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Google just announced that its âloss of pulse dectectionâ feature for the Pixel Watch 3 has received FDA clearance and will be available to U.S. users by the end of March. Read on for more on what this feature does, how well it works (according to one early study), and how youâll be able to enable it.
The feature has been available in several European countries since late 2024. According to a Google help page on the feature, itâs currently available in âAustria, Belgium, Denmark, France, Germany, Ireland, Italy, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, and the United Kingdom.â
Google - Pixel Watch 3 (41mm) Smartwatch with Porcelain Band - LTE - Polished Silver
$449.99 at Amazon
Get Deal
Get Deal
$449.99 at Amazon
According to documents from Google, the feature is meant to sound an alarm and contact emergency services whenever the person wearing the watch loses their pulse. This could be from a heart attack, poisoning, overdose, or other cause of respiratory or circulatory failure, according to Googleâs documents on what they had in mind when developing the feature.
When the watch detects a âloss of pulse eventâ (it thinks you are wearing the watch but cannot detect a pulse with the regular heart rate sensor), the watch is programmed to do the following, in order:
The loss of pulse detection feature is promising for what are sometimes called âunwitnessedâ cardiac arrests, as a group of Italian healthcare professionals wrote in the journal Resuscitation. I wasnât able to find any real-world accounts of this feature saving someoneâs life, but to be fair itâs only been available for a few months.
Google emphasizes that the feature is not intended to provide any treatment or be expected to save your life, and definitely cannot replace medical monitoring devices that may have been prescribed or recommended to you by your provider. It canât prevent a loss of pulse, or determine the cause of a loss of pulse, and it canât even be sure that its emergency calls will go through.
Importantly, the loss of pulse detection process has not been tested in a variety of real-world situations that may increase the risk of false alarms, or of missing a real event. These are some of the people who might be most interested in this feature, so itâs worth noting that the feature has not been tested for people identified as high risk for sudden cardiac death, or for people who are pregnant, under 22 years of age, who have chronic pain, poor blood flow to the wrist, peripheral nerve conditions, cognitive impairment, sickle cell disease, or who have a tattoo on their wrist that may interfere with the sensor.
Google has published a brief summary of the results of their testing from the watch, as part of this document that gives instructions for use. They tested the feature on 135 volunteers, includingâaccording to a press releaseâstunt actors who simulated falls while wearing a tourniquet.
The sensitivity in a clinical trial was 69.3%, meaning that the feature was activated 69.3% of the time that a person had an actual loss of pulse. The other 30.7% of the time, it didnât activate. Thatâs not great, but the idea seems to be that itâs a lot better than nothing.
The other metric of accuracy, specificity, Google described as amounting to â1 false positive call over 7.75 user-yearsâ with 131 of their users. (That would be compatible with 131 users wearing the watch for about three weeks each, resulting in one person getting a false positive, but Google didnât release the full results so we canât say whether thatâs exactly how the study went, or how their use compared to what you might be doing with your watch over the next 7.75 years.)
If you do get a false positive, youâll have a few chances to cancel the alert before it gets as far as calling emergency services. If you tap that âIâm OKâ button, the watch will ask if you were doing anything innocuous that may have triggered it. Sleeping on your arm is one of the options; so are a loose fit on the watch band, and not wearing the watch at all. Google also notes that other factors like ambient light, or pressure on the skin, may sometimes result in false positives.
Once the feature is available here, it will be an option when you're setting up a new watch. (So far it hasn't been announced for any Fitbit models or older Pixel watches, just the Pixel Watch 3 in both sizes.) To turn on loss of pulse detection for the Pixel Watch 3 that you already have, go into the Pixel Watch app, tap Safety & Emergency, and look for Loss of Pulse Detection. There is a switch that allows you to turn the feature on or off.
Full story here:
Google just announced that its âloss of pulse dectectionâ feature for the Pixel Watch 3 has received FDA clearance and will be available to U.S. users by the end of March. Read on for more on what this feature does, how well it works (according to one early study), and how youâll be able to enable it.
The feature has been available in several European countries since late 2024. According to a Google help page on the feature, itâs currently available in âAustria, Belgium, Denmark, France, Germany, Ireland, Italy, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, and the United Kingdom.â
Google - Pixel Watch 3 (41mm) Smartwatch with Porcelain Band - LTE - Polished Silver
$449.99 at Amazon
Get Deal
Get Deal
$449.99 at Amazon
What is âloss of pulse detectionâ?
According to documents from Google, the feature is meant to sound an alarm and contact emergency services whenever the person wearing the watch loses their pulse. This could be from a heart attack, poisoning, overdose, or other cause of respiratory or circulatory failure, according to Googleâs documents on what they had in mind when developing the feature.
When the watch detects a âloss of pulse eventâ (it thinks you are wearing the watch but cannot detect a pulse with the regular heart rate sensor), the watch is programmed to do the following, in order:
Perform additional checks (taking about 20 seconds) to be sure that itâs not detecting movement or a pulse. For example, it can use brighter lights in the optical heart rate sensor, and check for movement from accelerometers.
Buzz your wrist and ask if you are OK. You can tap an âIâm OKâ button to clear the alert. This phase lasts for 15 seconds.
Play an audible alarm while displaying a 20-second countdown stating that it will place an emergency call (âNo pulse detected / Calling 911 inâŚâ)
Call 911 through the watchâs LTE connection, or through a connected phone, and play a recorded message to them (not audible to you or to bystanders). The message states that your watch detected a loss of pulse and that you are unresponsive, and it gives your approximate location.
While the call is ongoing, there is a âtalk to 911â button displayed on the watch. You (or a bystander) can tap that button to interrupt the recorded message and speak to emergency services as a regular phone call.
What is (and isnât) loss of pulse detection good for?
The loss of pulse detection feature is promising for what are sometimes called âunwitnessedâ cardiac arrests, as a group of Italian healthcare professionals wrote in the journal Resuscitation. I wasnât able to find any real-world accounts of this feature saving someoneâs life, but to be fair itâs only been available for a few months.
Google emphasizes that the feature is not intended to provide any treatment or be expected to save your life, and definitely cannot replace medical monitoring devices that may have been prescribed or recommended to you by your provider. It canât prevent a loss of pulse, or determine the cause of a loss of pulse, and it canât even be sure that its emergency calls will go through.
Importantly, the loss of pulse detection process has not been tested in a variety of real-world situations that may increase the risk of false alarms, or of missing a real event. These are some of the people who might be most interested in this feature, so itâs worth noting that the feature has not been tested for people identified as high risk for sudden cardiac death, or for people who are pregnant, under 22 years of age, who have chronic pain, poor blood flow to the wrist, peripheral nerve conditions, cognitive impairment, sickle cell disease, or who have a tattoo on their wrist that may interfere with the sensor.
How well does loss of pulse detection work on the Pixel Watch 3?
Google has published a brief summary of the results of their testing from the watch, as part of this document that gives instructions for use. They tested the feature on 135 volunteers, includingâaccording to a press releaseâstunt actors who simulated falls while wearing a tourniquet.
The sensitivity in a clinical trial was 69.3%, meaning that the feature was activated 69.3% of the time that a person had an actual loss of pulse. The other 30.7% of the time, it didnât activate. Thatâs not great, but the idea seems to be that itâs a lot better than nothing.
The other metric of accuracy, specificity, Google described as amounting to â1 false positive call over 7.75 user-yearsâ with 131 of their users. (That would be compatible with 131 users wearing the watch for about three weeks each, resulting in one person getting a false positive, but Google didnât release the full results so we canât say whether thatâs exactly how the study went, or how their use compared to what you might be doing with your watch over the next 7.75 years.)
If you do get a false positive, youâll have a few chances to cancel the alert before it gets as far as calling emergency services. If you tap that âIâm OKâ button, the watch will ask if you were doing anything innocuous that may have triggered it. Sleeping on your arm is one of the options; so are a loose fit on the watch band, and not wearing the watch at all. Google also notes that other factors like ambient light, or pressure on the skin, may sometimes result in false positives.
How to enable (or disable) loss of pulse detection on the Pixel Watch 3
Once the feature is available here, it will be an option when you're setting up a new watch. (So far it hasn't been announced for any Fitbit models or older Pixel watches, just the Pixel Watch 3 in both sizes.) To turn on loss of pulse detection for the Pixel Watch 3 that you already have, go into the Pixel Watch app, tap Safety & Emergency, and look for Loss of Pulse Detection. There is a switch that allows you to turn the feature on or off.
Full story here:
![[DK]](/data/avatars/s/57/57999.jpg?1720990206){kind=avatar}
