Rules, baselines and fusion

Alarm fatigue is the enemy: a monitor that cries wolf gets ignored. These are the principles behind every rule.

Rules are written by measurement, not by sensor

“SpO2 below 90 for 10 s” applies to every resident who has an oximeter. Adding a sensor switches on the rules for what it measures, with no other change. For each resident, three sources count: their own wearables, the sensors of the bed they lie in, and the sensors of their room.

Missing data is never zero

A silent or disconnected radar never means “not breathing”. Rules only look at sensors that are approved and online, and a rule that needs ten seconds of readings needs ten seconds of fresh readings without gaps. A sensor that goes quiet raises Sensor offline instead.

Each resident against their own normal

Some rules compare a resident with their own usual values (“heart rate 20% above usual”). The usual value is a rolling average that leaves out the last two minutes, so an episode does not slowly become its own normal.

Two independent signs (fusion)

Some alerts need two signs at once, from different sensors: one odd reading alone stays quiet. A thud in the room and the resident leaving the bed within ten seconds is a possible fall; one oximeter showing two odd values is still one sign.

The room microphone supports, it does not decide

A microphone cannot tell which bed a sound came from. When it hears distress and a resident’s own signals agree, the alert is that resident’s. When nobody’s signals change, it raises a softer Check every bed alert for the room, five seconds after the sound, so a fall is not also reported as a room sound.