Objectives: To evaluate changes in oxygenation index (OI) in pediatric patients with ARDS during the first 24 h of prone positioning (PP), and to determine whether or not longer periods of PP (> 12 h) result in a more pronounced improvement in oxygenation.
Design: A retrospective chart review of patients with ARDS who had been placed in PP for their management.
Setting: Pediatric ICU of a children's hospital.
Measurements and main results: We retrieved the charts of patients with ARDS who had been admitted to our pediatric ICU over a 3-year period and placed in PP for their management. The patients received mechanical ventilation, were sedated and pharmacologically paralyzed, and underwent arterial blood gas analysis, with concomitant documentation of ventilator settings, at a frequency of once every 4 h or more often. We divided the first 24 h of PP into two periods, brief and prolonged. The brief period was defined as duration of PP between 6 h and 10 h, and the prolonged period was between 18 h and 24 h. We compared pre-PP OI values to values after brief periods and prolonged periods of PP. Values of the PaO(2)/fraction of inspired oxygen (P/F) ratio and the mean airway pressure (MAP) were similarly evaluated. We also evaluated the degree of OI fluctuations during 24 h of PP by identifying the time points at which the best OI and the worst OI were observed. Data from a total of 40 pediatric patients with ARDS were evaluated. Twenty-one of the patients were male, and 19 were female; their ages ranged from 1 month to 18 years (mean +/- SD, 6.22 +/- 6.27 years). Thirty-two patients received conventional mechanical ventilation, and 8 patients received high-frequency oscillatory ventilation. Thirty-three patients survived, and 7 patients (21%) died. The mean duration of PP was 67 +/- 64 h (2.8 +/- 2.7 days), the mean number of ventilator days was 32 +/- 32, and the mean interval between endotracheal intubation and placing the patients in PP was 107 +/- 108 h (4.5 +/- 4.5 days). Thirty-seven patients completed 20 h of PP or more. The mean post-PP time points at which OI values were actually evaluated for these patients were 8 +/- 2 h (brief) and 21 +/- 4 h (prolonged), respectively. Overall, the OI decreased from a pre-PP value of 24.8 +/- 13.0 to 16.7 +/- 13.7 after a brief period of PP (p < 0.05 when compared to baseline) and 11.4 +/- 6.3 after prolonged period (p < 0.05 when compared to baseline and brief period values). This improvement in OI followed the improvement seen in the P/F ratio, whereas the MAP remained unchanged. The best mean OI value, with patients in PP, was 11 +/- 9 (p < 0.05 when compared to baseline) that occurred at 16 +/- 6 h, and the worst was 22 +/- 15 (p = not significant when compared to baseline) that occurred at 9 +/- 7 h.
Conclusions: PP of pediatric patients with ARDS for prolonged periods (18 to 24 h) results in a more pronounced and more stable reduction in their OI values than those observed after brief periods (6 to 10 h). This improvement in OI was not associated with changes in MAP during the first 24 h of mechanical ventilation. OI values tend to fluctuate more during the first 12 h of PP then they do during the subsequent 12 h.