Published online August 31, 2007
PEDIATRICS
Vol. 120
No. 3
September 2007, pp.
687-688
(doi:10.1542/peds.2007-1754)
Oxygen Therapy for Bronchiolitis: In Reply
Joel L. Bass, MD
Department of Pediatrics
Newton-Wellesley Hospital
Mass General Hospital for Children
Harvard Medical School
Boston, MA 02462
David Gozal, MD
Department of Pediatrics
Kosair Children's Hospital Research Institute
University of Louisville
Louisville, KY 40202
Lieberthal essentially restates the position taken in the recommendations of the AAP subcommittee1 and dismisses the evidence documented in our comprehensive review of the relationship of hypoxia and cognition2 as not relevant to bronchiolitis. His main point is that the review only documented high-quality evidence for congenital heart disease (CHD) and sleep-disordered breathing (SDB). This is not accurate. Our evidence review included direct evidence analyzed in a systematic review, as well as a review of previously published comprehensive reviews of both direct and indirect evidence germane to the question. Direct evidence that showed impaired development and behavior in children was cited not only for CHD and SDB but also for asthma and respiratory instability in infants. The review article, however, in addition to citing evidence of an association, took the further step of analyzing each group of studies to determine if they fulfilled the far-more-rigorous criteria of causation that include, in addition to the strength and precision of the association, the evidence for a temporal relationship, consistency of relationship, biological plausibility, and dose-response and cessation effects.3 What Lieberthal has not recognized is that what the review concluded was that for CHD and SDB the criteria for causation were fulfilled in addition to the standard of association and that 2 of the domains of indirect evidence, viz, altitude studies and carbon monoxide poisoning, also fulfilled the criteria for both association and causality. This is extremely important evidence, because these 2 domains included controlled studies that demonstrated adverse effects of short-term exposure to hypoxia in adults that would be ethically impossible to perform in infants.
Lieberthal also states that a pulse oxygen saturation (SpO2) level of 90% is not very different physiologically from the traditionally accepted SpO2 level of 92%. That assertion overlooks the important fact that the actual reference range for SpO2 in preterm and term infants is 97% to 100%.4 Lieberthal cites the Collaborative Home Infant Monitoring Evaluation (CHIME) study5 as evidence that "normal" infants experience hypoxia. Although the CHIME study did demonstrate that hypoxia occurs in normal infants, these episodes were of very short duration (maximum of 6 seconds). This is a substantially different circumstance from the hours or even days of hypoxia that might be experienced by infants with bronchiolitis if the task force recommendations were to be implemented to their full extent.
It is also important to note that the quality of evidence cited in our review included a range of studies that correspond to the subcommittee report categories A (well-designed randomized, controlled studies), B (randomized, controlled studies with minor limitations), and C (observational studies). In contrast, the subcommittee recommendations 7a and 7b, which addressed the issue of oxygenation, are based on the lowest level of evidence, category D (expert opinion and reasoning from first principles). We therefore submit that as a logical conclusion when reviewing the full spectrum of evidence relevant to this issue objectively, most reasonable practitioners would feel that an element of caution is in order before reassuring a family that an SpO2 level of 90% of several days’ duration is no cause for concern. As we stated in our commentary, although there have been no bronchiolitis-specific studies, there is a substantial body of compelling and consistent biologically relevant evidence from a variety of observational pediatric studies in children and from high-quality experimental studies in adults. This evidence indicates that exposure to either intermittent or sustained hypoxia adversely affects cognition and that the degree of SpO2 decreases (2%–3%) required for such adverse effects to occur may well be much smaller than conventionally assumed.6,7 Thus, until definitive research on cognitive outcomes in bronchiolitis is forthcoming, we owe it to our patients to take this information, which is the current "best evidence" available, into account, and to proceed with caution when making decisions about patient care.
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. Available at: www.pediatrics.org/cgi/content/full/115/2/e204
PEDIATRICS (ISSN 1098-4275). ©2007 by the American Academy of Pediatrics
