S_pO2 Histograms in Preterm Infants: A Helpful Tool for Neonatologists?

In recent years, oxygen targeting has become a relevant topic in neonatal intensive care medicine.¹ Despite large S_pO2 targeting trials including numerous subjects and the available results of a meta-analysis of these data,^2,3 there is still an ongoing debate on the optimum S_pO2 target range in preterm infants. Both conditions, hyperoxia as well as hypoxia, frequently occur in extremely low birthweight infants⁴ and may contribute to the development of retinopathy of prematurity,⁵ bronchopulmonary dysplasia,⁶ and impaired neurodevelopmental outcome⁷ in this population. In addition, the duration and severity of hypoxemic episodes during the neonatal period might be associated with late death or neurological impairment at 18 months corrected age.⁸ It has been shown that some preterm infants only spend about half of the time within a specific S_pO2 target range.⁹ This might be a crucial point in the ongoing discussion about the optimum saturation ranges in preterm infants. Pulse oximetry monitoring without frequent surveillance of the obtained data (ie, percentage of time in target saturation range, detection of prolonged hypoxemic/hyperoxemic episodes) may diminish the possible benefits of oxygen targeting. How can we reach the target, if the target is out of sight?

Standard monitoring in the neonatal intensive care unit includes S_pO2 monitoring, and target oxygen saturation ranges are usually well defined, whereas the documentation of these data differs from unit to unit. Hand-transcribed S_pO2 documentation is still a widespread practice in neonatal intensive care units despite the evidence that this may underestimate S_pO2 fluctuations.¹⁰ Therefore, regular visualization and comparison of S_pO2 data over time seems to be a promising approach to guide therapeutic interventions (eg, adjustment of respiratory support, faster adjustment of F_IO2, and/or adapting methylxanthine treatment) and may improve neonatal outcome.

In the current issue of Respiratory Care, Viscardi et al¹¹ used S_pO2 histograms, provided by pulse oximetry, to visualize the percentage of time infants spent within specific oxygen saturation ranges. This approach may help to predict failure to wean from noninvasive respiratory support in preterm neonates. The authors were able to show that infants who spent ≥15% of time with S_pO2 <86% in the 24 h before transitioning were more likely to fail the transition from CPAP or high-flow nasal cannula to less invasive modes of oxygen delivery or room air. As the authors point out in their article, there is no clear indicator or general agreement on how to wean from noninvasive support CPAP and other modes of noninvasive support are mainly used to treat respiratory distress syndrome/chronic lung disease by stabilizing functional residual capacity, avoiding mechanical ventilation, and improving oxygenation. Therefore, it seems conclusive to use a parameter of oxygenation including S_pO2 to evaluate readiness for weaning from CPAP. The stability of S_pO2 adds important information to the whole picture. Clearly, it should be mentioned that the final decision to wean cannot be based on a single parameter only, especially since the outcome parameter of this study has very high specificity but low sensitivity. Judgment on how to wean should be based on the overall clinical condition of the baby and may also include parameters such as respiratory effort, apneic episodes, gestational age, and F_IO2 requirements.¹²

Nevertheless, the authors of this study were assessing an important tool that might not only affect weaning success. Frequent assessment of S_pO2 measurements, including the percentage of time infants spend within their desired target oxygen saturation range and the number of prolonged hypoxemic events could be an important and valuable strategy to adapt and reflect the intensity of therapeutic interventions and improve neonatal outcomes. This study, along with the recent findings of the large oxygen targeting trials, are encouraging in this regard.

• Copyright © 2016 by Daedalus Enterprises