Abstract:
The operational and functional aspects of one or more IMDs is controlled by physiological data acquired from an external device. Various externally deployed devices collect vital signals for transmission to the IMD. Upon receipt of the signals the IMD cooperatively modifies therapy and diagnostic procedures to be substantially compliant with the received signals. Further, the IMD may store some of the signals for future follow-up or patient data management as needed.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention generally relates to medical devices. Specifically, the invention relates to an apparatus and method whereby an implantable medical device (IMD) receives data from an external physiological signal sensor and utilizes the information to initiate, control, modify or program the delivery of therapy or store the data for later follow-up retrieval and diagnostic review of a patient. More specifically, the invention provides a dynamic closed loop self monitoring system in which one or more external medical devices measure physiological data such as blood pressure, cardiac output and other vital signs and transmit these measurements to the IMD to thereby provoke a response based on the transmitted signals.  
         BACKGROUND OF THE INVENTION  
         [0002]    Analysis of physiological signals can provide clinicians with highly sensitive and accurate indicators to help identify, diagnose and monitor a variety of medical conditions.  
           [0003]    The sensing of physiological data such as, for example, cardiac output is of great benefit for the controlled treatment and diagnosis of numerous diseases. Chronically implantable sensors of various types are currently used in treating and monitoring various disease states. Some typical examples of implantable sensors that have been utilized include pressure, oxygen saturation, flow sensors, microphones, intracardiac impedance and similar other implantable medical devices.  
           [0004]    There are various externally and internally installed medical devices that monitor physiological signals to provide clinicians accurate information on the medical condition of patients. Under current practice, implanted device sensors are used in conjunction with implanted devices such as pacemakers, defibrillators, neurological stimulators, drug delivery systems and the like. While the functional and technological aspects of these implanted sensors have improved over the years, there remain significant operational and maintenance/reliability problems to overcome. For example, implanted sensors are prone to tissue overgrowth/fibrosis which may limit or interfere with proper/reliable signal acquisition. Similarly, power depletion, current drain, long term signal stability and similar problems associated with chronic use pose various challenges in the successful and long term implementation of implantable sensors.  
           [0005]    External sensing systems are also implemented to monitor various vital signs and physiological conditions of a patient. For example, Peripheral Arterial Tone (PAT) is an important signal relating to peripheral vascular responses to automatic nervous system activity. The PAT measures arterial pulse volume changes in the finger tip which may mirror changes or anomalies in automatic nervous system activity and their related vascular events. Other external sensing systems include the finger cuff for blood pressure and the auto-inflating cuff for periodic blood pressure measurement.  
           [0006]    One of the advantages of externally implemented sensor over implanted sensors is the option to change, modify or upgrade without an invasive medical procedure on the patient. Further operational efficiency relating to adjustments, maintenance and other conditional adaptability favor external sensors.  
           [0007]    Accordingly, there is a need to enable a cooperation between an IMD and external sensors to overcome some of the problems associated with implanted sensors.  
         SUMMARY OF THE INVENTION  
         [0008]    One aspect of the present invention includes the use of externally deployed medical devices to provide medical data to one or more IMDs, to thereby influence the operations of the IMD vis-a-vis the dispensation of therapy including diagnoses.  
           [0009]    Another aspect of the invention provides the control of one or more IMDs on the basis of medical information gathered from externally mounted devices. Specifically, one or more sensors specialized to sense certain physiological condition are implemented in wireless communications with the IMD. The operations of the IMD such as delivery of therapy or diagnostic evaluation of the patient condition is substantially controlled by the input from the physiological data collected by the external device. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1A is a representation of the implementation of the present invention wherein a patient with at least one IMD is fitted with various external sensors being in data communications with the pacemaker.  
         [0011]    [0011]FIG. 1B is a block diagram representing the wireless data transmission scheme in accordance with the invention.  
         [0012]    [0012]FIG. 2 is a partially exploded view of a blood pressure sensing unit mounted on a wrist in accordance with one embodiment of the invention.  
         [0013]    [0013]FIG. 3 is a perspective view of a finger ring sensor according to an embodiment of the invention.  
         [0014]    [0014]FIG. 4 is a schematic representation of a patch sensor which is in contact with the monitored body.  
         [0015]    [0015]FIG. 5 is a perspective view of a sock incorporating four sensors according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0016]    The present invention provides an IMD or diagnostic device that is in data communication with an external medical device. The external medical device transmits medical data to the IMD, which data is used, inter alia, to initiate, control, modify the delivery of therapy by the IMD. Further, the medical data from the external device may be stored in the IMD for later follow-up, retrieval and diagnostic review. Such IMD medical devices include implantable cardiac pacemakers, cardioverter/defibrillators, pacemaker/cardioverter/defibrillators, drug deliver systems, cardiomyostimulators, cardiac and other physiologic monitors, electrical stimulators including nerve and muscle stimulators, deep brain stimulators, and cochlear implants, and heart assist devices or pumps, etc.  
         [0017]    [0017]FIG. 1A represents patent  10  with one or more implantable medical devices IMD  12 . In this representative sample, IMD  12  is one of the many cardiac devices delivering a pulse to heart  14  via lead  16 . IMD  12  is in data communications with various externally mounted devices equipped with various sensors. Without limitations, the sensors include wristwatch sensor  18 , ring sensor  20 , patch sensor  22  and sensor sock  24 . As is disclosed in FIG. 1B, these externally mounted devices are in operable wireless data communication with IMD  12 .  
         [0018]    Referring to FIG. 1B, the wireless communication system in accordance with the present invention is shown. Specifically, wireless system  30  is implemented in any one of the external devices  13  to provide communication with IMD  12  is disclosed. More specifically, the system implements wireless communication schemes and processes disclosed in U.S. Pat. No. 5,113,859 to Funke, U.S. Pat. No. 5,683,432 to Goedeke et al, U.S. Pat. No. 5,843,139 to Goedeke et al, U.S. Pat. No. 6,167,310 to Grevious, U.S. Pat. No. 6,200,265B1 to Walsh et al, and U.S. Pat. No. 6,201,993B1 to Kruse et al, all incorporated herein by reference in their entireties. The wireless communication scheme as illustrated, is provided with a sensor module that includes a sensor in bidirectional communication with a memory, a processor and a transmitter/receiver at the externally mounted device  13 .  
         [0019]    Referring now to FIG. 2, a wrist-wearable unit  18  includes an assembly  100  which further includes a support member  101  placed on the patient&#39;s wrist  102  with a suitable adhesive  103  on the underside of member  101 . The assembly includes an exciter  104  and a detector  105  mounted on the support member  101 . The assembly  100  may be further held in place by cover  107  which includes a recess  106  for the exciter  104 . Cover  107  is wrapped around the patient&#39;s wrist and held in place by Velcro hooks  108  and Velcro latches  109 . Electrical connections (not shown) are made to the detector and sensor by thin conductive film lead formed in the support member  101 . The leads terminate in a connector  111 . Thus, the exciter and detector are maintained in spaced relationship in contact with the patient by support member  101 .  
         [0020]    As disclosed in U.S. Pat. No. 5,904,654 to Wohltmann et al, incorporated herein by reference in its entirety, unit  18  includes an exciter and a detector mounted on a common support for inducing perturbations into the body and detecting the perturbations after they travel a distance through the body in order to detect a hemoparameter. Unit  18  is adapted to be in telemetry or wireless communication with implanted medical device (IMD)  12  such that IMD  12  receives physiological parameters that are measured by unit  18  on a continuous basis. The assembly of unit  18  may be held in intimate contact with the body of patient  10  by means of an adhesive, adhesive tape, vacuum or pressure or equivalent. The interface may include gel, fluid, rubber or foam. Thus, unit  18  may be attached to patient  10  in such a way that the overall pressure over the assembly can be varied in a controlled way in order to modify the pressure experience by the underlying tissue. An example would be the case of a single unit assembly for measurement of blood pressure in which the ability to modulate the transmural arterial pressure facilitates determination of the relationship between the velocity of propogation of the excitation along the artery and blood pressure, one of the physical parameters that may be under investigation. This information could be transferred to IMD  12  via the wireless transmission scheme disclosed hereinabove.  
         [0021]    Referring now to FIG. 3, finger ring sensor  20  may be worn by patient  10  to monitor various parameters and transmit signals to IMD  12 . A finger ring is nonintrusive and can be worn at all times. Even, for example, when taking a shower, people keep wearing rings. Accordingly, finger rings are an appropriate locus for invading patient monitoring sensors and wireless transmitter in order to keep track of the patient twenty-four hours a day. Other articles of apparel may also be used in the manner described below with respect to finger rings.  
         [0022]    Referring to FIG. 3 in more detail, consistent with the disclosure in U.S. Pat. No. 5,964,701 to Asada et al incorporated herein by reference in its entirety, finger ring  20  represents a sensor with a wireless transmitter. Specifically, one or more diodes  202  and one or more light emitting diodes  204  are embedded in a ring  210  facing each other inside finger ring  20 . LEDs may emit light in the visible or infrared and may be particularly chosen to emit light at one or more specified wavelength, such as the isopiestic wavelength discussed below.  
         [0023]    The pulse of patient  10  may be detected as a periodic change in the sensor output. Finger ring  20  may be placed on one of patient  10 &#39;s fingers. In a preferred embodiment, finger ring  20  is placed on the middle finger, which is not only convenient for wearing the ring, but also suitable for counting pulse. The outer skin of the middle finger is thin, particularly at the sides of the finger, and a digital artery runs right beneath the thin skin. With an appropriate threshold, the sensor detecting the beat produces a pulse train of on-off signals and the pulse train is sent to a transmitter (not shown), contained within electronic module  206 , which in a preferred embodiment, is realized as a flexible printed circuit board. When optical sensors are used, interference from the ambient light may corrupt the photo probe signals. As the patient moves, the ambient light coming to the ring photo probe varies, resulting in inconsistent data. A simple approach to preventing ambient light interference is to acquire the signal when all LEDs  204  are turned off and subtract this background effect from the measured signals.  
         [0024]    In accordance with an embodiment of the invention, the optical sources which may be LEDs  204  may be modulated and detection may be performed using synchronous detection techniques known to persons to ordinary skill in the art of signal processing. Specifically, as it relates to the present invention, finger ring  20 , communicates with implanted device  12  such that data relating to skin temperature, blood flow, blood concentration or pulse rate of patient  12  is transmitted to IMD  12  to thereby initiate a an appropriate diagnostic or therapeutic response/operation by IMD 12 .  
         [0025]    Referring now to FIG. 4, patch sensor or sensor  22  is shown in contact with the body of patient  10 , as disclosed in U.S. Pat. No. 5,724,025 to Tavori, incorporated herein by reference in its entirety. Sensor  22  includes at least two separate electrodes. One electrode is thick  326  while one is substantially thin  327 . Electrodes  326  and  327  are in contact with monitored body patient  10  and form a substantial base for mounting single or plurality of sensors. Also shown are mounting means  312  and a position on which an adhesive layer  341  can be implemented in order to allow sensor  22  to be mounted on a measured body surface. For ease of presentation, four sensors are represented:  328 ,  329 ,  330  and  331 . It is to be understood that more or fewer sensors may be used. As a non limiting example, sensors  328  can measure heart electro potentials for which potential and ground electrodes are needed. Sensor  329  can measure surface conductivity for which different polarity electrodes are needed. Sensors  330  can measure local vascular pressures and use electrodes  327  as a membrane or capacitor plate while sensor  331  can measure temperature and uses electrode  326  as a neat sink. Such an arrangement is not easily achieved, as different sensors may interfere with other sensors&#39; output.  
         [0026]    By way of a non-limiting example, a sensor which measures surface conductivity  329  forms an electrical short circuiting which will interfere with a sensor measuring electrical potential  328 . A switching-coupling element  342  is mounted on the electronic circuit  343 , thus providing means to alternately connect and disconnect sensors which may interfere with each other. The sensors provide their output in any convenient values such as voltage, current, frequency, capacitance, inductance, resistance, TTL and the like. As a non-limiting example, a thermocouple can indicate changes in external temperature through a change in voltage. Similarly, a piezoelectric crystal can be used to measure local pressure. By enabling the managing physician to define the type of sensor connected to sensor  22 , a measurement of voltage is achieved, however, differently interprinted to different sensors/logics. Furthermore, since the magnitude of these signals may vary by an order of magnitude or more, out of ranging may be implemented to shift results to manageable value ranges.  
         [0027]    Similar to sensor  18  and ring sensor  20 , patch sensor  22  is adapted to be in data communications with IMD  12 . Accordingly, sensor  22  would transmit data relating to vital signs of patient  10  to IMD  12  to thereby initiate control, modify the delivery of therapy or record the data for later follow-up retrieval and diagnostic review.  
         [0028]    Referring to FIG. 5, sensor sock  24  is shown fitted on the foot of patient  10  in accordance with the disclosure of U.S. Pat. No. 6,155,120 to Taylor, incorporated herein by reference in its entirety. Sensor sock  24  generally includes an array of piezoresistive force sensors that is inserted into a shoe or is incorporated into a sock that may be pulled over a foot. Sensor sock  24  may be implemented for forced sensing and mapping. The device includes an outer tubular raw lead-out tubular lamination  424 . Lead-out tubular lamination  424  is made from flextron material having etched through the thickness dimension thereof circumferentially and longitudinally disposed insulating paths  462  and  463  defining laterally disposed longitudinally flag appendages  464  connected to longitudinally disposed lead-out traces  465 .  
         [0029]    Generally, sensor sock  24  measures pressures exacted on the foot of patient  10 . Sock  24  comprises, preferably, a rectangular array of Piezoresistive force sensors encapsulated in a thin polymer package incorporated therein. The sensors are responsive to contact pressures and shear forces directed to the contact plane. The electrical resistance between the pads varies in a predetermined manner as a function of the shear force.  
         [0030]    Such a sensor could be used to measure a number of valuable physiological parameters including weight, ankle swelling for edema, and patient activity. Similar to sensors  18 , ring sensor  20 , and patch sensor  22 , sock sensor  24  is adapted to be in data communications with IMD  12 . Accordingly, sensor  24  would transmit data relating to vital signs of patent  10  to IMD  12  to thereby initiate control, modify the delivery of therapy or record the data for later follow-up retrieval and diagnostic review.  
         [0031]    The preceding specific embodiments are illustrative of the practice of the invention. It is to be understood, therefore, that other expedients known to those of skill in the art or disclosed herein may be employed without departing from the invention or the scope of the appended claim. It is therefore to be understood that the invention may be practiced otherwise than is specifically described, without departing from the scope of the present invention. As to every element, it may be replaced by any one of infinite equivalent alternatives, only some of which are disclosed in the specification.