Non-invasive systems and methods for monitoring physiological conditions

Abstract

Methods and systems for monitoring a physiological condition include illuminating a body tissue with at least one discrete wavelength and sensing at least two discrete wavelengths of light exiting from the body tissue, the two discrete wavelengths being determined based on a selected physiological condition. A quantitative relationship between data obtained from one wavelength of exited light and data obtained from a second wavelength of exited light, is used by a processor to determine an indication or assessment of the selected physiological condition.

Description

TITLENON-INVASIVE SYSTEMS AND METHODS FOR MONITORING PHYSIOLOGICAL CONDITIONSFIELD

[0001] The present invention relates to the field of non-invasive optical detection and monitoring of physiological conditions based on optical measurements. The physiological conditions may be related to hemoglobin and fluid balance in body tissues.BACKGROUND

[0002] The assessment and monitoring of a living body fluid balance is important for diagnosis, management and treatment of various diseases. Fluid imbalance in a living body can be caused by a variety of pathological and physiological conditions such as, trauma, surgery, cardiovascular diseases, heart failure, hormonal disturbance, kidney diseases, diarrhea, vomiting, severe blood loss, and high fever. The consequences of fluid imbalance may include, for example, reduction in circulating blood volume, lower venous return and, in profound cases, arterial hypotension, acidosis and, together with myocardial dysfunction, precipitate multi-organ failure. Thus, the main goals of fluid management in a body are to maintain normal fluid homeostasis to provide optimized and adequate perfusion pressure, circulating volume and blood oxygenation.

[0003] Pulse oximetry is a non-invasive method used to measure blood oxygenation, namely, oxygen saturation level of the blood. Pulse oximetry operates on the principle of photoplethysmography which relies on two main values: i) different absorption of light in red-infrared spectral regions for oxygenated and deoxygenated hemoglobin; and ii) different pulsation rates during blood flow for arteries and veins. Thus, a signal formed in this method provides time-varying absorption information.

[0004] Current devices proposed for the use of tissue hydration assessment are often based on electromagnetic, chemical, and acoustical properties of tissue and body fluids. One example of a current fluid management system is the Starling™ fluid management monitoring System by Baxter™ which is based on the analysis of frequency variations of an electrical signal as it traverses the thoracic cavity.

[0005] One suggested hydration monitoring method uses broadband white LED illumination and / or ambient light which is transmitted to a living subject and, based on spectral analysis of scattered light returning from the subject, components of the blood stream are measured and a measure of hydration is generated.

[0006] The current fluid monitoring techniques have variable accuracy and practicality outside of controlled environments.SUMMARY

[0007] Embodiments of the invention provide non-invasive systems and methods for monitoring physiological conditions based on assessment of intravascular and extravascular variables in living tissue, where the main intravascular variable is blood hemoglobin and the main extravascular variable is water. The evaluation of the balance between main tissue fluids, such as blood and water, in real-time, can provide an important parameter for some clinical applications, for example blood loss, anemia and tissue hydration status. Systems and methods according to embodiments of the invention are inexpensive and non-invasive and have no complications in comparison with invasive monitoring techniques.

[0008] A system for monitoring a physiological condition, according to one embodiment of the invention, includes a light source to illuminate a tissue of a body part with at least one discreet wavelength of irradiated light and a light sensor to sense at least a first discreet wavelength and a second discrete wavelength of emitted, transmitted or reflected light exiting from the body tissue. In one embodiment, the light sensor is positioned relative to the light source to allow for at least a predetermined minimal volume of tissue to be positioned between the light source and the light sensor (for example about 1 cm3). The positioning of the light sensor relative to the light source (e.g., an angle between the light sensor and light source), may be dependent on the body part. The system further includes a processor in communication with the light sensor. The processor can access a physiological conditions database and may determine, based on data obtained from the light sensor, a quantitative relationship between data obtained from the first wavelength and data obtained from the second wavelength, the first and second wavelengths being determined based on a physiological condition selected from a list of physiologicalconditions in the database. The processor may then output an indication of the physiological condition, based on the determined quantitative relationship.

[0009] Embodiments of the invention include a user interface (UI) device in communication with the processor to provide the indication of the physiological condition to a user. The indication of the physiological condition may be based on hemoglobin and fluid balance in the tissue.

[0010] The UI device enables to receive a user selection of a physiological condition, based on which selection a quantitative relationship between two specific wavelengths is determined and an indication of the selected physiological condition (e.g., the severity, progression, etc.) is determined and is presented to a user. Selection of a physiological condition by the user may also control which discreet wavelength is illuminated from the light source to irradiate the tissue.

[0011] Thus, embodiments of the invention provide systems and methods for monitoring selected physiological conditions, such as, oxygenation levels of body tissue, hydration level of the body tissue, disorders related to hemoglobin and oxygen delivery in the body and other disorders, e.g., diabetes, based on optical spectroscopy where irradiated light wavelengths and sensed light wavelengths are determined in accordance with a selected physiological condition (e.g., based on a user selection). The irradiated light wavelengths and sensed light wavelengths are tailored to provide information on the specific selected physiological condition.BRIEF DESCRIPTION OF THE FIGURES

[0012] The invention will now be described in relation to certain examples and embodiments with reference to the following illustrative figures so that it may be more fully understood. In the drawings:

[0013] Figs. 1A-D schematically illustrate systems for monitoring physiological conditions, according to embodiments of the invention;

[0014] Figs. 2A-E schematically illustrate examples of wearable systems for monitoring physiological conditions, according to embodiments of the invention;

[0015] Fig. 3 schematically illustrates a user interface device, according to embodiments of the invention;

[0016] Fig. 4 schematically illustrates a method for monitoring physiological conditions, according to embodiments of the invention; and

[0017] Figs. 5A-D demonstrate experimental data of monitoring physiological conditions, according to embodiments of the invention.DETAILED DESCRIPTION

[0018] Embodiments of the invention provide systems and methods for non-invasive assessment and monitoring of vital internal homeostasis variables such as intravascular and extravascular body fluid components. Systems and methods, according to embodiments of the invention, use optical spectroscopy to detect a change in levels of specific variables in intravascular or extravascular tissue compartment. Based on the detected change, a physiological condition of the body may be monitored.

[0019] In general, soft tissue consists of cells and blood vessels (vasculature, which typically accounts for about 5-8% of body tissue mass). Intracellular and extracellular water are the main extravascular fluid components of living tissue. Water does not absorb light in the visible (VIS) spectral region but has definite absorption bands in the infrared spectral range. The main intravascular fluid is blood, which transports red blood cells containing hemoglobin - a globular protein with embedded four heme molecules. Heme is a porphyrin (protoporphyrin IX) complexed with ferrous iron atom that reversibly binds oxygen. Oxidized hemoglobin and deoxidized hemoglobin (HbO2, dHb) are the major blood chromophores having strong specific absorption bands in the VIS and low absorption in the near infrared (NIR) spectral region. A glycated form of hemoglobin (HbAlc), which is elevated in diabetic patients, has a stronger absorption than hemoglobin in the green spectral region. These forms of hemoglobin are not fluorescent.

[0020] Additional porphyrins, such as protoporphyrin, uroporphyrin, and coproporphyrin and their derivatives, can normally be present in small amounts in human blood and differ from hemoglobin in light absorption properties. In addition, these chromophores demonstrate fluorescence under excitation in Soret band (around 405 nm). Increased levels of these porphyrins can be a sign of some disorders (e.g. porphyria, anemia, iron deficiency, lead poisoning).

[0021] A variety of physiological conditions (e.g. tissue edema, tissue dehydration, blood loss, anemia, hypoxemia, iron deficiency, diabetes and porphyria) can cause a change in an amount of tissue markers, namely, one or several blood constituents or tissue water content. For example, diabetes leads to an increase of HbAlc in red blood cells. Iron deficiency causes a decrease of hemoglobin level (anemia) and an elevated amount of Zn- protoporphyrin (ZnPP) that exhibits fluorescent properties. Blood loss (e.g., from trauma and / or bleeding) causes a decrease of hemoglobin level without an increase in ZnPP fluorescence. Cardiovascular or / and kidney diseases are often associated with peripheral tissue edema (increased amount of interstitial water) at normal hemoglobin level. Intravenous fluid infusion during patient hospitalization may cause water extravasation into the interstitial space leading to tissue edema without a change in hemoglobin parameters. Tissue dehydration may occur at insufficient water intake or during intensive physical activity while hemoglobin parameters may stay normal.

[0022] Thus, determination of a variable tissue marker which is associated with a physiological disorder (such as listed above), can be more accurate when a stable marker is used as a reference. According to embodiments of the invention, a combination of irradiating and sensing of light at predefined, typically discrete, wavelengths can indicate a balance between two main fluids such as blood and water in peripheral living body tissue.

[0023] Embodiments of the invention utilize optical spectroscopy for assessing tissue optical parameters e.g. reflectance / transmittance / scattering / fluorescence at specific discrete wavelengths in the visible / near infrared (VIS / NIR) spectral regions. In embodiments of the invention illumination elements (e.g. LEDs) and sensing elements (e.g. photodetectors (PDs)) are configured to illuminate and sense light at predetermined wavelength sets for detecting a change in tissue markers (e.g., blood constituents and / or tissue water content), a change that is associated with one or more specific physiological condition or disorder. Thus, a specific physiological condition or disorder may be monitored by checking changes in levels of specific tissue markers, by using a specific set of irradiation light (also termed illumination wavelength) and sensed light (also termed registration wavelength).

[0024] Table 1. shows examples of predefined wavelength sets for assessment of change in parameters associated with specific disorders and / or physiological conditions, according to embodiments of the invention.

[0025] Table 1

[0026] Illumination elements and sensing elements may be part of a wearable apparatus, such as a clip, patch, ring, bracelet and more, according to a specific body area and / or tissue being analyzed (e.g. lip, ear, finger, hand, leg, etc.).

[0027] Systems and methods according to embodiments of the invention, are exemplified below. In the following description, various aspects of the present invention will be described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the present invention. However, it will also be apparent to one skilled in the art that the present invention may be practiced without the specific details presented herein. Furthermore, well known features may be omitted or simplified in order not to obscure the present invention.

[0028] Unless specifically stated otherwise, as apparent from the following discussions, it is appreciated that throughout the specification discussions utilizing terms such as “analyzing”, "processing", "computing", "calculating", “comparing”, "determining", “detecting”, “identifying”, “displaying”, “producing”, “controlling”, “providing”,“receiving”, “assessing” or the like, refer to the action and / or processes of a computer or computing system, or similar electronic computing device, that manipulates and / or transforms data represented as physical, such as electronic, quantities within the computing system's registers and / or memories into other data similarly represented as physical quantities within the computing system's memories, registers or other such information storage, transmission or display devices. Unless otherwise stated, these terms refer to automatic action of a processor, independent of and without any actions of a human operator.

[0029] A system for monitoring a physiological condition (which may include an assessment of intravascular and extravascular variables in living tissue, e.g., to monitor homeostasis variables), according to one embodiment of the invention, is schematically illustrated in Fig. 1A.

[0030] The system includes a light source 105 which typically includes an illumination element such as an LED, to irradiate a body tissue with at least one (in some embodiments, at least two) discreet wavelengths and a light sensor 103 to sense light exiting the body tissue (e.g., by one or more of fluorescence, reflectance, transmittance and / or scattering). Light sensor 103 senses light in at least two discrete wavelengths (a first discrete wavelength and a second discrete wavelength) of emitted, transmitted or reflected light exiting from the body tissue. One of the discrete wavelengths is in the absorption band of a tissue marker (such as water or Hb levels), that is expected to be stable and can be used as a reference and the other discrete wavelength is in the absorption band of a tissue marker that may vary, depending on the physiological condition that is being monitored.

[0031] The discrete wavelengths being illuminated by light source 105 (also termed irradiated light) and the discrete wavelengths being sensed by light sensor 103 (also termed exited light) are determined in accordance with the specific physiological condition being monitored.

[0032] Light sensor 103 may be positioned at an angle relative to the light source 105, the angle possibly being dependent on the body part that is being irradiated. For example, a light source and light sensor may be positioned at a same angle relative to a body tissue when an elongated body part (such as a finger, arm or leg) is being monitored and may be positioned at a diagonal from each other if a rounded body part (e.g., lip or ear lobe) isbeing monitored. Typically, light source 105 and light sensor 103 are positioned at a relative position or relative angle that allows for at least a predetermined minimal volume of tissue (e.g., about 1 cm3) to be positioned between them, such that light irradiated from light source 105 travels at least a minimal distance through the issue until exiting from the tissue and being received at light sensor 103. Thus, different, body-part-dependent, relative positionings of light sources and light sensors are typically designed to allow irradiated light to travel at least a minimal distance through the body tissue before exiting the body.

[0033] The system further includes a processor 102 which is in communication with light sensor 103, to obtain data from light sensor 103, such as intensity of light or other properties of light exiting the tissue at discrete wavelengths. Processor 102 may access a physiological conditions database 108 that includes a list of physiological conditions (e.g., as detailed herein) linked to discrete wavelengths (either one or both of irradiated light wavelengths and exiting light wavelengths, e.g., as exemplified in Table 1 above). Thus, upon selection of a physiological condition, processor 102 may use the wavelengths linked to the selected physiological condition to determine, based on the data obtained from light sensor 103, a quantitative relationship between data related to the first wavelength of exited light and data related to the second wavelength of exited light. For example, the quantitative relationship may include a ratio between data related to the first wavelength and second wavelength, a linear regression between the two wavelength and / or other appropriate calculations that can be used to determine and analyze quantitative relationships between variables. Processor 102 to may then output an indication 104 of the physiological condition, based on the determined quantitative relationship. For example, data obtained from light sensor 103 may be indicative of different tissue marker (also termed variant) levels, such as total hemoglobin (THb), oxidized hemoglobin (HbCh) levels and fluid levels, in an examined body tissue. Processor 102 may calculate, based on the data received from light sensor 103, a quantitative relationship between variables of the tissue (e.g., between hemoglobin (Hb) content of the body tissue to fluid level of the body tissue) based on data related to exiting light at wavelengths in the absorption band of both variables. For each specific physiological condition, the level of one variable is expected to be stable whereas the level of the other variable may be inconsistent and changing.

[0034] Processor 102 may control operation of light sensor 103 to manage the wavelengths being sensed by the light sensor, typically, in accordance with a selected physiological condition. For example, processor 102 may control synchronization of sensor activity schedule with different wavelength illumination times or may control activation of specific sensors and / or filters, to ensure that specific discrete wavelengths are being sensed in accordance with the selected physiological condition. Processor 102 may also be in communication with light source 105 to control light source 105 and to synchronize between events of illumination from light source 105 and sensing of discrete wavelengths by light sensor 103.

[0035] As further detailed below, the analysis of the variables such as Hb and / or water is based on the spectral changes in specific wavelength regions corresponding to absorption bands of these variables. Thus, in some embodiments, an indication of a physiological condition is based on a hemoglobin and fluid balance in the tissue.

[0036] In other embodiments, an analysis of variables such as porphyrin is based on fluorescence properties of porphyrin and the indication of a physiological condition is based on fluorescent light being emitted from the tissue.

[0037] Typically, measured spectral changes may be affected by changes in pressure applied on the tissue. Thus, in some embodiments, a stable, unchanging pressure should be maintained while spectroscopy parameters are being measured.

[0038] In an embodiment, which is schematically illustrated in Fig. IB, the system also includes a pressure sensor 107 (which may include, for example, a piezoelectric sensor and / or transducer) and pump 109 (which may include, for example, a micropump and / or compressor), both which may be in communication with processor 102. Pressure sensor 107, may sense the pressure applied on the body tissue by the system or a part of the system (such as by the light sensor 103 and / or light source 105). Pressure sensor 107 may be in communication with processor 102 such that if, for example, a change in pressure is sensed at pressure sensor 107, a signal may be generated by processor 102 to control pump 109 to increase or decrease pressure in order to maintain a stable pressure on the body tissue. In some embodiments, processor 102 may generate a signal, e.g., to warn a user (such as a physician or caregiver), based on input from pressure sensor 107, so that the user may act to stabilize the pressure being applied on the tissue.

[0039] In another embodiment of the invention, which is schematically illustrated in Fig. 1C, the system also includes a user interface (UI) device 106 that is in communication with processor 102. The UI device 106 may display or otherwise present an indication of the physiological condition to a user.

[0040] UI device 106 may include a display, such as a monitor or screen, having a graphic user interface (GUI) for displaying buttons, information, instructions and / or notifications to a user (e.g., via text or other content displayed on the monitor). UI device 106 may also be designed to receive input from a user. For example, UI device 106 may include a keyboard and / or mouse and / or touch screen, to enable user input. In one embodiment, UI device 106 may be configured to receive a user selection of a specific physiological condition (e.g., from a drop-down list of conditions which may be displayed on UI device 106). For example, UI device 106 may include an inputting element, such as button 16, for a user to select the physiological condition, possibly, from a list of conditions. In another embodiment, UI device 106 may include an inputting element for a user to input one or more discrete wavelengths of irradiating light and / or wavelengths to be sensed by light sensor 103. The user selection may be used to determine which discrete wavelength will be illuminated by light source 105 and which discrete wavelengths will be sensed by light sensor 103.

[0041] Processor 102, which may be locally embedded or remote, may include, for example, one or more processing units including a central processing unit (CPU), a graphics processing unit (GPU), a digital signal processor (DSP), a field-programmable gate array (FPGA), a microprocessor, a controller, a chip, a microchip, an integrated circuit (IC), or any other suitable multi-purpose or specific processing or controlling unit.

[0042] In some embodiments, processor 102 may be in communication with a storage device such as a server (which may be connected locally or remotely, e.g., in the cloud). The storage device may store (e.g., in database 108) and allow processor 102 access to look up tables or otherwise indexed information associating variable levels and / or quantitative relationships of variable levels to specific tissues and to physiological conditions or to severity of physiological conditions and to sets of wavelengths, as described herein.

[0043] Processor 102 is typically in communication with a memory unit 112, which may store at least part of the data received from light sensor 103. Memory unit 112 may belocally embedded or remote. Memory unit 112 may include, for example, a random access memory (RAM), a dynamic RAM (DRAM), a flash memory, a volatile memory, a nonvolatile memory, a cache memory, a buffer, a short term memory unit, a long term memory unit, or other suitable memory units or storage units. In some embodiments, the memory unit 112 stores executable instructions that, when executed by processor 102, facilitate the performance of operations of processor 102, as described herein.

[0044] Light sensor 103 may include a photodetector or other light sensing chip (e.g., Charge-Coupled Device (CCD) or Complementary Metal-Oxide-Semi conductor (CMOS)) having appropriate spectral properties to sense light exiting from the body tissue. In some embodiments, light sensor 103 may be designed to sense light at specific wavelengths. For example, the light source 103 may include a suitable filter.

[0045] Light source 105 may include one or more LEDs illuminating in different wavelengths in the VIS / NIR range, such as in the 400 - 1200nm range, in specific discrete wavelengths corresponding to variables such as Hb and water absorption measured in living tissue. For example, one or more light source(s) can be designed to illuminate at around 550 nm, 600nm, 650 nm, 725nm, 800nm and / or 970 nm. In another embodiment, light source 105 includes an LED illuminating in a specific discrete wavelength band (e.g. around 405 nm) that corresponds to the absorption and excitation of porphyrins, (e.g. protoporphyrin, coproporphyrin, uroporphyrin) and their derivatives, resulting in fluorescence emission.

[0046] Components of the system may be in wired or wireless communication and may include suitable ports and / or network hubs.

[0047] Fig. ID shows an exemplary system for monitoring physiological conditions based on spectroscopy measurements of tissue in a person’s finger, according to an embodiment of the invention. The system demonstrated in Fig. ID(a) includes a light source 115 and an array of light sensors 113 embedded on a PCB (printed circuit board) strip 101 which further includes connectors and pinheads, drivers, data processing and / or data transmission interfaces to enable communication with a processor (not shown). The PCB strip 101 is located within a chassis or housing 111 which is fixed in place by bolts or screws 117. Housing 111 is designed to accept a person’s finger and fix it at a desired position so as to enable light from light source 115 to irradiate the finger at the fingertip and to enable lightsensors 113 to sense light exiting from the middle segment of the finger (as shown in Fig. ID(b)). This relative position of light source 115 and light sensors 113 enables irradiated light to travel through at least a minimal volume of finger tissue. The system further includes a cover 120 that can be placed over the system when a person’s finger is in place (as demonstrated in Fig. ID(c)) to create an environment essentially free of ambient light.

[0048] In some embodiments, the system may be wearable or may include a wearable device. In one example, which is schematically illustrated in Fig. 2A, a plurality of light sources 205 and light sensors 203 may be connected to a single flexible PCB strip 211 designed to be positioned or worn on a body part. The flexible PCB strip 211 may include an electronic board, with drivers, data processing and / or data transmission interfaces. In the embodiment illustrated in Fig. 2A an array of light sources 205 and one or more light sensors 203 are assembled on a flexible PCB strip 211 that can form a shape suitable for being placed on or being worn on a body part (such as a finger, arm or leg).

[0049] In some embodiments, a processor 202 may be located on flexible PCB strip 211.

[0050] In some embodiments, one or more light sources 205 are positioned at an angle relative to the light sensor 203 so as to allow for at least a predetermined minimal volume of tissue to be positioned between light sources 205 and light sensors 203. For example, as schematically illustrated in Figs. 2B, 2C and 2D flexible PCB strip 211 can be made into a semi-ring (in Fig. 2D) or a ring shape (in Figs. 2B and 2C) to be placed around the body part, e.g., a person’s finger 212. The ring or semi-ring shape enables a unique geometry of placement of light source(s) 205 relative to the body part (e.g., finger 212) and / or relative to light sensors 203.

[0051] In some embodiments light sources 205 and light sensors 203 are relatively positioned to enable at least a predetermined volume of body tissue (for example, at least 1 cm3of body tissue) to be located in between them, such that irradiated light can travel at least a minimal distance through the body tissue before exiting. Depending on the intensity of the light source and sensitivity of the light sensor, transmission through soft tissue can reach several centimeters, e.g., in the near infrared spectral region (~750-1000nm). Having a predetermined minimal distance between the irradiation point and the point of measuring exited light can be important for detecting the level of water in the tissue.

[0052] A pressure sensor 207 and pump 209 may be part of the flexible PCB strip 211 to make sure the PCB strip itself and / or light source 205 and / or light sensor 203 are not applying excessive or varying pressure on the finger which may distort the measurements, as discussed herein.

[0053] In another embodiment, which is schematically illustrated in Fig. 2E, one or more light source 205 and one or more light sensor 203 are attached to or are part of a single apparatus, such as, clip 201 that is configured to be fit onto a person’s lip. When worn on the lip, clip 201 is in a closed configuration bringing light source 205 to be positioned at a diagonal (illustrated by dashed line D) across from light sensor 203, thereby increasing the volume of lip tissue located between light source 205 and light sensor 203 and ensuring at least a minimal distance for irradiated light to travel through the lip tissue before exiting the tissue. A pressure sensor 207 and pump 209 may be attached to or may be part of clip 201.

[0054] In some embodiments the system may be substantially flat such that a light sensor that is placed on the tissue at a similar angle as the light source. In such a “flat” system or when the light sensor is not pressed onto the tissue and is not in direct close contact with the tissue the light received at the light sensor is typically scattered light. In other embodiments, where a light sensor is in direct close contact with the tissue (such as exemplified in Fig. 2B and 2E) the light received by the light sensor is typically transmitted light.

[0055] Fig. 3 schematically illustrates a UI device, according to an embodiment of the invention. UI device 306 (which may be part of a system for monitoring a physiological condition, e.g., via monitoring homeostasis variables) may include a display 36 to enable monitoring the measured variables in real time or substantially real time. For example, an indication of a physiological condition (or severity of condition) of a tissue or patient may be displayed to a user. The display 36 may show at least hemoglobin and fluid balance in a body tissue.

[0056] UI device 306 is typically in communication with and / or controlled by a processor (such as processor 102). For example, UI device 306 may receive from the processor an indication of a physiological condition 304 (or severity of the condition) of a tissue or patient, to be displayed on display 36.

[0057] In one embodiment, the UI device 306 includes an inputting element, such as a window or a button 32 to allow a user (e.g., a physician or caregiver) to input a specific disorder or condition, possibly to select the condition from a list of physiological conditions. The list of physiological conditions may be stored in a database accessible by the processor. As discussed herein, user input may control the determinations (e.g., calculations of quantitative relationships between variables) performed by the processor.

[0058] In another embodiment, UI device 306 may include a button 33 to allow a user to input a discrete wavelength. A list of discrete wavelengths and / or sets of irradiate and sensed wavelength may also be stored in the database accessible to the processor. Thus, user input may determine which variables will be measured.

[0059] Other buttons and / or graphics may be displayed to assist a user in operating a system for monitoring homeostasis variables, according to one embodiment of the invention.

[0060] Fig. 4 schematically illustrates a method for monitoring a physiological condition, according to embodiments of the invention. The method, which may be carried out by a processor (e.g., processor 102) includes the steps of receiving data from a light sensor (402) which is positioned relative to a body tissue to sense light emitted, transmitted or reflected from the body tissue, and calculating, from the received data a quantitative relationship between data related to a first wavelength of exited light and data related to a second wavelength of exited light (404), where one wavelength represents a reference tissue marker and the other represents a varying tissue marker. The quantitative relationship between data related to the first wavelength and data related to the second wavelength indicates a relationship between variables, such as between hemoglobin and fluid level. Based on the calculation, an assessment of a physiological condition of the tissue (or person) can be generated (406).

[0061] The data received from the light sensor is data relating to light emitted, transmitted or reflected from a body tissue. The method typically includes a prior step of irradiating the body tissue with one or more discrete wavelengths. In some embodiments the tissue is irradiated with at least two discrete wavelengths.

[0062] Experimental studies carried out by the inventors used biological phantoms, ex vivo and in vivo models to determine interrelations in scattered light spectrum between specificwavelength regions corresponding to Hb and water absorption bands. Algorithms for calculating tissue indexes for these variables were defined. Figs. 5A-D show examples of calculations that may be used to obtain a quantitative relationship between variables of a tissue.

[0063] Fig. 5A shows light of similar intensity emitted by LED light sources and which is irradiated onto body tissue (tissue of a person’s finger) at discrete wavelengths; around 600nm, 700 nm and 950 nm. Fig. 5B shows the light transmitted through the tissue, as received at light sensors of a grating-based spectrometer. Three peaks can be seen. The peak at 600nm can be used for calculation (assessment) of the amount (level) of total hemoglobin (THb) in the tissue. The peak at 700nm can be used for calculation of the amount (level) of oxidized Hb (HbO2) in the tissue and the peak at 970 nm can be used for calculation of the amount of fluid (water) in the tissue. Light at 800 nm can be used additionally or alternatively instead of 600 nm for measurement of THb level in the tissue.

[0064] In Fig. 5C an example of a quantitative relationship is plotted on a graph, generating a data line having a slope that is typical to the quantitative relationship of THb to HbCh. In Fig. 5D a relationship between the amount of water and HbCh in the tissue is plotted in a graph, generating a data line having a slope that is typical to the quantitative relationship of water to HbCh in the tissue. The typical slope or other characteristics of the quantitative relationship between variables in a tissue may be used (as in step 406 above) to generate an assessment of a physiological condition of the tissue. For example, slopes or other values that are typical to a specific tissue and specific physiological condition can be stored in association with the relevant tissue and / or physiological condition, such that a processor (e.g., processor 102) may use look up tables or otherwise indexed information in a database (e.g., database 108) or other storage, to determine a physiological condition of a tissue based on the optical measurements provided by the light sensor.

[0065] Thus, a database of typical values expected for different tissues and / or conditions can be created, according to embodiments of the invention. As such, a user may input (e.g., via UI device 106 or 306) desired physiological conditions to control the specific wavelength of light being emitted from the light source and / or control the specific wavelength of light that will be sensed by the light sensor and / or to control the specificalgorithm that will be used by the processor to calculate the quantitative relationship and determine an indication of a specific physiological condition.

[0066] Embodiments of the invention use simple and sensitive technology to provide reliable and specific data for changes (indexes) in hemoglobin and tissue water levels, e.g., during medical procedures. Embodiments of the invention provide noninvasive and real time monitoring of vital variables in critical conditions, such as, surgical intervention and management of patients suffering from cardiovascular and kidney disorders.

Claims

CLAIMS1. A system for monitoring a physiological condition, the system comprising: a light source configured to illuminate a tissue of a body part with at least one discreet wavelength of irradiated light; a light sensor to sense at least a first discreet wavelength and a second discrete wavelength of emitted, transmitted or reflected light exiting from the body tissue, the light sensor positioned relative to the light source; and a processor in communication with the light sensor, the processor to access a physiological conditions database and to determine, based on data obtained from the light sensor, a quantitative relationship between data obtained from the first wavelength and data obtained from the second wavelength, the first and second wavelengths being determined in accordance with a physiological condition selected from a list of physiological conditions in the database, the processor to output an indication of the physiological condition, based on the determined quantitative relationship.

2. The system of claim 1 wherein positioning of the light sensor relative to the light source is dependent on the body part.

3. The system of claim 1 wherein positioning of the light source relative to the light sensor allows for at least a predetermined minimal volume of tissue to be positioned between the light source and the light sensor.

4. The system of claim 3 wherein the minimal volume of tissue comprises about 1 cm3.

5. The system of claim 1 comprising a pressure sensor and a pump in communication with the processor, the pressure sensor to sense a pressure applied on the body tissue by the system or a part of the system and the processor to control the pump in accordance with the sensed pressure.

6. The system of claim 5 wherein the processor generates a signal to provide a warning based on input from the pressure sensor.

7. The system of claim 1 wherein the light source and light sensor are both connected to a single flexible strip, the strip configured to be worn on the body part.

8. The system of claim 7 wherein the strip is configurable into a ring or semi-ring.

9. The system of claim 1 wherein the body part comprises a person’s lip and wherein the light source and light sensor are both connected to a single apparatus configured to beattached onto the lip such that at least a minimal volume of tissue is positioned in between the light source and the light sensor.

10. The system of claim 1 comprising a user interface (UI) device in communication with the processor, the UI device to provide the indication of the physiological condition to a user.

11. The system of claim 1 comprising a UI device in communication with the processor, the UI device configured to receive a user selection of the physiological condition, the first and second wavelengths being determined in accordance with the user selection.

12. The system of claim 1 wherein the processor controls the wavelengths being sensed by the light sensor, in accordance with the selected physiological condition.

13. The system of claim 1 wherein the light source is configured to be controlled by the processor to illuminate at one or more specific discreet wavelength based on the selected physiological condition.

14. The system of claim 1 wherein the indication of the physiological condition is based on a hemoglobin and fluid balance in the tissue.

15. The system of claim 1 wherein the indication of the physiological condition is based on fluorescent light being emitted from the tissue.

16. A UI device comprising a display to show an indication of a physiological condition based on sensed light exiting a body tissue, the UI device comprising an inputting element for a user to select the physiological condition from a list of conditions.

17. The UI device of claim 16 comprising an inputting element for a user to input one or more discrete wavelengths of irradiating light.

18. A method for monitoring a physiological condition, the method comprising: controlling a light source to irradiate a body tissue with at least one discrete wavelength of light; receiving data from a light sensor which is positioned relative to the light source to enable at least a minimal volume of body tissue to be positioned between the light source and light sensor, the light sensor to sense at least a first discrete wavelengths and a second discrete wavelength of light emitted, transmitted or reflected from the body tissue; determining a quantitative relationship between data obtained from the first wavelength and data obtained from the second wavelength; andbased on the determined quantitative relationship, generating an indication of the physiological condition.

19. The method of claim 18 comprising controlling the light source to irradiate the body tissue with at least two discreet wavelengths.

20. The method of claim 18 comprising receiving user input regarding the physiological condition and controlling sensing of two discrete wavelengths by the light sensor based on the user input.

21. The method of claim 18 comprising receiving pressure measurements from a pressure sensor placed on the body tissue and controlling a pump based on the measurements, to ensure stable pressure on the tissue.

22. The method of claim 18 wherein the physiological condition is based on a hemoglobin and fluid balance in the tissue.

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