No data related to critical or important outcomes were identified by the literature review. For the outcome of time to first shock, we identified very-low-quality evidence (downgraded for risk of bias and indirectness) from 1 case series (n=76) involving text-message alerts to lay responders within 1000 m of a suspected cardiac arrest demonstrating a median call to first shock time of 8 minutes (interquartile range, 6:35–9:49 minutes).(Zijlstra 2014, 1444) In the same study, the median time from call to first shock when emergency medical services personnel arrived first was 10:39 minutes (interquartile range, 8:18–13:23 minutes). For the outcome of first responder on scene, we identified very-low-quality evidence (downgraded for risk of bias and indirectness) from 1 case series involving computer-generated phone calls and text messages to lay responders within 500 m of a suspected cardiac arrest, demonstrating that responders notified via this system arrived first in 44.6% of suspected cardiac arrest episodes, compared with emergency medical services providers in 55.4% of the episodes.(Ringh 2011, 1514)