The impact of PEEP on hemodynamics, respiratory mechanics, and oxygenation of children with PARDS

Abstract

ABSTRACTObjectiveTo assess the impact of increasing positive end-expiratory pressure (PEEP) on hemodynamics, respiratory system mechanics, and oxygenation in children with pediatric acute respiratory distress syndrome (PARDS).DesignProspective single-center study.SettingTertiary care, university-affiliated PICU.PatientsMechanically ventilated children with PARDS.InterventionsPEEP was sequentially changed to 5, 12, 10, 8, and again to 5 cmH2O. After 10 minutes at each PEEP level, hemodynamic and respiratory variables were registered. Aortic and pulmonary blood flows were assessed through transthoracic echocardiography, while respiratory system mechanics were measured using the least squares fitting method.Measurements and Main ResultsA total of 31 patients were included, with median age and weight of 6 months and 6.3 kg, respectively. The main reasons for PICU admission were respiratory failure caused by acute viral bronchiolitis (45%) and community-acquired pneumonia (32%). At enrollment, most patients had mild or moderate PARDS (45% and 42%, respectively), with a median oxygenation index of 8.4 (IQR 5.8–12.7). Oxygen saturation improved significantly when PEEP was increased. However, although no significant changes in blood pressure were observed, the median cardiac index at PEEP of 12 cmH2O was significantly lower than that observed at any other PEEP level (p=0.001). Fourteen participants (45%) experienced a reduction in cardiac index of more than 10% when PEEP was increased from 5 cmH2O to 12 cmH2O. Also, the estimated oxygen delivery was significantly lower at 12 cmH2O PEEP. Finally, respiratory system compliance significantly reduced when PEEP was increased. At a PEEP level of 12 cmH2O, static compliance suffered a median reduction of 25% (IQR 39.7–15.2) in relation to the initial assessment (PEEP of 5 cmH2O).ConclusionsDespite the improvement in oxygen saturation, increasing PEEP in hemodynamically stable children with PARDS can cause a significant reduction in cardiac output, oxygen delivery, and respiratory system compliance.Key PointsQuestion:What is the impact of positive end-expiratory pressure on hemodynamics, respiratory mechanics and oxygenation in children with acute respiratory distress syndrome?Findings:In this prospective single-center study, we found a significant reduction in stroke volume index and cardiac index when PEEP was increased to 12 cmH2O. Furthermore, despite the improvement in oxygenation, the increase in PEEP was associated with a significant reduction in the estimated oxygen delivery and respiratory system compliance.Meaning:In addition to oxygenation, PEEP titration in children should include close monitoring of hemodynamics and respiratory mechanics.RESEARCH IN CONTEXTLung-protective ventilation using positive end-expiratory pressure (PEEP) remains the mainstay of respiratory management in ARDS.High PEEP levels have the potential to impact cardiac function and lung mechanics.Due to concerns about the adverse effects of high PEEP levels, hypoxemia is often managed by increasing the fraction of inspired oxygen rather than escalating PEEP.AT THE BEDSIDEAlthough it can improve peripheral oxygen saturation, high levels of PEEP have the potential to decrease cardiac output and thereby decrease oxygen delivery.As no changes in blood pressure were observed during PEEP titration, it cannot be used as a surrogate for cardiac output monitoring.Lung recruitability should be carefully evaluated in children with PARDS, as increasing PEEP may lead to reduced compliance of the respiratory system.