Optic Nerve Sheath Diameter in Preterm Infants: Relationship with Respiratory Support and the Influence of Gestational Maturity.

Background/Objective: Bedside ultrasonographic measurement of optic nerve sheath diameter (ONSD) has increasingly been used as a non-invasive method for evaluating intracranial dynamics. In preterm infants, interpretation of these measurements is complicated by the strong influence of gestational maturity. The objective of this study was to examine the relationship between ONSD and respiratory support in preterm infants and to determine whether this relationship reflects an independent physiological effect or is mainly related to maturational confounding. Methods: This retrospective single-center study included 110 preterm infants. ONSD measurements were obtained at the bedside using a standardized ultrasonographic technique. Infants were categorized according to the need for invasive mechanical ventilation. Associations between ONSD, respiratory parameters, and clinical variables were evaluated with correlation analyses and multivariable logistic regression after adjustment for gestational age and birth weight. Results: ONSD values were lower in infants who required invasive mechanical ventilation and who also had lower gestational age and birth weight. After adjustment for these variables, the association between ONSD and invasive ventilation became less pronounced. Although ONSD showed a moderate unadjusted correlation with SpO2, no consistent independent association with respiratory parameters remained after adjustment for maturational factors. The difference in ONSD between groups was small (0.48 mm) and within the expected range of measurement variability. Conclusions: In this cohort, differences in ONSD according to respiratory support appeared to be more closely related to maturational status than to respiratory disease severity. ONSD measurements in preterm infants should therefore be interpreted within the clinical context of prematurity rather than used alone as indicators of respiratory status.