| 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 | during sleep |
| SpO2 (oxygen saturation) | red (660nm), IR (940nm) LED, photodiode | | see SpO2 note | | 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 Sleep Apnea | | *screening | |
| Chronic stress | skin temp, EDA electrodes (electrodermal activity)/sweat sensing, | HRV, resting HR, RR | | | lower RMSSD = generally more stress (over time) | |
| Arrhythmia, Bradycardia, Tachycardia | accelerometer | HR | irregular pulse algorithm | PPG + accel | | probably during sleep? |
| Hypoxemia (low blood 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
| during sleep |
| 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:
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gps?
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SOM
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does this interface with sensors directly?
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averaging/smoothing functions
- lots of things are over time measurements
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filtering (mentioned above)
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esp important for HR
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other things that require extensive filtering - i noted to measure during sleep. unsure though
-
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skin temp correlates with menstrual cycle & possibly other hormones - def worth
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ambient light sensor to tune LED readings
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use IMU for exercise/activity tracking
- did not get to it in the table
thoughts:
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option to turn on/off these readings
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term for screenings - “flags” or “risk alerts”
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children vs adults?