Loss of Pulse Detection

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February 25, 2025 Fitbit Dinesh Puppala Regulatory Affairs Lead 215 Fremont Street San Francisco, California 94105 Re: K242967 Trade/Device Name: Loss of Pulse Detection Regulation Number: 21 CFR 870.2790 Regulation Name: Photoplethysmograph Analysis Software For Over-The-Counter Use Regulatory Class: Class II Product Code: SDY Dated: September 25, 2024 Received: September 26, 2024 Dear Dinesh Puppala: We have reviewed your section 510(k) premarket notification of intent to market the device referenced above and have determined the device is substantially equivalent (for the indications for use stated in the enclosure) to legally marketed predicate devices marketed in interstate commerce prior to May 28, 1976, the enactment date of the Medical Device Amendments, or to devices that have been reclassified in accordance with the provisions of the Federal Food, Drug, and Cosmetic Act (the Act) that do not require approval of a premarket approval application (PMA). 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See the DICE website (https://www.fda.gov/medical-device-advice-comprehensive-regulatory {2}------------------------------------------------ assistance/contact-us-division-industry-and-consumer-education-dice) for more information or contact DICE by email (DICE@fda.hhs.gov) or phone (1-800-638-2041 or 301-796-7100). Sincerely, # Jennifer W. Shih -S Jennifer Kozen Assistant Director Division of Cardiac Electrophysiology, Diagnostics, and Monitoring Devices Office of Cardiovascular Devices Office of Product Evaluation and Quality Center for Devices and Radiological Health Enclosure {3}------------------------------------------------ # Indications for Use Form Approved: OMB No. 0910-0120 Expiration Date: 07/31/2026 See PRA Statement below. Submission Number (if known) K242967 Device Name Loss of Pulse Detection ### Indications for Use (Describe) Loss of Pulse Detection is a software-only mobile medical application that is intended to be used with compatible consumer wrist-worn products to analyze pulse data to identify loss of pulse events and provide audio, visual, and haptic alerts to the user. If the user remains unresponsive to these alerts, Loss of Pulse Detection will attempt to prompt a call to emergency services through the user's connected compatible hardware, such as a smartphone or smartwatch. Loss of Pulse Detection is intended for over-the-counter (OTC) use. It is not intended to provide a notification on every loss of pulse event and the absence of an alert is not intended to indicate that no such event has occurred; rather the Loss of Pulse Detection is intended to opportunistically surface an alert of possible loss of pulsatility when sufficient data are available for analysis. These data are only captured when the user is still. Loss of Pulse Detection is not intended to replace traditional methods of diagnosis, treatment, or monitoring. Loss of Pulse Detection has not been tested for and is not intended for use in people under 22 years of age. It is also not intended for use in individuals previously diagnosed with a high risk for sudden cardiac death such as those with coronary artery disease, cardiomyopathy and/or unexplained syncope/fainting. Type of Use (Select one or both, as applicable) Prescription Use (Part 21 CFR 801 Subpart D) X Over-The-Counter Use (21 CFR 801 Subpart C) # CONTINUE ON A SEPARATE PAGE IF NEEDED. 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Send comments regarding this burden estimate or any other aspect of this information collection, including suggestions for reducing this burden, to: > Department of Health and Human Services Food and Drug Administration Office of Chief Information Officer Paperwork Reduction Act (PRA) Staff PRAStaff(@fda.hhs.gov "An agency may not conduct or sponsor, and a person is not required to respond to, a collection of information unless it displays a currently valid OMB number." {4}------------------------------------------------ Image /page/4/Picture/0 description: The image shows the Fitbit logo. The logo consists of a stylized letter 'f' made up of a collection of dots on the left, followed by the word 'fitbit' in a sans-serif font. The word 'fitbit' is written in lowercase letters, and there is a registered trademark symbol to the right of the word. ## 510(K) Summary - 1. Submitter Information: Fitbit LLC 215 Fremont Street. San Francisco, CA 94105 Contact Person: Dinesh Puppala Regulatory Affairs Lead Phone: (650)-267-1263 Email: puppalad(@google.com Date Prepared: Feb 19, 2025 - 2. Subject Device Information Name of Device: Loss of Pulse Detection Common or Usual Name: Loss of Pulse Detection Classification Name: Photoplethysmograph Analysis Software For Over-The-Counter Use Regulatory Class: Class II Product Code: SDY - 21 CFR 870.2790 - 3. Predicate Device Fitbit Irregular Rhythm Notifications (K212372) ### 4. Indications for Use Loss of Pulse Detection is a software-only mobile medical application that is intended to be used with compatible consumer wrist-worn products to analyze pulse data to identify loss of pulse events and provide audio, visual, and haptic alerts to the user. If the user remains unresponsive to these alerts. Loss of Pulse Detection will attempt to prompt a call to emergency services through the user's connected compatible hardware, such as a smartphone or smartwatch. Loss of Pulse Detection is intended for over-the-counter (OTC) use. It is not intended to provide a notification on every loss of pulse event and the absence of an alert is not intended to indicate that no such event has occurred; rather the Loss of Pulse Detection is intended to opportunistically surface an alert of possible loss of pulsatility when sufficient data are available for analysis. These data are only captured when the user is still. Loss of Pulse Detection is not intended to replace traditional methods of diagnosis, treatment, or monitoring. Loss of Pulse Detection has not been tested for and is not intended for use in people under 22 years of age. It is also not intended for use in individuals previously diagnosed with a high risk for sudden cardiac death such as those with coronary artery disease, cardiomyopathy and/or unexplained syncope/fainting. Confidential {5}------------------------------------------------ Image /page/5/Picture/0 description: The image shows the Fitbit logo. The logo consists of a stylized "f" made up of small circles on the left and the word "fitbit" in a sans-serif font on the right. The logo is black and white. ### Device Description న. ## Intended Use Photoplethysmograph analysis software for over-the-counter use. A photoplethysmograph analysis software device for over-the-counter use analyzes photoplethysmograph data and provides information for identifying loss of pulse. This device is not intended to provide a diagnosis. ## Technological Characteristics The Loss of Pulse detection SaMD is intended to be used for the detection of loss of pulse using photoplethysmography (PPG) and accelerometer sensors present in a wrist worn consumer wearable device. Upon detection of loss of pulse, when the smartwatch is worn, the feature will prompt haptic and audio alerts and notifications to the user and prompt the user's compatible hardware to call emergency services if the user is unresponsive to the notifications and alerts. This is an opt-in feature and will be off bv default. The Loss of Pulse detection SaMD comprises a software component that resides on the compatible consumer wearable device (from here on referenced as a "smartwatch") and a user facing mobile application that resides on general purpose compatible consumer mobile devices such as a smartphone (from here on referenced as "Smartphone"). The software component on the smartwatch analyzes pulse data collected by photoplethysmography (PPG) and accelerometry sensors from qualified smartwatch, using an algorithm employing digital signal processing (DSP) and features-based machine learning based on a convolutional neural network (CNN) to detect possible loss of pulse events. | | Subject Device<br>Loss of Pulse Detection<br>K242967 | Predicate Device<br>Fitbit Irregular Rhythm<br>Notification<br>K212372 | Equivalence<br>Discussion | |----------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | Intended Use | Photoplethysmograph<br>analysis software for<br>over-the-counter use. A<br>photoplethysmograph analysis<br>software device for<br>over-the-counter use analyzes<br>photoplethysmograph data<br>and provides information for<br>identifying loss of pulse. This<br>device is not intended to<br>provide a diagnosis. | Photoplethysmograph analysis<br>software for over-the-counter<br>use. A photoplethysmograph<br>analysis software device for<br>over-the-counter use analyzes<br>photoplethysmograph data<br>and provides information for<br>identifying irregular heart<br>rhythms. This device is not<br>intended to provide a<br>diagnosis. | Same | | Indications for<br>Use | Loss of Pulse Detection is a<br>software-only mobile medical<br>application that is intended to be<br>used with compatible consumer<br>wrist-worn products to analyze<br>pulse data to identify loss of<br>pulse events and provide a<br>notification to the user.<br><br>If the user remains unresponsive<br>to these alerts, Loss of Pulse<br>Detection will attempt to prompt<br>a call to emergency services<br>through the user's connected<br>compatible hardware, such as a<br>smartphone or smartwatch.<br><br>Loss of Pulse Detection is<br>intended for over-the-counter<br>(OTC) use. It is not intended to<br>provide a notification on every<br>loss of pulse event and the<br>absence of a notification is not<br>intended to indicate no disease<br>process is present; rather the<br>Loss of Pulse Detection is<br>intended to opportunistically<br>surface a notification of possible | The Fitbit Irregular Rhythm<br>Notifications is a software-only<br>mobile medical application that<br>is intended to be used with<br>compatible consumer wrist-worn<br>products to analyze pulse rate<br>data to identify episodes of<br>irregular heart rhythms<br>suggestive of atrial fibrillation<br>(AFib) and provide a notification<br>to the user.<br><br>The Fitbit Irregular Rhythm<br>Notifications is intended for<br>over-the-counter (OTC) use. It is<br>not intended to provide a<br>notification on every episode of<br>irregular rhythm suggestive of<br>AFib and the absence of a<br>notification is not intended to<br>indicate no disease process is<br>present; rather the Fitbit Irregular<br>Rhythm Notifications is intended<br>to opportunistically surface a<br>notification of possible AFib<br>when sufficient data are available<br>for analysis.<br><br>These data are only captured | Similar<br><br>Both devices are software-only<br>mobile medical applications<br>intended for use with<br>compatible consumer<br>wrist-worn products. They both<br>utilize PPG analysis software to<br>identify potential irregular heart<br>rhythms, analyze pulse data,<br>and provide notifications to the<br>user if an irregular heart rhythm<br>is detected. Neither device is<br>intended to provide a diagnosis<br>or monitor the outcome of their<br>alerts. Additionally, both<br>devices are intended for users<br>over 22 years old and are not<br>intended for individuals with<br>pre-existing cardiac conditions. | | | pulselessness when sufficient<br>data are available for analysis.<br><br>These data are only captured<br>when the user is still. Loss of<br>Pulse Detection is not intended<br>to replace traditional methods of<br>diagnosis or treatment.<br><br>Loss of Pulse Detection has not<br>been tested for and is not<br>intended for use in people under<br>22 years of age. It is also not<br>intended for use in individuals | when the user is still. Along with<br>the user's risk factors, the Fitbit<br>Irregular Rhythm Notifications<br>can be used to supplement the<br>decision for AFib screening. The<br>Fitbit Irregular Rhythm<br>Notifications is not intended to<br>replace traditional methods of<br>diagnosis or treatment.<br><br>The Fitbit Irregular Rhythm<br>Notifications has not been tested<br>for and is not intended for use in<br>people under 22 years of age. It<br>is also not intended for use in<br>individuals previously diagnosed<br>with AFib. | | | | previously diagnosed with a high<br>risk for sudden cardiac death<br>such as those with coronary<br>artery disease, cardiomyopathy<br>and/or unexplained<br>syncope/fainting. | | | | Use Environment | Home/General Use | Home/General Use | Same<br><br>Both are intended for home<br>use. | | Anatomical Site | Wrist-worn consumer wearable<br>with PPG sensors. | Wrist-worn consumer wearable<br>with PPG sensors. | Same<br><br>Both use consumer grade<br>wrist-worn devices to gather<br>signals from PPG sensors. | | User interface | Mobile application run within<br>the Pixel watch consumer app. | Mobile application run within<br>the Fitbit consumer app | Same<br><br>Both devices include a mobile<br>application component that is<br>run within a consumer<br>application on the user's<br>mobile device (smartphone).<br>This mobile application serves<br>the purpose of the User<br>Interface for both devices. | | Use Method | Collects and analyzes pulse data<br>during periods that meet input | Collects and analyzes<br>tachograms (based on pulse data)<br>during periods of stillness or<br>sleep using input from PPG<br>sensors. | Similar<br><br>Both devices analyze sensor<br>data from the PPG sensor and<br>only analyze data that meet<br>input signal quality<br>requirements. Stillness is part<br>of both devices' input signal<br>quality requirements. Both<br>devices limit the analysis<br>window to time periods<br>relevant to the irregular heart<br>rhythm being detected. The<br>use of the term "tachogram"<br>by the predicate device refers<br>to subsets of the PPG sensor<br>data cropped to approximate<br>individual R-R intervals, and<br>does not meaningfully alter<br>the use method, as both the | | | | | subject and predicate devices<br>use signal processing<br>algorithms to analyze PPG<br>sensor data.<br><br>Both devices are passive<br>background screening tools<br>and users cannot initiate<br>readings.<br><br>Both devices opportunistically<br>surface a notification to the<br>user. | | Limiting Factors | Motion, hand, and finger<br>movements during pulseless<br>period; tattoos on the wrist;<br>inadequate blood flow.<br><br>Does not continuously monitor<br>for signs of loss of pulse<br><br>A lack of notification does not<br>indicate an absence of an<br>underlying loss of pulse | Motion, hand and finger<br>movements, dark tattoos on the<br>wrist, inadequate blood flow.<br><br>Does not continuously monitor<br>for signs of AFib.<br><br>A lack of notification does not<br>indicate an absence of AFib. | Same<br><br>Both devices have similar<br>limiting factors.<br><br>Both devices are not intended<br>for continuous monitoring.<br><br>A lack of notification does not<br>indicate an absence of an<br>irregular rhythm for both<br>devices. | | Compatible<br>devices | Consumer wrist-worn products<br>with PPG sensors (e.g.,<br>smartwatch) that have been<br>qualified for use with the Loss of<br>Pulse Detection feature | Consumer wrist-worn products<br>with PPG<br>sensors (e.g., smartwatch or<br>fitness tracker) that have been<br>qualified for use<br>with Fitbit Irregular Heart<br>Rhythm Notifications | Same<br><br>Both devices are compatible<br>with qualified wrist worn<br>products with PPG sensors<br>that have been qualified for<br>use with the respective feature.<br>The subject device is<br>compatible with a subset of<br>consumer wrist-worn products<br>on which the predicate is<br>qualified (i.e., smartwatches). | | Principles of<br>Operation | Pulse rate data is gathered from a<br>consumer wrist-worn device.<br>The algorithm analyzes the data<br>and classifies it as having signs<br>of an irregular heart rhythm, loss<br>of pulse, or no signs thereof.<br>When signs of loss of pulse are<br>detected, a notification is<br>surfaced to the user. | Pulse rate data gathered from a<br>consumer wrist-worn device is<br>uploaded to a server. The<br>algorithm analyzes the data and<br>classifies it as having signs of<br>AFib or no signs of AFib. When<br>signs of AFib are detected a<br>notification is surfaced to the<br>user through the mobile | Similar<br><br>Both devices have the same<br>basic principle of operation,<br>with nonmaterial differences<br>stemming from the particular<br>irregular pulse rhythm that is<br>intended to be detected. Both<br>devices analyze pulse data | | | | application. | from consumer wrist-worn<br>devices. Apparent differences<br>such as algorithmic analysis<br>on the watch in the subject<br>device and the server on the<br>predicate have no material<br>impact on safety or<br>effectiveness. Both devices<br>opportunistically surface<br>notifications to the user if an<br>irregular pulse rhythm is<br>detected. | # Summary of Substantial Equivalence {6}------------------------------------------------ Image /page/6/Picture/0 description: The image shows the Fitbit logo. The logo consists of a stylized, geometric shape made up of small circles on the left, followed by the word "fitbit" in a sans-serif font. The wordmark is in lowercase letters, and there is a registered trademark symbol to the right of the "t". {7}------------------------------------------------ Image /page/7/Picture/0 description: The image shows the Fitbit logo. The logo consists of a stylized, geometric pattern of dots on the left, followed by the word "fitbit" in a sans-serif font. A registered trademark symbol is located to the right of the word "fitbit". {8}------------------------------------------------ {9}------------------------------------------------ ### 6. Performance Data Testing verifying the performance requirements of the subject device was conducted and is included in this premarket notification, the results of which support substantial equivalence. A summary of the testing is included below: ## Algorithm Development The Loss of Pulse Detection algorithm identifies potential loss of pulse events. The algorithm includes a machine learning component that consists of a convolutional network, which analyzes data from photoplethysmography (PPG) and accelerometer sensors. The algorithm was developed on a dataset consisting of over one hundred thousand hours of free-living data across hundreds of participants who experienced no loss of pulse events and 99 participants who experienced simulated loss of pulse events induced by an arterial occlusion model. The dataset used for model development was split at the participant level into training, validation, and held-out test sets The Loss of Pulse Detection algorithm was trained on the training split and evaluated on the validation set. When algorithm development was complete, the algorithm was locked and the algorithm was evaluated on the held-out test set. The training, validation, and test splits used for development included data from diverse participants with varied age, sex, BMI, and skin tone. ### Bench Testing/Non-Clinical Testing The Loss of Pulse Detection utilizes signals derived from compatible consumer grade wrist-worn products. The wrist-worn products were qualified for use with the software to ensure that the data provided could meet signal attribute and quality requirements necessary for heart rhythm analysis and detect adequate PPG signal quality. Bench testing included product signal acquisition testing, aggressor testing for known challenge conditions potentially impacting the quality of PPG signal acquisition, and accuracy assessment of the inputs to the Loss of Pulse Detection that were derived from the wrist-worn products. Qualification testing was repeated for all qualified wrist-wearable products. The algorithm was tested to ensure that it accepted and rejected data correctly and that it can correctly analyze the input data. {10}------------------------------------------------ Image /page/10/Picture/0 description: The image shows the Fitbit logo. The logo consists of a stylized "fitbit" text in a sans-serif font, with a small registered trademark symbol to the right of the "t". To the left of the text is a geometric design made up of several small circles arranged in a pattern resembling a stylized star or snowflake. The Loss of Pulse Detection presents a "Basic Documentation" Software Documentation Level based on the risks of device software function in the context of the device's intended use as defined in FDA's Guidance for the Content of Premarket Submissions for Device Software Functions (June 14, 2023) (Guidance Document). Testing of the mobile application demonstrates that the Loss of Pulse Detection feature adequately performs all the necessary functionalities including education/onboarding and generating user notifications when pulselessness is identified. ## Human Factors Testing Summary A Human Factors Validation Study was designed to evaluate the critical and noncritical tasks associated with the use of the device. The Human Factors Validation Study was performed using a simulated version of the Loss of Pulse Detection within the Pixel watch mobile app, representative of the final app. 19 users were recruited from the general population for the study, with the goal of recruiting at least 15 intended users. During the test session, each participant performed various tasks within representative, naturalistic use scenarios. These tasks included setup and onboarding to an initial check-in, responding to an escalation, triggering emergency response services, and passive feature use. The first evaluation activity (setup and onboarding) included a self-selection component where participants indicated whether or not they are an intended Loss of Pulse Detection application user, resulting in 16 intended and 3 unintended users. Participants also performed a knowledge task to evaluate critical tasks that could not be evaluated during the simulated use scenarios. During each evaluation activity, use errors, instances of moderator assistance, close calls, and difficulties were documented. Open-ended questions were used to collect participants' subjective assessments of the root cause(s) associated with any such event and to collect participants' feedback on the product's use-safety. Data was consolidated and analyzed with a focus on events with the potential for serious harm (critical tasks). The human factors testing found that the loss of pulse detection feature was safe and effective for the intended users, uses, and use environments. ### Real World Evidence Summary Real-world evidence (RWE) indicates users are able to respond to haptic, audio, and visual feedback and de-escalate based solely on reading the device labeling. A sample of data from RWE shows that users clear >98% of notifications from the pre-phone call gates in real-world free-living conditions. There was, on average, 1 phone call placed by Loss of Pulse Detection in 75 person-years of real-world use. ### Clinical Testing Summary The Loss of Pulse Detection (LPD) software, intended for use with wrist-worn devices, was clinically validated in a study. The study aimed to evaluate the software's ability to detect loss of pulse events and initiate an emergency call. A total of 135 participants were enrolled in one clinical study and 21 participants in another clinical study. The participants included a racially and ethnically diverse population, including adults of diverse sex and age. The results from the clinical validation study showed a sensitivity of 69.3% (95% C1: 64.3% 74.1%) ## Confidential {11}------------------------------------------------ Image /page/11/Picture/0 description: The image shows the Fitbit logo. The logo consists of a stylized "fitbit" text in a sans-serif font, with a small registered trademark symbol to the right. To the left of the text is a geometric pattern made up of 13 circles of varying sizes, arranged in a diamond shape. across 135 users and a sensitivity of 64.5% (95% CI: 55.7% to 74.2%) after adjusting for performance after a simulated collapse. The specificity was analyzed using evaluable data from 131 participants from the first study. It showed a day-level specificity of 99.965% (95% CI 99.804, 99.999). A total of 5 adverse events were reported. No adverse events reported were related to the LPD software. Most adverse events were identified as possible anticipated risks in the study protocol, namely skin irritation from wearing a consumer wrist-worn device. Demographic characteristics of the study population are summarized in the table below. | | Clinical validation study<br>(pulseless and pulsatile) | Clinical validation study<br>(pulseless) | |------------------------------------|--------------------------------------------------------|------------------------------------------| | N | 135 | 21 | | Age | | | | <35 | 16.3% (22) | 14.3% (3) | | 36-59 | 38.5% (52) | 61.9% (13) | | 60+ | 45.2% (61) | 23.8% (5) | | Sex | | | | Female | 60.7% (82) | 47.6% (10) | | Male | 39.3% (53) | 52.4% (11) | | Monk skin tone | | | | 1-4 | 40.7% (55) | 28.6% (6) | | 5-6 | 35.6% (48) | 66.7% (14) | | 7-8 | 20.7% (28) | 4.8% (1) | | 9-10 | 3.0% (4) | 0.0% (0) | | Individual<br>typology angle scale | | | | 1 | 3.0% (4) | 0.0% (0) | | 2 | 5.9% (8) | 9.5% (2) | | 3 | 11.1% (15) | 28.6% (6) | | 4 | 11.1% (15) | 33.3% (7) | | 5 | 43.0% (58) | 19.0% (4) | | 6 | 25.9% (35) | 9.5% (2) | | Body mass index | | | | <18.5 | 0.7% (1) | 4.8% (1) | | | Clinical validation study<br>(pulseless and pulsatile) | Clinical validation study<br>(pulseless) | | 18.5–<25 | 18.5% (25) | 47.6% (10) | | 25–<30 | 27.4% (37) | 38.1% (8) | | ≥30 | 53.3% (72) | 9.5% (2) | {12}------------------------------------------------ Image /page/12/Picture/0 description: The image shows the Fitbit logo. The logo consists of a stylized "f" made up of a grid of dots on the left and the word "fitbit" in a sans-serif font on the right. The logo is black and white. ### 7. Conclusion The Loss of Pulse Detection and its predicate have the same Intended Use, similar Indications for Use, similar technological characteristics and principles of operation. The technological differences between the subject Loss of Pulse Detection and its predicate, Fitbit Irregular Rhythm Notifications, are in relation to the very specific formulation of the respective algorithms. However, any such differences do not raise new or different questions of safety or effectiveness. Moreover, testing and clinical data provided in the submission demonstrate that the subject device meets all Special Controls and operates in a manner that is as safe and effective as the predicate device. Therefore, Loss of Pulse Detection is considered substantially equivalent to the predicate device.