Prehospital use of ventilators by emergency medical services (EMS) during 911 calls is increasing. This study described the impact of prehospital mechanical ventilation on prehospital time intervals and on mortality.This retrospective matched-cohort study used 4 consecutive public releases of the US National Emergency Medical Services Information System dataset (2011-2014). EMS activations with recorded ventilator use were randomly matched with activations without ventilator use (1 to 1) on age (range ± 2 years), gender, provider's primary impression, urbanicity, and level of service.A total of 5740 EMS activations were included (2870 patients per group). Patients in the ventilator group had a mean age of 69.1 (±17.3) years with 49.4% males, similar to the non-ventilator group. Activations were mostly in urban settings (83.8%) with an advanced life support level of care (94.5%). Respiratory distress (77.8%) and cardiac arrest (6.8%) were the most common provider's primary impressions. Continuous positive airway pressure was the most common mode of ventilation used (79.2%).Mortality was higher at hospital discharge (29.0% vs 21.1%, P = .01) but not at emergency department (ED) discharge (8.4% vs 7.4%, P = .19) with prehospital ventilator use. Both total on-scene time and total prehospital time intervals increased with reported ventilator use (4.10 minutes (95% confidence interval [CI]: 2.71-5.49) and 3.59 minutes (95% CI: 3.04-4.14), respectively).Ventilator use by EMS agencies in 911 calls in the US is associated with higher prehospital time intervals without observed impact on survival to ED discharge. More EMS outcome research is needed to provide evidence-based prehospital care guidelines and targeted resource utilization.