The Science Journal of the American Association for Respiratory Care

2010 OPEN FORUM Abstracts

EFFECT OF CIRCUIT VARIATIONS ON TIDAL VOLUME DELIVERY DURING HIGH FREQUENCY OSCILLATORY VENTILATION.

Christine Kearney1, Natalie Spencer1, Stephen B. Hepditch1, W Lee Williford1, David A. Turner2, Ira Cheifetz1,2; 1Respiratory Care Services, Duke University Medical Center, Durham, NC; 2Pediatric Critical Care Medicine, Duke Children’s Hospital, Durham, NC

Introduction. Substantial variation exists in current practice for the setup of high frequency oscillatory ventilation (HFOV) circuits based on clinician preference, departmental policies, and individual patient requirements. Clinicians may place an elbow suction catheter in-line, use a Y-adapter suction catheter, and/or add a flexible adapter to better position the circuit as the patient is turned or moved. Other providers prefer not to place any adapters in the circuit due to the belief that these alterations attenuate amplitude and may be detrimental to tidal volume delivery (VT). Circuit variations have important clinical implications as the circuit must be opened for suctioning unless an in-line suction catheter is used. We hypothesize that inserting any adapter in-line affects delivered VT. Methods. To assess the effect of an in-line adapter with a HFOV ventilator circuit, we conducted a bench study using a test lung, a 3100A Oscillator (CareFusion), and a flexible circuit. VT at the ETT was measured with a COS2MO+ monitor (Philips) and a neonatal flow sensor. A 4.5 mm ETT was attached leak-free to a test lung. Constant HFOV settings included: MAP 26 cm H2O, inspiratory time 33%, bias flow 20 LPM. Circuit variations studied were: an elbow adapter, an 8-French in-line suction catheter with a Y-adapter, and a flexible adapter. Data were collected at amplitudes of 25 and 45 cm H2O and frequencies ranging from 4 to 10 Hz in increments of 2 Hz. The circuit was not humidified. Fifty VT measurements were obtained at each combination of frequency, amplitude, and adapter. The effects of frequency, amplitude, and adapter on VT were determined by paired t-tests. Statistical significance was defined as p < 0.05. Results. 400 measurements were obtained per circuit setup. Mean VT was significantly higher with no adapter than with any of the in-line connectors (Table). Mean VT differences between types of adapter were not significantly different. Conclusion. The addition of any connector to a HFOV circuit can decrease the delivered VT regardless of the type of connector that is integrated. While statistically significant, it must be stressed that this study cannot conclude whether the changes in VT are clinically significant or whether the loss of VT outweighs the risk of opening the circuit for suctioning. However, these findings indicate that the potential impact on VT must be considered when adaptors of any form are added to a HFOV circuit. Sponsored Research - None Tidal volume delivery for each circuit variation. Data are displayed as mean (ml) ± standard deviation.