Reliability of pulse oximetry in hypoxic newborn pigs

Abstract

Objective: The reliability of pulse oximetry in the lower SaO₂-ranges has not been fully investigated. We wanted to investigate pulse oximeter performance in a pig model of perinatal asphyxia.

Methods: Asphyxia was induced in 22 newborn pigs. Pulse oximetry-values for SpO₂, as well as SaO₂ from blood gas analyses were recorded multiple times before, during and after asphyxiation. The relationship between SpO₂ and SaO₂ in normoxia and hypoxia in this model was quantified. Calculations were made for 5% increments of SaO₂ increasing successively from ≥95% to ≥20%.

Results: The pigs became severely hypoxic, acidotic and hypotensive. The bias in the total data was +13.7 (p < 0.001), i.e. SpO₂ was on average higher than SaO₂ for the entire interval of SaO₂. However, bias was not significantly different from zero in most SpO₂-ranges. Accuracy and precision were considerably higher than stated by the manufacturer in all SpO₂-ranges, with both accuracy and precision increasing when SpO₂-values down to 60% and lower were included.

Conclusion: Pulse oximetry was less reliable at SaO₂-values below 60%. Tissue acidosis and reduced peripheral perfusion may have contributed to this. It is unknown whether the difference between SpO₂ and SaO₂ is clinically relevant.

• Hypoxia
• newborn
• reproducibility of results