The safest oxygen level for an infant on a ventilator is the lowest level that delivers enough oxygen to sustain the life of vital organs. The right amount of oxygen differs with each case and the course of the underlying disease and therapy over time. The safest level can be anywhere between 21 percent, room air and 100 percent, pure oxygen. Oxygen toxicity as a cause of blindness in infants has been known since the early 1950s.
Oxygen Toxicity
At one time, premature infants in the most advanced neonatal care centers got pure oxygen at birth simply because oxygen was known to be necessary for life. In 1950s, research revealed the mysterious cause -- too much oxygen was blinding newborns by damaging their retinas and caused lifelong sightlessness. The condition, retrolental fibroplasia, also called retinopathy of prematurity (ROP), was identified as preventable. Premature infants would get only as much oxygen as necessary to reach normal growth milestones. This was almost always less than 100 percent. However, cases still appear, probably when high oxygen is the only, unavoidable lifesaving intervention, as reported in a 2004 review article published by researchers at Pennsylvania's Villanova University, College of Nursing, chronicling the early history of the research, published in the journal "Neonatal Networking." All infant ventilator care since then is governed by the principle of giving no more oxygen than necessary.
Hypoxemia
Hypoxemia is too little oxygen in arterial blood. Without enough oxygen, vital organs die within minutes. Infants have a subtly different kind of hemoglobin, the red blood cell pigment that carries oxygen. It absorbs oxygen more powerfully and delivers it more efficiently. Due to the work of transitioning from the womb to the air, some infants need short-term assistance from a ventilator. But hypoxemia that would be dangerous for an adult is slightly safer in an infant, allowing a little lower oxygen level to suffice.
Paralysis
An infant who is on a ventilator because of paralysis, possibly due to birth trauma or neurological problems, may have perfectly normal lungs. In this case, a ventilator may be set to deliver room air, only 21 percent oxygen.
Lung Disease
An infant born with respiratory disease or immature lungs cannot breathe well enough to get sufficient oxygen from room air. A mechanical ventilator can do the work of breathing while oxygen is added in increments until blood levels are just high enough. This may be as low as 28 to 30 percent, but it may be as high as 80 to 100 percent. Special ventilator techniques and medicines are applied as quickly as possible to help the infant's lungs heal so oxygen levels can be lowered. A few hours at high levels can be tolerated, but toxicity develops rapidly.
Alternatives
The danger of too much oxygen encourages research into new kinds of ventilators. High-frequency jet ventilation (HFJV) and high-frequency oscillation (HFO) ventilators attempt to move more air, with high breathing rates, to the oxygen-absorbing membranes of an infant's lungs. More air at a low-oxygen concentration can be as good as less air at a higher concentration. Research and clinical experience has shown this to help lower oxygen levels in some cases, as reported by researchers at the University of Southern California Division of Neonatal Medicine, Children's Hospital Los Angeles and and the Women's and Children's Hospital in Los Angeles, in a 2003 edition of the "Journal of Maternal, Fetal and Neonatal Medicine."
