[0073] Figure 3 A schematic flow chart showing an overview of the operation of a computer program product according to an embodiment of the present invention. DETAILED DESCRIPTION

[0074] Figure 1 A schematic diagram showing a method according to an embodiment of the present invention is shown.

[0075] An oxygen-free blood sample is obtained from a particular subject for which an arterial oxygen saturation value is not available. The blood sample is analyzed using an associated blood gas analyzer (not shown). The blood gas analyzer provides an oxygen-free blood gas value and provides it to a mathematical model. The mathematical model converts the oxygen-free blood gas value and provides a predefined default oxygenation saturation value as an alternative value I, and provides an estimated / calculated aerobic blood gas value to a user (such as a physician or other health care personnel) based on the oxygen-free blood gas value and the alternative value I. It should be understood that the oxygen-free blood sample can be a venous blood sample and the aerobic blood gas value can be an arterial blood gas value.

[0076] Figure 2 Another schematic diagram of a method according to an embodiment of the present invention is shown. A peripheral venous blood sample from a specific subject is provided, for which an arterial oxygen saturation value is not available. The peripheral venous blood sample is analyzed using a blood gas analyzer BGA, and the venous blood gas values ​​from the blood gas analyzer BGA (such as pH, pCO2, pO2, sO2, Hb, fMETHb and fCOHbv) are input into a mathematical model, preferably into a VTAC algorithm. The mathematical model then converts the venous blood gas value and a predefined default arterial oxygen saturation value (alternative value I) into an output representing a calculated arterial blood gas value (such as pH, PCO2, BE, HCO3, tO2 and tCO2). It should be understood that for the input, v represents the vein, and the output a, c represent the artery and are calculated separately.

[0077] Figure 3 A schematic flow chart showing an overview of the operation of a computer program product according to an embodiment of the present invention. The flow chart shows a computer-implemented method for converting a venous blood gas value of a subject to an arterial blood gas value when a measured or estimated arterial oxygen saturation value (SpO2) for the subject is not available, the method comprising the steps of:

[0078] a. Provide a predefined default arterial oxygen saturation value as an alternative value I,

[0079] b. optionally adjusting the replacement value I by input from the user,

[0080] c. providing a venous blood gas value of a provided venous blood sample from the subject,

[0081] d. Applying mathematical models to venous blood gas values ​​and surrogate values ​​I, and

[0082] e. Providing an estimated arterial blood gas value based on mathematical modelling applied to the value provided in step c and the replacement value I.

[0083] The present invention can be implemented by hardware, software, firmware or any combination of these. The present invention or some of its features can also be implemented as software running on one or more data processors and / or digital signal processors.

[0084] As an example for a specific subject, arterial blood gases are estimated according to the following 4 steps.

[0085] Step 1: A sample of oxygen-free venous blood is drawn from the subject and analyzed using standard blood gas analysis techniques to provide acid / base and / or blood gas values ​​(pH, pCO2, pO2, sO2, Hbv, METHb, COHb) of the venous blood.

[0086] Step 2: Since the arterial oxygen saturation value for a specific subject is not available, a predefined default arterial oxygen saturation value is provided as an alternative value I.

[0087] Step 3: For the blood sample that passes from the artery through the tissue into the vein, the ratio of the amount of CO2 added due to aerobic metabolism (i.e., CO2 production rate (VCO2)) to the amount of O2 removed (i.e., O2 utilization rate (VO2)) is defined as the respiratory quotient (RQ=VCO2 / VO2). RQ is usually roughly estimated by measuring the inspired and expired gases collected at the mouth, by measuring the inspired oxygen fraction (FiO2) and the inspired carbon dioxide fraction (FiCO2) and the end-tidal oxygen fraction (Fe'O2) and the end-tidal carbon dioxide fraction (Fe'CO2) or the mixed exhaled oxygen fraction (FeO2) and the mixed exhaled carbon dioxide fraction (FeCO2), using the following equation:

[0088] RQ= Fe'CO 2 –FiCO 2 or RQ = FeCO 2 –FiCO 2

[0089] FiO2–Fe'O2 FiO2–FeO2

[0090] Rough estimates of RQ by this method usually give values ​​that vary widely. However, the true value of RQ at the tissue can only vary between 0.7 and 1.0, which is 0.7 for aerobic metabolism of fat and 1.0 for aerobic metabolism of carbohydrates. In this step, a mathematical model of blood acid / base and oxygenation state (e.g., Rees et al., 1996, 1997, etc.) is used for simulation, in which O2 is added and CO2 is removed from venous blood at a ratio determined by a constant respiratory quotient set in a physiologically possible range of 0.7 to 1.0. This simulation is performed until the simulated oxygen saturation is equal to the alternative value I of step 2.

[0091] Step 4: The model of blood acid / base and the surrogate value I is then used to calculate an estimate of the arterial acid / base state of the arterial blood. This is possible because the simulated removal of CO2 and O2 from the venous blood at a fixed RQ ensures that when the simulated arterial oxygenation matches the surrogate value I, then the simulated values ​​of the other arterial acid-base variables should also match the provided venous values.

[0092] The basic assumption inherent in this approach is that a constant RQ value can be used for the venoarterial conversion. This requires that little or no anaerobic metabolism occurs in the tissue where the venous blood sample is taken. If anaerobic metabolism occurs, the strong acid (H2O) produced by this process will + ) will react with bicarbonate (HCO3 - ) combine to form CO2 in the following reversible reaction

[0093]

[0094] The increase in CO2 produced by this reaction will mean that the apparent VCO2 will increase, while VO2 will not increase, and therefore RQ will increase. The degree of anaerobic metabolism depends on the patient's circulatory and metabolic state. In normal well-perfused peripheral limbs, anaerobic metabolism is unlikely to occur. The perfusion quality of the limbs can be assessed clinically by the following items: the presence of clearly discernible arterial pulsations determined by palpation, normal capillary responses, and normal color and temperature of the limbs. Central venous blood or mixed venous blood is a mixture of blood from several parts, and therefore may contain blood from body areas with anaerobic metabolism. Therefore, the selection of sample sites is very important.

[0095] Step 5: Output of arterial values ​​such as pH, pCO2, BE, HCO3, tO2 and tCO2.

[0096] It should be noted that since no measured or estimated arterial oxygen saturation values ​​are provided, this method is not currently capable of providing arterial pO2 as in the cited prior art, but is capable of providing the above arterial values, which may be valuable to a physician or other healthcare provider.

[0097] Simulations have been performed on data from the following three clinical studies in which the present invention has been used:

[0098] M et al. (2019). Calculated arterial blood gas values ​​from avenous sample and pulse oximetry: Clinical validation. PLoS ONE 14(4):e0215413. doi:10.1371 / journal.pone.0215413

[0099] Rees SE et al (2012). Calculating acid-base and oxygenation status during COPD exacerbation using mathematically arterialized venous blood. Clin ChemLab Med 50(12):2149-2154. doi:10.1515 / cclm-2012-0233Tygesen G et al (2012). Mathematical arterialization of venous blood in emergency medicinepatients. Eur J Emerg Med 19:363–372.

[0100] doi:10.1097 / MEJ.0b013e32834de4c6

[0101] A total of n = 472 data sets were used in this simulation.

[0102] Each data set consisted of arterial blood gas measurements (ABG) used as a reference and venous blood gas measurements (VBG) from a pulse oximeter and associated SpO2 measurements.

[0103] A simulation was performed in which the VBG was converted to arterial values ​​using:

[0104] Measured SpO2 for each data set.

[0105] A 90% constant for all data sets, used as an alternative value I.

[0106] A 94% constant for all data sets was used as an alternative value I.

[0107] The VBG and three conversion results are compared to the ABG reference using statistical methods to calculate:

[0108] Mean deviation (mean difference).

[0109] The 95% limit of agreement was calculated as 1.96*SD.

[0110] The table presented below lists the results separately for pH and pCO2.

[0111] pH results with ABG (reference):

[0112] Average Deviation 95%LoA VBG 0,0302 0,049 v-TAC, in SpO2 0,0002 0,028 The present invention, at 94% 0,0005 0,031 The present invention, in 90% 0,0046 0,030

[0113] pCO2 results and ABG (reference):

[0114]

[0115] This simulation demonstrates that the present invention is able to convert venous pH and pCO2 (but not pO2) values ​​to arterial values ​​using predefined, patient-independent constants with an accuracy and precision approaching that of using measured SpO2 for individual volume data sets and significantly better than using VBG values ​​alone without conversion by the present invention.

[0116] Briefly, the present invention provides a computer-implemented method, system and decision support system adapted to provide arterial venous blood gas values ​​in the absence of an arterial oxygenation saturation value or an arterial blood gas value. The method comprises providing an arterial blood gas value from a subject for whom only a venous blood gas value is provided by providing a mathematical model adapted to convert the venous blood gas value with a provided predefined default arterial oxygenation value to output the arterial blood gas value for the subject. Thus, the present invention provides a method for providing an arterial blood gas value from a specific subject without requiring a painful arterial blood draw to provide an arterial blood sample and without requiring an arterial oxygenation saturation value for the subject, thereby reducing suffering for the patient and reducing the tasks of the associated health care personnel.

[0117] Preferred embodiments and aspects of the present invention are presented below in bulleted list form:

[0118] Item 1. A computer-implemented method of converting a venous blood gas value of a subject to an arterial blood gas value when a measured or estimated arterial oxygen saturation value for the subject is not available, the method comprising:

[0119] a. Provide a predefined default arterial oxygen saturation value as an alternative value I,

[0120] b. optionally adjusting the replacement value I by input from the user,

[0121] c. providing a venous blood gas value of a provided venous blood sample from the subject,

[0122] d. applying a mathematical model to the venous blood gas value and the surrogate value I, and

[0123] e. Providing an estimated arterial blood gas value based on mathematical modelling applied to the value provided in step c and the replacement value I.

[0124] Item 2. A computer-implemented method according to Item 1, wherein the venous blood gas value of step c is at least one of a venous acid / base parameter and a venous oxygenation parameter.

[0125] Item 3. A computer-implemented method according to Item 1 or 2, wherein the arterial blood gas value of step e is at least one of an arterial oxygenation parameter and an arterial acid-base status parameter.

[0126] Item 4. A computer-implemented method according to any of the preceding items, wherein the alternative value I of step a is based on clinical / medical guidelines, such as global health guidelines, national health guidelines, regional guidelines, hospital guidelines, or physician guidelines.

[0127] Clause 5. A computer-implemented method according to any of the preceding clauses, wherein the user input of optional step b is based on one or more of the following:

[0128] -Whether the subject is currently being treated with supplemental oxygen, and / or

[0129] - Physical parameters of the subject, the physical parameters comprising one or more of the following:

[0130] -age,

[0131] - Pathologies / diseases such as COPD,

[0132] -gender,

[0133] - weight, and

[0134] - User estimated fat percentage.

[0135] Item 6. A computer-implemented method according to any of the preceding items, wherein step c further comprises:

[0136] - providing a haemoglobin value of a provided venous blood sample from said subject, and

[0137] Step d further comprises:

[0138] - applying the mathematical model to the provided haemoglobin value, and wherein the estimated arterial acid-base status value and the blood gas value provided in step e) are further based on the mathematical modelling of the haemoglobin value.

[0139] Item 7. A computer-implemented method according to any of the preceding items, wherein the mathematical model in step d is further applied as follows: the true value of the respiratory quotient (RQ) can only vary between 0.7 and 1.0, which is 0.7 for the aerobic metabolism of fat and 1.0 for the aerobic metabolism of carbohydrates.

[0140] Item 8. A computer-implemented method according to any one of the preceding items, wherein the mathematical model in step d is further mathematically applied as follows:

[0141] - by setting a constant respiratory quotient (RQ) within the physiologically possible range of 0.7 to 1.0

[0142] The determined ratio, such as adding O2 and removing CO2 from venous blood at a fraction of the RQ set at 0.82, and

[0143] - Performing simulations until said estimated arterial blood gas value is correlated with the provided venous blood gas value and said replacement value I of step a or step b.

[0144] Item 9. A computer-implemented method according to any one of the preceding items, further comprising providing a machine learning algorithm, and the following additional steps after step e:

[0145] f: providing a measured arterial oxygenation value of said subject,

[0146] g: comparing the replacement value I of step a and / or step b with the measured arterial oxygenation value, and

[0147] h: The subsequent substitute value I of step a is adjusted based at least on the comparison performed by the learning algorithm in step g.

[0148] Item 10. A computer-implemented method according to Item 1, wherein the replacement value I of step a is an arterial oxygen saturation fraction between 0.85 and 1.00.

[0149] Item 11. A system adapted to convert a venous blood gas value of a subject to an arterial blood gas value when a measured or estimated arterial oxygen saturation value is not available for the subject, the system comprising:

[0150] - a user interface, such as a touch screen, configured to provide information to a user and receive input from the user,

[0151] - an input / output device configured to receive data from a peripheral device such as a blood gas analysis system or device,

[0152] - a processor configured to process the data and apply an algorithm, a mathematical blood gas model or a simulation, preferably wherein the processor is configured to apply a mathematical model according to item 1,

[0153] wherein the system is configured to provide the user with an estimated arterial blood gas value when the system is provided with:

[0154] - a venous blood gas value from a venous blood sample taken from said subject, and

[0155] - an alternative value I, where I is a predefined default oxygen saturation value, or

[0156] - The user input represents an alternative value I for the oxygen saturation value.

[0157] Item 12. A system according to Item 11, wherein the system is a decision support system configured to provide decision support to a user regarding a subject, such as decision support regarding the flow of oxygen from a supplemental oxygen device to a patient.

[0158] Item 13. A decision support system according to Item 12, which is further adapted to adjust the flow of supplemental oxygen to the subject based on one or more user inputs, wherein the user has received decision support regarding the flow of supplemental oxygen from the decision support system.

[0159] Item 14. A computer program product which, when downloaded or uploaded to a computer system, enables the computer system, preferably a portable computer system, to perform the method according to Item 1.

[0160] Item 15. Use of the system of Item 11, wherein the user adjusts the flow of supplemental oxygen to the patient based on estimated blood gas values ​​provided by the system.

[0161] Item 16. A method of treating hypoxia in a subject receiving supplemental oxygen, the method comprising

[0162] - perform the steps according to item 1,

[0163] - determining whether the estimated arterial blood gas value is within a threshold range, and if said estimated arterial blood gas value is outside said threshold range,

[0164] - treating said subject based on said estimated arterial blood gas value, such as by adjusting the rate of supplemental oxygen per minute.

[0165] Item 17. A lung ventilation device adapted to ventilate a subject, the device comprising:

[0166] -Ventilator,

[0167] - a processor adapted to execute a mathematical model enabling the conversion of venous blood gas values ​​and SpO2 values ​​into estimated ABG values,

[0168] - an input interface data-connected to the processor, the input interface being adapted to receive at least the venous blood gas and SpO2 values ​​measured from the subject,

[0169] -user interface,

[0170] a controller in data connection with the processor and the ventilator, the controller being adapted to control and adjust the ventilator based on the estimated arterial blood gas values ​​from the processor,

[0171] Wherein, if no SpO2 value is received from the subject, the device performs the computer-implemented method according to item 1.

[0172] Item 18. A device according to Item 17, wherein the device further alerts the user of the unreceived SpO2 value, the implementation of the substitute value I, and the value of I to provide an estimated ABG value required for the device to ventilate the subject, and optionally asks the user for approval of the value of I.

[0173] Item 19. A computer-implemented method according to Item 1, wherein the estimated arterial blood gas values ​​provided in step e consist of pH, pCO2, BE, HCO3, tO2 and tCO2.

[0174] Item 20. A computer-implemented method according to Item 1, wherein the estimated arterial blood gas value provided in step e consists of one or more of the following items: pH, pCO2, BE, HCO3, tO2 and tCO2.

[0175] In the context of the present invention, the following definitions and abbreviations may be used:

[0176]

[0177]

[0178] The various elements of the embodiments of the present invention can be implemented physically, functionally and logically in any suitable manner, such as with a single unit, with multiple units or as a part of a separate functional unit. The present invention can be implemented with a single unit, or physically and functionally distributed between different units and processors.

[0179] Although the present invention has been described in conjunction with specific embodiments, it should not be interpreted as being limited in any way to the examples presented. The scope of the present invention is interpreted in accordance with the appended claims. In the context of the claims, the terms "comprise" or "include" do not exclude other possible elements or steps. In addition, references such as "one" or "an" should not be interpreted as excluding multiple. The use of reference numerals in the claims relative to the elements indicated in the drawings should not be interpreted as limiting the scope of the present invention. In addition, the various features mentioned in different claims can be advantageously combined, and the mention of these features in different claims does not exclude that the combination of features is impossible and advantageous.

Claims

1. A computer-implemented method of converting a venous blood gas value of a subject to an arterial blood gas value when a measured or estimated arterial oxygen saturation value for the subject is unavailable, the method comprising: a. Provide a predefined default arterial oxygen saturation value as an alternative value I, b. optionally adjusting the replacement value I by input from the user, c. providing a venous blood gas value of a provided venous blood sample from said subject, d. applying a mathematical model to the venous blood gas value and the surrogate value I, and e. providing an estimated arterial blood gas value based on mathematical modelling applied to said value provided in step c and said replacement value I.

2. The computer-implemented method of claim 1, wherein the venous blood gas value of step c is at least one of a venous acid / base parameter and a venous oxygenation parameter.

3. The computer-implemented method of claim 1 or 2, wherein the arterial blood gas value of step e is at least one of an arterial oxygenation parameter and an arterial acid-base status parameter.

4. A computer-implemented method according to any of the preceding claims, wherein the alternative value I of step a is based on clinical / medical guidelines, such as global health guidelines, national health guidelines, regional guidelines, hospital guidelines or physician guidelines.

5. The computer-implemented method of claim 1, wherein optional user input of step b. is applied, and wherein the user input is based on one or more of: -Whether the subject is currently being treated with supplemental oxygen, and / or - Physical parameters of the subject, the physical parameters comprising one or more of the following: -age, - Pathologies / diseases such as COPD, -gender, - weight, and - User estimated fat percentage.

6. The computer-implemented method of any one of the preceding claims, wherein step c further comprises: - providing a haemoglobin value of a provided venous blood sample from said subject, and Step d further comprises: - applying the mathematical model to the provided haemoglobin value, and wherein the estimated arterial acid-base status value and the blood gas value provided in step e) are further based on the mathematical modelling of the haemoglobin value.

7. A computer-implemented method according to any of the preceding claims, wherein the mathematical model in step d is further applied as follows: the true value of the respiratory quotient (RQ) can only vary between 0.7 and 1.0, which is 0.7 for aerobic metabolism of fat and 1.0 for aerobic metabolism of carbohydrates.

8. The computer-implemented method according to any one of the preceding claims, wherein the mathematical model in step d is further mathematically applied as follows: - adding O2 and removing CO2 from venous blood at a rate determined by setting a constant respiratory quotient (RQ) within the physiologically possible range of 0.7 to 1.0, such as at a fraction of the RQ set at 0.82, and - Performing simulations until said estimated arterial blood gas value is correlated with the provided venous blood gas value and said replacement value I of step a or step b.

9. The computer-implemented method according to any one of the preceding claims, further comprising providing a machine learning algorithm, and the following additional steps after step e: f: providing a measured arterial oxygenation value of said subject, g: comparing the replacement value I of step a and / or step b with the measured arterial oxygenation value, and h: The subsequent substitute value I of step a is adjusted based at least on the comparison performed by the learning algorithm in step g.

10. The computer-implemented method of claim 1, wherein the substitute value I of step a is an arterial oxygen saturation fraction between 0.85 and 1.

00.

11. A system adapted to convert a venous blood gas value of a subject to an arterial blood gas value when a measured or estimated arterial oxygen saturation value is not available for the subject, the system comprising: - a user interface, such as a touch screen, configured to provide information to a user and receive input from the user, - an input / output device configured to receive data from a peripheral device such as a blood gas analysis system or device, - a processor configured to process the data and apply an algorithm, a mathematical blood gas model or a simulation, preferably wherein the processor is configured to apply a mathematical model according to claim 1, wherein the system is configured to provide the user with an estimated arterial blood gas value when the system is provided with: - a venous blood gas value from a venous blood sample taken from said subject, and - an alternative value I, where I is a predefined default oxygen saturation value, or - The user inputs a replacement value I representing the oxygen saturation value.

12. The system of claim 11, wherein the system is a decision support system configured to provide decision support to the user regarding the subject, such as decision support regarding the flow of oxygen from a supplemental oxygen device to a patient.

13. The decision support system of claim 12, further adapted to adjust the flow of supplemental oxygen to the subject based on one or more user inputs, wherein the user has received decision support from the decision support system regarding the flow of supplemental oxygen.

14. A computer program product which, when downloaded or uploaded into a computer system, enables the computer system, preferably a portable computer system, to perform the method according to claim 1.

15. Use of the system of claim 11, wherein a user adjusts the flow of supplemental oxygen to the patient based on estimated blood gas values ​​provided by the system.

16. A method of treating hypoxia in a subject receiving supplemental oxygen, the method comprising - performing the steps according to claim 1, - determining whether the estimated arterial blood gas value is within a threshold range, and if said estimated arterial blood gas value is outside said threshold range, - treating said subject based on said estimated arterial blood gas value, such as by adjusting the rate of supplemental oxygen per minute.

17. A lung ventilation device adapted to ventilate a subject, the device comprising: -Ventilator, - a processor adapted to execute a mathematical model enabling the conversion of venous blood gas values ​​and SpO2 values ​​into estimated ABG values, - an input interface data-connected to the processor, the input interface being adapted to receive at least the venous blood gas and SpO2 values ​​measured from the subject, -user interface, a controller in data connection with the processor and the ventilator, the controller being adapted to control and adjust the ventilator based on the estimated arterial blood gas values ​​from the processor, Wherein if no SpO2 value is received from the subject, the device performs the computer-implemented method of claim 1.

18. The device of claim 17, wherein the device further prompts a user regarding a non-received SpO2 value, achievement of the substitute value I, and a value of I to provide the estimated ABG value required for the device to ventilate the subject, and optionally asks the user for approval of the value of I.

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