Impact of Building Height and Volume on Cardiac Arrest Response Time

<p>Emergency medical services (EMS) care may be delayed when out-of-hospital cardiac arrest (OHCA) occurs in tall or large buildings. We hypothesized that larger building height and volume were related to a longer <i>curb-to-defibrillator activation</i> interval. We retrospectively evaluated 3,065 EMS responses to OHCA in a large city between 2003–13 that occurred indoors, prior to EMS arrival, and without prior deployment of a defibrillator. The two-tiered EMS system uses automated external defibrillator-equipped basic life support firefighters followed by paramedics dispatched from a single call center. We calculated three time intervals obtained from the computerized dispatch report and time-synchronized defibrillators: initial 911 call to address curb arrival by first unit (<i>call-to-curb</i>), curb arrival to defibrillator power on (<i>curb-to-defib on</i>), and the combined <i>call-to-defib on</i> interval. Building height and surface area were measured with a validated program based on aerial photography. Buildings were categorized by height as short (<25 ft), medium (26–64 ft) and tall (>64 ft). Volume was categorized as small (<60,000 ft<sup>3</sup>), midsize (60,000–1,202,600 ft<sup>3</sup>) and large (>1,202,600 ft<sup>3</sup>). Intervals were compared using the two-tailed Mann-Whitney test. EMS responded to 1,673 OHCA events in short, 1,134 in medium, and 258 in tall buildings. There was a 1.14 minute increase in median <i>curb-to-defib on</i> interval from 1.97 in short to 3.11 minutes in tall buildings (<i>p</i> < 0.01). Taller buildings, however, had a shorter <i>call-to-curb</i> interval (4.73 for short vs 3.96 minutes for tall, <i>p</i> < 0.01), such that the difference in <i>call-to-defib on</i> interval was only 0.27 minutes: 6.87 for short and 7.14 for tall buildings. A similar relationship was observed for small-volume compared to large-volume building: longer <i>curb-to-AED</i> (1.90 vs. 3.01 minutes, <i>p</i> < 0.01), but shorter <i>call-to-curb</i> (4.87 vs. 4.05, <i>p</i> < 0.01); the difference in <i>call-to-defib on</i> was 0.18 minutes. Both taller and larger-volume buildings had longer <i>curb-to-AED</i> intervals but shorter 911 <i>call-to-curb</i> arrival intervals. As a consequence, building height and volume had a modest overall relationship with interval from call to defibrillator application. These results do not support the hypothesis that either taller or larger-volume buildings need cause poorer outcomes in urban environments.</p>