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Your March 2007 article1 on oxygen saturation validity was an excellent review of oxygen saturation and the limits of present technology; however, it ends with what I believe is an invalidated and potentially dangerous conclusion. The authors state without qualification that it is preferable to maintain SpO2 at greater than 95% in neonates "to prevent desaturation events."1(p176)
This statement flies in the face of virtually all current recommendations on the prevention of blinding retinopathy of prematurity in the very preterm neonatal population; I suggest a review and a correction. Most units have reduced their lower oxygen saturation limits to below 85% to 90% based on published reports of increased retinopathy of prematurity with increased oxygen saturations.2,3
There is an ongoing clinical trial that should eventually shed more light on the exact targets, but for now oxygen must be used with caution, especially in babies less than 28 weeks’ gestational age. I fear that if nurses and other clinicians do what is suggested by the authors they will create blindness in their neonates.
Monroe Carell Jr Children’s Hospital at Vanderbilt, Nashville, Tennessee
REFERENCES
Our thanks to Dr Walsh for his important letter. At the Rainbow Babies & Children’s Hospital in Cleveland where I (S.-Y. P. K. S.) was trained, it was considered unsafe for pulse oximeter readings to be less than 90% in neonatal study protocols. In our article, my colleague and I suggested lower and upper limits of 95% to 97% based on results of wavelength tests.
We have concerns about the studies Dr Walsh cites here. The first, by Chow and colleagues,1 uses insufficient data. The second study, by Tin et al,2 was conducted in England from 1990 to 1994 (when the technology on fetal hemoglobin was not available for validation) in 5 nurseries using 4 different pulse oximeter models with 2 groups. These varying models may well have used entirely different technology for adjustment before arriving at the nurseries.
Furthermore, the policy ranges of pulse oximetry in the study were 70% to 90% versus 88% to 98% (also mentioned were 84% to 94% and 85% to 95% ranges). The 10% upper-lower limit range was set according to adult literature based on adult hemoglobin. Staff members in the study always aimed at the higher limit; however, no attempts were made to document compliance. These findings do not establish causation; they are based more on chance than even a weak association.
In addition, subjects who developed eye complications were predominantly aged 23–25 weeks; these were the smallest babies in the nurseries and they have low survival rates in the United Kingdom. It is our understanding that survival rates are much higher for this population in the United States (75% minimum depending on the nursery) and that cerebral palsy rates are lower here (<5% in most nurseries). Babies do not live when deprived of oxygen; close to 50% of the babies died in the UK study.
Such a protocol would not survive many institutional review boards in the United States. Other studies (many of which we included in our paper) suggest higher limits of pulse oximeter readings for neonates. We stand behind our scientific findings.
University of Houston-Victoria, University of Houston System at Sugar Land (S-YPKS), Sugar Land, Texas Baylor College of Medicine (C-NO) Houston, Texas
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