At the end of the trial, the computer scientists were pleased to learn the network was rock solid. Data were reliably received more than 99 percent of the time.
Sensing reliability was much lower, only 81 percent. Occasionally, a patient was wearing nail polish, which can block oximeter readings. Patient movement, such as gesturing, caused short bursts of failures, and some oximeters fell off or were removed, which led to long outages.
Because most of the failures occurred in short bursts, the scientists decided they could improve sensing reliability by over-sampling, that is, taking measurements at a rate higher than the one specified by clinical needs.
The best way to deal with disconnections, they decided, was to send an alarm if data failed to arrive for 10 or 15 minutes, a threshold that would result in an alarm rate low enough not to burden the nursing staff.
Lu says he was often asked why the team built a separate network instead of using the Wi-Fi network Barnes-Jewish recently installed for the convenience of their physicians and patients.
The mesh network uses less power, costs much less to install (because no wiring is needed), and can be deployed on demand, he says.
Did it work?
During the prototype trial, the condition of two patients deteriorated and a third patient was diagnosed with life-threatening sleep apnea.
Physicians looked at the vital-sign traces from the mesh network after the fact and confirmed that in all three cases the clinical deterioration could have been picked up from the traces.
The computer scientists also retroactively tested the ability of an algorithm that detects statistically significant changes in a
|Contact: Diana Lutz|
Washington University in St. Louis