Each preterm infant cardio-respiratory traces will be recorded during two 4-hours periods of time (the first one at the time of occurrence of apnea-bradycardias and the second one during the following week). During those periods, the alarms of the monitors usually used in the units will also be recorded through automatic detection and these alarms will be compared with the alarms generated by the algorithm tested, for false positive and precocity of the detection. A false positive alarm is a detection which is not associated with a bradycardia of less than 80 bpm. The system will be considered efficient if it allows an earlier detection of severe bradycardias without increasing the number of false positive detection.