Comparison of SpO2 to PaO2 based markers of lung disease severity for children with acute lung injury.

OBJECTIVE: Given pulse oximetry is increasingly substituting for arterial blood gas monitoring, noninvasive surrogate markers for lung disease severity are needed to stratify pediatric risk. We sought to validate prospectively the comparability of SpO2/Fio2 to PaO2/Fio2 and oxygen saturation index to oxygenation index in children. We also sought to derive a noninvasive lung injury score. DESIGN: Prospective, multicentered observational study in six pediatric intensive care units. PATIENTS: One hundred thirty-seven mechanically ventilated children with SpO2 80% to 97% and an indwelling arterial catheter. INTERVENTIONS: Simultaneous blood gas, pulse oximetry, and ventilator settings were collected. Derivation and validation data sets were generated, and linear mixed modeling was used to derive predictive equations. Model performance and fit were evaluated using the validation data set. MEASUREMENTS AND MAIN RESULTS: One thousand one hundred ninety blood gas, SpO2, and ventilator settings from 137 patients were included. Oxygen saturation index had a strong linear association with oxygenation index in both derivation and validation data sets, given by the equation oxygen saturation index = 2.76 1 0.547*oxygenation index (derivation). 1/SpO2/Fio2 had a strong linear association with 1/PaO2/Fio2 in both derivation and validation data sets given by the equation 1/SpO2/Fio2 = 0.00232 1 0.443/PaO2/Fio2 (derivation). SpO2/Fio2 criteria for acute respiratory distress syndrome and acute lung injury were 221 (95% confidence interval 215-226) and 264 (95% confidence interval 259-269). Multivariate models demonstrated that oxygenation index, serum pH, and Paco(2) were associated with oxygen saturation index (p < .05); and 1/PaO2/Fio2, mean airway pressure, serum pH, and Paco2 were associated with 1/SpO2/Fio2 (p < .05). There was strong concordance between the derived noninvasive lung injury score and the original pediatric modification of lung injury score with a mean difference of 20.0361 α0.264 sd. CONCLUSIONS: Lung injury severity markers, which use SpO2, are adequate surrogate markers for those that use PaO2 in children with respiratory failure for SpO2 between 80% and 97%. They should be used in clinical practice to characterize risk, to increase enrollment in clinical trials, and to determine disease prevalence.

The diagnostic dilemma of ventilator-associated pneumonia in critically ill children.

OBJECTIVE: A review of the existing literature on ventilator-associated pneumonia in children with emphasis on problems in diagnosis. DATA SOURCES: A systematic literature review from 1947 to 2010 using Ovid MEDLINE, PubMed, Cochrane Central Register of Controlled Trials, and ISI Web of Science using key words "ventilator associated pneumonia" and "children." Where pediatric data were lacking, appropriate adult studies were reviewed and similarly referenced. STUDY SELECTION: Two hundred sixty-two pediatric articles were reviewed and data from 48 studies selected. Data from 61 adult articles were also included in this review. DATA EXTRACTION AND SYNTHESIS: Ventilator-associated pneumonia is the second most common nosocomial infection and the most common reason for antibiotic use in the pediatric intensive care unit. Attributable mortality is uncertain but ventilator-associated pneumonia is associated with significant morbidity and cost. Diagnosis is problematic in that clinical, radiologic, and microbiologic criteria lack sensitivity and specificity relative to autopsy histopathology and culture. Qualitative tracheal aspirate cultures are commonly used in diagnosis but lack specificity. Quantitative tracheal aspirate cultures have sensitivity (31-69%) and specificity (55-100%) comparable to bronchoalveolar lavage (11-90% and 43-100%, respectively) but concordance for the same bacterial species when compared with autopsy lung culture was better for bronchoalveolar lavage (52-90% vs. 50-76% for quantitative tracheal aspirate). Staphylococcus aureus and Pseudomonas species are the most common organisms, but microbiologic flora change over time and with antibiotic use. Initial antibiotics should offer broad-spectrum coverage but should be narrowed as clinical response and cultures dictate. CONCLUSIONS: Ventilator-associated pneumonia is an important nosocomial infection in the pediatric intensive care unit. Conclusions regarding epidemiology, treatment, and outcomes are greatly hampered by the inadequacies of current diagnostic methods. We recommend a more rigorous approach to diagnosis by using the Centers for Disease Control and Prevention algorithm. Given that ventilator-associated pneumonia is the most common reason for antibiotic use in the pediatric intensive care unit, more systematic studies are sorely needed.