Patent Application
20090177145
1. Field of the Invention
The present invention generally relates to cardiac pacing systems and, in particular, to a method and an implantable medical device for monitoring physiological parameters such as hematocrit and SvO2 levels of a patient to determine a patient status.
2. Description of the Prior Art
Physiological parameters such as hematocrit and SvO2 are common parameters used by physicians to diagnose and monitor patients. The hematocrit indicates the proportion of cells and fluids in the blood. The hematocrit is, in practice, the percent of whole blood that is composed of red blood cells (Erythrocytes). In men 39-55% of the blood volume is made up of red blood cells and in women 36-48%. A low hematocrit value may be the result from either an increased plasma volume (hemodilution) or from a reduced red blood cell volume (true anaemia). In patients suffering from CHF, low hematocrit values has been found to be of a frequent occurrence and is, also, associated with a poor prognosis, see, for example, “Hemodilution is Common in Patients with Advanced Heart Failure”, Androne et al., Circulation. 2003; 107:226-229.
In “The Cardio Renal Anaemia (CRA) Syndrome: Congestive Heart Failure, Chronic Kidney Insufficiency, and Anaemia”, Silverberg et al., Dialysis Times, News & Views from RPI, Volume 10, No. 1, it is shown that the presence of anaemia is associated with a more severe degree of CHF and with an increased mortality in CHF. In addition, it is shown that there exists a strong correlation between the severity of anaemia and hospitalization and/or length of stay. The anaemia caused by the CHF is not merely hemodilutional, but also due to a reduction in red cell volume, which, in turn, may be due to primarily two factors: the renal damage caused by the CHF causes a reduced production of EPO (erythropoietin) in the kidneys and CHF itself may cause anaemia. Animal studies have confirmed that anaemia is common in CHF.
In inflammatory bowel disease, anaemia is an indicator of disease severity and in HIV/AIDS patients anaemia has a serious impact on the quality of life of the patients and is also strongly associated with disease progression and in an increased risk of death.
SvO2 is a measure of a relation between oxygen delivery and oxygen consumption. SvO2 varies directly with cardiac output and SaO2 and inversely with VO2 (oxygen consumption). The normal SvO2 is about 75%, which indicates that under normal conditions, tissues extract 25% of the oxygen delivered. An increase in VO2 or a decrease in arterial oxygen content (SaO2×Hb) is compensated by increasing CO or tissue oxygen extraction. When the SvO2 is less than 30%, tissue oxygen balance is compromised and anaerobic metabolism ensues. A normal SvO2 does not ensure a normal metabolic state but suggests that oxygen kinetics are either normal or compensated. SvO2 is thus a global parameter indicating how well oxygenated the body is.
Hence, it would be a great benefit if a trend over the changes in hematocrit and SvO2 could be determined, for example, for a physician handling a patient suffering from a condition such as congestive heart failure (CHF), as well as for patients suffering from other diseases such as chronic kidney disease. Hematocrit and SvO2 can thus also be used to guide drug titration, monitor progression/regression of a disease and alert for deterioration of the patient.
Drug titration is an area where the treatment of the patients can be improved significantly. A number of outside factors such as the amount of exercise, food habits (consumption of coffee, salt alcohol etc) will change the amount of drugs required on a day to day basis. Currently the patient usually takes one dose of medication regardless these external factors, leading to an over consumption/under consumption of the drug. An over consumption is unbeneficial since the drugs often come with bi-effects and an under consumption would not lead to an effective therapy. Optimizing the drug consumption would therefore be very beneficial to the patient.
Monitoring the long term progression and regression of a disease is of essence for the physician to make therapeutic decisions for the patients. Also, having parameters such as hematocrit and SvO2 monitored continuously (and not just measurements taken during visits to the physician) would provide a better and more complete picture of the disease progression.
Another area of patient care that would benefit from monitoring a trend over SvO2 and hematocrit is alerting and avoiding acute de-compensation of the patient. Avoiding hospitalization would be very beneficial, if not life saving, to the patient but would also reduce costs for the society.
CHF patients are prone to have co-morbidities and the same or similar symptoms can thus be caused by many different pathophysiological factors, some are life threatening and require immediate attention and others are less damaging to the patient and may only require a change in medication or dosage of medication. Accordingly, there would be an advantage if further physiological parameters including body temperature, heart rate, activity and/or minute volume could be monitored to obtain an increased degree of sensitivity/specificity. Thereby, it would be possible to detect truly acute episodes from episodes that does not require immediate medical attention since a more global picture of the patient's health is obtained. For example, the limited cardiac output of a heart failure patient might alter body temperatures and the dynamics of response to altered thermal conditions and exercise. A specific example is the known tendency for body core temperature to fall when heart failure patients exercise.
Consequently, there is a need within the art of systems for monitoring hematocrit and SvO2 to determine a patient status in order to provide an improved patient care. It would also be an advantage if physiological parameters including body temperature, heart rate, activity and/or minute volume being indicative of the health status of a patient could be monitored and used to determine a patient status in order to provide a further improved patient care.
In light of this, a number of solutions in which different physiological parameters are monitored and used to determine a status or condition of a patient have been presented. In United States Patent Application Publication No. 2006/0149145 an apparatus including implantable optical sensors for measuring hematocrit and SvO2 is disclosed. The sensor is connected to an extracorporeal analyzing and monitoring device enabling a monitoring of blood characteristics over a long term to determine, for example, a condition of a patient.
Further, EP 1 107 158 discloses a system and method for determining a reference base line of patient status for an individual patient for use in an automated collection and analysis patient care system. A set of measures including SvO2 and hematocrit is collected from an implanted medical device and stored in an external database, which is organized to store one or more patient care records. The collected measures are processed into a set of reference measures, wherein each reference measure is representative of at least one of measured or derived patient information. The reference measures set is stored into the patient care record indicating an initial patient status.
In United States Patent Application Publication No. 2005/0153885 methods are disclosed for treating a patient for a condition caused by an abnormality in the autonomic nervous system by modulating the autonomic nervous system with at least one aldosterone antagonist. SvO2 or hematocrit is measured by means of implantable mechanical or electrical sensors in order to collect data for determining the modulation. The treatment can be performed by means of an implanted drug pump.
Accordingly, despite numerous solutions for sensing SvO2 and/or hematocrit in monitoring and diagnosing purposes, there has not hitherto been presented an overall solution taking all the above mentioned aspects of patient care into consideration and, thus, there is still a need within the art to be able to automatically collect SvO2 and hematocrit values of a patient and to determine a patient status using the collected values in monitoring and therapeutic purposes over a long term period.
An object of the present invention is to provide an improved method and an implantable medical device for automatically collecting SvO2 and hematocrit values of a patient and for determining a patient status for monitoring and/or therapeutic purposes over a long term period.
Another object of the present invention is to provide an improved method and an implantable medical device for automatically collecting SvO2 and hematocrit values of a patient and determining a reliable and overall patient status for monitoring and/or therapeutic purposes.
A further object of the present invention is to provide an improved method and an implantable medical device that are capable of, in an accurate and reliable way, measuring the hematocrit and SvO2 of a patient in vivo using an optical sensor to detect or monitor a change of a condition of a patient, such as CHF, cancer, chronic kidney disease, diabetes, rheumatoid arthritis, inflammatory bowel disease and HIV/AIDS.
Still another object of the present invention is to provide an improved method and medical device that are capable of measuring the hematocrit and SvO2 on a substantially continuous basis, as well as during different time points of the day, for example, during the night.
Yet another object of the present invention is to provide a method and medical device that are capable of providing an improved patient care.
According to an aspect of the present invention, an implantable medical device for monitoring a hematocrit level and a SvO2 level of a patient connectable to at least one medical lead includes an optical sensor module adapted to measure at least one hematocrit value and at least one SvO2 value by means of at least a first, a second, and a third light radiation wavelength. The implantable medical device has a blood constituent determining device that obtains measured hematocrit values and SvO2 values, to determine a present hematocrit level by means of the at least one hematocrit value and to determine a present SvO2 level by means of the at least one SvO2 value, and a patient status determining device that determines a patient status based on an evaluation of the present hematocrit level and the present SvO2 level, wherein a change of a condition of the patient can be derived.
According to a second aspect of the present invention, a method for monitoring a hematocrit level and a SvO2 level of a patient is implemented in an implantable medical device connectable to at least one medical lead including an optical sensor module adapted to measure at least one hematocrit value and at least one SvO2 value by means of at least a first, a second, and a third light radiation wavelength. The method includes the steps of: measuring hematocrit values and SvO2 values; determining a present hematocrit level by means of the at least one hematocrit value and to determine a present SvO2 level by means of the at least one SvO2 value; and determining a patient status based on an evaluation of the present hematocrit level and the present SvO2 level, wherein a change of a condition of the patient can be derived.
According to a third aspect of the present invention, a computer-readable medium encoded with programming instructions is directly loadable into an internal memory of an implantable medical device, the programming instructions causing the implantable medical device to perform steps in accordance with the aforementioned method.
The basis of the present invention is to automatically monitor physiological parameters that provide a global picture of a patients health and status. SvO2 and hematocrit and the development of these parameters over time have been found to provide valuable information, for example, for a physician handling a patient suffering from a condition such as congestive heart failure (CHF), as well as for patients suffering from other diseases such as chronic kidney disease, and in use for guidance of drug titration, in monitoring of progression/regression of a disease, and in alerting for a deterioration of the patient. Monitoring the long term progression and regression of a disease is of essence for the physician to make therapeutic decisions for the patients. By continuously and automatically monitoring hematocrit and SvO2 (and not just measurements taken during visits to the physician) provides an improved and more complete picture of the disease progression. Another area of patient care that benefits from monitoring a trend over SvO2 and hematocrit is alerting and avoiding acute decompensation of the patient. Avoiding hospitalization is very beneficial, if not life saving, to the patient and may also reduce costs for the society. Hence, the present invention provides for an improved patient comfort taking a large number of different aspects of patient care into account.
According to an embodiment of the present invention, the blood constituents determining device is adapted to obtain measured hematocrit values and SvO2 values continuously or at predetermined intervals, wherein at least one sequence over time of hematocrit levels and SvO2 levels, respectively, can be determined.
In a further embodiment of the present invention, the implantable medical device further includes a therapy determining device that obtains a target range for the hematocrit level and the SvO2 level, respectively, and to compare the obtained target ranges with the present hematocrit level and the present SvO2 level, respectively, to determine a therapy for the patient. In one certain embodiment, the therapy determining device is adapted to determine a dosage of a drug, which may be performed on a continuous basis. Thereby, it is possible to optimize the drug dosage over time taking variations in the hematocrit level and the SvO2 level into consideration. A number of outside factors such as the amount of exercise, food habits (consumption of coffee, salt alcohol etc) will change the amount of drugs required on a day to day basis. Today, the patient usually takes one dose of medication regardless these external factors, leading to an over consumption/under consumption of the drug. An over consumption is unbeneficial since the drugs often come with bi-effects and an under consumption would not lead to an effective therapy. Optimizing the drug consumption would therefore be very beneficial to the patient. The determined dosage may be communicated to the patient via a communication unit of the implantable medical device and an external device such as a portable user equipment, e.g. a mobile phone, or a stationary home monitoring unit such as a programmer. Accordingly, the patient care can be further improved by dynamically determining a drug dosage over time.
In accordance with a further embodiment of the present invention, the therapy determining device is connected to a drug delivering device and is adapted to control the drug delivering device so as to deliver a drug to the patient based on the determined dosage and/or patient status. Thereby, the drug delivery can be adjusted automatically and continuously in response of changing physiological conditions of the patient such that an optimal drug dosage can be delivered despite outside factors such as the amount of exercise, food habits (consumption of coffee, salt alcohol etc) out of control for a physician determining the drug dosage at prescription of the medication. The physician can also be updated continuously and automatically with the current dosage via a monitoring device, e.g. a PC, connected to a communication network with which the implantable medical device is able to communicate with via an external device such as a user equipment (e.g. a mobile phone) or a home monitoring unit (e.g. a programmer). In addition, the patient may be updated continuously and automatically with the current dosage by means of the user equipment or the home monitoring unit.
According to embodiments of the present invention, the implantable medical device has further sensors that sense or measure other physiological parameters such as a body temperature sensor adapted to sense a body temperature of the patient. Thereby, the device is capable of obtaining body temperature values continuously or at predetermined intervals, wherein at least one sequence over time of body temperature values can be determined. The sensed body temperature values may be used in the evaluation of the present hematocrit level and the present SvO2 level to determine a patient status, wherein a change of a condition of the patient can be derived. Furthermore, the therapy or dosage of a drug or a progression/regression of a disease may also be determined by taking the body temperature, as well as hematocrit and SvO2 into account. Thereby, it is possible to provide a more thorough picture of the patient's health and a drug dosage can be determined with a higher degree of accuracy and reliability.
In yet another embodiment of the present invention, the implantable medical device has an activity sensor that senses an activity level of the patient. The device is accordingly capable of obtaining sensed activity levels continuously or at predetermined intervals, wherein at least one sequence over time of an activity level can be determined. The sensed activity levels can be used in the evaluation of the present hematocrit level and the present SvO2 level to determine a patient status, wherein a change of a condition of the patient can be derived. Moreover, the obtained activity levels can also be used, in addition to the hematocrit and SvO2 to determine a therapy, a dosage of a drug, or a progression/regression of a disease. Thereby, it is possible to provide a more thorough picture of the patient's health and a drug dosage can be determined with a higher degree of accuracy and reliability.
In another embodiment of the present invention, the implantable medical device comprises an impedance measuring circuit measures a transthoracic impedance, the impedance measuring circuit being connected to electrodes of the at least one medical lead and/or to a housing of the implantable medical device. The impedance measuring circuit, during impedance measurement sessions, generates electrical signals to be applied between at least a first electrode and at least a second electrode and to measure the impedance in the tissue between the at least first electrode and the at least second electrode to the applied electrical signals. The patient status determining device obtains sensed impedance values continuously or at predetermined intervals, wherein at least one sequence over time of impedance values can be determined, and to determine at least one sequence of a minute ventilation of the patient using the impedance values. The minute ventilation can be used to determine a patient status together with the hematocrit and SvO2, wherein a change of a condition of the patient can be derived. Further, the minute ventilation can also be used, in addition to the hematocrit and SvO2, to determine a therapy, a dosage of a drug, or a progression/regression of a disease. Thereby, it is possible to provide a more thorough picture of the patient's health and a drug dosage can be determined with a higher degree of accuracy and reliability.
In yet another embodiment of the present invention, a heart rate sensor is included in the implantable medical device adapted to sense a heart rate of the patient. The patient status determining device is adapted to obtain sensed heart rate level values continuously or at predetermined intervals, wherein a sequence over time of heart rate level values can be determined. The sensed heart rate can be used in the evaluation of hematocrit and SvO2, to determine a patient status, wherein a change of a condition of the patient can be derived. In addition, the heart rate can also be used, in addition to the hematocrit and SvO2, to determine a therapy, a dosage of a drug, or a progression/regression of a disease. For example, if it is found that SvO2 is within a predetermined range defining normal values for a particular patient, that hematocrit decreases and the heart rate increases, it is an indication of anaemia. Hence, it is possible to provide a more thorough picture of the patient's health and a drug dosage can be determined with a higher degree of accuracy and reliability.
In further embodiments of the present invention, one of, some of, or all of the parameters heart rate, patient posture, body temperature, activity, minute ventilation is (are) used together with the hematocrit and SvO2 to determine a patient status, a therapy, a dosage of a drug, or a progression/regression of a disease. For example, if it is found that SvO2 and hematocrit is within predetermined ranges, respectively, defining normal values for a particular patient, that body temperature increases and the heart rate increases, it is an indication of that the patient has an infection. Hence, it is possible to provide an even more thorough picture of the patient's health and, for example, a progression/regression of a condition or disease or a drug dosage can be determined with a higher degree of accuracy and reliability. Many heart failure patients have comorbities and the same symptom can originate for different disorders in the patient (dyspnea for instance can be a sign of volume overload in the lung but can also be a sign of poor oxygenation of the patient due to low hematocrit). Trends over several physiological parameters including heart rate, patient posture, body temperature, activity, minute ventilation, hematocrit and SvO2 will provide the physician with an efficient an accurate tool to establish the cause of a deterioration and grade of the severity of the problem.
Furthermore, different combinations of parameters can be used to provide indications of different conditions and a set of criteria may be defined for that purpose. Each criterion may give rise to an alert signal and there may hence be a number of different signals each signalling, for example, a crossing of certain parameter limit. The patient status determining device may send such an alert signal to the user equipment and/or the home monitoring unit informing the patient that he or she should see his/her physician.
Another use of a patient status determining device is in the common situation when a patient is under a home medical care program. An example is an elderly patient that lives at home and has a weekly visit by a nurse. The nurse will check the patient status and distribute the daily dosage of drugs for the week to come. It would be very beneficial to read out the trended data collected during the last week using a monitoring device. Changes in the patient status can then be alerted. Consultations with a physician may be initiated to change the dosage of drugs. Infections that need antibiotic treatment can be alerted. An example is urinary tract infections which untreated may lead to an infection of the kidneys (pyelonephritis). Acute pyelonephritis can be a severe conditions with a high mortality and in people who are immunosuppressed, for example, people suffering from cancer of AIDS.
Moreover, the therapy determining device and/or the patient status determining device may send an information message and/or alert signal, e.g. that a monitored parameter or a combination of monitored parameters has exceeded or fallen below the predetermined limits, respectively, to the patient and/or the physician. If the physician receives an alert signal together with collected data of the parameters, the physician/nurse may rate the level of acuteness of the deterioration and be guided whether the patient have to visit the hospital or care institution at once or within the next few weeks, or only be prescribed a new medication. It may also be established in an early phase which physician branch (nephrologist, cardiologist, pulmonologist, internal medicine) the patient should see if a hospital visit is required. It would also be beneficial in an in-clinic scenario where the information could eliminate certain pathophysiological factors and thus eliminate tests thereby reducing costs and provide the physician with the relevant information. Also, in a regular follow-up it would provide insight to patients general health and help guide the physician of the overall therapy. In a remote follow-up scenario it would provide the physician with physiological/hemodynamic information to provide better quality of the follow-up.
A patient may also be notified on a situation where a monitored parameter or a combination of monitored parameters assumes abnormal values. This may be done, for example, by causing a vibration unit of the implantable medical device to vibrate thereby informing the patient of the event, or sending a signal to an external device such as a user equipment, e.g. a mobile phone, a personal digital assistant or a pager, or a home monitoring unit. The message may be in form of a text message informing the patient of the event or a signal causing a lamp to start twinkle. Thus, the patient may be alerted that he or she should contact his or hers physician.
As will be understood by those skilled in the art, steps of the methods of the present invention, as well as preferred embodiment thereof, are suitable to realize as a computer program or a computer readable medium.
The features that characterize the invention, both as to organization and to method of operation, together with further objects and advantages thereof, will be better understood from the following description used in conjunction with the accompanying drawings. It is to be expressly understood that the drawings is for the purpose of illustration and description and is not intended as a definition of the limits of the invention. These and other objects attained, and advantages offered, by the present invention will become more fully apparent as the description that now follows is read in conjunction with the accompanying drawings.
a illustrates the principles of the oxygen saturation measurements using the sensor module of
b illustrates the principles of the hematocrit measurements using the sensor module of
c illustrates the principles of the hematocrit measurements using the sensor module of
d illustrates the principles of the calibration of the sensor module of
In the following, the present invention will be discussed in the context of medical systems comprising at least an implantable medical device such as a pacemaker or an ICD, and connectable to medical leads such as an atrial lead and a ventricular lead.
With reference to
With reference now to
Furthermore, the optical sensor module 50 is connected to a blood constituent determining device 30 adapted to obtain measured hematocrit values and SvO2 values from the optical sensor module 50, to determine a present hematocrit level by means of the at least one hematocrit value and to determine a present SvO2 level by means of the at least one SvO2 value. The hematocrit values may be obtained at a regular basis, i.e. at regular intervals, or continuously. Thereby, it is possible to obtain a sequence over time of hematocrit values and SvO2 values. Each value may be calculated as an average value over a predetermined number of values or of values obtained over a predetermined period of time or as a weighted average value over a predetermined number of values or of values obtained over a predetermined period of time.
A patient status determining device 31 is connected to the blood constituent determining device 30 and is adapted to determine a patient status based on an evaluation of the present hematocrit level and the present SvO2 level. The patient status may be used to derive a change of a condition of the patient. The patient status determining device 31 is also connected to sensors 35 of which only one is shown in
Moreover, a therapy determining device 32 is connected to the patient status determining device 31. The therapy determining device 32 may be adapted to obtain a patient status from the patient status determining device 31 to determine a therapy for the patient. Further, the therapy determining device 32 may be adapted to obtain a target range for the hematocrit level and the SvO2 level, respectively, and to compare the obtained target ranges with the present hematocrit level and the present SvO2 level, respectively, to determine a therapy for the patient including to determine a dosage of a drug based on the determined therapy. Accordingly, an optimal dosage for the patient may be determined taking into account changing outside factors such as the amount of exercise, food habits (consumption of coffee, salt, alcohol, etc.), which will change the amount of drugs required on a day to day basis Furthermore, according to this embodiment, the therapy determining device 32 is connected to a drug delivering device 34, which may be incorporated in the implantable medical device 20 or located outside the implantable medical device 20 and connected to the therapy determining device 32. The therapy determining device 32 is adapted to control the drug delivering device 34 so as to deliver a drug to the patient based on the determined dosage. In one embodiment, the drug delivering device 34 is a device for delivering diuretics, wherein the therapy determining device 32 is adapted to check whether a present hematocrit level is within the target range for the hematocrit level and to instruct the drug delivering device to adjust a delivery of diuretics such that the hematocrit level is maintained within the target range. In another embodiment, the drug delivering device 34 is a device for delivering a medication that affects the heart function of a patient. The therapy determining device 32 is adapted to monitor the SvO2 level by obtaining values from the patient status determining device 31 and the hematocrit level to check whether the SvO2 level is within a heart function target range for the SvO2 level, to check whether the present hematocrit level is within a heart function target range for the hematocrit level by obtaining values from the patient status determining device 31; to determine that a change in the SvO2 level is caused by a change of the heart function if the present hematocrit level is within the heart function target range; and to instruct the drug delivering device 34 to adjust a delivery of the medication such that the SvO2 level is maintained within the heart function target range if the SvO2 level change is determined to be caused by a changed heart function.
Detected signals from the patients heart are processed in an input circuit 33 and are forwarded to the microprocessor of the control circuit 27 for use in logic timing determination in known manner. The implantable medical device 20 is powered by a battery (not shown), which supplies electrical power to all electrical active components of the medical device 20. Data contained in, for example, the memory circuit of the control circuit 27, the patient status determining device 31, or the therapy determining device 32 can be transferred to a extracorporeal device such as a programmer (not shown) via a programmer interface (not shown) and the telemetry communication unit 37 for use in analyzing system conditions, patient information, etc. The telemetry communication circuit 37 is adapted for two-way communication with at least one extracorporeal device including a communication unit, see
With reference now to
In embodiments of the present invention, the patient status determining device 31 may transfer patient status data and/or trend data of the different measured parameters including hematocrit, SvO2, body temperature, heart rate, activity level, patient posture and/or minute ventilation to the extracorporeal devices 41, 42, 44 via the telemetry communication unit 37. As the skilled person realizes, there are other physiological/hemodynamical parameters that may be monitored such as cardiovascular pressure, cardiac output, or PR interval (or AR interval). The patient is hence able to monitor a progression/regression of a disease and/or a trend of a certain parameter or certain parameters at the user equipment 42 and/or the home monitoring unit 41. This information may also be transferred to the monitoring device 44 at the care institution via the communication network 43, either directly or via the home monitoring unit 41 or the user equipment 42, thereby allowing a physician to view a progression/regression of a disease and/or a trend of a certain parameter or certain parameters. The trend may either be displayed to the physician at a follow-up of the patient or upon an inquiry sent to the implantable medical device 20 from the monitoring device 44 via the communication network 43 and the home monitoring unit 41. The information can be used to guide long term therapy, such as if the patient should be equipped with a different device or if the type of medication should be changed. The information may also be used by the physician to determine a dosage of a drug.
Furthermore, predetermined upper or lower limits may be set for one of, some of, or all of the parameters including hematocrit, SvO2, body temperature, heart rate, activity level, patient posture and/or minute ventilation within which limits they are allowed to fluctuate between. Thus, different combinations of parameters can be used to provide indications of different conditions and a set of criteria may be defined for that purpose. Each criterion may give rise to an alert signal and there may hence be a number of different signals each signalling the crossing of a limit for a certain parameter. The patient status determining device 31 may send such an alert signal to the user equipment 42 and/or the home monitoring unit 41 informing the patient that he or she should see his/her physician. In another embodiment, the medical device 20 may include an alarm means adapted to cause the device to vibrate or to deliver a beeping sound in order to alert the patient of the situation, the alarm means may be integrated into the control circuit 27 or the patient status determining device 31. Alternatively, or as a complement, this information together with the progression of the trend may be sent with an alert signal to the physician to be viewed on the monitoring device 44 so that he or she can decide whether the patient should be called in for a visit. For example, hematocrit is a good parameter for establishing how well the kidney is functioning and may thus be used as an indicator of the kidney function as well as for patients with kidney disease to guide their medication. Furthermore, many heart failure patients has co-morbidities and the same symptom can originate for different errors in the patient, dyspnea for instance can be a sign of volume overload in the lung but can also be a sign of poor oxygenation of the patient due to low hematocrit. A trend over several physiological parameters including hematocrit, SvO2, body temperature, heart rate, activity level, patient posture and/or minute ventilation will provide the physician with a tool to establish the cause of a deterioration and grade of the severity of the problem. If the physician receives an alert signal together with collected data of the parameters, the physician/nurse may rate the level of acuteness of the deterioration and be guided whether the patient have to visit the hospital or care institution at once or within the next few weeks, or only be prescribed a new medication. It may also be established in an early phase which physician branch (nephrologist, cardiologist, pulmonologist, internal medicine) the patient should see if a hospital visit is required. It would also be beneficial in an in-clinic scenario where the information could eliminate certain pathophysiological factors and thus eliminate tests thereby reducing costs and provide the physician with the relevant information. Also, in a regular follow-up it would provide insight to patients general health and help guide the physician of the overall therapy. In a remote follow-up scenario it would provide the physician with physiological/hemodynamic information to provide between quality of the follow-up. For example, if the SvO2 level decreases but the hematocrit level remains more or less the same, it is an indication that there is something wrong with the absorption of oxygen. If SvO2 remains more or less the same but the level of hematocrit goes down and the heart rate increases, there is indication for anaemia. Further, if SvO2 remains within normal limits, hematocrit remains within normal limits, body temperature increases and heart rate increases, there is an indication of that the patient has an infection.
According to other embodiments, the therapy determining device 32 may transfer data including a determined dosage to the extracorporeal devices 41, 42, 44 via the telemetry communication unit 37. The patient is able to view a determined dosage by means of the user equipment 42 or the monitoring device 41 and may thus be informed of, for example, a change of dosage. This is of great use since many outside factors such as the amount of exercise, food habits (consumption of coffee, salt, alcohol, etc.) will change the amount of drugs required on a day to day basis. Thus, the patient will obtain dosage information such that he or she will be able to adjust the dosage in order to cope with the above mentioned changing outside factors. The patient is thereby able to avoid over consumption as well as under consumption. An over consumption is unbeneficial since the drug often is associated with bi-effects and an under consumption will lead to an ineffective therapy. The dosage information may also, or instead, be transferred to the monitoring device 44 at the care institution thereby allowing a physician to monitor the medication of the patient.
Referring now to
Referring now to
Optionally, a validity check may be performed in order to check or judge whether the obtained parameter values are reasonable or valid. This can be performed, for example, by checking that the obtained value is within a preset range including the preceding value. If the obtained value is found to be invalid, i.e. the value is outside the preset range, the value or signal is rejected. In one embodiment, a new measurement session is initiated after a delay period of a predetermined length and if this is repeated a preset number of times without a valid signal has been obtained, the procedure returns to the idle mode.
Then, at step S603, present parameter levels are determined. The levels may be determined as a mean value of respective measured parameter value over a predetermined period of time or as mean of a predetermined number of values. Further, the parameter levels may be relative or absolute. The determined parameter levels may be stored as a trend over the progression of the parameter. Subsequently, at step S604, an evaluation of the determined parameters are performed. For example, reference values for the evaluated parameters, e.g. hematocrit and SvO2, may be obtained by the patient status determining device 31 from an internal memory of, for example, the control circuit 27 or the patient status determining device 31, or from the database 45 via the communication network 43. The reference values may constitute an initial patient status and may thus be used for comparison with later levels of the parameters to evaluate the trend. For example, it may be determined that the level SvO2 decreases and that the hematocrit level is more or less the same, or that SvO2 remains more or less the same but the level of hematocrit decreases and the heart rate increases, or that SvO2 is within normal limits, hematocrit is within normal limits, body temperature increases and heart rate increases. This data is used to determine a patient status in step S605. For example, if the level SvO2 is determined to decrease but the hematocrit level remains more or less the same, it is an indication the there is something wrong with the absorption of oxygen. Further, it is determined that SvO2 remains more or less the same but the level of hematocrit goes down and the heart rate increases, there is indication for anaemia. If SvO2 is determined to be within normal limits, hematocrit to be within normal limits, body temperature to increase and heart rate to increase, there is an indication of that the patient has an infection. The procedure is then terminated at step S606.
As the skilled man realizes, the steps described above with reference to
With reference now to
If the procedure in step S703 finds that the patient is on a medication, for example, that the patient is provided with a heart function affecting drug, it proceeds to step S707 where a check whether the dosage should be adjusted is performed on basis of the evaluation. For example, if it is verified that a present SvO2 level is within a heart function target range for the SvO2 level and that the present hematocrit level is within a heart function target range for the hematocrit level, it may be determined that the change in the SvO2 level is within normal variations and that no change of medication is required. In his case, the procedure proceeds to step S708 where the a present drug dosage is maintained. However, if it, on the other hand, is verified that a present SvO2 level is not within a heart function target range for the SvO2 level and that the present hematocrit level is within a heart function target range for the hematocrit level, it may be determined that the change in the SvO2 level is caused by a change of the heart function and thus that change of the heart function affecting drug dosage is required. In such a case, the procedure proceeds to step S709 where a new dosage of a drug is determined. Information regarding a present drug dosage is held in the patient medication protocol and if a new drug dosage is determined, the protocol may be updated with this new information. This new dosage information may be communicated to the patient by means of the user equipment 42 or the home monitoring unit 41 and/or to the physician by means of the monitoring device 44. In this described embodiment, the therapy determining device 32 is connected to a drug delivering device 34, which may be implanted, and, in step S710, the present dosage is adjusted in the drug delivering device 34. Subsequently, the procedure proceeds to an iterative drug delivery adjustment procedure, which will be described with reference to
As the skilled man realizes, the steps described above with reference to
Turning now to
As those skilled in the art will realize, the steps described above with reference to
Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventors to embody within the patent warranted heron all changes and modifications as reasonably and properly come within the scope of their contribution to the art.
| Number | Date | Country | Kind |
|---|---|---|---|
| 06026522.0 | Dec 2006 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/SE2007/000165 | 2/22/2007 | WO | 00 | 1/12/2009 |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11363922 | Feb 2006 | US |
| Child | 12373356 | US |
