2012 OPEN FORUM Abstracts
COMPARISON OF CALCULATED AND MEASURED TRACHEAL PRESSURES DURING AUTOMATIC TUBE COMPENSATION ON THE DRAEGER XL AND THE E-VENT MEDICAL INSPIRATION 7-I VENTILATORS.
Mark S. Siobal, Roberto Bautista; Anesthesia, SFGH/UCSF, San Francisco, CA
Background: Automatic Tube Compensation (ATC) is dependent on the calculation of tracheal pressure. The eVent Inspiration 7i uses the tube length in addition to the tube diameter to calculate the resistance of the endotracheal tube where as the Drager XL uses just the ETT diameter. This study compared the accuracy of the calculated tracheal pressure on the Drager XL and the Inspiration 7i during ATC with varying peak inspiratory muscle effort. The Inspiration 7i evaluated was equipped with the ATC feature not yet available in the USA. Method: An ASL 5000 Advance Breathing Simulator was set to a RR = 15, Rise Time = 10 %, Insp Hold = 20%, Release Time = 10 %, Resistance = 5 cm H2O/L/sec, and Compliance = 50 mL/cm H2O. Pmus was varied between 5, 10, 15, and 20 cm H2O using ETT sizes 6.0, 7.0, and 8.0 mm. Both ventilators were set in the Pressure Support mode, PIP = 15, PEEP = 5, Flow Trigger = 3 L/min, with the minimum Rise Time. Tests were performed at each Pmus setting with each ETT size at 100% compensation. Each test condition was recorded using a Ventrak 1550 monitor with Analysis Plus software version 5.0. A series of 3 consecutive breaths from each test condition was analyzed. The lowest tracheal pressure drop during the simulated inspiratory effort was recorded by the Ventrak at the distal end of the ETT. This was compared to the calculated tracheal pressure determined by the ventilator measurement displayed or by the scalar method from the flow waveform graphic. Results: During each test condition the Inspiration 7i under estimated tracheal pressure drop during the simulated inspiratory effort. The under estimation by the Inspiration 7i increased as Pmus increased for each ETT size tested but the magnitude of the difference deceased at ETT size increased. The Drager XL over estimated tracheal pressure in 6 of 12 test conditions. Over estimation by the Draeger XL was highest at ETT sizes of 6.0 and 7.0 mm. Conclusion: There is marked variability in the accuracy of the calculated tracheal pressure changes during ATC on the Inspiration 7i and Draeger XL ventilators. The implications of these invitro test results needs to be determined in the clinical setting. Sponsored Research - Equipment on loan to perform bench testing.