2. Preoxygenation
In general, studies have not yet shown the optimal level or duration for the use of preoxygenation for ETS.4 In adults, the common practice is to preoxygenate with 100% oxygen before, during, and for some period after performing ETS.1,3 Prolonged hyperoxia may lead to free-radical tissue damage, absorption atelectasis (nitrogen washout), and loss of lung volume.2,3 In preterm infants, the practice of using 100% oxygen is avoided because of the possible deleterious effects of hyperoxia that can cause retinopathy of prematurity.1,2 Also in preterm infants, the level of brain oxygenation decreases in parallel with the drop in oxygen saturation, but is also ameliorated with a sustained increase of 10% in the oxygen setting.2 Also in infants there is a possibility of bradycardia and apnea when preoxygenation is not provided.2 Therefore, many neonatal intensive care units (NICUs) have a protocol whereby the oxygen is increased by 10% to 20% before ETS.1 Another concern is providing hyperoxia to patients in cardiac units who have cyanotic heart disease, since the hyperoxia may cause pulmonary vascular dilation and decreased preload to the left heart resulting in systemic hypotension.5