Abstract:
Sensing is carried out from locations at considerable remove from the stomach. Cooperating sensor electronics are placed at each of two wrists of the patient. The potential discomfort and inconvenience of an abdominal patch are reduced or eliminated. And alternative power sources become available.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority pursuant to 35 U.S.C. §119 to U.S. application Ser. No. 61/300,435 filed Feb. 1, 2010, and entitled “Two-wrist data-gathering system”. The foregoing is incorporated by reference in its entirety. 
     
    
     INTRODUCTION 
       [0002]    It is not easy to know whether a patient has taken his or her medication. 
         [0003]    The assignee of the present invention has given much attention in recent years to ways of detecting ingestion of medications such as pills. Through great effort, the assignee of the present invention has devised systems involving pills each containing a device with communication means, e.g., conductive communication means, etc., and involving a receiver such as a patch applied to the skin of a patient, so that when one of the pills reaches the stomach, gastric acids activate the device which communicates a current signature. The patch picks up the current signature, thus detecting the ingestion of the pill. The patch can then pass along this event to other equipment and systems. For example the patch may use a Bluetooth protocol to send news of the event to a mobile telephone, which in turn can pass the event to other equipment. A typical patch location is the abdomen. 
         [0004]    While the assignee of the present invention has had good results in its systems that use a patch in this way, the patch is sometimes inconvenient. It may be uncomfortable. It needs to be able to be flexible, since it adheres to skin that flexes. It is not easy to provide much of a man-machine interface (“MMI”) on a patch located at the abdomen. Keyboards and displays are not very workable if they are on a planar surface adhered to the abdomen. 
         [0005]    An abdominal patch has a power source, typically a battery or electrochemical cell (here for convenience of reference we will use the term “cell” to refer both to multicell batteries and to single cells). The cell has only a limited service life, defined in large part by the capacity of the cell and by the energy budget of the patch. When the battery is run down, the patch needs to be taken out of service and a different patch needs to be put into service. This can also be inconvenient. 
         [0006]    When the pill gets triggered, it emits a signal, sends a communication, etc. . . . An exemplary pill and communication are described in detail in, for example, in the following US patent publications: 
         [0000]                                    US Publication   Publication           number   date   Title                   20080284599   Nov. 20, 2008   Pharma-informatics system       20080306359   Dec. 11, 2008   Medical diagnostic and               treatment platform using               near-field wireless               communication of information               within a patient&#39;s body       20090082645   Mar. 26, 2009   In-body device with virtual               dipole signal amplification       20090227204   Sep. 10, 2009   Pharma-informatics system       20100022836   Jan. 28, 2010   In-body device having a               multi-directional transmitter       20100081894   Apr. 01, 2010   Communication System with               Partial Power Source       20100312188   Dec. 09, 2010   Pharma-informatics system                    
each of which is incorporated herein by reference for all purposes as if reproduced fully within. Actual tests with real pills, real patches, and real human subjects have achieved reliable detection of communications from such pills. This is remarkable given prior-art failures to achieve such reliable detection, and the many ways in which nature, human physiology, and materials science conspire to make these results difficult to achieve.
 
         [0007]    As a general matter, conventional electromagnetic radiation is emitted by a dipole and detected and received by a dipole, and conventional models assume that the signal strength falls away with distance at a rate determined by the permittivity and permeability of the medium (here, human tissue). Many investigators in this general area thus proceed with the assumption that the receiver, such as a patch, needs to be as nearby as possible to the transmitter (that is, nearby to the stomach). 
         [0008]    It would be very desirable if some way could be found to detect the triggering of the pill transmitters that would avoid the inconveniences related to patches as just described, while nonetheless achieving the reliable detection that has been accomplished using patches. There are other physiological measurements that would also be desirable to carry out if only it could be accomplished reliably and accurately without undue discomfort or inconvenience to the patient. 
       SUMMARY 
       [0009]    It is very counter-intuitive to carry out sensing from locations at considerable remove from the stomach, given that in general one might think the receiver needs to be as close as possible to the transmitter. And yet that is precisely what is described here. Cooperating sensor electronics are placed at each of two wrists of the patient. Once the counter-intuitive nature of this arrangement is put out of mind, other potential benefits become readily available, for example a man-machine interface can be provided. The potential discomfort and inconvenience of an abdominal patch are reduced or eliminated. And alternative power sources become available. 
     
    
     
       DESCRIPTION OF THE DRAWING 
         [0010]    The invention is described with respect to a drawing in several figures, of which: 
           [0011]      FIG. 1  shows a patient  101  with a wristwatch  102  and a bracelet  103  according to an aspect of the invention; 
           [0012]      FIG. 2  shows the wristwatch  102  with elastic band  203 ; 
           [0013]      FIG. 3  shows the bracelet  103  with elastic band  203 ; 
           [0014]      FIG. 4  shows the wristwatch  102  in cross section, with electrode  202  in intimate juxtaposition with wrist  105 , and with chip  401 ; 
           [0015]      FIG. 5  shows the bracelet  103  in cross section, with electrode  302  in intimate juxtaposition with wrist  106 , and with chip  501 ; 
           [0016]      FIG. 6  shows chip  401  in functional block diagram form; and 
           [0017]      FIG. 7  shows chip  501  in functional block diagram form. 
       
    
    
       [0018]    To the extent possible, like elements have been denoted with like reference numerals. 
       DETAILED DESCRIPTION 
       [0019]      FIG. 1  shows a patient  101  with a wristwatch  102  and a bracelet  103  according to an aspect of the invention. Wristwatch  102  is on right wrist  105  and bracelet  103  is on left wrist  106 . (It will be appreciated that this left-right arrangement is quite arbitrary and one could exchange the positions of the wristwatch and bracelet without departing from the invention.) One of the chief goals is to detect a transmitted signal or communication from pill  104  when it is triggered by gastric juices. 
         [0020]    It will be appreciated that while this invention is described in an exemplary aspect where stomach juices trigger the pill, other variants could be devised such as aspects where the triggering does not occur until the pill reaches, say, the small intestine. One could also devise a staged approach where a first signal is triggered at a first point of progress through the gastro-intestinal system and a second signal is triggered at a second point of progress. 
         [0021]    Turning now to  FIG. 2 , we see an exemplary wristwatch  102  with elastic band  203 . The elastic band helps to keep the electrode  202  in intimate contact with skin of the patient. A display  204 , such as an LCD, is shown. A pushbutton  205  is also shown. In this way a man-machine interface (MMI) is provided. It will be appreciated, of course, that the MMI need not be limited to what is shown here. Other elements of an MMI, such as a piezo beeper or other sound source, could be provided. A touch screen or other human input device (HID) could be used. The LCD and pushbutton are merely exemplary. 
         [0022]    While this aspect is described with respect to elastic wristbands, other approaches such as a Speidel Twist-o-flex® watchband could be employed to keep each skin electrode in intimate contact with the skin. 
         [0023]      FIG. 3  shows the bracelet  103  with elastic band  203 . The elastic band keeps electrode  302  in intimate contact with skin of the patient. 
         [0024]    In the exemplary arrangements that follow, the electrodes  202 ,  302  will be described as electrodes in intimate (conductive) contact with skin. Perhaps less preferred, but also workable, would be electrodes  202 ,  302  in capacitive coupling with skin, that is, with some dielectric such as plastic film therebetween. Perhaps even less preferred, but maybe also workable, would be an arrangement in which the wristband  203  is not elastic at all but is of constant circumference, permitting the electrodes  202 ,  302  to be in a spaced relationship relative to skin, sometimes having an air gap or partial air gap therebetween. 
         [0025]      FIG. 4  shows the wristwatch  102  in cross section, with electrode  202  in intimate juxtaposition with wrist  105 , and with chip  401 . Chip  401  is communicatively coupled, preferably metallically connected, with skin electrode  202  and with a second electrode  402 . The second electrode  402  is open to the air, and provides what might be modeled as a counterpoise for the skin electrode  202 . A nonconductive casing  403  provides structure between the two electrodes.  FIG. 5  shows the bracelet  103  in cross section, with electrode  302  in intimate juxtaposition with wrist  106 , and with chip  501  in communicative coupling with skin electrode  302  and second electrode  502 . The bracelet electrodes together with housing or casing  503  function similarly to their counterparts in the wristwatch. 
         [0026]      FIG. 6  shows wristwatch chip  401  in functional block diagram form. Previously mentioned electrodes  202 ,  402  may be seen, communicatively coupled with transceiver  605 . Cell  603  and power circuitry  604  provide power to transceiver  605  and to controller  606 . Controller  606  controls transceiver  605  and provides MMI such as LCD  204  and pushbutton  205 , and optionally other MMI such as a piezo beeper or other sound emitter. LCD  204  is controlled by multiline bus  607 . 
         [0027]    Interestingly, a technology that seems rather old-fashioned, the self-winding mechanical watch, offers possible benefits here. As shown in  FIG. 6 , a pendulum  601  has an opportunity to move around as the human user moves around. A strong permanent magnet in the pendulum induces currents in a winding or windings  602 . This permits the cell  603  to be a rechargeable cell, or perhaps an ultracapacitor, mediated by power circuitry  604 . Bluetooth or other protocol system(s)  607  can communicate with external equipment such as a cell phone or personal computer. 
         [0028]      FIG. 7  shows bracelet chip  501  in functional block diagram form. The elements shown there correspond closely with elements in  FIG. 6 . 
         [0029]    The day-to-day function of the system (the pills, the bracelet, the wristwatch, and other equipment such as a mobile phone) will now be described in an exemplary aspect. 
         [0030]    A chief goal is to detect, at the bracelet  103  and wristwatch  102 , a signal from a pill. To this end, the bracelet may carry out a real-time nearly continuous detection of signals at the skin electrode  302  relative to counterpoise  502 . This detection is A-to-D (analog-to-digital) converted, e.g., by an ADC (not shown in  FIG. 7 ), preferable at a resolution higher than 16 bits, and the measured signal (communicated digitally and preferably as compressed data) is communicated via a wireless link to the wristwatch  102 . The wristwatch likewise carries out a real-time nearly continuous detection of signals at the skin electrode  202  relative to counterpoise  402 . This detection is A-to-D (analog-to-digital) converted, preferable at a resolution higher than 16 bits. The data streams from the two sensors (one at the bracelet, one at the wristwatch) are then communicated externally to other equipment that can do signal processing and can detect signals of interest such as the signal from the pill when it is triggered. 
         [0031]    In a preferred arrangement, all of the noise would be common-mode and the signals of interest would be differential signals measured at the two arms. 
         [0032]    As mentioned above, it is rather counterintuitive to take the step of moving the sensors to points that are about as far from the pill  104  as can be imagined. Once the counterintuitive nature of this move is accepted and put out of mind, many other interesting capabilities become available that would likely not have been available at all in prior-art arrangements such as an abdominal patch. 
         [0033]    Technology suitable for such sensing is discussed in a paper entitled “A low-noise, non-contact EEG/ECG sensor” by Thomas J Sullivan, Stephen R. Deiss, and Gert Gauwenberghs of the University of California, San Diego, Biomedical Circuits and Systems Conference, 2007, BIOCAS 2007, IEEE, 27-30 Nov. 2007 Pages 154-157, Digital Object Identifier 10.1109/BIOCAS.2007.4463332, incorporated herein by reference. 
         [0034]    Sensing things from further away from the body is discussed in PCT publication WO 2009/055733 entitled “Fluid transfer port information system”, incorporated herein by reference, and in US published application US 2009-0112178 A1 with the same title, likewise incorporated herein by reference. Sensing blood volume is discussed in U.S. patent application No. 61/160,265 filed Mar. 13, 2009 and entitled “Volume-sensing device, system, and method”, incorporated herein by reference. Other related technology is discussed in U.S. patent application No. 61/240,571 filed Sep. 8, 2009 and entitled “Body-associated device”, incorporated herein by reference. 
         [0035]    As one potential benefit mentioned above, the move to the wrists permits the provision of a workable MMI. Wrists also tend to move around more than abdomens, making the self-winding feature more likely to serve its purpose. 
         [0036]    More subtle and interesting capabilities, however, present themselves once the stimulus/sensing platform of a bracelet and wristwatch are available. 
         [0037]    The heart function (essentially a two-electrode EKG) can be measured. 
         [0038]    Energy can be transmitted at one of the two points (for example at the bracelet) at some frequency, which propagates through the body to the other point (in this example at the wristwatch) with some measured delay and some measured level of absorption, or measured impedance. Separately, energy can be transmitted at one of the two points (again for example at the bracelet) at a different frequency, which propagates through the body to the other point (again in this example at the wristwatch) with a non-identical measured delay and a non-identical measured level of absorption, or measured impedance. This probing of the body amounts to spectroscopy, and permits measuring bodily qualities such as amount of fluid in the body relative to other tissue materials. In this way, blood volume can be indirectly measured. Real-time measurement of blood volume has rarely if ever been achieved except by keeping a patient stationary during measurements, with large, bulky, and stationary measuring equipment. This approach permits real-time measurement even as a patient is ambulatory. 
         [0039]    These measurements may permit real-time measurement of cardiac output or stroke volume at the heart. 
         [0040]    It will be appreciated that one of the important parts of analysis of data collected at electrodes  202 ,  302  (at the bracelet and at the watchband) is the time-correlation of measured data. One might think that this requires a highly accurate clock running in each of the bracelet and watchband, the two clocks being extremely closely synchronized. 
         [0041]    But in fact it is quite workable to allow the two clocks to be less expensive (and less power-hungry) clocks that are permitted to drift relative to each other. At the wristwatch, synchronization events (simultaneous detection of common-mode impulse signals from the environment, for example) permit receiving a time signal from the bracelet which will then be understood to match a time value at the wristwatch. Drift of one clock relative to the other can be detected and corrected in this way. 
         [0042]    The wristwatch and bracelet can be stylish. They need not look “clunky”. The patient might actually enjoy wearing a recognizable or distinctive wristwatch and bracelet. 
         [0043]    The A-to-D conversions at the two sensing locations are likely 18-bit, but might be sixteen-bit or twelve-bit. 
         [0044]    Communication from the bracelet to the wristwatch might be open-loop (one way from bracelet to watchband) but it is thought preferable that the communication be bidirectional, at least to provide handshaking. 
         [0045]    The communication may use an inductive coupling through the body at a high-frequency RF signal (higher than the sensed information that is expected to be in the range of 0.1 Hz to perhaps 100 Hz). Alternatively the communication can be optical infrared (bouncing off the surrounding walls and structures). 
         [0046]    The MMI might provide a reminder to take a particular pill. And the MMI might provide an audible or visual acknowledgment when the patient has taken a particular pill. 
         [0047]    Accelerometers in the bracelet or watchband or both will permit measurement of a physical activity level, and may permit detecting times of sleep. These could likewise be reported external to the patient. 
         [0048]    The allocation of computational resources can be varied somewhat. For example it may be workable to do most of the computations in the wristwatch, comparing the signals as measured at the bracelet and at the wristwatch. Alternatively it is workable to do the computations elsewhere (e.g. at a distant computer) and to have the wristwatch simply pass along the information which it received from the bracelet. 
         [0049]    The needed bandwidth from bracelet to wristwatch, and from wristwatch to distant equipment, is such at a carrier of 10 MHz should be adequate. 
         [0050]    The alert reader will have no difficulty devising myriad obvious improvements and variants of the invention, all of which are intended to be encompassed by the claims which follow.