Room Air Challenges for BPD
Safety, Reliability, and Validity of a Physiologic Definition of Bronchopulmonary Dysplasia. Walsh WC, Wilson-Costello D, Zadell A, et al. J Perinatol (Sep 2003) 23: 451-6.
Objective: Bronchopulmonary dysplasia (BPD) is the focus of many intervention trials, yet the outcome measure when based solely on oxygen administration may be confounded by differing criteria for oxygen administration between physicians. Thus, we wished to define BPD by a standardized oxygen saturation monitoring at 36 weeks corrected age, and compare this physiologic definition with the standard clinical definition of BPD based solely on oxygen administration.
Methodology: A
total of 199 consecutive very low birth weight infants (VLBW, 501 to 1500 g
birth weight) were assessed prospectively at 36±1 weeks corrected age.
Neonates on positive pressure support or receiving >30% supplemental oxygen
were assigned the outcome BPD. Those receiving 
30%
oxygen underwent a stepwise 2% reduction in supplemental oxygen to room air
while under continuous observation and oxygen saturation monitoring. Outcomes
of the test were "no BPD" (saturations 
88%
for 60 minutes) or "BPD" (saturation <88%). At the conclusion of the test, all
infants were returned to their baseline oxygen. Safety (apnea, bradycardia,
increased oxygen use), inter-rater reliability, test-retest reliability, and
validity of the physiologic definition vs. the clinical definition were
assessed.
Results: A
total of 199 VLBW were assessed, of whom 45 (36%) were diagnosed with BPD by
the clinical definition of oxygen use at 36 weeks corrected age. The
physiologic definition identified 15 infants treated with oxygen who
successfully passed the saturation monitoring test in room air. The
physiologic definition diagnosed BPD in 30 (24%) of the cohort. All infants
were safely studied. The test was highly reliable (inter-rater reliability, 
=1.0;
test-retest reliability, =0.83)
and highly correlated with discharge home in oxygen, length of hospital stay,
and hospital readmissions in the first year of life.
Conclusions: The physiologic definition of BPD is safe, feasible, reliable, and valid and improves the precision of the diagnosis of BPD. This may be of benefit in future multicenter clinical trials.
Comments: The fact is that we need a better definition for BPD than supplemental oxygen requirement at 36 weeks corrected gestational age (CGA.) Whether a baby “requires” supplemental oxygen depends in large part on what level of oxygen saturation (or desaturation) is considered acceptable for growing premature infants. In the present study, Walsh and colleagues challenged these infants with room air to see if they really needed the supplemental oxygen. If they maintained an oxygen saturation > 88% for 1 hour in room air, they were considered to have “No BPD” by the “physiologic” definition. They found that 1/3 of the babies who would have been labeled as having BPD by the clinical definition (oxygen at 36 weeks), had “No BPD” based on the results of the room air challenge. We now recognize that using oxygen to keep saturations > 95% in premature infants is associated with adverse outcomes, and many NICUs have begun “targeting” oxygen saturations in at lower levels. This requires that the high-saturation alarm limits be set at 93-95%, and that the FIO2 is weaned whenever these limits are exceeded. If this is done, babies with “No BPD” are weaned off oxygen much sooner, and doing a room air challenge at 36 weeks CGA becomes unnecessary. ABK