The Science Journal of the American Association for Respiratory Care

2000 OPEN FORUM Abstracts

USE OF SHORT RELEASE TIME IN AIRWAY PRESSURE RELEASE VENTILATION. A PEDIATRIC CASE STUDY

James Martin, RRT, Dennis M. Super, MD, Jason Foland, MD, Terry Novotny, RRT, Maroun Mhanna, MD, Departments of Pediatrics, and Pulmonary Services, MetroHealth Medical Center, Cleveland, OH

INTRODUCTION: Airway Pressure Release Ventilation (APRV) is a mode of respiratory support that incorporates an intermittent, time cycled reduction in airway pressure during continuous positive airway pressure (CPAP). During APRV, CPAP is maintained allowing the patient to breathe spontaneously without a significant fluctuation in airway pressures. Spontaneous breathing at elevated pressures (P high) with a prolonged inspiratory time (T high) promotes oxygenation. A rapid change to exhalation (T low) to a lower pressure (P low) allows for passive exhalation and induces carbon dioxide elimination, this is also known as release time. We sought to use APRV on a patient with Acute Respiratory Distress Syndrome (ARDS) to improve oxygenation and ventilation by prolonging the inspiratory time (T High) and shortening the expiratory time (T Low) allowing for a quick dump of exhaled gases. CASE SUMMARY: A 2 and a half year old, 17 Kg, male with mental retardation and cerebral palsy was admitted to the Pediatric Intensive Care Unit for Respiratory Synctial Virus (RSV) induced respiratory failure, requiring intubation and mechanical ventilatory support. On admission his Chest X ray revealed a LLL infiltrate which evolved within a few days into ARDS. Initially the patient was volume ventilated on the Dragger Dura 2 Ventilator in the SIMV / PS mode with Auto-Flow. Later a rapid deterioration in the patient's oxygenation despite bag-valve and conventional ventilation warranted a trial of APRV. Initially the release time was set at 2.2 seconds then reduced to 0.2 seconds resulting in a marked improvement in oxygenation (see chart). The patient tolerated well the short release time and prolonged T high without further sedation or use of neuromuscular blockade. 5 days later the patient was successfully extubated.

Mode F1O2 Ti /Te End Pressure Peak MAP SpO2 MV
SIMV / PS .50 0.7/2.3 PEEP 8 31 14 94 2.6
APRV Long Release 1.0 1.8/2.2 P Low 8 28 16 95 2.8
ABG pH 7.37 PaCO2 69 PaO2 78 (PaO2 / F1O2 = 69)
APRV Short Release 1.0 1.5/0.2 P Low 8 26 22 100 2.7
ABG pH 7.32 PaCO2 65 PaO2 250 (PaO2 / F1O2 = 250)
Ti = inspiratory time, Te = expiratory time, MV = minute ventilation

DISCUSSION: The use of APRV with a short release time improved oxygenation and maintained ventilation. Both long and short release times produced peak pressures lower then conventional ventilation. APRV seems to be a safe and effective alternative to conventional mechanical ventilation in children with ARDS secondary to RSV.

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