In an analysis of a critical incident reporting system (CIRS) in out-of-hospital emergency medicine, it was demonstrated that in 30% of cases deficient communication led to a threat to patients; however, the analysis did not show what exactly the most dangerous work processes are. Current research shows the impact of poor communication on patient safety.An out-of-hospital workflow analysis collects data about key work processes and risk areas. The analysis points out confounding factors for a sufficient communication. Almost 70% of critical incidents are based on human factors. Factors, such as communication and teamwork have an impact but fatigue, noise levels and illness also have a major influence.(I) CIRS database analysis The workflow analysis was based on 247 CIRS cases. This was completed by participant observation and interviews with emergency doctors and paramedics. The 247 CIRS cases displayed 282 communication incidents, which are categorized into 6 subcategories of miscommunication. One CIRS case can be classified into different categories if more communication incidents were validated by the reviewers and four experienced emergency physicians sorted these cases into six subcategories. (II) Workflow analysis The workflow analysis was carried out between 2015 and 2016 in Jena and Berlin, Germany. The focal point of research was to find accumulation of communication risks in different parts of prehospital patient care. During 30 h driving with emergency ambulances, the author interviewed 12 members of the emergency medical service of which 5 were emergency physicians and 7 paramedics. A total of 11 internal medicine cases and one automobile accident were monitored. After patient care the author asked in a 15-min interview if miscommunication or communication incidents occurred.(I) CIRS analysis Between 2005 and 2015, 845 reports were reported to the database. The experts identified 247 incident reports with communication failure. All communication aspects were analyzed and classified. We identified 282 communication incidents. (II) Workflow analysis The analysis showed three phases of prehospital patient care: 1. incoming emergency call and dispatch of ambulance service, 2. prehospital treatment, 3. transportation to a hospital. Overall, the number of incidences is increasing as a consequence of parallel workflows. Category 1 was particularly significant and predominantly, paramedics criticized that emergency physicians did not acknowledge their advice (n = 73 vs. n = 9). Category 3 with n = 63, category 4 with n = 20 and category 2 with n = 13 were the major reasons for incidents.A better interface communication helps to coordinate patient transfer and is an option for optimizing resources. Frequent training in communication is an option to avoid incidents.