FIELD 
       [0001]    The present invention relates generally to medical electrodes, more particularly, to a wireless medical electrode. 
       BACKGROUND 
       [0002]    As is known in the art, a wide variety of sensors for obtaining physiological parameters are available. For example, electrocardiograph (ECG) systems include sensors for detecting cardiac information from a patient. A conventional ECG system includes a series of patch electrodes for attachment to the chest and other locations. The patch electrodes are coupled to a base system, which typically includes a display monitor to allow medical personnel to monitor the patient heartbeat pattern, pulse rate etc. It will be appreciated that the number of wires extending from the patient to the monitor can be significant. In addition, if other medical equipment is connected to the patient, it can be challenging to maintain the correct connections to the patient, particularly for uncooperative patients. Further, in the event that a patient must be moved quickly due to a medical emergency, connections to medical equipment can be problematic. 
         [0003]    To address excessive mechanical connections to a patient, wireless systems have been developed. For example, wireless ECG systems typically include electrodes extending from a patient&#39;s skin to a base system secured to the patient&#39;s bed. The base system wirelessly transmits sensor information to a remote monitor, which can be secured to the wall of a hospital room and/or nursing station. However, this arrangement still requires significant mechanical connections from the patient to a base system. 
         [0004]    Wireless electrodes have been developed to provide self-contained sensors that are attachable to a patient. The wireless electrodes wirelessly transmit physiological information to a remote monitor. While wireless electrodes eliminate the need for mechanical connections to a patient, the electrodes have certain limitations, such as battery life. It will be appreciated that battery life is at a premium. In conventional wireless electrodes, the battery may transmit information even when the electrode is not connected to a patient. This can result in a reduction in the useful life of a wireless electrode by wasting battery power. In addition, it may result in a sensor not monitoring patent information due to a depleted battery, which can have disastrous results. Also, wasting battery power results in medical personnel spending more time to replace and/or recharge batteries, time which is then not spent directly for patient care. 
       SUMMARY 
       [0005]    The present invention provides method and apparatus for a wireless electrode that transmits only when a transmitter is attached to a patient. In exemplary embodiments, a radio module can be coupled to the electrode to activate the device. While illustrative embodiments are shown having certain configurations, structures, and applications, it is understood that the invention is applicable to electrodes in general for which it is desirable to conserve power. 
         [0006]    In one aspect of the invention, a wireless electrode comprises an interface surface to contact a patient, a sensor coupled to the interface surface to detect patient cardiac information, a radio module coupled to the sensor to wirelessly transmit the cardiac information, an energy source to power the radio module, and an activation mechanism coupled to the energy source, the activation mechanism having an activated state in which power from the energy source is delivered to the radio module and a non-activated state in which power from the energy source is not delivered to the radio module. 
         [0007]    The electrode can further include one or more of the following features: the activation mechanism requires manual manipulation to transition to the activated state, the activation mechanism comprises a deformable receptacle to receive a manually insertable structure for transition to the activated state, the radio module comprises a transmitter insertable into the electrode, insertion of the transmitter into the electrode transitions the activation mechanism to the activated state, a temperature sensor, the radio module is disabled when the temperature sensor does not sense a temperature greater than a threshold, the radio module transmits information from the temperature sensor, the energy source comprises a battery, the energy source further comprises a photovoltaic device coupled to the battery, and/or the electrode comprises an ECG electrode. 
         [0008]    In another aspect of the invention, a system to obtain patient information comprises: a plurality of wireless electrodes, each comprising: an interface surface to contact a patient, a sensor coupled to the interface surface to detect patient cardiac information, a radio module coupled to the sensor to wirelessly transmit the cardiac information, an energy source to power the radio module, and an activation mechanism coupled to the energy source, the activation mechanism having an activated state in which power from the energy source is delivered to the radio module and a non-activated state in which power from the energy source is not delivered to the radio module, and a transmit/receive module to receive the cardiac information from the radio module, and a monitor in communication with the transmit/receive module to display the cardiac information and generate alerts based upon the cardiac information. 
         [0009]    The system can further include one or more of the following features: at least one of the wireless electrodes includes a temperature sensor, the radio module is disabled when the temperature sensor does not sense a temperature greater than a threshold, the energy source comprises a photovoltaic mechanism coupled to a battery, and/or the activation mechanism cannot transition to the activated state unless the radio module is present, wherein the radio module comprises a transmitter insertable into the electrode, and insertion of the transmitter into the electrode transitions the activation mechanism to the activated state. 
         [0010]    In a further aspect of the invention, a method of providing a wireless electrode comprises: providing an interface surface to contact a patient, providing a sensor coupled to the interface surface to detect patient cardiac information, providing a radio module coupled to the sensor, the radio module including a transmitter to wirelessly transmit the cardiac information, providing an energy source to power the radio module, and providing an activation mechanism coupled to the energy source, the activation mechanism having an activated state in which power from the energy source is delivered to the radio module and a non-activated state in which power from the energy source is not delivered to the radio module. 
         [0011]    The method can further include providing a temperature sensor, wherein the radio module is disabled when the temperature sensor does not sense a temperature greater than a threshold, and/or insertion of the transmitter into the electrode transitions the activation mechanism to the activated state. 
         [0012]    In a further aspect of the invention, a method comprises: applying a wireless electrode to a patient to obtain patient cardiac information, manipulating an activation mechanism of the wireless electrode from a non-activated state in which power from an energy source is not delivered to a radio module to an activated state in which power from the energy source is delivered to the radio module, and monitoring the cardiac information transmitted by the radio module. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The foregoing features of this invention, as well as the invention itself, may be more fully understood from the following description of the drawings in which: 
           [0014]      FIG. 1  is a schematic representation of a wireless electrode having power conservation in accordance with exemplary embodiments of the invention; 
           [0015]      FIG. 2  is functional block diagram of a wireless electrode having power conservation in accordance with exemplary embodiments of the invention; 
           [0016]      FIG. 3A  shows a wireless electrode and a radio module in a non-engaged first position and  FIG. 3B  shows the wireless electrode and the radio module in an engaged second position; 
           [0017]      FIG. 4  shows a schematic representation of an exemplary activation mechanism having a first portion on the electrode and a second portion on the radio module; and 
           [0018]      FIG. 5  is a flow diagram showing exemplary steps to activate a wireless electrode. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]      FIG. 1  shows an exemplary patient monitoring system  100  having wireless electrodes  102   a -N with radio modules  104   a -N, or portions thereof, that can be selectively attached to the electrodes. The wireless electrodes  102  can monitor patient information, such as cardiac information, as part of a wireless ECG (electrocardiograph) system. In other embodiments, the electrodes monitor blood pressure, temperature and/or other physiological information. 
         [0020]    The patient monitoring system  100  includes a transmit/receive module  106  to wirelessly receive information from the electrodes  102 . The transmit/receive module  106  can be wirelessly or mechanically connected to a monitor module  108 , which can include a display  110  to enable medical personnel to view the patent heartbeat, for example. The monitor module  108  can further include an alert module  112  to generate an alert in the event of cardiac arrest or other cardiac stress condition. It is understood that the processing of patient cardiac data and alert generation are well known in the art. 
         [0021]      FIG. 2  shows an exemplary wireless electrode  200  with a discrete transmit module  202  that can be engaged with the electrode to activate the device in accordance with exemplary embodiments of the invention. The wireless electrode  200  includes an interface  204  for electro-mechanical contact with the skin of a patient. A sensor  206  is coupled to the interface  204  to receive electrical waveform information, such as heartbeat information. An analog-to-digital converter (ADC)  208  digitizes the analog sensor information in a conventional manner. 
         [0022]    The electrode  200  includes a battery  210  to power a radio module  212  to which the transmit module  202  is selectively attachable. In general, if the transmit module  202  is not present, the radio module  210  is not enabled. In one embodiment, the radio module  210  is not enabled in that no power is drawn from the battery if the transmit module is not present. In one particular embodiment, a photovoltaic device  211  is coupled to the battery  210 . 
         [0023]    In one embodiment, no power is drawn from the battery  208  by the wireless electrode unless the transmit module  212  is present. In this arrangement, a physical connection is made by mechanical manipulation of the transmit module  212 . In an alternative embodiment, no power is drawn unless a receive module is present. 
         [0024]    It is understood that radio module refers to a module that may or may not include a transmitter and/or receiver at any given time. For example, during operation of the wireless electrode, the radio module  212  includes the transmitter  202  and a receiver (if the electrode is to receive information). As described above, the device may not be active unless the radio module contains the transmit and/or receive module. 
         [0025]    In one particular embodiment shown in  FIGS. 3A and 3B , a transmit module  300  includes an activation mechanism ( 214  in  FIG. 2 ) having a protrusion  302  shaped for an interference fit, e.g., snap-fit, into a cavity  304  in a radio module  306  having a shape complementary to the protrusion. The protrusion  302  can be pressed into the cavity  304 . Once inserted, the protrusion  302  presses a first contact  310  into electrical contact with a second contact  308 , as shown in  FIG. 3B . The first and second contacts  308 ,  310  complete a circuit to indicate that the transmit module  300  is present for allowing the transmit module  300  to draw power from a battery and to transmit sensor information. 
         [0026]    It is understood that a wide variety of suitable mechanical, electromechanical, optical, and other types of mechanisms can be used to detect the presence of the transmit module. The mechanisms can detect a structure, presence, and/or material to determine whether the device should be activated. 
         [0027]      FIG. 4  shows an exemplary wireless electrode  400  coupled to a radio module  402 . An activation mechanism  404  can detect the presence of the radio module  402 , or components of the radio module, and activate the electrode to enable transmission of patient data. 
         [0028]    In an exemplary embodiment, the activation mechanism  404  has a first portion  406   a  on the electrode and second portion  406   b  on the radio module  402 . In one embodiment, the first portion  406   a  of the activation mechanism  404  includes an optical detector and the second portion  406   b  of the activation mechanism includes a low power light source. When the optical detector  406   a  detects photons from the light source after engaging the radio module  402  (or component) with the electrode  400 , the activation mechanism  404  enables operation of the device, such as by closing a circuit to the battery. 
         [0029]    In an alternative embodiment, the first portion  406   a  of the activation mechanism includes a magnet and the second portion  406   b  includes a ferrous structure. When the radio module  402  is engaged with the electrode  400 , the magnet urges the ferrous structure to close a circuit which causes the activation mechanism to enable the battery to power the device. 
         [0030]    In a further embodiment, the first portion  406   a  of the activation mechanism includes a proximity sensor, such as a Hall effect device, and the second portion  406   b  includes a ferrous portion. When the radio module  402  is engaged with the electrode  400 , the Hall effect device  406   a  detects the ferrous portion  406   b  and the activation mechanism enables the battery to power the device. 
         [0031]    In a further alternative embodiment, the first portion  406   a  of the activation mechanism includes an ultrasound device and the second portion  406   b  is at least partly formed from a material that is effective to reflect sound energy. When the radio module  402  is engaged with the electrode  400 , the ultrasound device  406   a  detects sound energy reflected from the sound reflective material of the second portion after which the activation mechanism enables the battery to power the device. Similarly, an infra red device could be used instead of a sound device and a light reflective material can form at least part of the second portion of the activation mechanism. 
         [0032]    The electrode  400  can further include an optional temperature sensor  408 . In one embodiment, the radio module  402  is disabled when the temperature sensor  408  does not sense a temperature greater than a threshold. The electrode can transmit temperature data if desired. 
         [0033]    In another embodiment, a wireless electrode includes an integrated radio and transmit module, i.e., the transmit module is not detachable. The wireless electrode requires the manual insertion of a pin, snap, or other structure into the radio module to enable the radio module to draw power from the battery. 
         [0034]      FIG. 5  shows an exemplary sequence of steps for selective activation of a wireless electrode. In step  500 , a radio module/component is engaged with the electrode, such as by a nurse. After engagement, an activation mechanism enables operation of the device in step  502 . That is, the electrode can transmit and optionally receive information. By preventing operation of the device until the complete radio module is coupled to the electrode, battery power is not used until the device is ready to be used for a patient. In step  504 , the electrode is attached to the patient and in step  506 , the device transmits patient information, such as ECG signals. It is understood that the radio module can be coupled to the electrode before or after the electrode is placed on the patient&#39;s skin. 
         [0035]    While the term transmit module is used herein, it is understood that the term “transmit module” requires transmit functionality and can further include receive functionality. That is, the wireless electrode can be transmit only, or transmit and receive. 
         [0036]    In addition, transmit or transmit/receive modules tend to be a relatively expensive component of the electrode. With this arrangement, the transmit/radio module can be re-used. That is, the once an electrode is removed from a patient for example, the transmit module can be removed from the electrode and saved until needed for an electrode on a new patient. 
         [0037]    Having described exemplary embodiments of the invention, it will now become apparent to one of ordinary skill in the art that other embodiments incorporating their concepts may also be used. The embodiments contained herein should not be limited to disclosed embodiments but rather should be limited only by the spirit and scope of the appended claims. All publications and references cited herein are expressly incorporated herein by reference in their entirety.
Methods and apparatus provide a wireless electrode having energy conservation. In one embodiment, a wireless electrode includes a radio module coupled to the sensor to wirelessly transmit the cardiac information, an energy source to power the radio module, and an activation mechanism coupled to the energy source, the activation mechanism having an activated state in which power from the energy source is delivered to the radio module and a non-activated state in which power from the energy source is not delivered to the radio module.