[The emergency telephone number--the essential weak link in an emergency system. Prospective studies involving cardiac arrests observed by bystanders].

The first link in the "chain of survival" concept is the activation of the emergency medical system (EMS) by a bystander after recognition of cardiac arrest (CA) or its immediate prodrome. Our ongoing study is aimed at evaluating the current effectiveness of bystander EMS activation for all cases of CA in the city and area of Mainz. Methods. Starting February 1991, we began to prospectively examine collapse-intervention intervals in all cases of CA treated by our physician-manned ambulance. Precision voice recorders carried by the ambulance crews are activated and linked to the EMS dispatcher to time the arrival of the ambulance vehicle. Time intervals starting from the time of collapse are then reconstructed from the dispatcher's time and the tapes. The emergency phone number dialled initially by the bystander and the time of collapse in witnessed cardiac arrests are identified. RESULTS. Sixty-six CAs were witnessed and included in this study. In 20% of those cases, the number dialled initially by the bystander was 19222 (EMS dispatcher), in 38% 110 (police), and in 42% other numbers (family practitioners or their on-call service, fire department). The time interval, as median (25th percentile; 75th percentile), between collapse and receipt call by the emergency dispatchers was 4 min (2; 8) for all patients (n = 66), and 6.5 min (3; 12) whenever numbers other than emergency phone numbers were dialled. All following time intervals (start of BLS or ACLS procedures) showed differences (P less than 0.05) between the 110 or 19222 group [BLS: 8.5 min (4.8; 13.1) or 10 min (7.35; 12.1); ACLS: 11.3 min (9.1; 13.45) or 12.9 min (10.6; 21.5)] vs the group, in which other phone numbers were initially dialled [BLS: 15.25 min (9.25; 19.4); ACLS: 20.11 min (12.6; 28.3)]. The first ECG rhythm showed VF in 56% and 54% in case 110 and 19222 were dialled, but only in 32% in the other group. CONCLUSION. Even one single weak link in the "chain of survival" can lower overall survival rates. An indispensable, but apparently underrated component of an effective EMS includes an informed citizenry able to call swiftly for help. Lack of an unequivocal emergency number, well known and accepted by the citizens, produces confusion and delays. In our systems, the correct medical emergency phone number (19222) was dialled in 20% of the cases only, thus demonstrating clearly the lack of public awareness of this 5-digit number. In a higher percentage, the three-digit police number (110) was dialled. In cases where numbers other than emergency numbers were dialled (42%), the longest time intervals between collapse and receipt of call by the dispatchers occurred, associated with the longest time intervals until initiation of CPR and the lowest percentage of patients found in ventricular fibrillation. We conclude that establishment of a simple three-digit EMS phone number, preferentially Europe-wide, in combination with an intensification of public awareness, could be a vital step not only to reduce time intervals between collapse and CPR in our EMS system but also to improve survival.