We have read with much interest the article of Zimmerman et al. (1),
who report the incidence and outcome of children with acute lung injury
(ALI) in a 1-year study period in King County, WA (United States). This
study confirms the previously reported relative low incidence and
mortality associated with pediatric ALI (2-4), as compared to adult ALI
patients. Together with emerging experimental studies that suggest age-
related differential lung responses to injurious events (5,6), this once
more highlights the need for better insight in the influence of age and
lung development on the susceptibility and outcome of ALI (7).
One issue in the study of Zimmerman et al. (1) needs some further
attention. To the casual reader it may look that infection by respiratory
syncytial virus (RSV) is an uncommon cause of ALI in children, as stated
in their Results and Table 2. However, the opposite might be true, as
several studies suggest severe RSV disease is a relatively important risk
factor for ALI in previously healthy infants (2,3). In the study of
Dahlem et al. (2), RSV disease was associated with 15% of the children
with ALI (Dutch study population: >2 kg body weight and <18 year).
Erickson et al. (3), reported that bronchiolitis was the cause of ALI in
approximately 20% of children (Australian study population: >36 weeks
corrected gestational age and <15 years). From that study it is
unclear which agent was responsible for bronchiolitis, but it has been
well established that RSV is the leading pathogen in bronchiolitis in
children (8). In the study of Zimmerman et al. (1), children <6
months, which are most susceptible to severe RSV disease, were excluded.
As such, this is likely the reason for finding a low incidence of RSV-
induced ALI. Because in our own experience infants < 6 months
represent a relatively large part of intensive care unit admissions, it
would be interesting to note how many patients fulfilling ALI criteria
were not included in the Zimmerman study.
Based on the above findings we feel that the importance of RSV-
induced ALI in children was underestimated. At the same time, it is
interesting to note that RSV-induced ALI appears to follow a relatively
benign course in infants upon supportive treatment with mechanical
ventilation and oxygen therapy (9). In our own experience, the vast
majority of patients with RSV-induced ALI has no medical history, and
mortality is rare in these patients. Based on the comparison to high
mortality rates in children with ALI due to other clinical disorders, such
as sepsis, it is possible that RSV infection induces a type of ALI that to
a lesser extent correlates with histopathological findings of diffuse
alveolar damage (10), although the non-specific clinical AECC criteria for
ALI are met.
References
1. Zimmerman JJ, Akhtar SR, Caldwell E, Rubenfeld GD. Incidence and
outcomes of pediatric acute lung injury. Pediatrics. 2009;124(1):87-95.
2. Dahlem P, van Aalderen WM, Hamaker ME, Dijkgraaf MG, Bos AP.
Incidence and short-term outcome of acute lung injury in mechanically
ventilated children. Eur Respir J. 2003;22(6):980-985.
3. Erickson S, Schibler A, Numa A et al. Acute lung injury in
pediatric intensive care in Australia and New Zealand-A prospective,
multicenter, observational study*. Pediatr Crit Care Med. 2007;8(4):317-
323.
4. Flori HR, Glidden DV, Rutherford GW, Matthay MA. Pediatric acute
lung injury: prospective evaluation of risk factors associated with
mortality. Am J Respir Crit Care Med. 2005;171(9):995-1001.
5. Mao Q, Gundavarapu S, Patel C, Tsai A, Luks FI, De Paepe ME. The
Fas system confers protection against alveolar disruption in hyperoxia-
exposed newborn mice. Am J Respir Cell Mol Biol. 2008;39(6):717-729.
6. Smith LS, Gharib SA, Martin TR. Transcriptional Analysis of
Pulmonary Gene Expression in Adult and Juvenile Mice Treated with
Mechanical Ventilation and Lipopolysaccharide. Am J Respir Crit Care Med
179, A2053. 2009.
7. Bem RA, Bos AP, Matute-Bello G, van TM, van Woensel JB. Lung
epithelial cell apoptosis during acute lung injury in infancy. Pediatr
Crit Care Med. 2007;8(2):132-137.
8. Hall CB, Weinberg GA, Iwane MK et al. The burden of respiratory
syncytial virus infection in young children. N Engl J Med. 2009;360(6):588
-598.
9. Hammer J, Numa A, Newth CJ. Acute respiratory distress syndrome
caused by respiratory syncytial virus. Pediatr Pulmonol. 1997;23(3):176-
183.
10. Hemptinne de Q, Remmelink M, Brimioulle S, Salmon I, Vincent JL.
ARDS: a clinicopathological confrontation. Chest. 2009;135(4):944-949.
Conflict of Interest:
None declared
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