Patent Application
20110208013
The present invention relates generally to sensors of physiological parameters, such as pressure transducers and fluid monitors, and, more particularly, to disposable physiological sensors and associated patient monitor interfaces.
When diagnosing and treating various bodily ailments, such as with patients suffering from shock or cardiovascular problems, medical personnel often find it desirable to measure or monitor a patient's blood pressure and/or other physiological parameters. Advantageously, by measuring or monitoring physiological parameters of these and other types of patients, medical personnel are better able to detect medical difficulties and other problems at an early stage. As a result, the use of physiological sensors and associated monitoring may increase the likelihood that a patient can be successfully treated or provided with needed emergency assistance.
A variety of methods are currently used for measuring or monitoring blood pressure. For example, medical personnel frequently use various indirect blood pressure measurement techniques, such as measuring a patient's blood pressure with a pressure cuff and a stethoscope. In addition, blood pressure measurements can also be made using a number of direct measurement and monitoring techniques, such as use of a disposable pressure transducer (DPT) or with other disposable medical devices (such as a catheter) that have an integrated/embedded DPT. Notably, when diagnosing or treating critically ill patients, such direct techniques are usually preferred over any of the indirect techniques. Direct blood pressure measurement and monitoring techniques are generally accurate to within about one percent and facilitate the continuous monitoring of a patient's blood pressure on a beat-to-beat basis. Direct blood pressure monitoring also enables the rapid detection of a change in cardiovascular activity, and this may be of significant importance in emergency situations.
For direct, or invasive, blood pressure monitoring systems a catheter is inserted into a patient's circulatory system with the end of the catheter having an opening to the blood stream, typically in a major or peripheral blood vessel. First, a needle is inserted into a peripheral blood vessel. For example, if it is desired to monitor arterial blood pressure, the needle may be inserted into the radial artery. If, on the other hand, venous blood pressure is to be monitored, the needle may be inserted into the antecubital, radial, jugular, or subclavian veins. Once the needle is properly inserted, a special catheter is threaded through the needle and into the blood vessel until the tip of the catheter is positioned at the particular point within the body at which it is desired to make the blood pressure measurement. Then, with the catheter in place, the needle may be withdrawn.
An I.V. set attaches to the proximal end of the catheter protruding from the patient so that a solution flows through the catheter and into the patient. The I.V. solution provides a fluid “column” through which pressure pulses are transmitted, and a pressure transducer positioned along the fluid column monitors those pressure pulses. Generally, the pressure transducer consists of a dome that functions as a reservoir for the I.V. fluid. The dome includes a resilient diaphragm that attaches to an electrical transducer. The transducer senses pressure fluctuations in the diaphragm and converts them into electrical signals which are then transmitted through a cable to a monitor for amplification and display. In modern systems a single silicon chip comprises both the pressure diaphragm and the measuring circuitry of the pressure transducer. The cable includes a connector so that the transducer and associated portion of the cable can be discarded after use, whereas the mating connector and Cable hard-wired to the monitor can be reused. Such disposable blood pressure transducers (DPTs) are the standard of care in the OR, ICU or CCU.
Due to the separable nature of the transducer and monitor, different transducers may be connected to any one monitor, as long as the cable connectors are compatible. However, transducers from different sources may exhibit different performance characteristics and may require specific calibration or signal processing or conditioning. Unfortunately, the environments of the OR, ICU or CCU are ill-suited for rapid recognition and registration of disparate components of pressure monitoring systems, and safety concerns necessitate the least amount of such preparation be involved.
Furthermore, pressure data are often required by two separate monitoring devices, such as a patient monitor and a cardiac output monitor, or a patient monitor and an aortic balloon pump. Typically, an arterial line is placed in the patient and a DPT connected to a patient monitor is used for pressure monitoring. Instead of invasively setting up a second arterial line and DPT, the signal from the first DPT may be supplied to a second monitor via the patient monitor (or via the cabling by splitting the signal). However, this “piggyback” connection may introduce pressure monitoring errors from delays and distortion of the signals.
Movement of a patient from one location to another also can present problems. The monitor is usually immobile and stays behind when the patient is moved. Removing and reinserting a sensor in the patient is generally undesirable, therefore the sensor usually remains in the patient and is then plugged into a new monitor at the new location. Data continuity is disrupted, therefore, each time a patient is moved.
Despite a relatively mature market for disposable medical pressure transducers, there remains a need for an improved transducer (and other body parameter sensor systems) that when interfaced with the appropriate monitoring device ensures accuracy and continuity of sensor data. There is also a need for a system that authenticates the sensor and/or for storing data in memory local to the sensor that can be transported with the sensor from location-to-location.
One aspect of the invention is a sensor system for sensing a physiological parameter in a human or animal. The system includes a physiological sensor, and memory and a microprocessor local to and fixedly attached to the sensor. The sensor can be any of a variety of sensors that output a sensor signal representative of a sensed physiological parameter. An authentication algorithm is stored in the memory that is local to the sensor, and the system is configured to engage in an authentication process to authenticate the sensor when queried by a remote processor. In one embodiment, the memory is configured to receive and store data from a remote processor, which may be as one example data that is representative of a physiological parameter sensed by the sensor. In one particular implementation, the microcontroller is configured for bi-directional communication with a remote processor over a single wire.
The system may be configured to receive and dynamically store a history of physiological parameters over a predetermined period of time, as well as a wide variety of other information, such as but not limited to: patient identification, patient information such as age, gender, weight, body mass index and/or other information, device identification such as serial number, model number, lot number and/or other information, calibration data or other data pertaining to the sensor itself, scaling factors, monitored physiological parameters over a predetermined period of time (e.g. over the past 8 hours, the past 24 hours, or other time period as desired), data about a cable or cables that connect the sensor system to the patient monitor, data about the patient monitor or monitors used in conjunction with the sensor, the date the sensor was manufactured, the shelf life of the sensor, the date and time when the sensor was first put into use and/or the length of time the sensor has been in use, the maximum time the sensor may be used, time since the patient monitor was first put into use, time since a patient cable was first put into use, location of the patient, signal quality indicators, fault or alarm codes, identification of doctor or other staff members, and/or other data that may be useful in a particular in a particular setting.
The invention further encompasses a method of sensing a biomedical parameter with a sensor having a local microprocessor and memory. The method may include, for example, transmitting a signal from a physiological sensor system over a cable. In one specific approach, a single wire protocol is employed to receive and transmit authentication data over a single wire between the sensor system and an external processor. The method also includes processing the sensor signal externally from the system at a remote processor, and then receiving data from the remote processor over a single wire of the cable and storing the data in memory.
The method may further include disconnecting the sensor system from a first external processor unit, such as a patient monitor or data box for example, at a first location. The sensor system, including the sensor and the microprocessor and memory that are local to the sensor, is transported to a second location, where the sensor system is connected to a second external processor unit. The sensor is authenticated at the second location. Data stored in the second memory is uploaded to the second external processor unit. The data may be any of a variety of different information, such as a history of physiological measurements over time, and/or other data.
Another aspect of the invention includes a method of sensing a biomedical parameter with a sensor system having a memory. Authentication information that is stored in the sensor memory is accessed by a remote processor to authenticate the sensor system. A sensor signal representative of a physiological parameter is transmitted from the sensor, and the sensor signal is processed at a remote processor. Data representative of a physiological parameter sensed by the sensor is then received from the remote processor and is stored in the sensor memory. In one approach, the data received from a remote processor and stored in the sensor memory includes a history of at least one physiological parameter of a patient over a predetermined period of time. The steps of accessing authentication information and receiving data from a remote processor may optionally utilize a single wire protocol.
Other objects, features and advantages of the invention will become apparent from a consideration of the following detailed description, the drawings, and the claims.
Having thus described aspects of the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:
Aspects of the present invention now will be described more fully with reference to the accompanying drawings, in which some but not all embodiments of the invention are shown. Indeed, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.
Generally, the present invention includes all, or portions of, a sensing system 10 (
Various embodiments of the invention will also be presented herein using flow charts. It will be understood to one of ordinary skill in the art in view of this disclosure that some of the steps or actions described in a flow chart as taking place in a certain order may, in other embodiments, take place in a different order. Likewise, some of the steps or actions described in the flow charts may, in other embodiments, be performed simultaneously or combined into a single step or action.
As will be appreciated by one of skill in the art, the present invention may be embodied as a method (including, for example, a computer-implemented process), an apparatus (including, for example, a system, device, computer program product, etc.), or a combination of the foregoing. Accordingly, embodiments of the present invention may take the form an entirely hardware embodiment (e.g., an application-specific integrated circuit), or an embodiment combining software and hardware aspects that may generally be referred to herein as a “system.” Furthermore, embodiments of the present invention may include a computer program product on a computer-readable medium having computer-executable program code embodied in the medium. As used herein, a processor may be “configured to” perform a certain function in a variety of ways, including, for example, by having one or more general-purpose circuits perform the function by executing particular computer-executable program code, and/or by having one or more application-specific circuits perform the function.
Computer-executable program code for carrying out operations of embodiments of the present invention may be written in an object-oriented, scripted or unscripted programming language such as Java, Perl, Smalltalk, C++, or the like. However, the computer-executable program code for carrying out operations of embodiments of the present invention may also be written in conventional procedural programming languages, such as the “C” programming language, the “BASIC” programming language or a variation thereof, or similar programming languages.
Embodiments of the present invention are described below with reference to flowchart illustrations and/or block diagrams of methods, apparatus, and computer program products. It will be understood that blocks of the flowchart illustrations and/or block diagrams, and/or combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions embodied in computer-executable program code. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a particular machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function/act specified in the flowchart and/or block diagram block(s).
The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions/acts specified in the flowchart and/or block diagram block(s). Alternatively, computer program implemented steps or acts may be combined with operator or human implemented steps or acts in order to carry out an embodiment of the invention.
In one embodiment of the present invention, and referring to
In
In one embodiment, the disposable unit 10 connects to the patient monitoring instrument 18 with a five wire cable 20. Referring to
In other embodiments, the cable may have more or fewer than five wires, depending on the configuration of the monitoring system. For instance, in an alternative embodiment, two wires may be provided for communication between the microcontroller and the monitoring system. In other embodiments, the cable (e.g. cable 20 in
Memory 14, 22 that is local to the sensor is also provided (
Additional memory 22 is provided in which to store data that is useful to transport with the disposable sensor. For example, in a typical cardiac procedure in a hospital, the patient moves from pre-op to the operating room to the Intensive Care Unit and so on. At each location, there may be a separate patient monitor. The disposable device 10 may be disconnected from a first monitor at a first location, and then moved with the patient to a second location at which there is a second, different monitor. Data stored in the memory 22 on the disposable device may then be uploaded to the new monitor.
In one embodiment, this additional memory 22 is provided as an EEPROM. In one embodiment, the EEPROM may be a Microchip Technology Inc. EEPROM, such as the EEPROM 11AA160, which is a family of 16 Kbit serial electrically erasable PROMs. The devices are organized in blocks of x8-bit memory and support the single I/O UNI/O serial bus. By using Manchester encoding techniques, the clock and data are combined into a single, serial bit stream (SCIO), where the clock signal is extracted by the receiver to correctly decode the timing and value of each bit.
The microcontroller serves, among other things, to communicate with the external monitoring system, to execute the authentication function, and to write information to be stored onto the ROM. Non-limiting specific examples of particular suitable microcontrollers are the PIC 12F508/509/16F505 devices from Microchip Technology and the Atmel ATmega168P-10MU. These are highly-integrated, low cost, high performance, 8-bit, fully static, Flash-based CMOS microcontrollers, for their intended use as part of a disposable sensor. The microcontroller employs a RISC architecture with only 33 single-word/single-cycle instructions. All instructions are single cycle (200 μs) except for program branches, which take two cycles. The 12-bit wide instructions are highly symmetrical. The easy-to-use and easy to remember instruction set reduces development time significantly, as compared to microcontrollers using more complicated instruction sets. This type of microcontroller has sufficient processor speed, memory capacity, and cost efficiency, and has a sufficiently small footprint for use in conjunction with sensors of physiological sensors.
The PIC 12F508/509/16F505 products are equipped with special features that reduce system cost and power requirements. The Power-on Reset (POR) and Device Reset Timer (DRT) eliminate the need for external Reset circuitry. There are four oscillator configurations to choose from (six on the PIC16F505), including INTRC Internal Oscillator mode and the power-saving, LP (Low-Power) Oscillator mode. Power-Saving Sleep mode, Watchdog Timer and code protection features improve system cost, power and reliability.
Examples of data that may be stored in sensor memory 22 include patient identification, patient information such as age, gender, weight, body mass index and/or other information, device identification such as serial number, model number, lot number and/or other information, calibration data or other data pertaining to the sensor itself, monitored physiological parameters over a predetermined period of time (e.g. over the past 8 hours, the past 24 hours, or other time period as desired), data about the cable or cables that connect the sensor to the patient monitor such as serial number and/or lot, data about the patient monitor or monitors used with the sensor, the date the sensor was manufactured, the shelf life of the sensor, the date and time when the sensor was first put into use and/or the length of time the sensor has been in use, the maximum time the sensor may be used, time since the patient monitor was first put into use, time since a patient cable was first put into use, location of the patient, signal quality indicators, fault or alarm codes, name of doctor or other staff members, and/or other data that may be useful in a particular embodiment.
Considering now the processing of signals from the sensor 12, in a presently preferred embodiment, data from the sensor 12 is communicated over cable 20 to the patient monitor 18, at which one or more processors process the raw signals from the sensor. The patient monitor 18 then sends all or selected portions of the processed data over wire 20e (
In some embodiments, it may be desirable to store raw signals from the sensor 12 in the sensor memory 22. In most embodiments, the raw signals from the sensor 12 would first be sent to the patient monitor 18, which would then retransmit the raw sensor signals or selected raw sensor signals to the microcontroller 16 for storage in the sensor memory 22. In this alternative embodiment, the sensor 12 would be equipped with a significant amount of memory to accommodate hours and/or days of raw sensor data and/or processed algorithm data. In one such embodiment in which raw sensor data is stored, the sensor includes at least 2 gigabytes and preferably 8 gigabytes of memory on which to store raw sensor data.
Fault codes may also be stored in the memory 22 so that, for example, if the monitoring system 18 or sensor 12 or cable 20 or other component fails at some point, a time and/or date stamped record of the fault codes at about the time of the failure may later be accessed for analysis purposes. Other information, such as for example patient height, weight, or BMI, how many and what type of catheters have been used on the particular patient monitor, information about the monitor itself, the version of software the monitor is running, information about the hospital that the monitor is in, and/or other information that might be used for later analysis and business decision-making may also be stored.
Some information stored in the sensor memory, such as sensor calibration data, manufacturing lot number, serial number, time and/or date of production, may be written onto memory at the manufacturing facility. Other information may be stored by the patient monitor or other means at a treatment site. Considering calibration information in particular, sensor performance measurements may be written to the memory during the manufacturing/testing process. Consequently, if there is an offset of for example 2 mm of mercury for a particular sensor, that information may be stored in memory on the sensor at the manufacturing facility. In use, the patient monitor 18 may use the calibration information stored in the sensor memory to make more accurate calculations from signals received from the sensor 12. The authentication function may be used to ensure that the sensor is of a type that has such calibration information stored thereon.
Considering the embodiment of
In an alternative embodiment, the patient monitoring system acts as a hub. It gathers certain information from a sensor or sensors, makes appropriate calculations, displays information and/or performs other functions. Other information may be input into the patient monitoring system manually, such as by a nurse or other medical personnel, and/or collected from other sources. The monitoring system then sends selected information that it has gathered, calculated or otherwise obtained to memory connected to the sensor for storage on the sensor. This information stored on the sensor memory is then portable with the sensor even when the sensor is disconnected from the monitoring system. The patient may move from room-to-room or place-to-place and, when the patient arrives at a new room or place, the sensor may be connected to another monitoring system that then uploads data stored on the sensor memory. In instances where the sensor is sent to a manufacturing facility, a lab, or the like, the information stored on the sensor may be accessed for analysis.
While in a preferred embodiment of the present invention the sensor 10 is provided with a microprocessor, in an alternative embodiment, a single wire interface EEPROM may interface directly with a monitoring system, without a microcontroller. Non-limiting examples of presently suitable single wire interface EEPROMS for this alternative embodiment include the Maxim DS28E01 and the Microchip 11AA160 EEPROM. This approach is advantageous over EEPROMs that require additional wires in the cable, a greater number of pins and/or significant power requirements.
A further alternative embodiment is to utilize a microprocessor having embedded cryptographic capability, such that it is not necessary to store an authentication algorithm in ROM separately from the microcontroller. Suitable microcontrollers for this purpose are available from Atmel Corporation of San Jose, Calif., among others.
In embodiments in which the sensor is a blood glucose sensor, specific information that may be stored in memory that is local to the sensor may include information of the blood access device to which the sensor is connected, such as manufacturer, size, length, model number, lumen and lumen volume and information on the type of flow profile that is needed, as well as other information specifically helpful to the functioning of a blood glucose sensor. Also, a check in the manufacturing process may be instituted in which a standard sensor test is made during the manufacturing process. The values sensed by the sensor are recorded and stored on the sensor memory. In the field, an optional test may be made in which the values sensed by the sensor are compared with the values stored in the sensor memory from the earlier test. If the values are significantly different, it may indicate that the sensor is damaged and should no longer be used. The patient monitor, for example, may decline to use a sensor that is possibly damaged, or may raise a flag to medical personnel to indicate a possible problem with the sensor.
On the other hand, if the sensor does not issue the proper response, the sensor is not validated. For an invalid sensor, the patient monitoring unit may be configured to respond in any of a variety of different ways. The monitoring unit may simply refuse to accept signals from the sensor, make no calculations of data based on the signals, and generally decline to undertake the monitoring function, as at step 106 in
At step 108, the sensor transmits sensed signals to the external processor which, at step 110, processes the signals from the sensor. At step 112, the external processor transmits data to be stored on the memory that is local to the sensor. In one embodiment, the data is transmitted over a cable and, in a further embodiment, over a single wire of the cable using a single wire protocol.
In
While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention not be limited to the specific constructions and arrangements shown and described, since various other changes, combinations, omissions, modifications and substitutions, in addition to those set forth in the above paragraphs, are possible. Those skilled in the art will appreciate that various adaptations and modifications of the just described embodiments can be configured without departing from the scope and spirit of the invention, and that particular embodiments of the invention may have additional advantages, such as EMI noise reduction and/or providing an environment for using multiple instruments simultaneously. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.
