The Science Journal of the American Association for Respiratory Care

2010 OPEN FORUM Abstracts


Joshua Dillon, Jody Lester; Respiratory Care, Boise State University, Boise, ID

BACKGROUND: Leaks are not uncommon when ventilating neonatal patients due to cuff-less endotracheal tubes. The purpose of this study was to evaluate the effect of various percentages of leaks on end-expiratory pressure (PEEP). METHOD: We performed all required pre-use tests and then connected each ventilator to the IngMar NeoLung with a 3.5 ETT. Calibrated pressure and flow sensors were put in the inspiratory and expiratory limbs of the ventilator circuit and settings were selected to simulate ventilation of a 1250 gram neonate (Vt target of 5 ml/kg). Sensitivity was set to avoid auto-triggering. Avea settings: PC mode, RR 30, Ti 0.3, Ti Rise 5, PEEP 5, Inspiratory pressure 7 (above PEEP), tube compensation off and a hot wire flow sensor was used. Servo-i settings: PC mode, RR 30, Ti 0.3, Ti Rise 0.15, PEEP 5, and Inspiratory pressure of 4 (above PEEP). Using these settings, we created 0, 25, 50, and 75 percent leaks and collected data (every 30 ms) for at least two minutes; leaks were created by adjusting a stopcock valve on the NeoLung. The Avea was tested with leak compensation on and off, and with bias flow set at 1 and 3 LPM. RESULTS: Even with large leaks, measured PEEP did not drop below set PEEP for all tests on the Avea regardless of whether leak compensation was turned on or off. The Avea consistently delivered measured PEEP at levels slightly higher than set PEEP (5.01-5.26cmH2O). The Avea required a higher PIP (12 cmH2O) than the Servo-i (9 cmH2O) to deliver a similar target Vt in PC mode. For all tests on the Servo-i, measured PEEP values in both the inspiratory and expiratory limbs were slightly less than set PEEP (4.86-4.91cmH2O); this difference was greatest at the 75 percent leak. When comparing the PEEP measurements in the inspiratory versus the expiratory limbs, the Servo-i had measurements within 0.01 cmH2O of each other; measurements for the Avea were 0.17- 0.2 cmH2O higher in the inspiratory limb (these differences were less when bias flow was set at 1). CONCLUSIONS: With leaks up to 75 percent, the Avea ventilator was able to deliver measured PEEP levels at or above set PEEP even with leak compensation off. Measured PEEP values for the Servo-i were slightly below set PEEP with the largest difference at 75 percent leak. More research is needed to determine if the results of this study are clinically significant and whether similar results would be found using different modes and pediatric or adult settings. Sponsored Research - None