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

Abstract

Objective: To 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). Design: Prospective single-center study. Setting: Tertiary care, university-affiliated PICU. Patients: Mechanically ventilated children with PARDS. Interventions: PEEP 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 Results: A 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). Conclusions: Despite 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.