1 Department of Pediatrics, Harvard Medical School, and Boston Lying-In Hospital
Dr. Comroe once stated (in conversation) that while it may sometimes be difficult to prove the value of oxygen therapy, there is ample evidence of its hazards. This is particularly true in premature infants. Should oxygen, therefore, be used at all in the premature nursery? If so, for what infants? And how can they be protected from its misuse?
1. Progressive hypoxemia leads to anoxia in most severe or fatal disease in newborn and premature infants. Circumstances associated with anoxia are often followed by brain damage. Therefore, a severely reduced blood oxygen saturation or tension in a sick premature or term newborn should be raised if this can be done safely.
2. Thus, additional oxygen should be used for those infants whose arterial blood (when they breathe air) is carrying significantly less oxygen, than that to be expected of normal infants in air.
3. Oxygen is misused if it increases blood oxygen much above that normal in air-breathing. Such misuse is not only wasteful. It may cause retrolental fibroplasia. Impaired vision from this cause is still being seen, and we cannot yet be positive that excess oxygen causes no other pathologic changes in prematures besides those in the retina.
The problem of misuse may be better stated in terms of oxygen tension (or pressure hence pO2) than of oxygen percentage or concentration. As 21% of the atmosphere, oxygen has a partial pressure of 160 mm Hg in air at sea level and pO2 in the pulmonary alveoli of normal term and premature infants is (like that of adults about 105 mm Hg.2 In the arterial blood of such infants pO2 is usually within or near a range of 70-80 mm Hg, so that a normal gradient or pressure loss of 25-35 mm Hg occurs between alveolus and capillary.