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EP-4512321-B1 - WEARABLE DEVICE FOR DETECTING A CARDIAC ARREST

EP4512321B1EP 4512321 B1EP4512321 B1EP 4512321B1EP-4512321-B1

Inventors

  • HANSE, Iddo Johanan Gideon
  • EBRAHIMKHEIL, Kambiz

Dates

Publication Date
20260513
Application Date
20240612

Claims (15)

  1. A light-emitting wearable device for processing a photoplethysmography signal and detecting a cardiac arrest of a wearer, wherein the photoplethysmography signal comprises a plurality of pulses wherein a pulse is the photoplethysmography signal between two consecutive valleys, characterized in that the wearable device is configured for: - calculating at least one of the following values for a pulse of the photoplethysmography signal: ∘ a pulse wave amplitude left by calculating a difference between amplitudes of a first peak and a first valley of the pulse; ∘ a pulse wave amplitude right by calculating a difference between amplitudes of the first peak and a second valley of the pulse; ∘ a pulse wave duration by calculating a difference between a time of the second valley and a time of the first valley of the pulse; ∘ a rise time by calculating a difference between a time of the first peak and a time of the first valley of the pulse; ∘ a systolic-to-diastolic duration ratio by calculating the ratio between the rise time and a difference between the time of the second valley and the time of the first peak of the pulse; - eliminating a photoplethysmography pulse when: ∘ the rise time of said pulse is outside a first time range; or ∘ the pulse wave duration of said pulse is outside a second time range; or ∘ a ratio between the pulse wave amplitude right and the pulse wave amplitude left is smaller than a first threshold value; or ∘ the systolic-to-diastolic duration ratio is larger a second threshold value; - eliminating a current photoplethysmography pulse when: ∘ a ratio between the rise time of a preceding photoplethysmography pulse and the rise time of said current photoplethysmography pulse is larger than a third threshold value; or ∘ a ratio between the pulse wave duration of a preceding photoplethysmography pulse and the pulse wave duration of said current photoplethysmography pulse is larger than a fourth threshold value; or ∘ a ratio between the pulse wave amplitude of a preceding photoplethysmography pulse and the pulse wave amplitude of said current photoplethysmography pulse is larger than a fifth threshold value; - calculating an average value of amplitudes of non-eliminated photoplethysmography pulses; - monitoring a predetermined number of plural consecutive pulses after detecting a photoplethysmography pulse with an amplitude lower than a pre-determined fraction of said average value; - triggering an alarm when an amplitude of said plurality of consecutive pulses is lower than said fraction of the average value.
  2. The wearable device according to claim 1, characterized in that the wearable device is configured for filtering the photoplethysmography signal by preferably removing frequencies outside a predefined frequencies range using a bandpass filter, and using said filtered photoplethysmography signal in the remaining steps of the method.
  3. The wearable device according to claim 1 or 2, characterized in that the wearable device is configured for stopping the alarm when detecting, within a preset first time duration, a plurality of consecutive pulses having amplitudes higher than said fraction of the average value.
  4. The wearable device according to any one of claims 1 - 3, characterized in that the wearable device is configured for stopping the alarm when: - the wearer presses a button on the wearable device for indicating a false alarm; and - the wearer presses said button within a preset second time duration.
  5. The wearable device according to any one of claims 1 - 4, characterized in that wearable device is configured for using GPS components of the wearable device to collect location coordinates of the wearer and sharing said location coordinates with a third party.
  6. The wearable device according to any one of claims 1 - 5, characterized in that the wearable device is configured for performing the operations of claims 1-5 only when a result of a wearing detection test is positive.
  7. The wearable device according to claim 6, characterized in that the wearable device is configured for: - registering a lowest amplitude and a highest amplitude of the filtered photoplethysmography signal during a third time duration after detecting a pulse wave with an amplitude higher than a sixth threshold value; - calculating a fluctuation range by subtracting the lowest amplitude from the highest amplitude; and - registering a negative result to the wearing detection test when the fluctuation range is lower than a seventh threshold value, and registering a positive result to the wearing detection test when the fluctuation range is higher than the seventh threshold value.
  8. The wearable device according to claim 7, characterized in that the wearable device is configured for: - calculating a mean value of the lowest amplitudes of a plurality of wearers; and - setting the seventh threshold value at a fraction of said mean value.
  9. The wearable device according to any one of claims 6 - 8, characterized in that the wearing detection test comprises the steps of: - measuring an acceleration of the wearable device movements; and - registering a negative result to the wearing detection test when said acceleration is lower than an eighth threshold value during a fourth time duration, registering a positive result to the wearing detection test when said acceleration is higher than the eighth threshold value during the fourth time duration.
  10. The wearable device according to claim 9, characterized in that wearable device is configured for: - measuring the acceleration of the wearable device movements and collecting a lowest acceleration of the wearable device movements during a fifth time duration; - calculating a mean value of the lowest acceleration of the wearable device movements of a plurality of wearers; and - setting the eighth threshold value at a fraction of said mean value.
  11. The wearable device according to claim 10, characterized in that wearable device is configured for measuring an acceleration of the wearable device movements comprises the steps of: - collecting acceleration data of axis x, axis y and axis z from an accelerometer imbedded in the wearable device; - calculating a time derivative of the acceleration data of axis x, a time derivative of the acceleration data of axis y and a time derivative of the acceleration data of axis z; - calculating the acceleration of the wearable device movement by calculating a square root of a sum of each time derivative of the acceleration data squared.
  12. The wearable device according to any one of claims 1 - 11, characterized in that wearable device is configured for registering a fall event when the acceleration of the wearable device movement is larger than a ninth threshold value within a sixth time duration.
  13. The wearable device according to claim 12, characterized in that the wearable device is configured for: - collecting a timestamp of peak acceleration when registering the fall of the wearer within the sixth time duration; - collecting a timestamp of impact start when the acceleration of the wearable device movement is lower than a tenth threshold value within the sixth time duration; - collecting a timestamp of impact end when the acceleration of the wearable device movement is larger than an eleventh threshold value within the sixth time duration; and - calculating acceleration parameters proportional to the acceleration of the wearable device movement at each time stamp or at an arithmetic combination of at least two timestamps.
  14. The wearable device according to any one of claims 12 - 13, characterized in that the wearable device is configured for training a neural network for detecting a cardiac arrest using a gradient boosting model and a training dataset comprising the calculated acceleration parameters and the registered fall events by minimizing a loss function on the training dataset.
  15. The wearable device according to any one of the preceding claims wherein said wearable device comprises a computer loaded with a computer program, characterized in that said program is arranged for causing the computer to carry out the operations according to any one of preceding claims.

Description

General description The invention relates to a wearable device for non-invasively detecting a cardiac arrest of a wearer, using multi-wavelength photoplethysmography (PPG) signals obtained by said wearable device from peripheral blood vessels. This approach holds potential in enabling early detection of cardiac arrest, which is of paramount importance for improving patient outcomes and enhancing survival rates. Photoplethysmography (PPG) is a non-invasive optical technique that measures blood volume changes in the microvascular bed of tissue. It works by shining a light source, typically an LED, onto the skin and detecting the amount of light that is transmitted or reflected back to a photodetector. This optical signal can be used to derive information about blood flow, heart rate, and other physiological parameters. Scientific literature consistently underscores the criticality of timely recognition and intervention in cardiac arrest cases. Rapid identification of cardiac arrest triggers immediate initiation of life-saving measures, including vital procedures such as cardiopulmonary resuscitation (CPR) and defibrillation. Studies have unequivocally demonstrated that each minute of delay in commencing CPR and defibrillation reduces survival rates by 7-10%. Hence, early intervention significantly enhances the prospects of restoring normal heart rhythm, preventing irreversible damage to vital organs, and saving lives. Trained emergency response personnel and medical staff in hospitals or skilled nursing care facilities were the main users of defibrillator devices in the past, primarily when responding to a cardiac arrest incident at the location of the individual. US20200305737 proposes a method for monitoring heart rhythm disturbance based PPG signals wherein a heart rhythm disturbance is detected when the PPG signals drop below a predetermined threshold. Nowadays, there are widely available automated versions of defibrillators known as "automated external defibrillators" (AEDs). An automated external defibrillator (AED) is a portable electronic device used to treat sudden cardiac arrest (SCA). It is designed to deliver an electric shock to the heart, known as defibrillation, to restore a normal heartbeat. AEDs are user-friendly and equipped with built-in instructions to guide bystanders in their use. They analyze the heart's rhythm and determine if a shock is needed. When applied promptly, typically within minutes of SCA onset, AEDs greatly increase the chances of survival. These life-saving devices are often found in public spaces, workplaces, and healthcare settings to ensure immediate access during emergencies and are designed to be used by individuals with minimal or no medical training. Promptly alerting individuals and emergency services when a cardiac arrest occurs remains a critical need. The presence of CPR training and automated AED technology, although widely available, may go unnoticed during the crucial initial minutes in various settings such as offices, homes, or care facilities. This oversight can lead to tragic outcomes, as potential responders may not be aware of the situation. Effective notification systems are vital to ensure swift intervention. By immediately notifying family members, neighbors, office workers, and care facility staff of a cardiac arrest incident, the chances of timely life-saving interventions significantly increase, and the risk of sudden cardiac death is reduced. It is an object of the current invention to correct the shortcomings of the prior art and to provide a solution for accurate single-site measured PPG signals in order to detect potential cardiac arrests. This and other objects which will become apparent from the following disclosure, are provided with and a light-emitting wearable device, having the features of one or more of the appended claims. In a first aspect of the invention, the light-emitting wearable device for processing a photoplethysmography signal and detecting a cardiac arrest of a wearer, wherein the photoplethysmography signal comprises a plurality of pulses wherein a pulse is the photoplethysmography signal between two consecutive valleys, wherein the wearable device is configured for: filtering the photoplethysmography signal by removing frequencies outside a predefined frequencies range using a bandpass filter;calculating at least one of the following values for each pulse of the filtered photoplethysmography signal: ∘ a pulse wave amplitude left by calculating a difference between amplitudes of a first peak and a first valley of the pulse;∘ a pulse wave amplitude right by calculating a difference between amplitudes of the first peak and a second valley of the pulse;∘ a pulse wave duration by calculating a difference between a time of the second valley and a time of the first valley of the pulse;∘ a rise time by calculating a difference between a time of the first peak and a time of the first valley of the pulse;∘ a systolic-to-diastolic d