The Life-Pak 4 was introduced by the Physio-Control Corporation in 1974. It followed the previous introduction of the Life-Pak 3 a year earlier. The Life-Pak 4 featured an adjustable joule setting defibrillator, a scope and introduced the companies first portable unit with an EKG paper print-out. The Life-Pak 4 is still regarded to this day as one of the most durable devices ever manufactured for pre-hospital care.