Abstract:
An apparatus and method for obtaining one or more physiological measurements associated with a user using a portable device alone or in combination with a detachable unit is disclosed herein. One or more of different types of sensor sets are included in one or more planar surfaces of the portable device and/or the detachable unit in communication with the portable device. The accuracy of physiological measurements is automatically ensured by the fixed positioning of the sensors relative to each other. A variety of different physiological measurements can be obtained using a portable device that users normally carry around and use on a daily basis, instead of requiring use of a separate/dedicated medical device.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to obtaining physiological measurements in general, and in particular embodiments, to obtaining physiological measurements using a portable device. 
       BACKGROUND 
       [0002]    The current standard of care for blood pressure measurement is using a brachial cuff in the doctor&#39;s office or at home. Brachial cuff measurements comprise oscillometric measurements in which an air inflated cuff is positioned radially around a patient&#39;s arm in the vicinity of his/her brachial artery. Using a brachial cuff, however, is cumbersome and inadequate for a number of reasons. The cuff is uncomfortable and may even cause bruising. Brachial cuff measurements are susceptible to motion artifacts. Air pressure cuff devices tend to be large and not amendable to miniaturization. Brachial cuff measurements are also inadequate for thoroughly understanding a patient&#39;s blood pressure and changes in blood pressure. High blood pressure can be missed at the doctor&#39;s office if a patient&#39;s blood pressure is only high at certain times of the day. In this case, the opportunity to diagnose and treat high blood pressure is missed. Conversely, the patient may exhibit high blood pressure only when at the doctor&#39;s office. In this case, the patient may be unnecessarily placed on daily medication to lower blood pressure. Moreover, brachial cuff measurements provide peripheral blood pressure measurements (e.g., blood pressure at the arteries in the arms or legs) which can differ from central blood pressures (e.g., blood pressure at or near the aorta). For diagnostic and treatment purposes, central blood pressure measurements are preferred because they are a more accurate indicator of cardiovascular health. 
         [0003]    Increasingly, the standard of care is moving toward ambulatory, non-invasive methods of obtaining physiological measurements. In the case of blood pressure measurements, a plurality of measurements obtained over a 24 hour or longer time period are of increasing importance in the practice of medicine. Such measurements provide better diagnosis and/or treatment of cardiovascular problems. Blood pressure is an important health statistic for overall health and wellness. When miniaturizing or configuring blood pressure measuring devices for home use, increasing their accuracy is an important consideration. Especially since patients are less well-versed in how to take measurements than medical personnel, it would be beneficial for measurement accuracy to be more or less built into the measurement device. 
         [0004]    Other types of physiological measurements that may be tracked by individuals over an extended period of time and which are of value for overall health and wellness include, but are not limited to, electrocardiogram (ECG), body fat, and body water content measurements. So that individuals need not carry around multiple devices, it would be beneficial if a single device could capture one or more types of physiological measurements. It would also be beneficial if individuals can use an already existing device, which they would carry around anyway, to additionally perform physiological measurement functions. 
       BRIEF SUMMARY 
       [0005]    In certain embodiments, a portable device obtains one or more psychological measurements associated with a user. In some embodiments, the portable device is configured to be a handheld device. The portable device may be a unitary structure, or may include a base unit and a detachable unit. For example, the base unit may contain at least a portion of the processing capability and, in some embodiments a user interface such as a touch screen display; and the detachable unit might include sensors for the physiological measurements. For either configuration, the sensors have fixed positioning and distance on a rigid planar surface of the portable device (or detachable unit, as appropriate). Such sensor configuration automatically increases measurement accuracy, decreases improper sensor positioning, and the like. Moreover, the user&#39;s natural gripping motion of a handheld portable device provides automatic additional sensor contact locations to ensure contact with body parts on each of the left and/or right sides of the user&#39;s body. The processing and communication capabilities of the portable device can be harnessed to provide a beginning-to-end measurement experience to the user. Physiological measurements include, but are not limited to, blood pressure measurements, ECG measurements, heart rate measurements, body temperature measurements, galvanic skin response measurements, stress level indications, body water content measurements, and/or body fat content measurements. 
         [0006]    Other features and aspects of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the features in accordance with embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Some embodiments are illustrated by way of example and not limitations in the figures of the accompanying drawings, in which: 
           [0008]      FIGS. 1A-1B  illustrates embodiments of an example system for obtaining one or more types of physiological measurements according to some embodiments. 
           [0009]      FIGS. 2A-2D  illustrates example portable devices of  FIGS. 1A-1B  used to obtain physiological measurements according to some embodiments. 
           [0010]      FIG. 3  illustrates the portable device in contact with a body part of a user to obtain a physiological measurement (e.g., blood pressure) according to some embodiments. 
           [0011]      FIG. 4  illustrates the portable device in contact with the user to obtain one or more physiological measurements (e.g., blood pressure, temperature, electrocardiogram (ECG), body fat content, body water content, heart beat, etc.) according to some embodiments. 
           [0012]      FIGS. 5A-5C  illustrates an example flow diagram for obtaining physiological measurements using the system of  FIGS. 1A-1B  according to some embodiments. 
           [0013]      FIG. 6  illustrates an example block diagram showing modules configured to facilitate the process of flow diagram  500  according to some embodiments. 
           [0014]      FIGS. 7A-7D  illustrates user interface screens provided on the portable device  101  to provide physiological parameters capture instructions to the user according to some embodiments. 
           [0015]      FIG. 8  illustrates blood pulse waveforms detected by a pair of optical sensors in accordance with some embodiments. 
           [0016]      FIG. 9  depicts a block diagram representation of an example architecture for the controller assembly according to some embodiments. 
       
    
    
       [0017]    The headings provided herein are for convenience only and do not necessarily affect the scope or meaning of the terms used. 
       DETAILED DESCRIPTION 
       [0018]    The following detailed description refers to the accompanying drawings that depict various details of examples selected to show how the present invention may be practiced. The discussion addresses various examples of the inventive subject matter at least partially in reference to these drawings, and describes the depicted embodiments in sufficient detail to enable those skilled in the art to practice the invention. Many other embodiments may be utilized for practicing the inventive subject matter than the illustrative examples discussed herein, and many structural and operational changes in addition to the alternatives specifically discussed herein may be made without departing from the scope of the inventive subject matter. 
         [0019]    In this description, references to “one embodiment” or “an embodiment,” or to “one example” or “an example” mean that the feature being referred to is, or may be, included in at least one embodiment or example of the invention. Separate references to “an embodiment” or “one embodiment” or to “one example” or “an example” in this description are not intended to necessarily refer to the same embodiment or example; however, neither are such embodiments mutually exclusive, unless so stated or as will be readily apparent to those of ordinary skill in the art having the benefit of this disclosure. Thus, the present invention can include a variety of combinations and/or integrations of the embodiments and examples described herein, as well as further embodiments and examples as defined within the scope of all claims based on this disclosure, as well as all legal equivalents of such claims. 
         [0020]    For the purposes of this specification, a “processor-based system” or “processing system” as used herein, includes a system using one or more microprocessors, microcontrollers and/or digital signal processors or other devices having the capability of running a “program,” (all such devices being referred to herein as a “processor”). A “program” is any set of executable machine code instructions, and as used herein, includes user-level applications as well as system-directed applications or daemons. 
         [0021]      FIGS. 1A and 1B  illustrate examples of a system  100  for obtaining one or more types of physiological measurements according to some embodiments. In  FIG. 1A , one embodiment of the system  100  comprises a portable device  101 . The portable device  101  of  FIG. 1  includes a touch sensor panel  102  (also referred to as a touch screen) and a controller assembly  104 . The touch sensor panel  102  includes an array of pixels to sense touch event(s) from a user&#39;s finger, or other body part, or a stylus or similar object. Examples of touch sensor panel  102  includes, but is not limited to, capacitive touch sensor panels, resistive touch sensor panels, infrared touch sensor panels, and the like. The controller assembly  104  is configured to provide processing and control capabilities for the portable device  101 . The controller assembly  104  can include, but not limited to, machine-executable instructions, software applications (apps), circuitry, and the like. 
         [0022]    The portable device  101  also includes a first sensor  120  spaced a fixed, known distance  124  apart from a second sensor  122 , both sensors provided on a same planar surface of the portable device  101  (e.g., a bottom  106 ). The first and second sensors  120 ,  122  can be provided on any surface, such as the front, back, top, bottom, or any side edge, of the portable device  101 . The plane of the portable device  101  containing both of the first and second sensor  120 ,  122  is placed in contact with a body part proximate to a major artery to optically obtain blood pressure measurements. Examples of suitable body parts include, but are not limited to, the upper arm (containing a brachial artery), wrist (containing radial and ulnar arteries), chest (containing an ascending aorta), neck (containing a carotid artery), or leg (containing a femoral artery). 
         [0023]      FIG. 1B  shows an alternative embodiment of the system  100  comprising the portable device  101  and a detachable unit  110 . In this embodiment, the first and second sensors  120 ,  122  are located on a planar surface of the detachable unit  110  instead of the portable device  101 . (The physiological measurement obtained from the first and second sensors  120 ,  122  provided on the detachable unit  110 , nevertheless, is the same as when the sensors are provided on the portable device  101 .) The first and second sensors  120 ,  122  can be provided on any surface of the detachable unit  110  that can be placed in contact with a body part containing a major artery, such as the front, back, top, bottom, or any side edge of the detachable unit  110 . The detachable unit  110  can be detachably attached to one or more data ports of the portable device  101 , for example, a 30-pin connector or universal serial bus (USB) port (either directly or via a cable therebetween). Alternatively, the detachable unit  110  can communicate with the portable device  101  using a wireless connection, such as Bluetooth. The detachable unit  110  can comprise, but is not limited to, a detachable dongle, cover/sleeve, or an accessory of the portable device  101 . 
         [0024]      FIGS. 2A-2D  illustrates examples of the portable device  101  according to some embodiments. A portable device includes any of a variety of processor-based devices that are easily portable to a user, including, for example, a mobile telephone or smart phone  200 , a portable tablet  250 , an audio/video device  270  (such as an iPod or similar multimedia playback device), a computer  290  such as a laptop or netbook, or a dedicated portable device specific for the purpose of making measurements of the types generally described herein (such as the detachable unit  110  in  FIG. 1B ); and further includes an external component that operatively couples to another portable device, such as through a USB port, a 30-pin port or another external interface port. Such external component can be in any of a variety of form factors, including a dongle coupled directly or through a cable to the port or another configuration that mechanically engages coupled portable device (such as a case structure, for example). Where one portable device is coupled to another portable device to function together, though each is a discrete “portable device,” the combination of the two devices should also be considered to be a “portable device” for purposes of this disclosure. 
         [0025]    While many of the portable devices will be expected to include a touch screen, such is not necessarily required (see for example, computer  290  having a display  210 , but not a touch screen), except for configurations herein which depend specifically on receiving inputs through such a touch screen, as will be apparent from the discussion to follow; though most embodiments will include some form of display though which to communicate with a user. Each of the portable devices includes a controller assembly  104  including one or more processors, which will provide the functionality of the device. Each portable device may also include additional controls or other components, such as: a power button, a menu button, a home button, a volume button, a camera, a light flash source for the camera, and/or other components to operate or interface with the device. In  FIG. 2 , the example touch screens  102  and controller assemblies  104  have been numbered similarly, though as will be readily apparent to those skilled in the art, such numbering is not intended to suggest that such structures will be identical to one another, but merely that the identified elements generally correspond to one another. 
         [0026]      FIG. 3  illustrates the portable device  101  in contact with a body part of a user  302  to obtain a physiological measurement (e.g., blood pressure) relating to the user  302  according to some embodiments. The sensor set is shown exaggerated in  FIG. 3A  for ease of illustration. The bottom  106  plane of the portable device  101  is pressed against (e.g., is in pressure contact with) a wrist (or near the wrist or lower arm near the wrist) of the user  302 . In this particular example, the skin of the wrist (or near the wrist) that is near the user&#39;s  302  thumb—as opposed to the inner wrist or the side of the wrist closest to the pinky finger—is contacted by the portable device  101  in order to measure the blood flow at a radial artery  304 . The other artery located at the wrist is an ulnar artery  306 . It is understood that a variety of body parts of the user  302  can similarly be contacted to obtain the physiological measurement. 
         [0027]    Each of the first and second sensors  120 ,  122  comprises an optical type of sensor, and in particular, a reflective type photoplethysmography (PPG) sensor. Each of the first and second sensors  120 ,  122  includes a light source (e.g., a light emitting diode (LED)) and a photo detector. In each of the first and second sensors  120 ,  122 , the light source and the photo detector are positioned relative to each other such that the portion of the light emitted by the light source that is reflected back by the body part can be captured by the photo detector. 
         [0028]    In one embodiment, the wavelength of the light source of the first sensor  120  is different from the wavelength of the light source of the second sensor  120 . For example, one of the first and second sensors  120 ,  122  can operate at about 630 nanometers (nm) and the other sensor can operate at about 820 nm. In another embodiment, both of the first and second sensors  120 ,  122  can operate at the same wavelength, such as about 940 nm. In either case, the wavelength(s) are selected to be within a range of approximately 600 to 900 nm. Skin is (sufficiently) transparent to and blood (sufficiently) absorbs light that is in the range of approximately 600 to 900 nm. 
         [0029]    The remaining light beam characteristics are the same for the first and second sensors  120 ,  122 . Each of a first light beam  320  for the first sensor  120  and a second light beam  322  for the second sensor  122  is configured to impinge the blood flowing in the radial artery  304  with minimal or no interference from each other. Each of the first and second light beams  320 ,  322  comprises a collimated or converging beam (with focal point within the radial artery  304 ). One or more lenses, collimator, or other optics can be provided at the output of the light source to achieve a desired beam width and/or minimize one beam crossing over into the detection area of the other sensor. The power requirement of each of the first and second sensors  120 ,  122  is low, in the order of a few milliWatts (mW). 
         [0030]    The distance  124  is a fixed, known distance selected based on a number of factors. The distance  124  is configured to be small enough so that when the side of the portable device  101  with the first and second sensors  120 ,  122  contacts the skin, both sensors likely experience the same or nearly the same degree of contact pressure and coupling with the skin and the radial artery  304 . Generally the smaller the distance, the better the possibility of achieving similar contact pressure and coupling for both sensors. The distance  124  is also configured to be not too small so as to cause overlap between the first and second light beams  320 ,  322 . The beam width of each of the first and second light beams  320 ,  322  is configured to be a small percentage of the distance  124 , such as 5%. Generally the greater the distance  124  relative to the beam width, less care can be taken regarding the beam profiles of the first and second light beams  320 ,  322 . As an example, the distance  124  can be 10-25 mm. 
         [0031]    By fixing the locations of the first and second sensors  120 ,  122  relative to each other (and by extension the distance  124  therebetween), the uncertainty of the distance traveled by the blood pulse between the two sensors common in traditional pulse oximetry is automatically eliminated. Knowing the exact distance aids in accuracy of the blood pressure measurement. Moreover, having a relatively small distance also facilitates similar contact pressure between the sensor and the skin for both sensors also facilitates accuracy of the blood pressure measurement. 
         [0032]    Accordingly, as discussed in detail below, each of the first and second sensors  120 ,  122  is configured to measure the blood pulses arriving at the respective portions of the radial artery  304  as a function of time. A given blood pulse arrives first at the portion of the radial artery  304  irradiated by the first sensor  120  (because this portion of the radial artery  304  is closer to the user&#39;s  302  heart), and then travels to the portion of the radial artery  304  irradiated by the second sensor  122 . In other words, there is a time delay between the given blood pulse arriving at each of the first and second sensors  120 ,  122 . This time delay or difference is referred to as a difference in a pulse arrival time (Δ PAT) or a difference in a pulse transit time (Δ PTT). The Δ PAT is then converted into a blood pressure measurement. 
         [0033]      FIG. 4  illustrates the portable device  101  in contact with the user  302  to obtain one or more physiological measurements (e.g., blood pressure, temperature, electrocardiogram (ECG), body fat content, body water content, heart beat, etc.) according to some embodiments. In  FIG. 4 , the first and second sensors  120 ,  122  (separated by the distance  124 ), a first electrode  400 , a third electrode  420 , and a fourth electrode  422  are provided on a same planar surface of the portable device  101  (e.g., bottom  106 ). A second electrode  402  and a temperature sensor  410  are provided on another same planar surface of the portable device  101  (e.g., a side edge  430 ). 
         [0034]    Each of the first and second sensors  120 ,  122 ; first, second, third, and fourth electrodes  400 ,  402 ,  420 ,  422 ; and temperature sensor  410  can be located on any surface, such as the front, back, top, bottom, or any side edge, of the portable device  101 . All of the first and second sensors  120 ,  122 ; first, second, third, and fourth electrodes  400 ,  402 ,  420 ,  422 ; and temperature sensor  410  can be located on the same surface of the portable device  101  relative to each other, except that the first and second electrodes  400 ,  402  are located relative to each other so as to respectively contact opposite sides of the user&#39;s  302  body (e.g., left and right sides of the user&#39;s  302  body such as the left and right extremities) and the third and fourth electrodes  420 ,  422  are positioned (on the same planar surface of the portable device  101 ) to both contact the same side of the user&#39;s  302  body. The temperature sensor  410  is provided, for example, on the side edge  430  with the second electrode  402  because of space constraints on the bottom  106 . The location of and/or the distance between each of the sensors/electrodes relative to each other on a given planar surface (with the exception of the first and second sensors  120 ,  122 ) is not limited to that shown in  FIG. 4 . 
         [0035]    The bottom  106  of the portable device  101  is placed in contact with the skin of the wrist (or near the wrist or lower arm near the wrist) proximate to the radial artery  304  (similar to the contact in  FIG. 3 ). All of the first and second sensors  120 ,  122  and first, third, and fourth electrodes  400 ,  420 ,  422  provided on the bottom  106  are thus in contact with the user&#39;s  302  skin and proximate to the radial artery  304  of a left arm  450  of the user  302 . The portable device  101  is held against the wrist area by a right hand  452  of the user  302 . The natural holding/gripping motion of the portable device  101  causes portions of the right hand  452  to make contact with the second electrode  402  and temperature sensor  410  located on the side  420 . Note that one contact area of the user&#39;s  302  body (e.g., left arm  452 ) is across the torso of the other contact area of the user&#39;s  302  body (e.g., right hand  452 ), the relevance of which is explained below. 
         [0036]    The first, second, third, and fourth electrodes  400 ,  402 ,  420 ,  422  (also referred to as sensors, conductors, conductive electrodes, contact locations, contact regions, contact areas, etc.) comprises a conductive material such as, but not limited to, a metallic material, conductive hydrogel, silicon, conductive yarns including silver coated nylon, stainless steel yarn, silver coated copper filaments, silver/silver chloride, and the like. The temperature sensor  410  can comprise a thermocouple, thermopile, or resistance temperature detector (RTD) type of sensor. The first and second electrodes  400 ,  402  are configured to obtain ECG, heart rate, body water content, and/or body fat content measurements. The temperature sensor  410  is configured to obtain a (skin surface) temperature measurement, a type of body temperature measurement. The third and fourth electrodes  420 ,  422  are configured to obtain a galvanic skin response measurement. 
         [0037]    Although the system  100  of  FIG. 4  comprises the portable device  101  including various types of sensors/electrodes, it is understood that one or more of these sensors/electrodes can be located on the detachable unit  110  and one or both of the portable device  101  and the detachable unit  110  may be used to obtain the physiological parameters corresponding to the physiological measurements. Moreover, less than four sets of sensors/electrodes may be included in the portable device  101  and/or detachable unit  110 , in any combination with each other. 
         [0038]      FIGS. 5A-5C  illustrates an example flow diagram  500  for obtaining physiological measurements using the system  100  according to some embodiments.  FIG. 6  illustrates an example block diagram showing modules configured to facilitate the process of flow diagram  500  according to some embodiments. The modules shown in  FIG. 6  are included in the controller assembly  104  of the portable device  101 . The modules of  FIG. 6  comprise conceptual modules representing instructions encoded in a computer readable storage device. When the information encoded in the computer readable storage device are executed by the controller assembly  104 , computer system or processor, it causes one or more processors, computers, computing devices, or machines to perform certain tasks as described herein. Both the computer readable storage device and the processing hardware/firmware to execute the encoded instructions stored in the storage device are components of the portable device  101 . Although the modules shown in  FIG. 6  are shown as distinct modules, it should be understood that they may be implemented as fewer or more modules than illustrated. It should also be understood that any of the modules may communicate with one or more components external to the portable device  101  via a wired or wireless connection, such as the detachable unit  110 .  FIGS. 5A-5C  will be described in conjunction with  FIG. 6 . 
         [0039]    At a block  502 , a calibration module  602  is configured to perform calibration with respect to the user  302  in preparation of obtaining usable physiological measurement(s). The need to perform calibration depends on the type of physiological measurement to be obtained. In one embodiment, calibration is performed for measurements that use blood pulse transit time or blood pulse velocity that is converted into central aortic blood pressure measurements. An information display module  604  may be configured to cause the portable device  101  to display calibration instructions on the touch sensor panel  102 . For example, the calibration instructions may instruct the user  302  to use a brachial cuff to obtain one or more blood pressure measurements while simultaneously having the first and second sensors  120 ,  122  obtain physiological parameters (e.g., blood pulse waveforms as a function of time). The brachial cuff blood pressure measurement(s) may be automatically transmitted to the portable device  101 , or the portable device  101  may provide input fields on the touch sensor panel  102  for the user  302  to manually input the blood pressure obtained from the brachial cuff. 
         [0040]    At or approximately the same time that the brachial cuff measurement(s) is being made, the portable device  101  (or the detachable unit  110 , as appropriate) is configured to obtain one or more blood pressure measurements using the first and second sensors  120 ,  122 . Using both sets of blood pressure measurements, the calibration module  502  is configured to determine one or more scaling factor to properly calibrate the conversion of the blood pulse transit time (or blood pulse velocity) obtained using the first and second sensors  120 ,  122  from the user  302  to a central (e.g., aortic) blood pressure measurement. The conversion function between the blood pulse transit time (or blood pulse velocity) and desired blood pressure measurement is known, as discussed in detail below, but the scaling up or down of the conversion function for each particular user is obtained from the calibration process. 
         [0041]    In another embodiment, calibration is performed for physiological measurements using skin impedance detection (e.g., body fat content measurement). The information display module  604  may be configured to cause display of calibration instructions relating to skin impedance measurements on the touch sensor panel  102 . Calibration instructions may instruct the user  302  to enter his/her height, weight, age, and gender prior to measuring the user&#39;s  302  skin impedance. The calibration module  602  is configured to use the user-specific information to calibrate the user&#39;s skin impedance measurement to report an accurate body fat content information to the user  302 . 
         [0042]    The type of calibration(s) may be automatically determined based on the types of sensor(s) provided on the portable device  101  and/or detachable unit  110 . Alternatively, the calibration(s) are performed based on the types of physiological measurements specified by the user  302 . One or more calibration may be performed at the block  502  for a particular user. Calibration may be performed each time before a physiological measurement is made, it may be performed periodically (e.g., once a month), or it may be a one-time event for a given user. The calibration schedule for one type of physiological measurement may be the same or different from another type of physiological measurement. 
         [0043]    In still another embodiment, the calibration block  302  may be omitted. For example, in the case of electrocardiogram (ECG) measurements, no calibration with respect to particular individuals is required to calculate an ECG measurement from electro-physiological parameters detected from individuals. As another example, no calibration may be required for providing body temperature measurements to users. As still another example, if it is assumed that peripheral blood pressure (e.g., radial blood pressure) is the same or sufficiently the same as central aortic blood pressure or peripheral blood pressure is the desired physiological measurement, then calibration for determining blood pressure may be omitted. 
         [0044]    Next at a block  504 , the information display module  604  is configured to cause display of physiological parameter(s) capture instructions on the touch sensor panel  102 . The physiological parameters capture instructions comprise one or more user interface screens providing instructions, tips, selection options, and other information to the user  302  to facilitate proper detection of physiological parameter(s) corresponding to desired physiological measurement(s). 
         [0045]    In one embodiment, a user interface screen  702  ( FIG. 7A ) at the portable device  101  provides measurement selection options to the user  302 . The user  302  can select one or more physiological measurements such as, but not limited to, blood pressure, ECG, heart beat, body temperature, galvanic skin response/stress level, body water content, body fat content, etc. Next at a user interface screen  704  ( FIG. 7B ), instructions on how to hold and place the portable device  101  with respect to the user  302  is provided. A user interface screen  706  ( FIG. 7C ) provides additional instructions to achieve proper positioning and contact between the sensors/electrodes included in the portable device  101  and the user  302 . The user interface screen  706  may be provided in response to an indication that one or more of the sensors/electrodes (corresponding to those measurements selected by the user  302  in the user interface screen  702 ) is not detecting physiological parameters or the detected signals are incorrect (out of range, too low signal, etc.). As an example, if contact with the first and/or second sensors  120 ,  122  is improper, a user interface screen  708  can be provided to the user  302  to interactively aid in proper positioning of the first and second sensors  120 ,  122  to a particular portion of the user&#39;s  302  body to obtain an accurate blood pressure measurement. 
         [0046]    The amount of skin-to-sensor contact pressure with which each of the first and second sensors  120 ,  122  contacts the user  302  is proportional to the amplitude of the respective blood pulse waveforms detected by the first and second sensors  120 ,  122 . The greater the contact pressure for a given sensor, the greater the amplitude of that sensor&#39;s detected blood pulse waveform. The distance  124  between the first and second sensors  120 ,  122  is selected to be small enough such that both sensors are likely to experience similar contact pressures when the bottom  106  containing both sensors is placed in contact with the user  302 . However, in the case that sufficiently different contact pressure is detected between the two sensors (via differences in their respective blood pulse waveform amplitudes), then a real-time graphic (e.g., a pair of bars) indicative of the amount of contact pressure for each of the first and second sensors  120 ,  122  can be provided to aid the user  302  to correct positioning of the portable device  101 . The real-time graphic can also be used to guide the user  302  to find the desired peripheral artery. For example, if the user  302  initially places the portable device  101  against a portion of the left lower arm that is not proximate to the radial artery  304  or the ulnar artery  306 , then the first and second sensors  120 ,  122  would detect no blood pulses and the real-time graphic can correspondingly register such low or no signal state. The portable device  101  can guide the user  302  to move the portable device  101  until appropriate blood pulses are detected. 
         [0047]    In another embodiment, the user interface screen  702  can be omitted since the portable device  101  is configured to automatically provide the physiological measurements based on whatever sets of sensors/electrodes are provided on the portable device  101 . In still another embodiment, the portable device  101  can be configured to perform a check on the adequacy of the signals detected by the appropriate sensors/electrodes included in the portable device  101 , but only provide the user interface screen  708  (or other similar user interface screens) if inadequate signals are detected. 
         [0048]    Next at a block  506 , a physiological parameters capture module  606  is configured to control the sensors/electrodes provided on the portable device  101  corresponding to the physiological measurements designated (implicitly or explicitly) in the block  504 , to cause those sensors/electrodes to obtain physiological parameter(s) from the user  302 . The physiological parameters capture module  606  provides the necessary input, timing, and/or power signals to these sensors/electrodes for periodic or continuous data capture. 
         [0049]      FIG. 5B  illustrates example sub-blocks  506   a - e  of the block  506  according to some embodiments. At a sub-block  506   a , the physiological parameters capture module  606  is configured to obtain a first blood volume change parameter from the first sensor  120  and a second blood volume change parameter from the second sensor  122 . When the first light beam  320  emitted from the first sensor  120  enters the user&#39;s  302  body, it is transmitted through the skin (and other structures between the surface of the user&#39;s  302  body to the radial artery  304 ) to be absorbed by the blood arriving at a first particular portion of the radial artery  304 . Some of the first light beam  320 , however, is not absorbed but is instead reflected by one or more physiological structures below the surface of the skin back toward the first sensor  120 . The reflected portion of the first light beam  320  is detected by the photo detector included in the first sensor  120 . The changing blood volume at the first particular portion of the radial artery  304  as a function of time is caused by the blood pulses arriving at that particular portion of the radial artery  304  as a function of time. The change in the blood volume as a function of time causes the reflected portion of the first light beam  320  to correspondingly change over time, the resulting reflected light resembling a train of light pulses. The first sensor  120  thus detects changes in the reflected light over time corresponding to a first blood pulse waveform  800 , as shown in  FIG. 8 . The amplitude or magnitude of the first blood pulse waveform  800  is proportional to the contact pressure between the first sensor  120  and the user&#39;s  302  body. 
         [0050]    A second blood pulse waveform  802  is similarly obtained from the second sensor  122  based on the reflected portion of the second light beam  322  at a second particular portion of the radial artery  304 , the peaks of the second blood pulse waveform  802  shifted in time (by an amount Δ PAT  804 ) relative to the peaks of the first blood pulse waveform  800 . This time difference between the two waveforms exists because a given blood pulse arrives first at the first particular portion of the radial artery  304  corresponding to the first sensor  120  before it arrives at the second particular portion of the radial artery  304  corresponding to the second sensor  122 . 
         [0051]    At a sub-block  506   b , the physiological parameters capture module  606  is configured to simultaneously obtain a first electrical parameter from the first electrode  400  and a second electrical parameter from the second electrode  402 . An electrical circuit is completed by the first electrode  400 , the second electrode  402 , and the user  302 . The first electrode  400  makes electrical contact with a portion of the user&#39;s left arm  450  while the second electrode  402  makes electrical contact with a portion of the user&#39;s right arm (e.g., right hand  452 ), as shown in  FIG. 4 . The first and second electrodes  400 ,  402  obtain resistive measurements from one side of the user&#39;s body to the other side, which are converted into ECG and/or heart beat measurements. 
         [0052]    At a sub-block  506   c , the physiological parameters capture module  606  is configured to obtain a first temperature parameter from the temperature sensor  410 . The first temperature parameter comprises a skin surface temperature associated with the user  302 . Skin (surface) temperature relates, among other things, to the user&#39;s stress level. Typically in a stressful situation, a person&#39;s peripheral circulation (including skin circulation) decreases, which causes the skin temperature to decrease. 
         [0053]    At a sub-block  506   d , the physiological parameters capture module  606  is configured to obtain both a first galvanic skin response parameter from the third electrode  420  and a second galvanic skin response parameter from the fourth electrode  422 . An electrical circuit is completed by the third electrode  420 , the fourth electrode  422 , and the user  302 . Both of the third and fourth electrodes  420 ,  422  are configured to make electrical contact with the user&#39;s left arm  450  (e.g., on the same side of the user&#39;s body), as shown in  FIG. 4 . The third and fourth electrodes  420 ,  422  obtain (skin) impedance measurements corresponding to the moisture level of the user&#39;s skin at the contact areas, the moisture level indicative of a galvanic skin response. Galvanic skin response, in turn, is an indication of a person&#39;s stress level (or the opposite of stress, relaxation level). 
         [0054]    At a sub-block  506   e , the physiological parameters capture module  606  is configured to obtain a first impedance parameter from the first electrode  400  and a second impedance parameter from the second electrode  402 . The first and second electrodes  400 ,  402  operate on the circuit-completion concept to obtain impedance measurements between one side of the user&#39;s body to the other side. Such measurements are converted into body water content measurements and/or body fat content measurements. 
         [0055]    Returning to  FIG. 5A , once one or more of the physiological parameter(s) have been obtained, if such parameters were captured from sensors/electrodes located on the detachable unit  110 , these parameters are communicated from the detachable unit  110  to the portable device  101  (block  508 ). The physiological parameters can be provided to the portable device  101  via a wire connection (e.g., data ports such as the 30-pin connector or USB port) or wireless connection (e.g., Bluetooth). Depending on the frequency of the physiological parameters from a given set of sensors/electrodes and/or the number of types of physiological parameters from different set of sensors/electrodes, physiological parameters from a given set of sensors/electrodes can be singularly provided to portable device  101  (e.g., in real- or near real-time) or it can be combined with physiological parameters from one or more of other sets of sensors/electrodes for a combined transmission to the portable device  101 . A communication module  608  is configured to coordinate communication of obtained physiological parameters from the detachable unit  110  to the portable device  101 . 
         [0056]    Next at a block  510 , a physiological measurement module  610  is configured to control signal processing and other pre-processing functions to ready the obtained physiological parameters suitable for conversion to appropriate physiological measurements. Depending on the state of the physiological parameters received at the portable device  101 , one or more of the following processing functions may occur: analog-to-digital (A/D) conversion, demultiplexing, amplification, one or more filtering (each filter configured to remove a particular type of undesirable signal component such as noise), other pre-conversion processing, and the like. The processing can be performed by hardware, firmware, and/or software. The type and extent of signal processing can vary depending on the type of physiological parameters. For example, physiological parameters obtained from the first and second sensors  120 ,  122  may undergo digitization, filtering, and other signal conditioning. Whereas physiological parameters obtained from the first and second electrodes  400 ,  402  may require little signal processing, e.g., merely A/D conversion. Additionally, in some embodiments, some or all of the signal processing may be performed by the sensors/electrodes themselves. For example, if the raw output of a certain sensor requires signal processing unique to that sensor (e.g., unique circuitry) and/or the sensor packaging can easily include signal processing functionalities, the raw output of a sensor may be processed by the sensor itself. An advantage of this approach is that the portable device  101  requires less circuitry, for example, that is dedicated for one function especially if the sensor set is located at the detachable unit  110 . Another advantage is that the portable device  101  may receive uniform physiological parameters from a variety of sensor sets. 
         [0057]    Next at a block  512 , the physiological measurement module  610  is configured to determine appropriate physiological measurements from the (conditioned) physiological parameters. Block  512  comprises additional processing to translate physiological parameters into physiological measurements that are well-understood by the user  302 .  FIG. 5C  illustrates example sub-blocks  512   a - e  of the block  512  according to some embodiments. Like suffix in sub-blocks  512   a - e  and sub-blocks  506   a - e  correspond with each other (e.g., sub-block  512   a  corresponds to sub-block  506   a ). Each of the sub-blocks  512   a - e  comprise use of a particular algorithmic method or functional relationship(s) established between given physiological parameters and physiological measurements to convert or translate those physiological parameters to appropriate physiological measurements. 
         [0058]    At the sub-block  512   a , the physiological measurement module  610  is configured to determine a central (aortic) blood pressure measurement based on the first and second blood volume change parameters obtained from the first and second sensors  120 ,  122 . The first and second blood volume change parameters comprise the first and second blood pulse waveforms  800 ,  802 , respectively (see  FIG. 8 ). As shown in  FIG. 8 , Δ PAT  804  is derived from the first and second blood pulse waveforms  800 ,  802 . The distance between the first and second sensors  120 ,  122  is known—distance  124 . Thus, a pulse wave velocity (PWV) is the difference in the distance between the first and second sensors  120 ,  122  divided by the difference in the pulse transit time between the first and second sensors  120 ,  122 : PWV=distance  124 /Δ PAT  804 . The PWV relates to the central aortic blood pressure (also referred to as the central arterial blood pressure (CABP)): PWV=f(CABP). 
         [0059]    In one embodiment, the translation or conversion of PWV to CABP can be performed using known algorithmic methods that specify the quantitative relationship or correlation between PWV and CABP. As an example, reference is made to http://en.wikipedia.org/wiki/Pulse_wave_velocity that provides example algorithmic methods for the functional relationship between PWV and CABP. The article includes the following equation showing the relationship between PWV and P (arterial blood pressure CABP): 
         [0000]    
       
         
           
             
               PWV 
               = 
               
                 
                   
                     
                        
                       P 
                     
                     · 
                     V 
                   
                   
                     ρ 
                     · 
                     
                        
                       V 
                     
                   
                 
               
             
             , 
           
         
       
     
         [0060]    where P is the density of blood and V is the blood volume. The article also provides an alternative expression of PWV as a function of P (arterial blood pressure CABP): 
         [0000]        PWV=P   i /(ν i ·ρ)= Z   c /ρ,
 
         [0000]    where ν is the blood flow velocity (in the absence of wave reflection) and ρ is the density of blood. 
         [0061]    In another embodiment, the functional relationship between Δ PAT (or PWV) and CABP can be empirically derived. For example, a human study can be conducted in which three simultaneous measurements are obtained from each subject: (1) Δ PAT via the first and second sensors  120 ,  122 , (2) a CABP by actually measuring the blood pressure at the subject&#39;s aorta during cardiac catheterization (adding a pressure sensor to a catheter that is snaked through the subject&#39;s arteries, including positioning the pressure sensor on the catheter in the subject&#39;s aortic arch to directly measure CABP), and (3) a brachial blood pressure (brachial BP) using a brachial cuff. A relatively small number of subjects are sufficient, such as about 50 subjects. The three simultaneous measurements for a given subject provide an empirical relationship between Δ PAT, CABP, and brachial BP. The empirical relationships from all the subjects are averaged, resulting in an empirically-derived functional relationship between Δ PAT and CABP. Alternatively, two simultaneous measurements (Δ PAT via the first and second sensors  120 ,  122 , and CAPB using cardiac catheterization) are sufficient to determine the correlation between Δ PAT and CABP. 
         [0062]    The empirically-derived relationship between Δ PAT, CABP, and brachial BP can also be used to calibrate each particular user from which Δ PAT will be obtained. In particular, as discussed above with respect to block  502 , a Δ PAT measurement and a brachial BP measurement are simultaneously obtained from a given user during calibration. Using these two known measurements associated with the given user in comparison with the derived functional relationship between Δ PAT and brachial BP, a scaling factor applicable to the particular user can be determined. The scaling factor typically adjusts the CABP up or down in value. Subsequently, when a Δ PAT measurement is actually obtained from that user using the first and second sensors  120 ,  122 , the portable device  101  can convert the measured Δ PAT to a provisional brachial BP using the derived functional relationship between Δ PAT and brachial BP and additionally apply the (calibration) scaling factor applicable to that user to the provisional brachial BP to determine a final brachial BP. The final brachial BP, in turn, is converted into the CABP using the derived functional relationship between brachial BP and CABP. 
         [0063]    In still another embodiment, the physiological measurement module  610  is configured to determine a peripheral blood pressure measurement using the calculated PWV. When the first and second sensors  120 ,  122  contact the left arm  450  proximate the radial artery  304 , the physiological measurement module  610  is configured to determine a radial blood pressure measurement. It may be assumed that the peripheral blood pressure and central blood pressure are sufficiently the same for a given user so that conversion to a central blood pressure is unnecessary. 
         [0064]    At the sub-block  512   b , the physiological measurement module  610  is configured to determine an ECG and/or heart beat measurement based on the first electrical parameter from the first electrode  400  and the second electrical parameter from the second electrode  402 . In one embodiment, the ECG measurements comprise Lead 1 ECG signal measurements. The detected Lead 1 ECG signals may undergo little or no processing/conversion to form the final ECG measurements. In another embodiment, the Lead 1 ECG signals may be converted into a heart rate measurement (also referred to as a pulse measurement) using known algorithmic methods. An example algorithmic method is discussed at http://en.wikipedia.org/wiki/Electrocardiography. An example algorithmic method is discussed at http://courses.kcumb.edu/physio/ecg%20primer/normecgcalcs.htm#The %20R-R %20interval/, which discusses identifying a particular point on consecutive signals of the ECG waveform and using the known time difference between such particular points on the consecutive signals to obtain the number of heart beats per unit of time. 
         [0065]    At the sub-block  512   c , the physiological measurement module  610  is configured to determine a skin surface temperature measurement or stress/relaxation level indication based on the first temperature parameter obtained from the temperature sensor  410 . In one embodiment, the first temperature parameter undergoes little or no processing/conversion to output a skin surface temperature measurement. As an example, the skin temperature may merely be a conversion of the first temperature parameter in accordance with a conversion table or equation. In another embodiment, a known or empirically-derived correlation between the skin surface temperature and stress level can be used to provide a stress/relaxation level indication based on the first temperature parameter (or a series of temperature readings). An example discussion of the relationship is provided in Lawrence Baker et al., “The relationship under stress between changes in skin temperature, electrical skin resistance, and pulse rate,”  Journal of Experimental Psychology , Vol. 48(5), 361-366 (November 1954). The Baker article discusses a study in which subjects were subjected to stress stimuli and corresponding quantitative changes to skin temperature from a rest/baseline state were recorded. The study revealed that there was significant increase in skin temperature under stress stimulation. 
         [0066]    At the sub-block  512   d , the physiological measurement module  610  is configured to determine a galvanic skin response measurement or stress/relaxation level indication based on the first and second galvanic skin response parameters obtained from the third and fourth electrodes  420 ,  422 . The first and second galvanic skin response parameters comprise a measure of the moisture level of the user&#39;s skin at the contact areas, and galvanic skin response is indicative of stress/relaxation level. Known or empirically-derived correlations between the skin moisture level, galvanic skin response, and stress/relaxation levels can be used to translate the first and second galvanic skin response parameters into the galvanic skin response measurement and/or stress/relaxation level indication. An example discussion of the relationship is provided in: Marjorie K. Toomin et al., “GSR biofeedback in psychotherapy: Some clinical observations,”  Psychotherapy: Theory, Research  &amp;  Practice , Vol. 12(1), 33-38 (Spring 1975). The Toomin article describes a study in which the galvanic skin response of subjects was manipulated using attention, excitation, or emotional provoking stimuli. The study observed that that the amount of reaction (change in galvanic skin response relative to a baseline) to a given stimuli across different subjects was variable—subjects could be classifies as over-reactors, under-reactors, or variable-reactors. This suggests that a series of galvanic skin response measurements may be made to determine a baseline for the user before indications of stress/relaxation levels start being provided to the user. For instance, assuming that stress stimuli in the real world are infrequent events, if a user has frequent significant changes in galvanic skin response, this may indicate that the user is a variable-reactor or over-reactor such that measurements of high (or non-insignificant) change after the baseline measurement period may not necessarily indicate stress. Conversely, a user who shows little change over time (e.g., an under-reactor) that registers a high (or non-insignificant) change after the baseline measurement period may actually be indicative of stress. 
         [0067]    At the sub-block  512   e , the physiological measurement module  610  is configured to determine a body fat content measurement and/or a body water content measurement based on the first and second impedance parameters obtained from the first and second electrodes  400 ,  402 . Use of body impedance information to generate physiological measurement comprises bioelectrical impedance analysis (BIA) measurements. For at least the body fat content measurement, the first and second impedance parameters may be converted to corresponding body fat content using known algorithmic methods, such algorithmic method taking into account the user&#39;s weight, height, gender, and/or age (previously provided by the user  302  at calibration block  502 ). In other embodiments, known algorithmic methods may be used for each of body fat content and body water content determination without calibration information. Examples of suitable algorithmic methods for body fat content determination are provided in Ursula G. Kyle et al., “Bioelectrical impedance analysis—part I: review of principles and methods,”  Clinical Nutrition , Vol. 23 (5): 1226-1243 (2004), and G. Bedogni et al., “Accuracy of an eight-point tactile-electrode impedance method in the assessment of total body water,”  European Journal of Clinical Nutrition , Vol. 56, 1143-1148 (2002) (available at http://www.nature.com/ejcn/journal/v56/n11/full/1601466a.html) for body water content determination. Tables 2 and 3 of the Kyle article provide a survey of equations reported in other articles for calculating the body fat as a function of the subject&#39;s measured resistance (which is quantitatively related to impedance), height, weight, age, gender, and/or other variables. Since these equations provide an estimation of the body fat, the amount of error inherent in each of the equations is also provided in the tables. For body water content determination, the Bedogni article provides tables and plots to empirically translate measured resistance for a certain body part (e.g., trunk, right arm, left arm, right leg, left leg) to a resistance value for the whole body and from that to the body water content value (referred to as total body water (TBW) in the article). 
         [0068]    With the determination of physiological measurement(s) completed in block  512 , the information display module  604  is configured to facilitate display of one or more user interface screens including such physiological measurement(s) on the touch sensor panel  102  (block  514 ). Associated information about the presented physiological measurement(s) may also be provided on the touch sensor panel  102  to aid the user  302  in understanding the measurements. For blood pressure measurements, for example, different range values and what each range means may be provided and for those range values indicative of health issues, recommendations may be given to see a doctor right away or the like. 
         [0069]    Last, at a block  516 , the calculated physiological measurement(s) along with related information (e.g., time and date stamp, user identifier, etc.) can be saved in the portable device  101  and/or transmitted to another device. A post-calculation module  612  is configured to facilitate saving the data to a memory included in the portable device  101 . The post-calculation module  612  is also configured to facilitate transmission of the physiological measurement(s) (and their associated information) over a network, such as over a cellular network or a WiFi network, to a remote device (e.g., another portable device, server, database, etc.). By saving and/or communicating one or more physiological measurements over time, such information may illuminate trends for useful health assessment. 
         [0070]    It is understood that one or more of blocks  502 - 516  may be performed in a different sequence than shown in  FIG. 5A . For example, block  516  may be performed prior to or simultaneously with block  514 . Sub-blocks  512   a - e  of  FIG. 5C  may be performed in any sequential order or simultaneously with each other depending on, for example, when a set of physiological parameters are received by the portable device  101  and/or the processing capacity of the portable device  101 . 
         [0071]    In this manner, a portable device alone or in combination with a detachable unit obtains one or more psychological measurements associated with a user. Unlike with traditional measurement methods, the fixed positioning and distance inherently provided by situating sensors on a rigid planar surface of the portable device (or detachable unit, as appropriate) automatically increases measurement accuracy, decreases improper sensor positioning, and the like. Moreover, the user&#39;s natural gripping motion of the portable device provides automatic additional sensor contact locations to ensure contact with body parts on each of the left and right sides of the user&#39;s body. The processing and communication capabilities of the portable device can be harnessed to provide a beginning-to-end measurement experience to the user. Physiological measurements include, but are not limited to, blood pressure measurements, ECG measurements, heart rate measurements, body temperature measurements, galvanic skin response measurements, stress level indications, body water content measurements, and/or body fat content measurements. 
         [0072]      FIG. 9  depicts a block diagram representation of an example architecture for the controller assembly  104 . Although not required, many configurations for the controller assembly  104  can include one or more microprocessors which will operate pursuant to one or more sets of instructions for causing the machine to perform any one or more of the methodologies discussed herein. 
         [0073]    An example controller assembly  900  includes a processor  902  (e.g., a central processing unit (CPU), a graphics processing unit (GPU) or both), a main memory  904  and a static memory  906 , which communicate with each other via a bus  908 . The controller assembly  900  may further include a video display unit  910  (e.g., a liquid crystal display (LCD) or a cathode ray tube (CRT)). The controller assembly  900  may also include an alphanumeric input device  912  (e.g., a keyboard, mechanical or virtual), a cursor control device  914  (e.g., a mouse or track pad), a disk drive unit  916 , a signal generation device  918  (e.g., a speaker), and a network interface device  920 . 
         [0074]    The disk drive unit  916  includes a machine-readable medium  922  on which is stored one or more sets of executable instructions (e.g., apps) embodying any one or more of the methodologies or functions described herein. In place of the disk drive unit, a solid-state storage device, such as those comprising flash memory may be utilized. The executable instructions may also reside, completely or at least partially, within the main memory  904  and/or within the processor  902  during execution thereof by the controller assembly  900 , the main memory  904  and the processor  902  also constituting machine-readable media. Alternatively, the instructions may be only temporarily stored on a machine-readable medium within controller  900 , and until such time may be received over a network  926  via the network interface device  920 . 
         [0075]    While the machine-readable medium  922  is shown in an example embodiment to be a single medium, the term “machine-readable medium” as used herein should be taken to include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated caches and servers) that store the one or more sets of instructions. The term “machine-readable medium” or “computer-readable medium” shall be taken to include any tangible non-transitory medium (which is intended to include all forms of memory, volatile and non-volatile) which is capable of storing or encoding a sequence of instructions for execution by the machine. 
         [0076]    Many additional modifications and variations may be made in the techniques and structures described and illustrated herein without departing from the spirit and the scope of the present invention. Accordingly, the present invention should be clearly understood to be limited only by the scope of the claims and equivalents thereof.