Inclusion Criteria:  Healthy term infants in room air at enrollment Term infants with perinatal asphyxia undergoing therapeutic hypothermia at enrollment Healthy preterm infants in room air at enrollment Preterm infants on continuous positive airway pressure at enrollment Preterm infants on conventional mechanical ventilation at enrollment Preterm infants on high frequency ventilation at enrollment Preterm infants on nasal intermittent positive end expiratory pressure at enrollment Preterm infants on continuous positive airway pressure at enrollment  Exclusion Criteria:  Congenital anomalies and surgical conditions (ex: gastroschisis, omphalocele, congenital diaphragmatic hernia) Congenital heart disorders Congenital skin infections or known conditions with fragile skin (such as epidermolysis bullosa)