Improved oxygenation 24 hours after transition to airway pressure release ventilation or high-frequency oscillatory ventilation accurately discriminates survival in immunocompromised pediatric patients with acute respiratory distress syndrome*

Abstract

Objectives: Children with an immunocompromised condition and requiring invasive mechanical ventilation have high risk of death. Such patients are commonly transitioned to rescue modes of nonconventional ventilation, including airway pressure release ventilation and high-frequency oscillatory ventilation, for acute respiratory distress syndrome refractory to conventional ventilation. Our aim was to describe our experience with airway pressure release ventilation and high-frequency oscillatory ventilation in children with an immunocompromised condition and acute respiratory distress syndrome refractory to conventional ventilation and to identify factors associated with survival.

Design: Retrospective cohort study.

Setting: Tertiary care, university-affiliated PICU.

Patients: Sixty pediatric patients with an immunocompromised condition and acute respiratory distress syndrome refractory to conventional ventilation transitioned to either airway pressure release ventilation or high-frequency oscillatory ventilation.

Interventions: None.

Measurements and main results: Demographic data, ventilator settings, arterial blood gases, oxygenation index, and PaO(2)/FIO(2) were recorded before transition to either mode of nonconventional ventilation and at predetermined intervals after transition for up to 5 days. Mortality in the entire cohort was 63% and did not differ between patients transitioned to airway pressure release ventilation and high-frequency oscillatory ventilation. For both airway pressure release ventilation and high-frequency oscillatory ventilation, improvements in oxygenation index and PaO(2)/FIO(2) at 24 hours expressed as a fraction of pretransition values (oxygenation index(24)/oxygenation index(pre) and PaO(2)/FIO(224)/PaO(2)/FIO(2pre)) reliably discriminated nonsurvivors from survivors, with receiver operating characteristic areas under the curves between 0.89 and 0.95 (p for all curves < 0.001). Sensitivity-specificity analysis suggested that less than 15% reduction in oxygenation index (90% sensitive, 75% specific) or less than 90% increase in PaO(2)/FIO(2) (80% sensitive, 94% specific) 24 hours after transition to airway pressure release ventilation were the optimal cutoffs to identify nonsurvivors. The comparable values 24 hours after transition to high-frequency oscillatory ventilation were less than 5% reduction in oxygenation index (100% sensitive, 83% specific) or less than 80% increase in PaO(2)/FIO(2) (91% sensitive, 89% specific) to identify nonsurvivors.

Conclusions: In this single-center retrospective study of pediatric patients with an immunocompromised condition and acute respiratory distress syndrome failing conventional ventilation transitioned to either airway pressure release ventilation or high-frequency oscillatory ventilation, improved oxygenation at 24 hours expressed as PaO(2)/FIO(224)/PaO(2)/FIO(2pre) or oxygenation index(24)/oxygenation indexpre reliably discriminates nonsurvivors from survivors. These findings should be prospectively verified.

Figure 1

Change in fractional oxygenation index (OI) (OI_NCV/OI_pre) over hours of nonconventional ventilation (NCV) between patients transitioned to airway pressure release ventilation (APRV) or high-frequency oscillatory ventilation (HFOV). The OI before transition to NCV is designated OI_pre. OI_NCV was calculated every 12 hr for the first 5 d after transition and is reported as a fraction of OI_pre. Values of OI_NCV/OI_pre are expressed as mean (± sem). Sample sizes for each grouping, representing patients with arterial access still alive on NCV, are given at hour 0, 24, 48, 72, 96, and 120. Patients were dropped from data collection if they lost arterial access, changed modes of ventilation, transitioned to extracorporeal support, or died. Multilevel mixed effects linear regression was used to test the relationship between the mode of NCV and the change in OI over time, with a significant effect (p = 0.022) of ventilator mode on OI_NCV/OI_pre over time.

Figure 2

A, Receiver operating characteristic (ROC) curves and associated calculated areas under the curve (AUC) for oxygenation index (OI) and Pao₂/Fio₂ (PF) 24 hr after transition to airway pressure release ventilation (APRV) as a fraction of pretransition values (OI₂₄/OI_pre and PF₂₄/PF_pre). AUCs are expressed as fractions (± sem). Kaplan-Meier survival curves for OI₂₄/OI_pre (B) and PF₂₄/PF_pre (C) after determination of optimal cutoffs from sensitivity-specificity analysis.

Figure 3

A, Receiver operating characteristic (ROC) curves and associated calculated areas under the curve (AUC) for oxygenation index (OI) and Pao₂/Fio₂ (PF) 24 hr after transition to high-frequency oscillatory ventilation (HFOV) as a fraction of pretransition values (OI₂₄/OI_pre and PF₂₄/PF_pre). AUCs are expressed as fractions (± sem). Kaplan-Meier survival curves for OI₂₄/OI_pre (b) and PF₂₄/PF_pre (C) after determination of optimal cutoffs from sensitivity-specificity analysis.