Method and apparatus for detecting blood flow changes in a subject's head - Patents.com

Abstract

A method for detecting blood flow changes in a subject's head includes measuring a value of a parameter of a cardiac bioelectrical signal at a scalp region of the subject compared to a reference cardiac bioelectrical signal. The method also includes comparing the value of the measured parameter to a predetermined value of the parameter to measure blood flow changes in the subject's head. The measured changes can be used to detect perfusion changes in the subject's brain, for example, as a result of anticoagulants used to dissolve blood clots in blood vessels in the brain of a subject who has experienced an ischemic stroke.

Description

[Technical field]

[0001] The present invention relates to an apparatus and method for detecting changes in blood flow in a subject's head.

[0002] The invention has been developed primarily for monitoring patients experiencing or likely to experience cranial perfusion changes and will be described hereinafter with reference to this application, although it will be understood that the invention is not limited to this particular field of use. [Background technology]

[0003] A stroke is caused by a sudden interruption in the blood supply in the brain. In an ischemic stroke, there is a blockage in an artery in the brain, preventing blood from accessing part of the brain.

[0004] CT and / or MRI scans are the most common methods for assessing and monitoring cerebral blood perfusion in stroke patients.

[0005] A CT or MRI scan can detect the presence or absence of blood in an area of ​​the body and can therefore detect blockages (in an ischemic stroke) or ruptured blood vessels (in a hemorrhagic stroke).

[0006] Such scans are also performed to monitor blood perfusion in blood vessels and the brain. In the case of an ischemic stroke, they can be used during treatment to evaluate the effectiveness of anticoagulants delivered to brain regions in dissolving blood clots. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2018 / 116308 Summary of the Invention [Problem to be solved by the invention]

[0008] However, these methods have several limitations: the patient needs to be scanned by a CT or MRI machine under specific conditions; CT and MRI machines are expensive and usually limited in number; CT and MRI machines tend to be large.

[0009] CT and MRI machines also do not provide continuous real-time monitoring of blood perfusion in the brain.

[0010] The present invention aims to provide a solution that overcomes or substantially ameliorates at least some of the deficiencies of the prior art, or at least to provide an alternative.

[0011] Where prior art information is referred to herein, it should be understood that such reference is not an admission that that information forms part of the general knowledge in the art in Australia or any other country. [Means for solving the problem]

[0012] In one aspect of the present disclosure, there is provided a method for detecting blood flow changes in a head of a subject, comprising: measuring a value of a parameter of the cardiac bioelectrical signal at the subject's scalp region in comparison to a reference cardiac bioelectrical signal; and A method of detecting changes in blood flow in the head of the subject is provided, comprising comparing the measured value of the parameter with a predetermined value of the parameter to measure changes in blood flow in the head of the subject.

[0013] The reference cardiac bioelectrical signal may be received by a reference electrode placed adjacent to the subject's heart.

[0014] This method is measuring a value of a parameter of the cardiac bioelectrical signal at the subject's thoracic region in comparison to the reference cardiac bioelectrical signal; and The method may further include calculating a ratio between a parameter of the cardiac bioelectrical signal measured at the subject's scalp region and a parameter of the cardiac bioelectrical signal measured at the subject's chest region.

[0015] The method may further include comparing the ratio to a predetermined ratio indicative of an uncompromised state of blood flow.

[0016] The method may further include comparing the ratio to a predetermined ratio indicative of a condition of impaired blood flow.

[0017] The reference cardiac bioelectrical signal may be an ECG (electrocardiogram) measurement taken on an area of ​​the subject's chest adjacent to the heart or on the entire chest area of ​​the subject.

[0018] The cardiac bioelectrical signal may be represented by a voltage versus time graph.

[0019] The parameter may be the average peak amplitude of a voltage versus time graph representing the measured cardiac bioelectrical signal.

[0020] In another aspect, there is provided a headgear apparatus for detecting changes in blood flow to a head of a subject, the headgear apparatus comprising: a reference electrode positionable, in use, on the subject's chest adjacent the heart; a first electrode positionable, in use, on a scalp region of the subject; headgear connected to each of the reference electrode and the first electrode; Equipped with The headgear comprises: A headgear arrangement is provided, the headgear arrangement including a processing unit configured to measure values ​​of parameters of the cardiac bioelectrical signal at a scalp region of the subject relative to a reference cardiac bioelectrical signal, and transmit the measured values ​​of the parameters of the cardiac bioelectrical signal to a computer configured to measure blood flow changes in the subject's head.

[0021] The headgear arrangement may further comprise a second electrode configured for placement on the subject's chest region, in use, and for receiving cardiac bioelectrical signals adjacent the subject's heart.

[0022] The processing unit may comprise a brain-computer interface (BCI) configured to process the cardiac bioelectrical signals received from the first electrode and the second electrode and to transmit a representation of the cardiac bioelectrical signals to a receiver.

[0023] One or more of the reference electrode, the first electrode and the second electrode may be wireless electrodes.

[0024] In yet another aspect, a system for detecting changes in blood flow in a head of a subject, comprising: a reference electrode positionable on the subject's chest; a first electrode positionable on a scalp region of the subject and configured to receive a bioelectrical signal relative to the reference electrode; a second electrode positionable, in use, on the subject's chest region and configured to receive cardiac bioelectrical signals adjacent the heart relative to the reference electrode; headgear connected to each of the reference electrode and the first electrode; Equipped with The headgear comprises: A system is provided, comprising: a processing unit configured to measure values ​​of parameters of the cardiac bioelectrical signal received at a scalp region of the subject in comparison with a reference cardiac bioelectrical signal received at a chest region of the subject, and transmit the measured values ​​of the parameters of the cardiac bioelectrical signal to a computer configured to measure blood flow changes in the subject's head.

[0025] The processing unit may be a Brain Computer Interface (BCI).

[0026] The system further comprises a receiver for receiving the transmitted cardiac bioelectrical signal; The receiver may be a radio receiver.

[0027] One or more of the reference electrode, the first electrode and the second electrode may be wireless electrodes.

[0028] In yet another aspect, a method for detecting changes in blood flow in a head region of a subject, comprising: providing said headgear apparatus; placing a reference electrode on the subject's chest adjacent to the heart; placing a first electrode on a scalp region of the subject; placing a second electrode on the subject's chest; obtaining a baseline cardiac bioelectrical signal; acquiring a cardiac bioelectrical signal at a scalp region of the subject; and A method for detecting blood flow changes in the head of the subject is provided, comprising transmitting an acquired reference cardiac bioelectrical signal and a cardiac bioelectrical signal acquired at a scalp region of the subject to a processor configured to measure blood flow changes in the head of the subject.

[0029] The processor may be configured to measure blood flow changes in the subject's head in accordance with a method according to claim 3.

[0030] The present invention may also be broadly described as consisting of any and all combinations of the parts, elements and features referred to or indicated in the specification of this application, and any combination of two or more of said parts, elements or features, individually or collectively, and where a particular integer having known equivalents in the art to which the invention pertains is referred to herein, such known equivalents are deemed to be incorporated herein as if individually set forth.

[0031] This invention as well as other aspects are disclosed. [Brief description of the drawings]

[0032] Notwithstanding other aspects falling within the scope of the invention, embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings in which: [Figure 1] FIG. 1 is a schematic diagram of a headgear apparatus according to one embodiment of the present invention. [Diagram 2] Figure 2 shows the setup and results of the experiments performed with artificially generated EMS signals. [Diagram 3] FIG. 3 is a chart showing the average cardiac biosignal amplitude before and after anaerobic exercise and the average amplitude before and after anaerobic exercise. [Figure 4] FIG. 4 is a graph of scalp cardiac biosignal amplitude as a percentage of thoracic cardiac biosignal amplitude before and after anaerobic exercise. [Diagram 5] FIG. 5 is a graph of a representation of a cardiac bioelectrical signal according to one embodiment of the present invention. [Figure 6] FIG. 6 is a perspective view of a headgear assembly according to one embodiment of the present invention. [Figure 7] FIG. 7 is a perspective view of a headgear assembly according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] The heart generates the largest electrical signal in the body. Blood is one of the most conductive components in the body and therefore provides the primary pathway for the propagation of electrical signals. Applicant has found that a decrease in cerebral blood flow (CBF) or blood flow through the subject's head reduces this propagation and reduces the amplitude of the extra-brain electrical signal detected in a region of the head, such as the entire scalp of the subject. The extra-brain electrical signal may be a cardiac bioelectrical signal or a bioelectrical signal generated by the subject's heart. The extra-brain bioelectrical signal may be another bioelectrical signal. The extra-brain bioelectrical signal may be the result of an artificially generated stimulus, such as an artificially generated electrical muscle stimulus.

[0034] 1 shows an example of a headgear arrangement 100 that can be used to detect changes in blood flow in a subject's head. In this embodiment, the extra-brain bioelectrical signal is a cardiac bioelectrical signal. In other embodiments, it is contemplated that other types of extra-brain bioelectrical signals may be used. The headgear arrangement includes an EEG headset configured to record EEG signals, and scalp electrodes operably coupled to the EEG headset and configured to receive and record bioelectrical signals, such as brain and extra-brain bioelectrical signals.

[0035] The headgear arrangement senses cardiac bioelectrical signals adjacent the heart (e.g., in the subject's chest region) and adjacent the head (e.g., at the subject's scalp). This information is transmitted to a processing unit in the headgear 40, which then transmits the information to a receiver. The receiver transmits the information to a computer including a processor. The processor can implement an algorithm to process the information and measure blood flow changes in the subject's head. The computer may be remote from the headgear arrangement or may be part of the headgear arrangement. The processor in the computer can then display an indication of the received signals and / or the measured blood flow changes on a display.

[0036] As shown in FIG. 1, in use, the reference electrode 10 is placed on the left side of the patient's chest (adjacent to the heart). The first electrode, or first recording electrode 20, is placed on the subject's scalp region. The first electrode 20 may be placed at any location on the subject's scalp region. For example, the first electrode may be placed on the scalp region at a location defined by the international 10-20 system for applying scalp electrodes in connection with EEG testing.

[0037] The first electrode 20 senses the cardiac bioelectrical signal at a region of the subject's head or scalp relative to a reference signal sensed by the reference electrode 10. Applicant has found that by placing the reference electrode 10 adjacent to the patient's heart, such as at the patient's chest region, and recording electrical activity at the patient's scalp region with the first electrode 20, a component of the electrical activity at the scalp related to the heart (cardiac bioelectrical activity at the subject's scalp region) can be pronounced or readily detected.

[0038] 1, a second recording electrode 30 is placed on the patient's chest region near the reference electrode 10. Applicants have found that the signal recorded by this second electrode relative to the reference signal is indicative of the bioelectrical activity closest to the subject's heart while the heart is pumping blood.

[0039] FIG. 6 shows cardiac bioelectrical signal readings obtained using a headgear arrangement according to an embodiment of the present invention shown in FIG. 1. AF3, T7, Pz, and AF4 each indicate the location of a recording electrode 30 on the scalp region of the subject. T8 indicates a recording electrode placed on the subject's chest region, like the second electrode 30 described above. In FIG. 6, the sensed cardiac bioelectrical signal is represented as voltage versus time, where voltage represents the relative strength of the signal. As can be seen, the voltage versus time graph representing the cardiac bioelectrical signal of electrode T8 has the highest peak amplitude since it is closest to the source of the cardiac electrical activity.

[0040] A method for detecting blood flow changes in the head of a subject includes measuring a value of a parameter of a cardiac bioelectrical signal at the scalp of the subject relative to a baseline cardiac bioelectrical signal.

[0041] For example, a parameter of a cardiac bioelectrical signal may be the average peak amplitude of the signal.

[0042] The voltage versus time signals shown in FIG. 5 from electrodes AF3, T7, Pz and AF4, respectively, are examples of cardiac bioelectrical signals taken at the subject's head region relative to a signal received by a reference electrode placed in the subject's chest region.

[0043] In Figure 5, the parameter is the amplitude of a voltage versus time graph representing the cardiac bioelectrical signal. Advantageously, the cardiac bioelectrical signal has a characteristic, repetitive feature that corresponds to the electrical activity required to repeatedly contract the heart over time.

[0044] The method further includes comparing the value of the measured parameter to a predetermined value of the parameter to determine any changes in blood flow in the subject's head.

[0045] If the parameter is a mean peak amplitude, the predetermined value of the parameter may be the mean peak amplitude in the same region where the first electrode is located recorded when blood flow in the patient's head is intact. For example, if a patient has impaired blood flow through the brain compared to when the predetermined value was measured, the measured value of the mean peak amplitude will be lower than the predetermined value of the mean peak amplitude for that patient.

[0046] Because cardiac bioelectrical activity may be patient-specific, a ratio may be calculated between a parameter of the cardiac bioelectrical signal measured at the scalp region of the subject and a parameter of the cardiac bioelectrical signal at the chest region of the subject. For example, the average peak amplitude of the cardiac bioelectrical signal recorded by a first electrode relative to a reference electrode may be divided by the average peak amplitude of the cardiac bioelectrical signal recorded by a second electrode relative to a reference electrode. This ratio may be compared to a predetermined ratio to determine whether a change has occurred in blood flow to the subject's head. For example, the predetermined ratio may be indicative of an average subject with unimpaired blood flow to the head. Or, the predetermined ratio may be indicative of the degree of blood flow impairment in the subject's head.

[0047] This method can be used to detect changes in blood flow in a patient's brain over time and to continuously monitor the patient. For example, during an ischemic stroke, a blood clot is present in a blood vessel in the brain, impairing blood flow in the brain. Using this method, the peak amplitude of the cardiac bioelectrical signal measured in the subject's head region will be relatively low while a blood clot is present in the blood vessel. When a drug is administered to the patient to dissolve the clot, the method and headgear device can be used to determine whether the clot is dissolved and whether blood flow in the brain is increased from before the drug was administered.

[0048] If the clot is successfully dissolved, the peak amplitude of the cardiac bioelectrical signal measured in the subject's head region is relatively higher than that measured while the clot is present in the blood vessel. The method and headgear can also be used in a variety of applications where it is beneficial to monitor blood flow in the subject's brain. For example, the method can be used to monitor conditions associated with impaired blood flow in the brain, such as delirium or traumatic brain injury.

[0049] FIG. 6 illustrates one embodiment of a headgear apparatus for detecting changes in blood flow in a subject's head.

[0050] The headgear device 200 comprises a headgear that can be worn on the head of a user. A reference electrode 210 extends from the headgear and can be positioned and applied to a chest region adjacent to the subject's heart. Thus, the reference electrode 210 can be positioned in the chest region adjacent to the subject's heart during use. One or more electrodes 220 can be positioned on the subject's scalp region. One of the electrodes 220 can be a first electrode. The electrodes 220 can be positioned throughout the major cerebrovascular regions to optimize monitoring of changes in cerebral blood flow.

[0051] The headgear assembly 200 is a wireless, portable EEG headset.

[0052] The headgear arrangement includes a second electrode 230 arranged to be placed on the chest region of the subject in use and to receive cardiac bioelectrical signals adjacent the heart in use.

[0053] Each electrode 220 is configured to sense and transmit bioelectrical signals when applied to the body and headgear arrangement during use.

[0054] Each of the reference electrode 210, the one or more electrodes 220, and the second electrode 230 is a scalp electrode operatively connected to an EEG headset to detect and receive bioelectrical signals and to transmit the bioelectrical signals to the EEG headset.

[0055] Each electrode 220 may be a dry or semi-dry electrode.

[0056] The headgear arrangement 200 includes a processing unit (not shown) for receiving the bioelectrical signals from each of the electrodes 210, 2200, 230. The processing unit (not shown) is configured to measure values ​​of parameters of the cardiac bioelectrical signals recorded at the subject's scalp region in comparison with a reference cardiac bioelectrical signal picked up by a reference electrode, and to transmit values ​​of parameters of the cardiac bioelectrical signals to a remote computer configured to measure blood flow changes in the subject's head according to the methods described above.

[0057] For example, a processing unit (not shown) of the headgear device 200 receives the bioelectrical signals from each of the electrodes 210, 220, 230 and transmits the cardiac bioelectrical signals to a receiver external to the headgear device. According to one embodiment, the processing unit can include a brain-computer interface, such as a BCI board that includes a microcontroller for on-board processing of the cardiac bioelectrical signals received from the electrodes. The BCI board can transmit the processed cardiac bioelectrical signals to a receiver.

[0058] This processed information can be sent to a receiver in a remote computer (not shown), which can use an algorithm to detect blood flow changes in the subject's head in accordance with the method embodiments described above. Those skilled in the art will appreciate that there are multiple ways to implement the above method embodiments.

[0059] In the embodiment shown in FIG. 6, the headgear arrangement 200 includes a comb-like portion 270 to clear the forehead of a user wearing the hair gear. This exposes the scalp for better electrode contact with the scalp. The headgear arrangement 200 includes a curved piece 280 that extends over the user's head during use. The headgear arrangement 200 includes an elastic band 290 that extends around the user's head during use. The electrodes 220 are positioned on the curved piece 280 and under the band. The band 290 is elastic so that it fits securely to heads of various sizes and shapes. The elastic band 290 and curved piece 280 are configured to fit securely on the patient's head to ensure proper contact between the electrodes and the user's scalp to produce accurate results.

[0060] The ear hooks 260 are configured to fit around the ears of a user when the headgear apparatus is placed on a user. The ear clips 240 include the reference electrodes 210. The ear clips 240 can be clipped to the ears to use the ear clips as a reference electrode instead of the reference electrode 210.

[0061] 7 shows another embodiment of a headgear arrangement. The headgear arrangement 300 has an elastic band 390 that includes an electrode 320. The headgear arrangement 300 has an ear clip 340 that can be used as a reference electrode. The headgear arrangement 300 has a reference electrode 310 that can be placed in the area of ​​the user's chest adjacent the user's heart, and an electrode 330 that can be placed on the user's chest.

[0062] Headgear apparatus 200 and / or 300 may also provide EEG-only functionality by changing the location of reference electrode 210 from adjacent the heart to another known reference location or by changing the reference method to that used for EEG acquisition. In one example, the reference electrode may be placed on the mastoid bone and the first and second electrodes may be moved to other recording locations, for example, as identified by the international 10-20 system of EEG electrodes.

[0063] In other embodiments, the headgear arrangement may include one or more of a variety of sensors, such as an accelerometer, a temperature sensor, a blood oxygen saturation sensor, an environmental noise sensor, and a quantitative EEG.

[0064] In addition to the cardiac bioelectrical signal at the scalp relative to a reference cardiac bioelectrical signal adjacent the user's heart, parameters measured by the headgear device may include:

[0065] 1) Quantitative EEG (qEEG) measures such as delta / alpha ratio (DAR).

[0066] 2) Cardiac and / or artificially generated electrical signals.

[0067] 3) Environmental (auditory and visual noise) evoked potentials.

[0068] 4) Accelerometer. The headset may have an integrated accelerometer to monitor the user's head movements as well as changes in fluid flow due to pulsatile perfusion events in the head.

[0069] 5) Temperature Sensor. The headset may include an infrared temperature sensor for monitoring the patient's temperature.

[0070] 6) Blood oxygen saturation measured by a built-in oximeter such as a near-infrared (NIR) sensor, near-infrared spectrophotometer (NIRS) or green light pulse oximeter.

[0071] The above sensors may be included within a headgear arrangement.

[0072] Thus, the headgear arrangement can be used for:

[0073] 1) Monitoring the change in skull position and electrical signal strength across the skull as a way to infer changes in blood flow to the head. This signal can be cardiac and / or artificially generated (e.g. EMS or proprietary signal generator). Cardiac signals can also be used to assess cardiac physiology and monitor heart rate.

[0074] 2) To monitor environmental stimuli affecting the brain, specifically photic and auditory stimuli relative to associated cortical evoked potentials, as a means of monitoring changes in brain function and cortical sensitivity in real time.

[0075] 3) The above method can be used in combination with standard EEG measurements to monitor brain function in real time, specifically the delta / alpha signal ratio changes over time to detect and monitor perfusion changes, seizures, delirium, and intracranial pressure.

[0076] 4) Monitoring the relative signal strength between electrodes can be used to map ischemic areas, changes due to treatment, vasospasm / delayed cerebral ischemia, long-term damage, and potential changes during recovery.

[0077] 5) Head movement is monitored (via accelerometer) whether due to gross patient movement or changes in fluid flow due to head pulsatile perfusion events. Temperature and blood oxygen saturation (NIR / green light pulse oximeter) are also monitored.

[0078] In embodiments other than the illustrated embodiment, it is envisioned that wireless electrodes may be used.

[0079] The headgear devices 200, 300 can be used to continuously or semi-continuously monitor blood flow in the brain. The headgear devices 200, 300 can be low voltage, low power wireless electronic devices so as to pose low electrical safety risks.

[0080] Embodiments of the headgear device and method can be used in many other applications, including paramedic assessment, emergency medicine, delirium, traumatic brain injury, seizures, intracranial pressure monitoring, and neurorehabilitation.

[0081] The described method of detecting changes in blood flow in a subject's head would allow a doctor or nurse to quantitatively monitor stroke patients during CT / MRI scans. This would allow stroke treatment to be monitored in real time and provide information on treatment outcome, which would guide next steps in the management of the patient. If the treatment is not working, the device would be able to alert the clinician to this sooner than current methods, allowing the patient to receive a secondary treatment if necessary.

[0082] The method and headgear device for detecting blood flow changes in a subject's head can also be used to detect vasospasm / delayed cerebral ischemia in patients who have experienced subarachnoid hemorrhage. These patients can be continuously monitored to detect the onset of vasospasm or decompression sickness (DCI). Transcranial Doppler ultrasound is currently used to detect vasospasm, but it is not a continuous method and is sometimes not very accurate. A new, rapid and accurate method of detecting vasospasm / DCI would allow patients to receive treatment as quickly as possible with current detection methods. This could prevent irreversible damage that could otherwise occur due to vasospasm / DCI.

[0083] The method and headgear device for detecting changes in blood flow in a subject's head can also be used for monitoring seizures, delirium, traumatic brain injury, intracranial pressure and neuro-rehabilitation.

[0084] In another embodiment, the headgear apparatus may be part of a "smart helmet" that may be used to monitor alertness in occupations where helmets are typically used.

[0085] Monitoring cardiac bioelectrical signals at the patient's head can also be used to assess cardiac physiology and monitor heart rate. Any changes in the cardiac signals during exercise can signal the state of the patient's cardiac physiology.

[0086] Experiment Report Experiments were conducted to verify the following hypotheses.

[0087] The heart generates the largest electrical signal in the body, and blood is one of the most conductive components in the body, thus providing the primary pathway for the propagation of electrical signals. It was hypothesized that a decrease in cerebral blood flow would decrease this propagation, and thus decrease the amplitude of cardiac electrical signals recorded across the scalp, compared to the amplitude of cardiac electrical signals recorded across the chest. It was hypothesized that an increase in cerebral blood flow would increase this propagation, and thus increase the amplitude of cardiac electrical signals recorded across the scalp, compared to the amplitude of cardiac electrical signals recorded across the chest. This method could be useful in monitoring patients with stroke, sleep apnea, delirium, traumatic brain injury, or other disorders associated with impaired cerebral blood flow.

[0088] The cardiac bioelectrical signal was detected across the EEG scalp electrodes by repositioning the reference electrode of the EMOTIV Insight EEG headset to a left chest position. Scalp electrode T8 was repositioned to a right chest position to record cardiac bioelectrical signals across the chest, as shown in FIG. 1. Applicant investigated (using the OpenBCIEEG headset) how a reduction in CBF due to anaerobic exercise (via push-ups) affects the amplitude of the cardiac bioelectrical signal (FIG. 2). Applicant also investigated how this affects the scalp cardiac bioelectrical signal amplitude as a percentage of the thoracic cardiac bioelectrical signal amplitude.

[0089] Results: After 1 min of anaerobic exercise, both the cardiac biosignal amplitude and the EMS-induced signal amplitude decreased at the scalp electrodes (P<0.05). Signal amplitude returned to baseline after 5 min (Figure 3). Scalp cardiac biosignal amplitude as a percentage of thoracic cardiac biosignal amplitude also decreased after 1 min of anaerobic exercise. It then increased toward baseline after 4 min (Figure 4).

[0090] The reduction in cardiac biosignal amplitude and EMS signal amplitude across the scalp and the reduction in scalp cardiac biosignal amplitude as a percentage of the observed thoracic cardiac biosignal amplitude may be due to the reduction in CBF (cerebral blood flow) induced by anaerobic exercise. The EMS signal is a control stimulus since it is independent of cardiac physiology. These findings provide preliminary evidence that a reduction in CCBF may be detected by a reduction in cerebral electrical signals recorded across the scalp.

[0091] The above method is based on the hypothesis that changes in blood flow alter the propagation of electrical signals. This hypothesis was tested using an artificially generated electrical signal (generated by an electrical muscle stimulator). The EMS signal acts as a control measure since its generation does not depend on the user's physiology. EMS pads were applied to the upper back. Stimulation was set at a constant frequency. The generated electrical signal was recorded using an EEG headset as shown in Figure 2.

[0092] Recordings of the EMS signals using an OpenBCI EEG headset, which measures scalp electrical activity, showed that signatures of artificially generated electrical signals were present in the head electrical activity measured close to the subjects' scalp.

[0093] Throughout this specification, references to "one embodiment" or "one embodiment" mean that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, the appearances of the phrases "in one embodiment" or "in one embodiment" in various places throughout this specification do not necessarily all refer to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.

[0094] Similarly, in the above description of exemplary embodiments of the invention, it should be understood that various features of the invention may be grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and facilitating understanding of one or more of the various inventive aspects. However, this method of disclosure should not be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, no inventive element is present in every feature of a single embodiment disclosed above. Thus, the claims following the detailed description of a particular embodiment are hereby expressly incorporated into the detailed description of the particular embodiment, with each claim standing on its own as a separate embodiment of the invention.

[0095] Furthermore, some embodiments described herein include some features that are included in other embodiments but not in other embodiments, but combinations of features of different embodiments are meant to be within the scope of the present invention and form different embodiments, as would be understood by one of ordinary skill in the art. For example, in the following claims, any of the claimed embodiments may be used in any combination.

[0096] In the description provided herein, numerous specific details are set forth. However, it will be understood that embodiments of the present invention may be practiced without such specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

[0097] In the following claims and in the foregoing description of the invention, unless the context requires otherwise by express language or necessary implication, the word "comprises" or variations such as "comprises" or "comprises" are used in their inclusive sense, i.e., to specify the presence of stated features but not to exclude the presence or addition of further features in various embodiments of the invention.

[0098] Any one of the terms "include", "comprise" or "including as used herein" is also an open term meaning to include at least the element / feature that follows the term, but not to exclude others. Thus, including is synonymous with and means including.

[0099] Thus, while what are considered to be illustrative embodiments of the invention have been described, those skilled in the art will recognize that other and further modifications may be made without departing from the spirit of the invention, and it is intended to claim all such changes and modifications that fall within the scope of the invention. For example, any formulas given above are merely representative of procedures that may be used. Functions may be added or deleted from the block diagrams, and operations may be interchanged between functional blocks. Steps may be added or deleted to methods described within the scope of the invention.

[0100] Although the invention has been described with reference to specific embodiments, it will be understood by those skilled in the art that the invention may be embodied in many other forms.

Claims

1. 1. A method for detecting changes in blood flow in a subject's head, comprising: sensing a cardiac bioelectrical signal at a scalp region of the subject and comparing the cardiac bioelectrical signal to a reference cardiac bioelectrical signal to determine a value of a parameter of the sensed cardiac bioelectrical signal at the subject's scalp; and comparing the measured value of the parameter with a predetermined value of the parameter to determine a change in blood flow in the subject's head; A method for detecting changes in blood flow in the head, wherein the parameter is a mean peak amplitude of a voltage versus time graph representing the sensed cardiac bioelectrical signal.

2. The method of claim 1 , wherein the reference cardiac bioelectrical signal is received by a reference electrode positioned adjacent to the subject's heart.

3. Measuring a value of the parameter with a first electrode; measuring, by a second electrode, a value of a parameter of the cardiac bioelectrical signal at the subject's thoracic region in comparison to the reference cardiac bioelectrical signal; and 3. The method for detecting changes in blood flow in the head of claim 2, further comprising calculating a ratio between a value of the parameter of the cardiac bioelectrical signal measured at the scalp region of the subject and a value of the parameter of the cardiac bioelectrical signal measured at the chest region of the subject.

4. 4. The method of claim 3, further comprising comparing said ratio to a predetermined ratio indicative of an intact blood flow condition.

5. The method for detecting a change in blood flow in the head according to claim 3 , further comprising: comparing the ratio with a predetermined ratio indicative of a state of blood flow disorder.

6. The method of claim 1 , wherein the reference cardiac bioelectrical signal is an ECG measurement taken over a thoracic region adjacent to the subject's heart or over the entire thoracic region of the subject.

7. 1. A system for detecting changes in blood flow in a head of a subject, comprising: a reference electrode positionable on the subject's chest; a first electrode positionable on a scalp region of the subject and configured to receive a bioelectrical signal relative to the reference electrode; a second electrode, in use, positionable on the subject's chest region and configured to receive cardiac bioelectrical signals; headgear connected to each of the reference electrode and the second electrode; Equipped with The headgear comprises: a processing unit configured to measure a value of a parameter of the cardiac bioelectrical signal received at the scalp region of the subject compared to a reference cardiac bioelectrical signal received at the chest region of the subject; The parameter is an average peak amplitude of a voltage versus time graph showing the cardiac bioelectrical signal, and the measured value of the parameter is compared to a predetermined value of the parameter to measure changes in blood flow in the subject's head.

8. The system of claim 7 , wherein the processing unit is a brain computer interface (BCI).

9. The headgear comprises: a curved piece that extends over the subject's head and an elastic band that extends around the subject's head to ensure contact between the first electrode and the subject's scalp during use; an ear hook extending from the curved piece and an ear clip extending from the curved piece; the ear hooks are configured to fit around the subject's ears when the headgear is placed on the subject; The system of claim 7 , wherein the ear clip comprises a reference electrode separate from the reference electrode, the separate reference electrode positionable on the subject's ear.

10. The system described in claim 7, wherein the processing unit is a brain-computer interface (BCI) configured to process the cardiac bioelectrical signal received from the first electrode and transmit the processed cardiac bioelectrical signal to a receiver.

11. a receiver for receiving the transmitted cardiac bioelectrical signal; The system of claim 7 , wherein the receiver is a radio receiver.

12. The system of claim 7 , wherein one or more of the reference electrode, the first electrode, and the second electrode are wireless electrodes.

13. 1. A method for detecting changes in blood flow in a subject's head, comprising: measuring a value of a parameter of the cardiac bioelectrical signal at the subject's scalp region in comparison to a reference cardiac bioelectrical signal received by a reference electrode positioned adjacent the subject's heart; measuring a value of a parameter of the cardiac bioelectrical signal received by electrodes placed on the subject's chest region in comparison with the reference cardiac bioelectrical signal; calculating a ratio between a value of the parameter of the cardiac bioelectrical signal measured at a scalp region of the subject and a value of the parameter of the cardiac bioelectrical signal measured at a chest region of the subject; comparing said ratio to a predetermined ratio indicative of intact blood flow to determine a change in blood flow to the subject's head; 11. A method for detecting blood flow changes in the head, wherein a parameter of the cardiac bioelectrical signal received by electrodes placed on the subject's chest region is a mean peak amplitude of a voltage versus time graph showing the cardiac bioelectrical signal.

14. The method for detecting changes in blood flow in the head as described in claim 13, further comprising comparing the ratio with a predetermined ratio indicative of a state in which blood flow is not impaired.

15. A method for detecting changes in blood flow in the head as described in claim 13, further comprising comparing the ratio with a predetermined ratio indicative of a state of blood flow disorder.

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