Contributed by Emma Cary, B.S.
Ever wonder how the Pod can measure your heart rate and breathing without you wearing anything? The secret lies in the ultra-sensitive sensors built right into the Pod. These sensors are so powerful that they can even pick up your pet’s heartbeat if they curl up on your bed.
Key takeaways
- The Pod utilizes a thin strip of health-grade piezoelectric sensors concealed within the cover to detect subtle vibrations from your heartbeat and breathing.
- Digital signal processing and machine learning transform those raw vibrations into accurate heart rate (HR), heart rate variability (HRV), and breath rate.
- The Pod’s measurements are highly accurate: 99% for HR, 95% for HRV, and 98% for breath rate compared to gold-standard clinical devices.
- You get effortless health insights every night, without needing to wear or charge anything.
The magic sensor: the piezoelectric strip
At the heart of this technology is a strip of piezoelectric sensors (or “piezo” for short). This strip runs across the Pod at chest level. Every time your heart beats or you breathe in and out, your body creates tiny vibrations. The piezo strip detects these small movements and turns them into a signal.
Think of it like a microphone that doesn’t capture sound, but instead listens to the subtle movements of your body. Importantly, the sensors are safe and produce electromagnetic fields that are even lower than the background in most homes (ref).
Figure 1. On the left is the piezo strip connected to the sensor board, on the right is the Pod with a light blue line indicating where the piezo strip lives.
From vibrations to insights
The raw signal from the sensors is full of information (see Figure 2):
- Slow waves show when you’re breathing.
- Sharp peaks reveal each heartbeat.
Figure 2.Piezo signals from the Pod Cover for a single individual across 30 seconds. The blue line represents the piezo signal, where the waves indicate the individual’s breaths and the sharp peaks are their heartbeats within that breath
On its own, the signal above looks messy. That’s where digital signal processing comes in to clean up the noise and make the waves and peaks crystal clear. Then, machine learning algorithms step in to measure:
- Heart Rate (HR): how many times your heart beats per minute.
- Heart Rate Variability (HRV): the variation in time between each heartbeat, a key marker of recovery and stress.
- Breath Rate: how many breaths you take per minute.
Figure 3. Filtered piezo signals from a single individual sleeping on the Pod cover across 30 seconds. The orange line represents the filtered piezo signal, from which we are able to determine HR based on the number of peaks over a minute, and then to calculate HRV we look at the time between peaks to calculate the RMSSD.
Tested, trained, and proven
The Pod’s accuracy didn’t happen overnight. Our algorithms were trained and validated against gold-standard devices used in sleep labs and hospitals:
- HR & HRV: Tested against medical-grade ECGs for over 400 lab hours and 1500 nights.
- Breath Rate: Tested against respiratory belts (the gold standard) over 360 nights.
The results? Accuracy levels that match or even rival medical devices:
- HR: 99% accurate
- HRV: 95% accurate
- Breath Rate: 98% accurate
Why it matters
These measurements aren’t just numbers; they power your sleep insights. HR, HRV, and breath rate are key inputs for detecting your sleep stages and understanding your recovery. And with the Pod, you get them passively, without wearing a watch, strap, or ring.
So now you know how the Pod collects your biometric data each night, by turning tiny vibrations into big insights about your body.
