New tools for estimating the EMS transport interval: implications for policy and patient care

Accuracy of Prehospital Services' Estimated Time to Arrival for Ground Transport to the Emergency Department

BACKGROUND

Emergency medical services (EMS) transporting patients to the emergency department (ED) typically call ahead to provide an estimated time to arrival (ETA). Accurate ETA facilitates ED preparation and resource allotment in anticipation of patient arrival.

OBJECTIVE

The study purposed to determine the accuracy of ETA provided by EMS ground units.

METHODS

We performed a single-center, prospective, observational study of ED patients arriving via EMS ground transport. The primary outcome was the time difference between EMS-reported ETA and actual time of arrival (ATA). The difference between ATA and ETA was compared using the two-sided Wilcoxon Signed-Rank Test. Subgroup analysis was performed to evaluate ETA accuracy for specific types of transports and assess variability by month and time of day.

RESULTS

We included 1176 patient transports in the final analysis. The overall median difference ATA-ETA was 3 min (interquartile range 1-5 min) with a range of -26-48 minutes (Z = -25.139, p < 0.001). EMS underestimated ETA in 961 cases (81.7%), and 94 ETAs (8.0%) were accurate to within 1 min. The largest difference between ATA and ETA occurred between 07:00-07:59 and 16:00-16:59 (5 min, interquartile range 2-7).

CONCLUSION

Our data demonstrate that prehospital providers underestimate time to ED arrival in most ground transports; however, the median difference between estimated and actual time to arrival is small.

Helicopter EMS and rapid transport for ST-elevation myocardial infarction: The HEARTS study

Background: Helicopter emergency medical services (HEMS) and ground EMS (GEMS) are both integral parts of out-of-hospital transport systems for patients with ST-elevation myocardial infarction (STEMI) undergoing emergency transport for primary percutaneous coronary intervention (PPCI). There are firm data linking time savings for PPCI transports with improved outcome. A previous pilot analysis generated preliminary estimates for potential HEMS-associated time savings for PPCI transports. Methods: This non-interventional multicenter study conducted over the period 2012–2014 at six centers in the USA and in the State of Qatar assessed a consecutive series of HEMS transports for PPCI; at one center consecutive GEMS transports of at least 15 miles were also assessed if they came from sites that also used HEMS (dual-mode referring hospitals). The study assessed time from ground or air EMS dispatch to transport a patient to a cardiac center, through to the time of patient arrival at the receiving cardiac unit, to determine proportions of patients arriving within accepted 90- and 120-minute time windows for PPCI. Actual times were compared to “route-mapping” GEMS times generated using geographical information software. HEMS' potential time savings were calculated using program-specific aircraft characteristics, and the potential time savings for HEMS was translated into estimated mortality benefit. Results: The study included 257 HEMS and 27 GEMS cases. HEMS cases had a high rate of overall transport time (from dispatch to receiving cardiac unit arrival) that fell within the predefined windows of 90 minutes (67.7% of HEMS cases) and 120 minutes (91.1% of HEMS cases). As compared to the calculated GEMS times, HEMS was estimated to accrue a median time saving of 32 minutes (interquartile range, 17–46). The number needed to transport for HEMS to get one additional case to PPCI within 90 minutes was 3. In the varied contexts of this multicenter study, the number of lives saved by HEMS, solely through time savings, was calculated as 1.34 per 100 HEMS PPCI transports. Conclusions: In this multicenter study, HEMS PPCI transport was found to be appropriate as defined by meeting predefined time windows. The overall estimate for lives saved through time savings alone was consistent with previous pilot data and was also generally consistent with favorable cost-effectiveness. Further research is necessary to confirm these findings, but judicious HEMS deployment for PPCI transports is justified by these data.

Accuracy of Perceived Estimated Travel Time by EMS to a Trauma Center in San Bernardino County, California

INTRODUCTION

Mobilization of trauma resources has the potential to cause ripple effects throughout hospital operations. One major factor affecting efficient utilization of trauma resources is a discrepancy between the prehospital estimated time of arrival (ETA) as communicated by emergency medical services (EMS) personnel and their actual time of arrival (TOA). The current study aimed to assess the accuracy of the perceived prehospital estimated arrival time by EMS personnel in comparison to their actual arrival time at a Level II trauma center in San Bernardino County, California.

METHODS

This retrospective study included traumas classified as alerts or activations that were transported to Arrowhead Regional Medical Center in 2013. We obtained estimated arrival time and actual arrival time for each transport from the Surgery Department Trauma Registry. The difference between the median of ETA and actual TOA by EMS crews to the trauma center was calculated for these transports. Additional variables assessed included time of day and month during which the transport took place.

RESULTS

A total of 2,454 patients classified as traumas were identified in the Surgery Department Trauma Registry. After exclusion of trauma consults, walk-ins, handoffs between agencies, downgraded traumas, traumas missing information, and traumas transported by agencies other than American Medical Response, Ontario Fire, Rialto Fire or San Bernardino County Fire, we included a final sample size of 555 alert and activation classified traumas in the final analysis. When combining all transports by the included EMS agencies, the median of the ETA was 10 minutes and the median of the actual TOA was 22 minutes (median of difference=9 minutes, p<0.0001). Furthermore, when comparing the difference between trauma alerts and activations, trauma activations demonstrated an equal or larger difference in the median of the estimated and actual time of arrival (p<0.0001). We also found month and time of day to be associated with variability in the difference between the median of the estimated and actual arrival time (p=0.0082 and p=0.0005 for month and time of the day, respectively).

CONCLUSION

EMS personnel underestimate their travel time by a median of nine minutes, which may cause the trauma team to abandon other important activities in order to respond to the emergency department prematurely. The discrepancy between ETA and TOA is unpredictable, varying by month and time of day. As such, a better method of estimating patient arrival time is needed.