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1. (WO2013126788) SYSTEM FOR DETECTION AND PROCESSING OF ELECTRICAL BIOIMPEDANCE SIGNALS IN AN ANIMAL OR HUMAN SEGMENT
Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

SYSTEM FOR DETECTION AND PROCESSING OF ELECTRICAL

BIOIMPEDANCE SIGNALS IN AN ANIMAL OR HUMAN SEGMENT

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of U.S. Provisional Application No. 61/602,000, filed on February 22, 2012 in the United States Patent and Trademark Office.

FIELD OF THE INVENTION

[0001] The present invention relates to signal processing, more specifically to a system for detection and processing of electrical bioimpedance (EB) signals in an animal or human segment.

BACKGROUND

[0002] Bioimpedance is the response of a living organism to an externally applied alternating electric current. It is a measure of the resistance to the flow of alternating electric current through tissue. The measurement of the bioimpedance (or bioelectrical impedance) of the humans and animals has proved useful as a non-invasive method for measuring such things as blood flow (often referred to as impedance plethysmography) and body composition (known as bioelectrical impedance analysis or simply BIA). There are bioimpedance devices that are used to measure cardiac output and circulating blood volume. However, electrical conductivity can also vary as a result of breathing. The technique is used in both routine clinical medicine and research.

[0003] Figure 1 is a diagram of a prior art system 100 for the generation, detection and processing of electrical bioimpedance signals currently used. Analog circuitry 102 consists of electrical bioimpedance constant magnitude, high frequency (HF) current generation. The analog circuitry also consists of electrical bioimpedance and HF signal detection, amplification and rectification. The normal ranges of the values of segmental impedance (¾), respiratory electrical bioimpedance change (ΔΖ^ρ) and cardiovascular electrical bioimpedance change (AZCV) for thoracic applications (for noninvasive Stroke Volume and Cardiac Output measurements), for this typical system are:

Zo = 10 - 50 Ω

esp 0.1 z 0,

ΔΖον ~ 0.0033 Zo

[0004] The respiratory electrical bioimpedance variation is considered an unwanted signal (noise) for a majority of thoracic cardiac output measurement applications. Thus the signal processing and recovery of the wanted AZCV signal with a 1:30 signal-to-noise ratio (AZCV /AZresp) is a challenging digital processing task. However, the detection and processing technique of the undesired Δ -esp signals, together with the reduction of the root mean square (RMS) value of the measurement current, are described in patents 5,503,157 and 5,529,072 previously granted to the above named inventor, and are incorporated into this application by reference in their entirety.

[0005] The output of the analog circuitry 102 of a typical electrical bioimpedance device is an analog signal, where voltage is directly proportional to the segmental impedance Z and time. The analog signal consists of the sum of: (a) a total base impedance Zo, determined by body fluid content within the segment, (b) respiratory variation, caused by variation of venous blood return and air volume in the lungs in thoracic applications, and (c) cardiovascular variation, caused by variation of the blood volume and blood velocity in the segmental arterial system. The analog voltage is then converted to digital data by an analog-to-digital (A/D) converter 104 and further processed by digital processing circuitry 106 in the system.

[0006] However, to be effective, at least 15 amplitude steps, or resolution bits in the analog-to-digital converter, are needed to obtain sufficient resolution and accuracy to digitally process the peak-to-peak values of the AZCV signal. A reliable and accurate electrical bioimpedance digital processing the system would need to have a 14-bit analog-to-digital converter with a corresponding 16,384 states. An analog-to-digital converter with at least 14-bits will produce the required resolution for accurate processing of AZCV data over the entire range of patient population with a range of Zo between 0 and 65 Ω.

[0007] Although 14-bit analog-to-digital converters do exist as stand-alone parts, they are very expensive, use more power than their 10-bit counterparts and, due to their increased package size, use more printed circuit board area than 10-bit converters. Additionally, multiple 10-bit analog-to-digital converters are a standard, built-in front-end feature of most currently available microcontrollers. Therefore, current designs only utilize the standard 10-bit analog- to-digital converter (1,024 states) for electrical bioimpedance processing and compensate for the lack of available bits by (a) narrowing the Zo range to 15 - 48 Ω, and (b) accepting a lower accuracy of results of the AZCV measurement.

[0008] Therefore there is a need for a device and method that is accurate and reliable for generation, detection and analysis of cardiovascular and respiratory electrical bioimpedance signals in an animal or human segment that do not have these disadvantages.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] These and other features, aspects and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying figures where:

[0010] Figure 1 is a diagram of a prior art system for the generation, detection and processing of electrical bioimpedance signals;

[0011] Figure 2 is a graph showing total segmental impedance as a function of time;

[0012] Figure 3 is a functional diagram of a circuit for the generation, detection and processing of electrical bioimpedance signals, according to one embodiment;

[0013] Figure 4 is a flowchart diagram of a method of using the device of Figure 3 for the generation, detection or analysis of cardiovascular and respiratory electrical bioimpedance signals; and

[0014] Figure 5 is a system for the generation, detection and processing of electrical bioimpedance signals.

SUMMARY

[0015] According to one embodiment there is provided a system for generation, detection and analysis of cardiovascular and respiratory electrical bioimpedance signals in an animal or human segment. The system comprises an analog device that provides an analog signal as a voltage, where the analog signal voltage is directly proportional to the segmental impedance and time. There is also provided a device for the generation, detection and analysis of cardiovascular and respiratory electrical bioimpedance signals that is electrically connected to the analog device. Additionally, there is an external host system communicatively coupled to the device for further analyzing the electrical bioimpedance segments.

[0016] In another embodiment, the device comprises a printed circuit board. The printed circuit board comprises a constant electrical bioimpedance current source generator, an electrical bioimpedance linear calibrated amplifier, a detector, an electrocardiogram amplifier and at least one microcontroller. The microcontroller further comprises at least three analog-to-digital converters and instructions executable on the microcontroller for calculating

predetermined electrical bioimpedance formulae and algorithms. The microcontroller also comprises instructions for algorithms and code executable on the microcontroller to calculate the different segmental impedances to provide accurate results from the analysis of the bioelectrical impedance. The microcontroller has a first analog-to-digital converter and a second analog-to-digital converter that are connected to the detector, the constant electrical bioimpedance current source generator, electrical bioimpedance linear calibrated amplifier and the electrocardiogram amplifier with an RC circuit to increase the resolution of the analog-to-digital input into the microcontroller. A third analog-to-digital converter on the microcontroller digitizes an output of the ECG amplifier. Additionally, the printed circuit board comprises a transmission means communicatively coupled to the external host system, where the transmission means are standard wired transmission protocols, wireless protocols, or both wired and wireless protocols. The external host system comprises instructions executable to processes the electrical bioimpedance and ECG data received from the printed circuit board.

[0017] In another embodiment, external host system comprises instructions for algorithms and code executable on the microcontroller to calculate the different segmental impedances to provide accurate results from the analysis of the bioelectrical impedance. The external host also comprises instructions for displaying the data as digitized analog signals and calculated digital values of SI, HR, CI, Z0, EPCI, LSI, PEP and VET, where

EPCI = (dZcv/dt)max/Z0

ISI = (d2Zcv/dt2)max/Z0

[0018] In another embodiment, the host system is a patient monitor, a hemodynamic management system or both a patient monitor and a hemodynamic management system.

[0019] In one embodiment there is provided a device for the generation, detection or analysis of cardiovascular and respiratory electrical bioimpedance signals in an animal or human segment. The device comprises an input voltage from analog circuitry, where the input voltage represents a direct image of segmental impedance as a function of time, a first analog-to-digital converter located on a microcontroller; and a second analog-to-digital converter located on the microcontroller operably connected to the first analog-to-digital converter to provide an equivalent 14-bit digitalization resolution of AZCV without using a 14-bit analog-to-digital converter. The input voltage is calibrated to match an analog-to-digital converter input range for various intended applications. Additionally, in one embodiment both the first analog-to-digital converter and the second analog-to-digital converter are 10-bit analog-to-digital converters, each having a 1,024-bits of resolution with an input range 0 - Vref, where Vref is the reference voltage. The microcontroller comprises instructions executable on the

microcontroller to calculate a stroke volume, SV = K(dZ/dt)max/Zo, from the higher resolution inputs from the first and second analog-to-digital converters.

[0020] In one embodiment there is provided a method for the generation, detection and analysis of cardiovascular and respiratory electrical bioimpedance signals in an animal or human segment. The method comprises the steps of first providing the system for the generation, detection and analysis of cardiovascular and respiratory electrical bioimpedance signals. Then, identifying if a patient has a disease or condition that affects electrical bioimpedance signals. Next, measuring a quantity of the electrical bioimpedance signals. And finally, monitoring a quantity of the electrical bioimpedance signals over a period of time.

[0021] In another embodiment, the step of measuring a quantity of the electrical

bioimpedance signals further comprises the steps of first creating one or more than one baseline segmental impedance for the patient. Then, calibrating the one or more than one baseline segmental impedance to a match an analog-to-digital converter input range for one or more than one monitoring application. And finally, calculating a stroke volume, preferably, the patient is a human but can be an animal as disclosed.

[0022] In another embodiment, the step of identifying if a patient has a disease or condition that affects electrical bioimpedance signals the disease or condition is selected from the group consisting of arterial insufficiency and deep venous thrombosis. Additionally, identifying the patient comprises performing one or more than one of action selected from the group consisting of performing a physical examination, performing a non-invasive imaging examination. The non-invasive imaging examination can be selected from the group consisting of magnetic resonance imaging, computerized tomography and ultrasound. The physical examination comprises identifying one or more than one marker for a disease, a condition or both a disease and a condition that affects electrical bioimpedance signals in a limb. The system can also be used in this method to measure and monitor a quantity in a thoracic application. The quantity of the thoracic application that is measured can be anesthesiology, cardiology, critical care medicine, emergency medicine, measuring the Base Impedance (¾), Cardiac Index (CI)

[1 min/m2], Ejection Phase Contractility Index (EPCI) [sec 1], Heart Rate (HR) [beats/min], Pre-ejection Period (PEP) [sec], Inotropic State Index (IS I) [sec 2], Stroke Index (SI) [ml/beat m2] and Ventricular Ejection Time (VET) [sec].

DETAILED DESCRIPTION

[0023] The present invention overcomes the limitations of the prior art by providing a device and method that is accurate and reliable for the generation, detection and analysis of cardiovascular and respiratory electrical bioimpedance signals in an animal or human segment.

[0024] According to one embodiment of the present invention, there is provided a device for the generation, detection or analysis of cardiovascular and respiratory electrical bioimpedance signals. According to another embodiment of the present invention, there is provided a method for the generation, detection and analysis of cardiovascular and respiratory electrical bioimpedance signals. In one embodiment, the method comprises providing a device according to the present invention. According to another embodiment of the present invention, there is provided a method for treating a patient, where the patient has a disease or condition that affects electrical bioimpedance signals in the patient. In one embodiment, the method comprises providing a device according to the present invention. The device and method will now be disclosed in detail.

[0025] All dimensions specified in this disclosure are by way of example only and are not intended to be limiting. Further, the proportions shown in these Figures are not necessarily to scale. As will be understood by those with skill in the art with reference to this disclosure, the actual dimensions and proportions of any system, any device or part of a system or device disclosed in this disclosure will be determined by its intended use.

[0026] Methods and devices that implement the embodiments of the various features of the invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not to limit the scope of the invention. Reference in the specification to "one embodiment" or "an embodiment" is intended to indicate that a particular feature, structure, or characteristic

described in connection with the embodiment is included in at least an embodiment of the invention. The appearances of the phrase "in one embodiment" or "an embodiment" in various places in the specification are not necessarily all referring to the same embodiment.

[0027] Throughout the drawings, reference numbers are re-used to indicate correspondence between referenced elements. In addition, the first digit of each reference number indicates the figure where the element first appears.

[0028] As used in this disclosure, except where the context requires otherwise, the term "comprise" and variations of the term, such as "comprising", "comprises" and "comprised" are not intended to exclude other additives, components, integers or steps.

[0029] In the following description, specific details are given to provide a thorough understanding of the embodiments. However, it will be understood by one of ordinary skill in the art that the embodiments may be practiced without these specific detail. Well-known circuits, structures and techniques may not be shown in detail in order not to obscure the embodiments. For example, circuits may be shown in block diagrams in order not to obscure the embodiments in unnecessary detail.

[0030] Also, it is noted that the embodiments may be described as a process that is depicted as a flowchart, a flow diagram, a structure diagram, or a block diagram. Although a flowchart may describe the operations as a sequential process, many of the operations can be performed in parallel or concurrently. In addition, the order of the operations may be rearranged. A process is terminated when its operations are completed. A process may correspond to a method, a function, a procedure, a subroutine, a subprogram, etc. When a process corresponds to a function, its termination corresponds to a return of the function to the calling function or the main function.

[0031] Moreover, a storage may represent one or more devices for storing data, including read-only memory (ROM), random access memory (RAM), magnetic disk storage mediums, optical storage mediums, flash memory devices and/or other machine readable mediums for storing information. The term "machine readable medium" includes, but is not limited to portable or fixed storage devices, optical storage devices, wireless channels and various other mediums capable of storing, containing or carrying instruction(s) and/or data.

[0032] Furthermore, embodiments may be implemented by hardware, software, firmware, middleware, microcode, or a combination thereof. When implemented in software, firmware,

middleware or microcode, the program code or code segments to perform the necessary tasks may be stored in a machine-readable medium such as a storage medium or other storage(s). One or more than one processor may perform the necessary tasks in series, distributed, concurrently or in parallel. A code segment may represent a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or a combination of instructions, data structures, or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and/or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc., may be passed, forwarded, or transmitted through a suitable means including memory sharing, message passing, token passing, network transmission, etc.

[0033] In the following description, certain terminology is used to describe certain features of one or more embodiments of the invention.

[0034] The term "generation, detection or analysis" refers to any combination of "generation, detection and analysis."

[0035] The term "stroke volume" refers to the volume of blood pumped from one ventricle of the heart with each beat.

[0036] The term "marker" refers to measurable characteristics that reflects the severity or presence of some disease state or anything that can be used as an indicator of a particular disease state or some other physiological state of an organism.

[0037] Various embodiments provide for a system for the generation, detection and processing of electrical bioimpedance signals. One embodiment of the present invention provides a circuit for the system useful for the generation, detection and processing of electrical bioimpedance signals. In another embodiment, there is provided a method for using the system. The system, circuit and method will now be disclosed in detail.

[0038] Referring now to Figure 2, there is shown graph 200 showing total segmental impedance 202 as a function of time 204. The graph 200 shows the total segmental impedance (Z) 202 along the y axis as a function of time 204 plotted along the x axis, where total segmental impedance (Z) 202 is shown as the output of analog circuitry 302, that is, the analog voltage input to the analog-to-digital converters 304 and 310 for typical thoracic application. For illustration, the effects of postural change, respiration and cardiovascular pulsation on Z are shown. As can be seen, when a patient takes a breath 206 in a supine position, the segmental

impedance is less than a heart beat 208 in a standing position 210. Additionally, the breath 206 occurs over a longer period of time compared to the heartbeat 208. Because of these differences, it will be understood that the starting impedances Zo will be different. The supine impedance Zo 212 will be lower than the standing impedance Zo 210. The device comprises algorithms and code executable on a microcontroller to calculate the different segmental impedances to provide accurate results from the analysis of the bioelectrical impedance.

[0039] Referring now to Figure 3, there is shown a circuitry diagram of a device 300 according to the present invention, where the combined outputs of a first analog-to-digital converter 304 and a second analog-to-digital converter 310 provides the equivalent of 14-bit digitalization resolution without using a 14-bit analog-to-digital converter. Both the first analog-to-digital converter 304 and the second analog-to-digital converter 310 are 10-bit analog-to-digital converters, each having a 1,024-bits of resolution with an input range 0 - Vref where Vref is the reference voltage. For example, Vref is +2.048 V in most 3.3V analog-to-digital converters that are similar to the 10-bit analog-to-digital converters that are used in the present invention. The device 300 comprises two 10-bit analog-to-digital converters rather than one 14-bit analog-to-digital converter, but the output is equivalent to the 14-bit digitization of the AZCV.

[0040] The output voltage at the output of the analog circuitry 302 represents a direct image of segmental impedance as a function of time, is shown in Figure 2. The output voltage is calibrated as to represent a match in analog-to-digital converter input range for various intended applications. Using a thoracic application as an example the values are: Zm\a = 0 Ω => 0V and Zmax = 65Ω => +2.048V.

[0041] The device 300 is a circuit for the generation, detection and processing of electrical bioimpedance signals, according to one embodiment. In order to understand the function of the device 300, the following summary of how the electrical bioimpedance data are processed to calculate the stroke volume [ml/beat]. For the thoracic applications, the stroke volume equation

:


Where: stroke volume is the volume of blood ejected per heartbeat [ml];

.fiT is an anthropometric and ejection time-related constant [ml. sec];

is the maximum value of the first derivative of dZcv [Ω/sec] in time;

V dt J max

Zo is the Base Impedance [Ω]

[0042] As can be seen, analyzing the stroke volume, using Eq. l above, requires the accuracy provided by 14-bit resolution, or 16,384 bits, only in the pulsatile component while

the denominator, processing only the Zo with superimposed and relatively slow variation of AZresp, can be satisfied with a 10-bit resolution, or 1 ,024 bits, without affecting the total accuracy of the stoke volume calculation.

[0043] A typical microcontroller of the type used in this invention comprises at least three built-in analog-to-digital converters. As can be seen, a device utilizing two of the available 10-bit analog-to-digital converters 304 and 310, of a standard microcontroller, are used to achieve an equivalent 14-bit resolution capability of the digitally processed electrical bioimpedance data.

[0044] The output, Z, of the analog circuitry 302 is the analog input voltage to the analog-to-digital converters 304 and 310 for typical thoracic application. The effects of postural change, respiration and cardiovascular pulsation are shown in Figure 2.

[0045] The output of the analog circuitry 302 results in an equivalent 14-bit digitization of AZCV using two 10-bit analog-to-digital converters 304 and 310. Both the first analog-to-digital converter 304 and the second analog-to-digital converter 310 are 10-bit analog-to-digital converters, each having a 1 ,024-bit resolution with an input range 0 - Vref, where Vref is the reference voltage. For example, + Vref can be 2.048 V as is standard in most currently available 3.3V analog-to-digital converters.

[0046] The output voltage Z at the output of analog circuitry 302 represents a direct image of segmental impedance as a function of time. The output voltage Z is calibrated to match an analog-to-digital input range for the intended application. Using a thoracic application as an example: Z^m = 0 Ω = 0 V and Zmax = 65 Ω = +2.048V.

[0047] The first analog-to-digital converter 304 is used to measure only the mean value of Zo, which is then utilized in the digital calculation of stroke volume as the value in the denominator in Eq. l.

[0048] The same calibrated Z signal is fed from the output of analog circuitry 302 via an Rl.C element into the input of a precision operational amplifier with a gain A = 16 (= 24) The time constant of the RC element, τ = Rl .C, is chosen to transfer the leading (ejection phase) edge of the AZCV signal of every heartbeat duration 208 without any distortion. The slope of this edge determines the value of (dZ/dt)max in Eq,l. The value is determined after a subsequent digital differentiation in the digital processing circuitry. A typical value of the Rl.C time constant has to be of several heartbeat duration 208 but less than one breath duration 206, i.e., τ = Rl.C ~ 3 sec. The capacitor C completely removes the direct current (DC) component from the analog signal Z, and also significantly suppresses the magnitude of the undesirable ΔΖ^ρ signal. This occurs because the duration of one breath cycle is always greater than τ. The output of this precision operational amplifier 308 is connected to the input of the second analog-to-digital converter 310, used to digitize only the AZCV signal. However, due to the additional amplification of the AZcv signal by 16, the resulting digital data of the AZCV signal at the output of the second analog-to-digital converter 310 represent an equivalent of digitization by a 14-bit analog-to-digital converter (10 + 4 = 14). In a 10-bit analog-to-digital converter, the 1,024-bit resolution equates to 210, the amplification by 16 equates to 24.

[0049] Referring now to Figure 4, there is shown a flowchart diagram 400 of a method of using the device 300 for the generation, detection or analysis of cardiovascular and respiratory electrical bioimpedance signals. The method comprises providing a device according to the present invention.

[0050] According to another embodiment of the present invention, there is provided a method for diagnosing a patient with a disease or condition that affects electrical bioimpedance signals in the patient. The method comprises identifying a patient with a potential disease or condition 402 that affects electrical bioimpedance signals in the patient. In a preferred embodiment, the patient is a human. In a preferred embodiment, the disease or condition that affects electrical bioimpedance signals in the patient's extremity is selected from the group consisting of arterial insufficiency and deep venous thrombosis. In one embodiment, identifying the patient comprises performing one or more than one of action selected from the group consisting of performing a physical examination, performing a non-invasive imaging examination, such as, for example, magnetic resonance imaging, computerized tomography and ultrasound, and identifying one or more than one marker for the disease or condition that affects electrical bioimpedance signals in the limb. In another embodiment, identifying the patient comprises consulting patient records to determine if the patient potentially has a disease or condition that affects electrical bioimpedance signals suitable for diagnosis by the present method.

[0051] In one embodiment, the method comprises using the device to measure and monitor a quantity in thoracic applications, such as in anesthesiology, cardiology, critical care medicine and emergency medicine, or selected from the group consisting of measuring the Base

Impedance (¾), Cardiac Index (CI) [1/min/m2], Ejection Phase Contractility Index (EPCI) [sec" ]], Heart Rate (HR) [beats/min], Pre-ejection Period (PEP) [sec], Inotropic State Index (ISI) [sec 2], Stroke Index (SI) [ml/beat m2] and Ventricular Ejection Time (VET) [sec].

[0052] According to another embodiment of the present invention, there is provided a method for treating a patient, where the patient has a disease or condition that affects electrical bioimpedance signals in the patient. The method comprises providing a device according to the present invention. In one embodiment, the method comprises diagnosing the patient according to the present invention. In another embodiment, the method comprises using the device provided to monitor one or more than one attribute of the patient over time.

[0053] Referring now to Figure 5, there is shown a system 500 for the generation, detection and processing of electrical bioimpedance signals. In this embodiment, the device 500 and the method 400 are used for noninvasive measurement and monitoring of a stroke index, SI

[ml/beat m2], Heart Rate, HR [beats/min], Cardiac Index, CI [1/min/m2], Base Impedance, ¾ (Ω), Ventricular Ejection Time, VET [sec], Pre-ejection Period, PEP [sec], Ejection Phase Contractility Index, EPCI [sec 1] and Inotropy State Index, ISI [sec 2]. The system comprises an input from an analog device, a printed circuit board 502 and an external host system 518 for further analyzing the electrical bioimpedance segments. The printed circuit board 502 comprises a constant electrical bioimpedance current source generator 504, an electrical bioimpedance linear calibrated amplifier 506, a detector 508 and an electrocardiogram (ECG) amplifier 510. This device will be placed at the output of the detector (see the output of the analog circuitry 302. The first analog-to-digital converter 304 and the second analog-to-digital converter 310 are standard inputs of the microcontroller 512 that is also placed on the printed circuit board 502. The microcontroller 512 processes digitized data from the outputs of the first analog-to-digital converter 304 and the second analog-to-digital converter 310 according to instructions executable on the microcontroller for predetermined electrical bioimpedance formulae and algorithms. A third analog-to-digital converter 514 on the microcontroller 512 digitizes the output of the ECG amplifier 510. The processed electrical bioimpedance and ECG data from the microcontroller 512 are then transmitted either via a wired or wireless link to a host system 518 using a communications module 516 also attached to the printed circuit board 502. The host system 518 further processes the electrical bioimpedance and ECG data and displays the data as digitized analog signals together with the calculated digital values of SI, HR, CI, Zo, EPCI, LSI, PEP and VET. In another embodiment, the host system 518, can be a patient monitor, a hemodynamic management system, or both a patient monitor and a hemodynamic management system.

[0054] As will be understood by those with skill in the art with reference to this disclosure, the device 300 can also be used in peripheral- vascular laboratory (quantification of arterial blood flow in a limb, and determination of the extent of deep venous thrombosis) and in cardiovascular applications (monitoring Cardiac Output, determining adequacy of Oxygen Delivery and hemodynamic and oxygen transport management) among other areas that use bioimpedance.

[0055] What has been described is a new and improved system and method for a remote control for portable electronic devices that is simple operate and operable with a single hand, overcoming the limitations and disadvantages inherent in the related art.

[0056] Although the present invention has been described with a degree of particularity, it is understood that the present disclosure has been made by way of example and that other versions are possible. As various changes could be made in the above description without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be illustrative and not used in a limiting sense. The spirit and scope of the appended claims should not be limited to the description of the preferred versions contained in this disclosure.

[0057] All features disclosed in the specification, including the claims, abstracts, and drawings, and all the steps in any method or process disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. Each feature disclosed in the specification, including the claims, abstract, and drawings, can be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. [0058] Any element in a claim that does not explicitly state "means" for performing a specified function or "step" for performing a specified function should not be interpreted as a "means" or "step" clause as specified in 35 U.S.C. § 112.