The Science Journal of the American Association for Respiratory Care

2012 OPEN FORUM Abstracts


Shannon Alten, Jessica Young, Stephen Rideout, Rick Amato, James Johnson, Cynthia White; Respiratory Care Division, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH

Background: Tubing compensation is available on most critical care ventilators to account for compressible volume loss in ventilator circuitry during mechanical ventilation. Use of this feature generally requires that the ventilator circuit be calibrated and volume loss corrected during a circuit test. Compressible volume loss is generally a higher percentage of total delivered volume (VT) during neonatal and pediatric mechanical ventilation in comparison to adults. Leaks are also more prevalent in this population resulting in more ventilator nuisance alarms. Due to limitations in lower alarm adjustment ability, the tubing compensation occasionally gets turned off in this population. In PC ventilation, this results in unreliable display of VT. Recent increase in use of PRVC in the NICU resulted in two instances where the tubing compensation was turned off in PRVC mode due to leaks and nuisance alarms. In both instances, the RT’s noticed a significant drop in Peak Inspiratory Pressure (PIP) and patient decompensation after the tubing compensation was turned off. Following these incidents, we conducted a bench test in the research lab to test the hypothesis that there was no difference in PIP and tidal volume delivered to the patient in PRVC mode with the tubing compensation turned on compared to with the tubing compensation turned off. Methods: A Servo i ventilator was calibrated according to manufacturer’s recommendations using an infant Evaqua circuit and connected to the infant lung on a TTL lung model 560li (Michigan Instruments, Grand Rapids, MI). Compliance and resistance were adjusted to achieve designated set VT. A Hans Rudolph pneumotachometer (Hans Rudolph, Shawnee, KS) was calibrated and placed at the patient wye to measure delivered pressure and volume. Ventilator settings: PRVC mode, RR-30BPM, I-time-0.5seconds, PEEP-5. Three different tidal volume (VT) conditions were tested with set a set VT of 15mL, 30mL, and 100mL. All VT conditions were tested with both the tubing compensation turned on and the tubing compensation turned off. VT and PIP measurements were monitored and recorded from both the pneumotach and Servo I monitor for six consecutive breaths at each testing condition. Results: See chart below Discussion: Turning off tubing compensation in PRVC mode significantly impacts delivered pressure and volume in infants and pediatric patients with VT less than 100 mL. Sponsored Research - None Tidal volume and PIP