1. Reliable Clinical Monitoring using Wireless Sensor Networks: Experience in a Step-down Hospital Unit Yetta

2. Outline Introduction Monitoring system Clinical study Clinical deterioration detection Conclusion

3. Introduction Clinical deterioration detection ICU / step-down unit / general care unit IEEE 802.15.4 / IEEE 802.11 Heart rate (HR) and blood oxygenation (spO2)

4. Monitoring System TelosB / OxiLink pulse-oximeter

5. Monitoring System CTP (collection tree protocol) – Low reliability because of user mobility DRAP (Dynamic Relay Association Protocol) – Isolate the mobility from multi-hop routing Single-hop to first relay Relay to base station

6. nodecost to root B2 C2 D1 E0 E D CB neighbor table of node A A

7. Monitoring System Radio power management Sensor component (OxiLink pulse-oximeter) – Control by TelosB – average over 8 sec Logging component – Batching flash writing

8. Clinical Study 1200m 2 18 relays 41 patients Pulse and oxygenation were measured at 30- and 60-second intervals

9. Reliability Network reliability Sensing reliability Time-to-failure Time-to-recover

10. Network Reliability Mean = 22.4 min 95% < 2.5 min

11. Sensing Reliability Significantly affected by patient movement, sensor disconnections, sensor placement, and nail polish

12. Improvement of Sensing Reliability Oversample Median reliability: 84%(30sec), 75%(60sec) Median = 1.81 min75% short burst Long-tailed => sensor disconnection

13. Improvement of Sensing Reliability Disconnection alarms

14. Clinical Deterioration Detection

15. CUSUM algorithm – detecting statistically significant changes in a series of measurements – Sliding window

16. Conclusion High network reliability System reliability dominated by sensor reliability – Oversampling – Disconnection alarms Show the potential of real-time detection of clinical deterioration