WO2009115944A1

WO2009115944A1 - Method and system for automatically controlling a physiological variable of a patient in a closed loop

Info

Publication number: WO2009115944A1
Application number: PCT/IB2009/051011
Authority: WO
Inventors: Gerhard Tivig; Rolf Neumann; Guenter Gegner; Harald Greiner
Original assignee: Philips Intellectual Property & Standards Gmbh; Koninklijke Philips Electronics N.V.
Priority date: 2008-03-17
Filing date: 2009-03-11
Publication date: 2009-09-24

Abstract

The invention relates to a closed loop system for automatically controlling a physiological variable of a patient(1), with a measuring unit(2)for measuring a value for the physiological variable of the patient(1), an actuator(3)for treating the patient (1)in order to affect the physiological variable, a controller (4)which is fed with the value for the physiological variable of the patient(1)and for controlling the actuator (3) based on a control algorithm using the measured value of the physiological variable, a protocol engine device(5)running at least one protocol and for notifying a user and a user interface (6)for indicating user notifications and for manually inputting additional information, wherein the protocol engine device(5)is adapted for automatically requesting input of additional information via the user interface(6), the additional information being used in the control algorithm for controlling the actuator(3). Accordingly, such a system for automatically controlling a physiological variable of a patient (1)in a closed loop is provided which is reliable, easy to handle, and especially highly accepted by the care givers.

Description

METHOD AND SYSTEM FOR AUTOMATICALLY CONTROLLING A PHYSIOLOGICAL VARIABLE OF A PATIENT IN A CLOSED LOOP

FIELD OF THE INVENTION

The invention relates to the field of automatically controlling a physiological variable of a patient, especially in a closed loop system. BACKGROUND OF THE INVENTION

The idea of a closed loop controller in clinical systems has been known for more than a decade. For research purposes, closed loop systems have been studied, but as of today, there is no generally accepted clinical use of such systems.

The main reason for this limited use is the large step from a manually controlled therapy to an automatic closed loop system. Applying such a large step to the care of patients generates ethical concerns and also very high regulatory hurdles. Moreover, the acceptance was limited due to missing transparency. With the available approaches of closed implementations, the system could be very simple but inflexible in its application or with an overwhelming, complex human interface.

Classic controller implementations have several disadvantages as reduced flexibility, difficulty to adapt to new requirements in terms of new measurements, different thresholds, modified timing and/or user interface, difficulty to upgrade functionality when new protocol requirements come out etc.

SUMMARY OF THE INVENTION It is the object of the invention to provide such a method and system for automatically controlling a physiological variable of a patient in a closed loop which are reliable, easy to handle, and especially highly accepted by the care givers.

This object is achieved by a method for automatically controlling a physiological variable of a patient in a closed loop system, comprising the following steps: automatically measuring a value for the physiological variable of the patient, and automatically treating the patient in order to affect the physiological variable based on a control algorithm using the measured value of the physiological variable, wherein input of additional information by a user is automatically requested, and wherein the additional information is used in the control algorithm for controlling the actuator. Accordingly, it is an essential feature of the invention to provide such a method for controlling the physiological variable which is flexible and which can be adapted to the needs of the patient during treatment since input of additional information by the user is requested automatically. Especially, using this method to implement a closed loop controller provides the following advantages: A natural way to guide the user through the various steps of the treatment is offered since an interactive way to incorporate user inputs is provided. By involving the user actively into the control mechanism the acceptance level to implement a closed loop system in the daily clinical use is highly increased. This way, increased flexibility to represent different phases of treatment is provided. It is to be noted that in this context, the term "patient" does not only apply to human beings but also to animals. Further, the term "patient" does not mean that the respective person/animal is disease-ridden and, thus, also healthy persons who make part of a medical system which is controlled by a closed loop will be referred to as "patients". Further, the term "physiological variable" refers to a specific variable describing the patient's condition with respect to a specific physiological state, i.e. the patient's blood hemoglobin saturation, while the term "value" or "value for the physiological variable" refers to a specific measure or indicator which is characteristic for the "physiological variable" and, thus, can also be an indirect measure, i.e. the varying part of the absorption spectrum of a pulse oximeter measurement in case of blood hemoglobin saturation.

In general it might be sufficient that only one value for one physiological variable is measured. However, according to a preferred embodiment of the invention, multiple values for one or more physiological variables are measured.

Further, according to a preferred embodiment of the invention, the controlling procedure is continuously documented in a log file. Such a log file can in general be at least partly done by paper. However, it is preferred, that the log file is exclusively electronic. Further, the log file preferably comprises at least one of: user inputs, measured values, and occurrence of predefined conditions. Furthermore, the log file is preferably not only accessible after the treatment but already during the controlling procedure. According to a preferred embodiment of the invention, the additional information which is requested to be input by the user comprises at least one of: a currently not available measurement value, a non-measureable value, and a treatment confirmation. This way, the control algorithm can be provided with such additional information which is hardly accessible via automatic measurements and which can highly enhance the automatic controlling process. Further, according to a preferred embodiment of the invention, input of additional information by a user is automatically requested periodically.

Moreover, according to a preferred embodiment of the invention, input of additional information by a user is automatically requested upon occurrence of a condition which is predefined in a protocol. With respect to this, a protocol engine is run on a patient monitoring platform that allows clinicians to run clinical protocols that can monitor developments in the patient's condition. This application notifies the clinicians when certain conditions or combinations of conditions occur and it documents developments in a log which can be stored for further inspections. In other words, according to this preferred embodiment of the invention, a protocol engine is incorporated into a patient monitor allowing clinicians to run multiple clinical protocols simultaneously. Preferably, all protocol specifics are collected into configuration settings files. It is further, preferred that these settings are localized and therefore are language and country specific. The settings information, e.g. all kind of definitions of states and their transitions, parameter and thresholds, advisories and prompts, timing, configuration switches, can be loaded into the monitor.

This architecture allows to react on protocol definitions changes being able to perform protocol updates in an easy way without updating software to new versions. Preferably, protocol updates are carried out in the field by a customer support organization. This architecture further allows for implementing different control loop levels, e.g. closed loop, supervised closed loop or open loop, or protocol variations of such a closed loop system to adapt to the current situation of the patient and the data currently available.

Above mentioned object is further addressed by a closed loop system for automatically controlling a physiological variable of a patient, with a measuring unit for measuring a value for the physiological variable of the patient, an actuator for treating the patient in order to affect the physiological variable, a controller which is fed with the value for the physiological variable of the patient and for controlling the actuator based on a control algorithm using the measured value of the physiological variable, a protocol engine device running at least one protocol and for notifying a user and a user interface for indicating user notifications and for manually inputting additional information, wherein the protocol engine device is adapted for automatically requesting input of additional information via the user interface, the additional information being used in the control algorithm for controlling the actuator. Preferred embodiments of the closed loop system according to the invention result from the preferred embodiments of the method according to the invention as described above.

Especially, according to a preferred embodiment of the invention, the protocol engine device is adapted for documenting the controlling procedure in a log file. Further, it is especially preferred that multiple measuring units are provided. Furthermore, according to a preferred embodiment of the invention, the user interface is adapted for visualizing information on the patient's conditions. Finally, it is preferred the user interface is adapted for indicating an alarm.

As a result, the invention is the realization of a closed loop controller using a protocol based implementation with preferably one or more of the following features:

Natural way to guide the user through the various steps of the treatment, by providing an interactive way to incorporate user inputs, e.g. by manually entries for measurements that are currently not available, confirmations, additional inputs for values that cannot be measured.

By involving the user actively into the control mechanism the acceptance level to implement a closed loop system in the daily clinical use is increased.

User inputs are only requested when necessary, but user can be reminded periodically to provide input.

Increased flexibility to represent different phases of treatment. Improved performance and adaptability to new clinical requirements by the capability to react on multiple inputs.

The human interface for the care giver is enhanced by providing multiple outputs that are optimized for the current situation, e.g. alarms, reminders, advisories, therapeutic recommendations or changes in the visualization of relevant data. Based on the current situation of the patient and the data currently available, the user can choose from a list of protocol variations.

Protocol definition files and/or configuration files can be used instead of providing different software engines.

An electronic log keeps track of all user inputs, all manually entered data and of all transitions to specific states. This protocol log can be reviewed during the patient treatment, can be printed for documentation purpose and is useful for audit trails on compliance to guidelines. The log can be exported to a central monitoring unit for further compliance tracking.

One of ordinary skill in the art will recognize that the purpose of controlling is not limited to a single type of control loop and includes several variations and different implementations of control loops, e.g. closed loop controls, supervised controls and open loop controls. Examples are: FiO2 control, infusion pumps medication control, e.g. to control the blood pressure of a patient, control for depth of anaesthesia, e.g. control of intravenous - aesthetic agents during non-volatile anaesthesia procedures, and glycemic control. One of ordinary skill in the art will appreciate many variations and modifications within the scope of this invention. This method and system will be used mainly for hospitalized patients, but there are also applications possible for mobile patients in the hospital environment, during transport or at home. Also devices could make use of this invention that are intended for healthy persons or even animals. BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

In the drawings:

Fig. 1 schematically depicts a system for a closed loop control according to a preferred embodiment of the invention,

Fig. 2 schematically depicts a system for a closed loop control according to another preferred embodiment of the invention, and

Fig. 3 schematically depicts a system for monitoring and controlling a patient according to still another preferred embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

According to a preferred embodiment of the invention, an optimized implementation approach of a physiologic closed-loop controller using a protocol engine as illustrated in Fig. 1 is provided. A further preferred embodiment is the implementation of a closed loop controller using a protocol engine inside a patient monitor as shown in Fig. 2.

As can be seen from Fig. 1, the closed loop system for automatically controlling a physiological variable of a patient 1 according to a preferred embodiment of the invention comprises a measuring unit 2 for measuring a value of the physiological variable of the patient 1, an actuator 3 for treating the patient in order to affect the physiological variable, and a controller 4 which is fed with the value for the physiological variable of the patient and for controlling the actuator 3 based on a control algorithm using the measured value of the physiological variable. Further, a protocol engine device 5 is provided which is running at least one protocol and which is further adapted for notifying a user. For such user notifications and for manually inputting additional information, a user interface 6 is provided.

As can be seen from Fig. 2, controller 4, protocol engine device 5, and user interface 6 are implemented in a patient monitor 7 according to a further preferred embodiment of the invention. In these closed loop systems the protocol engine device 5 is adapted for automatically requesting input of additional information via the user interface 6. This additional information is used in the control algorithm for controlling the actuator 3 as set out in detail in the following. As shown in Fig. 2, the protocol engine device is incorporated in patient monitor which allows clinicians to run multiple clinical protocols simultaneously. All protocol specifics are collected in configuration settings files. These settings are localized and therefore language and country specific. The settings information, i.e. all kind of definitions of states and their transitions, parameters and thresholds, advisories and prompts, timing, configuration switches are loaded into the patient monitor 7. This way, different control loop levels, e.g. closed loop, supervised closed loop or open loop, or protocol variations of such a closed loop system to adapt to the current situation of the patient and the data currently available can be achieved.

With respect to the implementation of controller 4, the protocol engine device 5, and the user interface 6 into patient monitor 7, the term "patient monitor" is defined as a device/system that combines a protocol engine with at least the following functions:

Measure at least one physiological signal, and Alarming capabilities for at least one measured signal and/or at least one interfaced physiological signal.

Further, a patient monitor may comprise one or more of the following features:

At least one external signal to control external, preferably medical, equipment. - User interface possibilities to visualize measured and interfaced physiological signals.

Trending possibilities for measured and interfaced physiological signals.

Possibilities to analyze actual and trended measured and interfaced physiological signals as done with clinical decision support systems: e.g. events, other protocol engines. - Possibilities to interact with the user and let the user enter data and comments of physiological and non physiological data, i.e. by manual entry.

Infrastructure to transfer captured and processed data to a wired or wireless connected medical system solution, e.g. a central station, a hospital information system, an electronic medical record.

Such a system allows reacting on multiple inputs and producing multiple outputs. A wide variety of input conditions is accepted: These can be either continuously monitored vital signs like SpO2, pulse, etc. Further, manual measurements like blood gas data, e.g. pH and PO2, user asked simple questions, like "Type of ventilation used?" or other monitor information like skin colour or patient category can be used. All these data can be combined using logic to information nodes which are parsed by the protocol engine to decide upon appropriate output actions. The base of all decisions is given by decision nodes. Input variables are connected by logical combinations, e.g. "If SpO2 available and Patient Category = Neonatal", and form decision nodes. Based on the evaluation of decision nodes actions can be executed. Actions are connected to decision nodes by rules.

The protocol summarizes all decision nodes, actions, rules and states: Decision nodes: Evaluate logical combinations of input variables.

Actions: Execute a specific action, e.g. change the screen. Rules: Connect the nodes with the actions.

States: Activate the appropriate rules.

One state is active at one point in time. Each state might have specific, specialized rules. For example: "If SpO2 available and patient category = neonatal" a state transition to the "acquiring" state follows. This "acquiring" state then is the starting point where all pertinent questions regarding the patient and any specific patient condition are inquired from the user. After this state is completed, i.e. the minimum required information is available, the protocol engine transfers to the "control" state in which the closed loop is applied. Based on specific pre-defined or user-defined conditions the protocol engine transfers to specific other states, e.g. a "wait" state during specific patient related procedures like suctioning or feeding.

Generally, any parameter combination, e.g. one or more SpO2 measurements, transcutaneous measurement, skin color, blood gases, etc. can be combined to act as input variables for decision node interpretation. The list of output actions includes the issuing of alerts, reminders and advisories, or switching to an application specific screen containing application specific graphical presentations like horizon trends, histogram view, events review or starting some application specific timers. Escalating notification levels can be implemented using graded severity alerts and advisories. Thus, this way, executing a clinical protocol in the patient monitor is allowed. It is an advantage of the preferred embodiment of the invention described above that the user can select from a list of several possible protocols, e.g. closed loop control, sepsis, ventilation weaning or ARDS (acute respiratory distress syndrome support, etc.) those which shall run simultaneously in the monitor. It is another advantage that all user interactions as well as user notifications are integrated into the overall patient monitor user interface. The user does not have to deal with an additional device for closed loop control. The protocol engine based closed loop controller acts "behind the scene". A further advantage of the integrated protocol engine is the capability to visualize for orientation purposes in which phase a specific protocol is and to inform the user whether the protocol is currently active or not on the same patient centric user interface.

For further elucidation of the principles of the invention, referring to Fig. 3, in the following a system is described as another preferred embodiment of the invention, wherein the SaO2 value of a patient is controlled by adjusting the FiO2 concentration of the gas mixture that is provided to the patient. For example, this can be implemented in a closed loop control of blood oxygen saturation in premature infants. As depicted in the Fig. 3, according to the preferred embodiment of the invention, a system for monitoring and controlling a patient 1 , is provided which comprises a patient sensor 2 for capturing a patient signal. The system further comprises a patient monitor 7 with an integrated closed loop controller 14 which is fed with the patient signal and which controls a patient treating device 15, in the present case a mechanical ventilator, for treating the patient 1, i.e. for providing the patient 1 with oxygen.

Further, a user interface 6 is provided. This user interface 6 is adapted indicating information, e.g. information on the patient 1, on a display 17. Furthermore, the user interface 6 comprises an input device 18, like a keyboard or a touch screen which can be identical with the display 17, which allows a user to input data. Requests for such data input by the user can be indicated via the display 17.

Furthermore, a monitoring processer 19 for processing the patient signal and for outputting processed data to the user interface 6, and a control processer 20 for processing the patient signal and for outputting processed data to the closed loop controller 14, are provided. As can be seen from Fig. 3, the monitoring processer 19 and the control processer 20 are fed with the same patient signal in the same pre-processing state. The system also comprises an alarming unit 21 which is fed with the patient signal and which is adapted for providing common alarm conditions for monitoring and controlling, e.g. via display 17.

In the closed loop case, i.e. under normal conditions, FiO2 is controlled automatically, i.e. closed loop control is performed. This means that control is exclusively performed by the closed loop controller 14. The display 17 is only used for indicating monitoring data and no external data input is requested. Due to intentionally induced changes in the FiO2 value and/or due to changes of the FiO2 value due to normal control activities, according changes in the captured SpO2 value are expected. This feedback is continuously kept under surveillance, and based on this feedback, there are the following actions of the system:

1. The current model of the transfer functions is confirmed within acceptable limits and, thus, no adjustments of the model are necessary.

2. The response does not match with the current model of the transfer functions, but the deviations are in a range that allows to automatically adjusting the model of the transfer functions accordingly. Optionally the user might get a low priority warning in regards to the model changes so the user can verify what triggered the changes of the transfer function and might want to correct those. For example, the 02 uptake of the lung is reduced due to accumulation of secretion, but with a slightly increase FiO2 level this can be compensated. As the care giver could improve the situation by sucking the patient airways this would trigger a medium or low urgency notification to the user.

3. The response does not match with the current model of the transfer functions and the deviations are so extreme or do not fit into the model that an automatically adjustment of the model is not feasible or too risky. In this case the user is informed of this situation with a higher urgency. The urgency level might also depend on the actual state of the patient variable, but in any case it is important the user is aware of the situation as it might be impossible for the closed loop system to properly react on potential degradation of the patient's conditions in the future. For example, due to airway obstruction there is nearly no air reaching the lungs so the SaO2 will drop quickly even when the FiO2 is set to the maximum. This is a change in the transfer function of the patient that cannot be compensated by the closed loop control system.

Accordingly, a high urgency notification is triggered to the user. According to another example, the 02 supply for the patient got disconnected and the patient is breathing room air. Depending on the current patients condition this might cause only a slight drop of SaO2 that might still be in the acceptable range, but the closed loop controller has no control anymore to provide higher FiO2 levels if the patient might require it in the future. This triggers a medium urgency notification to the user. However, in all these cases in which the response does not match with the current model of the transfer functions and the deviations are so extreme or do not fit into the model that an automatically adjustment of the model is not feasible or too risky, a change from closed loop to open loop is performed and input of external data from a user is requested. While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments.

Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. A method for automatically controlling a physiological variable of a patient (1) in a closed loop system, comprising the following steps: automatically measuring a value for the physiological variable of the patient (1), and automatically treating the patient (1) in order to affect the physiological variable based on a control algorithm using the measured value of the physiological variable, wherein input of additional information by a user is automatically requested, and wherein the additional information is used in the control algorithm for controlling the actuator.

2. The method according to claim 1, wherein multiple values for one or more physiological variables are measured.

3. The method according to claim 1 or 2, wherein the controlling procedure is continuously documented in a log file.

4. The method according to claim 3, wherein the log file comprises at least one of: user inputs, measured values, and occurrence of predefined conditions.

5. The method according to claim 3 or 4, wherein the log file is accessible during the controlling procedure.

6. The method according to any of claims 1 to 5, wherein the additional information which is requested to be input by the user comprises at least one of: a currently not available measurement value, a non-measureable value, and a treatment confirmation.

7. The method according to any of claims 1 to 6, wherein input of additional information by a user is automatically requested upon occurrence of a condition which is predefined in a protocol.

8. The method according to any of claims 1 to 7, wherein input of additional information by a user is automatically requested periodically.

9. A closed loop system for automatically controlling a physiological variable of a patient (1), with a measuring unit (2) for measuring a value for the physiological variable of the patient (1), an actuator (3) for treating the patient (1) in order to affect the physiological variable, a controller (4) which is fed with the value for the physiological variable of the patient (1) and for controlling the actuator (3) based on a control algorithm using the measured value of the physiological variable, a protocol engine device (5) running at least one protocol and for notifying a user and a user interface (6) for indicating user notifications and for manually inputting additional information, wherein the protocol engine device (5) is adapted for automatically requesting input of additional information via the user interface (6), the additional information being used in the control algorithm for controlling the actuator (3).

10. The system according to claim 9, wherein the protocol engine device (5) is adapted for documenting the controlling procedure in a log file.

11. The system according to claim 9 or 10, wherein multiple measuring units (2) are provided.

12. The system according to any of claims 9 to 11, wherein the user interface (6) is adapted for visualizing information on the patient's (1) condition.