Quantifying amplitude modulation of breathing in infants using the wavelet transform

Respiratory signals may provide information on the cause of Sudden Infant Death Syndrome (SLDS). One pattern found in breathing signals is an amplitude modulation of the primary breathing frequency, a modulation that is non-stationary in nature. Rhythmicity, a novel measure based on the wavelet transform, has been developed to assess the impact of amplitude modulation on respiration. Rhythmicity was evaluated for epochs of breathing during quiet sleep that exhibited amplitude modulation from five infants who succumbed to SIDS and five controls matched by age, gender and birth weight. The extent of amplitude modulation in breathing was greater for infants who later died from SIDS, compared with their matched controls. Further studies can now focus on amplitude modulation of breathing to provide information on mechanisms underlying SIDS.