The Science Journal of the American Association for Respiratory Care

2012 OPEN FORUM Abstracts


Carl R. Hinkson1, Dave R. Park1, Rob DiBlasi2; 1Harborview Medical Center, Seattle, WA; 2Respiratory Care, Seattle Children’s Hospital, Seattle, WA

Introduction: Patients with Acute Respiratory Distress Syndrome or Acute Lung Injury are typically managed with a tidal volume of 6mL/kg of PBW. This has been associated with increased work of breathing, double-triggering, and Auto-PEEP. Double-triggering can be refractory to adjusting inspiratory flow rates to meet demand. We have anecdotal experience that adding pause time during volume control ventilation can mitigate double-triggering. We conducted a bench test to determine if increasing pause time could reduce double-triggering in a simulated asynchronous lung model. Methods: An asynchronous patient on lung protective ventilation was simulated by connecting an Avea Ventilator to an Ingmar ASL 5000 test lung. The ventilator was set to Assist-Control, VT 480 mL, frequency 20, PEEP +5 cmH2O, FiO2 1.0, demand flow off, and square flow wave pattern. The test lung was set to 32 breaths/min, compliance 20 mL/cmH2O, airway resistance 5cmH2O/L/sec, and a negative transpulmonary pressure of -30 cmH2O to simulate an aggressive respiratory effort. A laptop was connected to the Avea for video capture and VT and total PEEP measurements were obtained through the Ingmar test lung. Measurements were collected for two minutes during each of the following pause times: 0.0s, 0.2s, 0.4s, and 0.6s. X2 test was used to determine differences in double-triggering between different pause times. Total-PEEP and VT are presented as mean ± standard for all breaths runs. Results: There were differences in the number of observed double-triggering events that were related to the preset inspiratory pause times (p< 0.000). There were 21 double-trigger events for pause times of 0.0s and 0.2s.There were no observed double—triggered breaths when the pause times were set at 0.4s and 0.6s. A nearly two-fold reduction in VT and Total PEEP was observed when the Pause Time was increased from 0.0s to 0.4s (figure). Conclusions: Based on these findings, double-cycling may result in excessive lung overdistension during lung protective ventilation. Increasing the inspiratory pause to 0.4s or 0.6s eliminates double-triggering in a simulated asynchronous patient. Further clinical investigation is needed. Sponsored Research - None