Intermittent hypoxemic episodes and severe retinopathy of prematurit

Retinopathy of prematurity (ROP) is a vasoproliferative disorder of the retina which may result in significant loss of vision in preterm infants. In the last decade, the controlled use of supplemental oxygen and a corresponding reduction in baseline oxygen saturation levels have reduced the incidence of ROP. However, this vision-threatening disease continues to be a significant problem in premature infants.
The onset of this condition is based upon some perturbations of the physiological retinal vascular development triggered by several factors, including oxygenation level. These disturbances of vascular development begin with a phase of delayed retinal vascular growth and/or vascular regression, during which hyperoxia suppresses vascular endothelial growth factor (VEGF), thus inhibiting normal vascularization. The second phase of ROP development consists of vascular over-proliferation initiated by hypoxia-induced elevated levels of VEGF and other growth factors: this results in pathological retinal neovascularization.
Although both hyperoxia and hypoxia have an important role in the development of ROP, the correlation between the frequency and time course of oxygen desaturation events and the development of ROP has been poorly explored to date.
On this basis, an American group used continuous noninvasive monitoring of oxygen saturation via pulse oximetry to document the incidence of intermittent oxygen desaturation events in preterm infants during the first 8 weeks of life, and investigated the association of these events with the development of ROP.
In particular, oxygen desaturation events were quantified in 79 preterm infants (gestational age, 24 to 27-6/7 weeks) during the first 8 weeks of life. Infants were classified as requiring laser treatment for ROP (n=16) versus having less severe or no ROP (n=63).
After controlling for all covariates, statistical analysis showed that the frequency of hypoxemic events increased during the first weeks of life for all infants (p<0.005) and a higher incidence of oxygen desaturation events was associated with laser therapy for ROP (p<0.001), male gender (p<0.02), and younger gestational age (p<0.003).
Overall, these findings suggest an increase in the frequency of hypoxemic episodes during the first 8 weeks of life in preterm infants, with a higher incidence of hypoxemic events associated with severe ROP requiring laser therapy. These results may be relevant in the current scientific debate, given the growing interest in protocols designed to optimize baseline levels of oxygenation in preterm infants and in new instrumentation for the automated control of inspired oxygen concentration. Because the automated control of oxygenation could significantly affect the pattern of intermittent hypoxemic episodes, this investigation suggests that this technology may have a beneficial effect in reducing the incidence of severe, potentially blinding ROP.

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