Periodic breathing (PB) is a respiratory pattern in infants defined as 3 episodes of apneas lasting longer than 3 seconds,separeted by continued respiration of 20 seconds or less.PB is generally thought to be benign, but sometimes PB is extreme (PB >6 SDs above the mean for corrective gestational age and >10% time in PB)with a  decline in SaO2, this condition can be associated with Brief Resolved Unexplained Events (BRUE)or others acute clinical events We hypothesized that low flow oxygen may reduce extreme PB in infants and improve the SaO2 Materials and Methods Subjects who completed an over night cardiorespiratory monitoring (Getemed V3100)at the Ped Sleep Center Insubria University from October 2017 to July 2018 with extreme PB with decreasing of SaO2 were included in the study.The subjects had over night cardiorespiratory monitoring during the second night subjects were given supplemental oxygen trial (0,5L/min via nasal cannula) and during the third night without supplemental oxygen.Variables were compared with a non parametric statistics and p value <0,05 was considered significant.Results 15 infants(10F);5 born 40-41+4 w gestational age,5 between37-39+6 w,4 between 31-33w and 1 of 27+3w. weight 3,12 Kg (2,81-3,295) %PB(14.5 first night;2.5 second night:9.4third night p value between 1°and 2° <0.001), number of PB episodes/night(49.6;14,5;32.5), number of apneas with SpO2 <90%(70;0:12 p value <0.001), % episodes of PB with SaO2 <90%, minimum SaO2(81.4;92:84.1 p value between1°and2°night<0.001) Conclusions Oxygen supplementation normalized the PB percentage in infants with extreme PB associated with decreasing of SaO2. This effect was not sustained when infants didn?t receive supplemental oxygen