The Science Journal of the American Association for Respiratory Care

2012 OPEN FORUM Abstracts

BENCH STUDY OF THE RELATIONSHIP BETWEEN HFOV AMPLITUDE AND ENDOTRACHEAL TUBE OCCLUSION.

Joel M. Brown, John S. Emberger; Christiana Care Health System, Newark, DE

Background: The SensorMedics 3100B (HFOV) is the only FDA approved high frequency oscillatory ventilator for the pediatric and adult population. One of the well-known issues with this device is its limited patient monitoring capabilities and diagnostic feedback. Tube occlusions are a major concern for HFOV patients due to humidification concerns and reduced suctioning attempts. When a patient requires HFOV there is no objective way to assess tube occlusion outside of bronchoscopy. In this bench study we investigated if there was a correlation between changes in HFOV amplitude (AMP) and oral endotracheal tube (OETT) occlusions. Methods: Three different adult sized OETT were used in this study (7.0, 7.5, and 8.0). Each OETT was fit with the SonarMed Airwave™ (SonarMed, Indianapolis, IN) airway monitoring device adapter to observe the percentage of occlusion. The OETT’s were attached to Michigan Instruments Dual Adult TTL® test lung with the Cst of 30 mL/cmH20 and Raw of 5 cmH20/L/sec. The HFOV was maintained at the following settings throughout the study: MAP 30, Hz 5, Power 5.0, It 33%, Bias Flow 30, and FiO2 1.0. A clamping device was used to obtain the following OETT occlusion percentages: 0% (baseline), 25%, 75%, and 100% (95-98% occlusion). The position of the occlusion was alternated to 3 different sections of the OETT. Each trial was repeated 3 times for accuracy. The resulting AMP was recorded for each trial. One additional trial was performed using a simulated epoxy airway occlusion instead of the clamping device which provided a 25%-28% occlusion in the OETT. This trial was performed to assure that the change in shape of the OETT was not a major factor in the results. Results: Change in AMP had a strong correlation to the percentage of occlusion in each OETT (average r=0.98). The position and type of occlusion (clamp vs simulated) had no effect on the resulting AMP. The largest change in AMP occurred between the 25% to 75% occlusions. There smaller changes in AMP during the 0% to 25% and 75% to 100% occlusion transitions. See the graph for more information. Conclusion: In this bench study we found that the amplitude increases consistently as the OETT occlusion worsens. This predictability could be a trending tool used to observe airway obstruction when managing patients on HFOV. Further studies will need to be performed to ascertain if the same trend is observed in vivo. Sponsored Research - None