Abstract

Introduction: Hyperoxia and variable oxygenation are associated with morbidity in preterm infants. The optimal range of oxygen tensions is not known. We aimed to determine whether care based on transcutaneous oxygen tension (TcPO₂) or saturation (SpO₂) monitoring is associated with less time spent with high oxygen tension and less variability of oxygenation.

Methods: SpO₂ and TcPO₂ were measured simultaneously during two 3-hour study periods allocated in random order. During one period supplemental oxygen was adjusted according to TcPO₂ (target range 6.0-9.0kPa) and during the other according to SpO₂ (target range 86-94%). During each period readings from the second monitor were not displayed. Both TcPO₂ and SpO₂ were downloaded every second. For each period the mean level and the variability (standard deviation) of SpO₂ and TcPO₂ and the percentage of time spent above and below target range were calculated and compared.

Results: Nineteen infants, 13 ventilated and 6 on CPAP, were studied at mean corrected gestational age of 27.2 weeks and mean postnatal age of 6.8 days. Their mean FiO2 at the start of the study was 0.34. Care based on SpO₂ monitoring was associated with more time spent with high oxygen tension (median increase 2.62%, p=0.01), more time with low oxygen tension (median increase 17.41%, p=0.01), more variability in oxygen tension (median increase 0.28kPa, p=0.02) and more variability in oxygen saturation (median increase 0.82%, p=0.01) than care based on TcPO₂ monitoring.

Conclusion: Within the target ranges studied SpO₂ monitoring was associated with significantly more variable oxygenation than TcPO₂ monitoring.