Leung KHB, , et al. - Researchers examined if in-hospital cardiac arrest-to-defibrillator distance could be reduced with mathematical optimization of in-hospital defibrillator placements vs existing defibrillators in a single hospital. From St. Michael's Hospital in Toronto, Canada, treated IHCAs and defibrillator placements were identified and mapped to a 3-D computer model of the hospital. An equal number of optimal defibrillator locations were identified with an optimization model that minimized the average distance between IHCAs and the closest defibrillator using a 10-fold cross-validation approach. Assessment of 433 treated IHCAs and 53 defibrillators was done. Of these, 167 IHCAs and 31 defibrillators were outside of ICUs, operating theaters, and the emergency department. Observations suggest that the distance from an IHCA to the closest defibrillator can be reduced with optimization-guided placement of in-hospital defibrillators. Equivalently, optimization can match existing defibrillator performance utilizing far less defibrillators.