Indirect assessment of oxygen requirements in newborn babies by monitoring deep body temperature.

The general availability of pure 02 in cylinders gave medicine a powerful therapeutic tool. Until 1952 oxygen was used freely in high concentrations in many premature baby units, in the knowledge that many babies were hypoxic and on the assumption that it would in any case do no harm. The demonstration that high concentrations of inspired 02 could lead to retrolental fibroplasia in premature babies (Patz, Hoeck, and De La Cruz, 1952) led to more caution, and it became a generally accepted practice to restrict added 02 so that inspired concentrations never exceeded 40% (Kinsey, 1956). This seemed particularly reasonable in view of the demonstration (Campbell, 1960) that 02 concentrations of 40% would be able to overcome any diffusion defect which at that time was thought to be the main cause of hypoxia in hyaline membrane disease (Craig, Fenton, and Gitlin, 1958). However, it has subsequently been shown that adherence to this limit may lead to an increased mortality in premature babies with respiratory distress (Avery and Oppenheimer, 1960) and to a higher incidence of neurological abnormality of the type associated with hypoxia (McDonald, 1963). Warley and Gairdner (1962) and Gupta (personal communication) have shown that individual babies with the respiratory distress syndrome may be grossly hypoxic in concentrations of inspired 02 as high as 40%, and that increasing the 02 concentration to levels previously considered dangerous may be necessary to achieve anything like a satisfactory P02 in the baby's arterial blood. There is now evidence from kittens that it is high 02 tensions in the blood, rather than high concentrations of ambient 02, that lead to retrolental fibroplasia (Ashton, 1964). The clinician is therefore in a dilemma: individual babies are liable to retrolental fibroplasia if exposed to high 02 concentrations, while other babies will