| To measure | sensors/hardware | readings needed | calculation | method | notes | how often to measure |
|---|---|---|---|---|---|---|
| Heart Rate | green LED (~530nm), photodiode accelerometer for noise, band pass filter | PPG | filter for 0.5-4 Hz (≈ 30–240 bpm) | |||
| Heart Rate Variability | HR reading | changes in time between heart beats RMSSD measured in milliseconds | PPG | measure during sleep, need continuous HR data for a period of measurement | ||
| SpO2 (oxygen saturation) | red (660nm), IR (940nm) LED, photodiode | see notes | how to account for differences in skin tone? only works on radial artery | |||
| Anemia | red, IR, green, blue LED, photodiode | compare rates of absorption of hemoglobin at different wavelengths | *screening high SpO2 != no anemia consistently low = flag measure during sleep | |||
| Sleep apnea | SpO2, RR | calculate drops in oxygen during sleep see notes | *screening | |||
| Chronic stress | skin temp, EDA electrodes (electrodermal activity)/sweat sensing, | HRV, resting HR, RR | lower RMSSD = generally more stress (over time) | |||
| Arrhythmia | accelerometer | HR | irregular pulse algorithm | PPG + accel | ||
| Hypoxia (low oxygen) | barometer (for altitude filtering) | SpO2 | low SpO2 over period of time: <92% low and <88% high risk | |||
| Respiratory Rate (RR) | green LED, photodiode, accelerometer *same as HR, but looks at different part of waveform | PPG + analysis | lower RR = better overall fitness higher overall = fatigue/stress combine with accel data to reduce motion noise normal ~12-20 breaths/min (adult) measure at night | |||
| VO2 Max | HR | find an algorithm | ||||
| Sleep | accelerometer for motion | HR, SpO2, RR, HRV | determine sleep phase, length of sleep | |||
| Hydration | skin conductivity/sweat sensing | high skin conductivity = more salt/electrolytes = less water = less hydration | ||||
| other hardware: |
- gps?
- SOM
- does this interface with sensors directly?
- averaging/smoothing functions
- lots of things are over time measurements
- filtering (mentioned above)
- esp important for HR
- other things that require extensive filtering - i noted to measure during sleep. unsure though
- skin temp correlates with menstrual cycle & possibly other hormones - def worth
- ambient light sensor to tune LED readings
- use IMU for exercise/activity tracking
- did not get to it in the table
thoughts:
- option to turn on/off these readings
- term for screenings - “flags” or “risk alerts”
- children vs adults?