Among infants presenting to an emergency department with mild to moderate bronchiolitis, those whose pulse oximetry readings were artificially elevated by 3 percentage points were significantly less likely to be hospitalized than were comparable patients whose pulse oximetry readings were unaltered, according to a report published online Aug. 19 in JAMA.
The accuracy of most oxygen-saturation monitors is approximately plus or minus 2%, and oximetry readings are subject to multiple sources of error, so "the actual physiological difference between the true and altered oximetry measurements in our study was of minor importance. Yet this difference had significant implications for hospitalization," said Dr. Suzanne Schuh, a pediatrician at the Hospital for Sick Children, Toronto, and her associates.
Their findings indicate that clinicians are relying too heavily on tiny differences in a single laboratory parameter – the pulse oximetry reading – to make clinical decisions in this patient population. The results of their experiment further suggest that the monitoring of oxygen saturation in this setting may need to be reevaluated, Dr. Schuh and her colleagues wrote (JAMA 2014;312:712-8).
The introduction and routine use of pulse oximetry in infants with mild to moderate bronchiolitis in the 1980s and 1990s coincided with more than a doubling of hospitalization rates for the disorder. Moreover, the somewhat arbitrary cutoff point of 90% oxygen saturation, which triggers the use of supplemental oxygen, has never been shown to correlate with bronchiolitis progression, yet many mildly ill infants are hospitalized solely because of that reading. Even expert opinion "cautions against overreliance on oximetry and argues for the use of clinical judgment when making disposition determinations," the investigators noted.
They performed this prospective, randomized, double-blind trial to determine whether artificially raising the pulse oximetry reading displayed to emergency department (ED) clinicians by an amount of "minor importance" would lead to fewer unnecessary hospitalizations in 213 otherwise healthy infants (aged 4-12 months) presenting to a single tertiary care pediatric ED during a 5-year period. The 13 physicians who cared for these patients were blinded to the study protocol and ordered supplemental oxygen and pharmacotherapy at their own discretion.
All the infants had a true oxygen saturation of 88% or higher, as well as comparable clinical characteristics and Respiratory Disease Assessment Instrument scores. The oxygen saturation reading was accurately displayed to treating clinicians in the 108 infants who were randomly assigned to "true" oximetry. In the other 105 infants, the oxygen saturation reading was increased by 3 points and displayed to treating clinicians.
All the infants in the study underwent concealed continuous oximetry for safety reasons. These hidden monitors were programmed to sound an alarm if oxygen saturation dropped to less than 92%, which would prompt a thorough clinical reassessment.
The primary outcome of the study was hospitalization for bronchiolitis within 72 hours of enrollment due to concerns about respiratory distress. This occurred in 41% of infants in the true-oximetry group, compared with only 25% of those whose oximetry reading was artificially increased – a significant 16% difference. Yet the medical outcomes of the two study groups were comparable, Dr. Schuh and her associates reported.
"Our results suggest an even lower cutoff might be appropriate and that among children with saturation levels of 88% and higher, disposition determination should be based primarily on the degree of respiratory distress and hydration status, rather than on a particular saturation value," they said.
This study was supported by the Thrasher Research Fund and the Physicians’ Services Incorporated Foundation; Masimo provided the oximeters but played no role in the design or conduct of the study. Dr. Schuh and her associates reported that they had no financial conflicts of interest.