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Abstract

Introduction: Airway pressure release ventilation (APRV) has been used extensively in adult patients with acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Purported advantages of APRV include increase in mean airway pressure (MAP), decrease in peak inspiratory pressures (PIP), and ability to spontaneously ventilate. It has not been studied extensively in pediatrics especially in the infant population with ALI/ARDS. We demonstrate two patients in which the APRV strategy was used to improve refractory hypoxemia (patient 1) and perform lung recruitment while on extra-corporeal membrane oxygenation (ECMO) (patient 2). Methods: Retrospective review of two patients’ charts; one in the Neonatal ICU and another in the Pediatric ICU. The patient’s ventilator modes, settings, blood gas measurements and radiographic imaging were analyzed. Results: Two patients’ charts were reviewed in whom APRV was used for refractory hypoxemia and to perform lung recruitment. Patient 1 was a 6 month old 3.9 kg ex-24 week preemie with recurrent bouts of necrotizing enterocolitis requiring bowel resection, status post stricturoplasty who was kept intubated post-op and returned to the NICU. During the procedure her PIP was 21 mm Hg, positive end expiratory pressure (PEEP) of 4, rate of 16 bpm, and FiO2 of 38% with SpO2 of 100% that delivered a MAP of 10.4 mm Hg. Venous blood gas at the end of the case demonstrated a pH 7.36, pCO2 45, pO2 37, HCO3 25, Lactate 1.9. Initially in the NICU her ventilator was set in pressure cycled assist controlled (PC/AC) with a rate of PIP 19, PEEP of 5, rate, rate of 33 bpm, PIP and FiO2 21% with SpO2 of 95% that delivered a MAP of 7 mm Hg. Over the next 26 hours she developed progressive hypoxemia requiring up titration in her PIP (26 mm Hg), PEEP (7 mm Hg) and FiO2 (85%) delivering a MAP of 12 mm Hg with SpO2 of 80–85%. Chest x-ray demonstrated a right upper lobe atelectasis along with low lung volumes. She was switched to APRV with a pressure high (PHIGH) of 25 mm Hg, pressure low (PLOW) of 0 mm Hg, time high (THIGH) of 2 seconds and time low (TLOW) of 0.2 seconds with MAP of 22 mm Hg, FiO2 40% with SpO2 97%. Chest radiography demonstrated improved aeration within approximately 1 hour of APRV initiation. She subsequently self extubated after 47 hours on APRV to 2 liters nasal cannula and remained extubated. Patient 2 was a 1 month old 5 kg male with a giant omphalocele who developed renal failure, volume overload and progressive respiratory failure requiring endotracheal intubation and eventual veno-venous (VV) ECMO. He was kept on rest lung settings PIP 25 mm Hg, PEEP 9 mm Hg, FiO2 40% and rate of 10 with a MAP of 11 mm Hg. He was on full VV-ECMO support with a flow of 760 mL/min and sweep gas of 0.8 L/min. His chest x-rays demonstrated bilaterally opacified lung fields with no expiratory tidal volumes. He was placed on APRV on post-ECMO day 6 at settings of pressure high (PHIGH) of 20 mm Hg, pressure low (PLOW) of 2 mm Hg, time high (THIGH) of 4 seconds and time low (TLOW) of 0.35 seconds with MAP of 18 mm Hg, while still on ECMO support. His lungs began to show aeration and evidence of recruitment at 12 hours on APRV with marked improvement in his lung aeration. He continued on APRV for 48 hours and then was transitioned to conventional ventilation. Conclusions: APRV is a useful ventilator strategy in cases of refractory hypoxemia and de-recruited lungs. We demonstrate the safe use of APRV in two patients less than 1 year of age with improvement in oxygenation and lung recruitment. Advantages of APRV were mentioned above. The disadvantages include air trapping and CO2 retention. While the disadvantages can be mostly mitigated with titration of the APRV settings, additional studies are needed to demonstrate efficacy and safety along with formulation of age appropriate pressure and time settings.