CADDiE Data Report
5/3/2021
OVERVIEW
The San Francisco EMS Agency’s Centralized Ambulance Destination Determination (CADDiE) program attempts to manage the distribution of EMS patients among local hospitals, in order to improve various EMS and hospital metrics believed to be impacted by poor distribution. This is accomplished with physicians and paramedics, utilizing real-time and daily system data, providing on-line direction to EMS crews in the field prior to making a transport decision.
Phases of the CADDiE program:
- Baseline: 30-day period between March 17, 2020 – April 15, 2020, beginning the day San Francisco’s shelter-in-place order was issued until the start of the CADDiE program. Dates were selected to ensure consistent EMS system conditions related to COVID-19.
- Phase 1: April 16, 2020 - July 3, 2020 - CADDiE operational 24-hours per day and hospital destination given to EMS crews was a recommendation.
- Phase 2: July 4, 2020 - October 26, 2020 - CADDiE operational 24-hours per day and hospital destination given to EMS crews was mandatory.
- Phase 3: October 27, 2020 - April 15, 2021 - CADDiE operational between 7am and Midnight, 7-days per week, and hospital destination given to EMS crews is a recommendation.
- Phase 4: April 16, 2021 - Present - CADDiE operational between 7am and 7pm, 7-days per week, and hospital distination given to EMS crews is a recommendation.
EMS OPERATIONAL METRICS
| Phase | Avg Response | Avg Transport | Avg Arrival-to-Clear | Avg Time-on-Task |
|---|---|---|---|---|
| Baseline | 8.41 | 16.75 | 34.57 | 76.95 |
| Phase 1 | 8.71 | 16.45 | 33.28 | 76.81 |
| Phase 2 | 9.15 | 16.74 | 34.26 | 79.04 |
| Phase 3 | 9.40 | 17.61 | 35.11 | 80.94 |
| Phase 4 | 9.58 | 17.77 | 34.99 | 81.26 |
AMBULANCE DISTRIBUTION
A ratio of EMS transports to Emergency Department size is used to assess relative transport volume and the distribution of ambulances among local hospitals. The “Transport-to-Bed” ratio measures the number of EMS patients transported to each hospital daily in relation to the number of licensed beds in that hospital’s Emergency Department.
A primary goal of CADDiE is to “level-load” the system, reducing the relative transport volume for heavily impacted hospitals and increasing volume at less impacted hospitals. The maximum daily ratio targeted by CADDiE is 1.0. The coefficient of variation (standard deviation in relation to the mean) among hospital ratios is used as a measure of relative variability, with lower variation suggesting improved ambulance distribution.
| Phase | Chinese | CPB | CPD | CPV | KSF | STF | STM | UCB | UCSF | VA | ZSFG | Variation |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Baseline | 0.3238 | 0.8125 | 0.5467 | 0.6022 | 0.5155 | 1.3300 | 0.7083 | 0.1250 | 0.6873 | 0.1911 | 1.0215 | 63.19687 |
| Phase 1 | 0.4123 | 0.9573 | 0.7089 | 0.6733 | 0.4955 | 1.1614 | 0.6725 | 0.0968 | 0.7211 | 0.2101 | 0.8796 | 59.36752 |
| Phase 2 | 0.5429 | 1.2734 | 1.0261 | 0.7764 | 0.5404 | 1.2743 | 0.8826 | 0.1257 | 0.7015 | 0.2151 | 0.7769 | 57.13473 |
| Phase 3 | 0.4979 | 1.1988 | 1.0544 | 0.8004 | 0.6088 | 1.3132 | 0.8015 | 0.1257 | 0.7420 | 0.2090 | 0.7706 | 56.91047 |
| Phase 4 | 0.3697 | 1.1691 | 0.9765 | 0.7419 | 0.6345 | 1.2471 | 0.8419 | 0.1382 | 0.7751 | 0.2157 | 0.6710 | 57.00499 |
HOSPITAL DIVERSION
DIVERSION AND EMS VOLUME
The plot below shows the correlative relationship between total system diversion and EMS transport volume.
- Blue line and shading: Trend line with confidence interval.
- R: Strength of linear relationship between the two variables. Numbers closer to 1 or -1 indicate stronger correlation and numbers closer to zero indicate weaker correlation.
The relationship between diversion and transports is visualized below for the three hospitals with the highest amount of diversion minutes since beginning CADDiE.
HOSPITAL SURGE
By improving ambulance distribution, CADDiE attempts to reduce “surge events” at local hospitals. For the purpose of this analysis, a surge event occurs when:
The number of ambulance arrivals to a hospital in a given hour exceeds 30% of their licensed ED bed count, or is equal or greater than 6, whichever is lowest.
The average rate of daily surge events is measured for the three hospitals with the highest transport volume since beginning CADDiE.
