The Science Journal of the American Association for Respiratory Care

2010 OPEN FORUM Abstracts


Britney L. Griffith, Jesse Ferguson, Lonny Ashworth; Respiratory Care, Boise State University, Boise, ID

Background: Tube Compensation (TC) is an option on some mechanical ventilators used to compensate for the imposed Work of Breathing (WOBi) of the endotracheal tube (ETT). When the problem that necessitates ventilatory support has resolved, a Spontaneous Breathing Trial (SBT) is conducted to see if the patient meets criteria for Extubation. Recent research indicates that TC may either over-compensate (provide more pressure than is needed to overcome the imposed resistance of by the ETT) or under-compensate (causing increased WOB because of the ETT). If the machine over-compensates, additional pressure and volume will be delivered to the patient; this could cause a patient to falsely pass an SBT. This is a bench study conducted to determine how delivered volume is impacted by patient effort, size of ETT, or by the ventilator itself during a simulated SBT. Methods: The Hans Rudolph HR 1101 Electronic Lung Simulator was interfaced using size 7.0, 7.5, 8.0 and 8.5 ETTs, to the Viasys Avea, the PB 840, and the Drager XL. Data was measured by the HR 1101 at intervals of 0.05 seconds. Settings on the HR 1101 were: Resistance 25 cmH2O/L/sec, Compliance 60 ml/cmH2O, rate 20/minute, slope 1, 20% inhale, target volume 3000 ml, effort type SHORTIE. The HR 1101 Amplitude (patient effort) was set at 5, 10, 15, 20 for each ETT size and for each ventilator. The ventilators were placed in CPAP mode, with 5 cmH2O CPAP, pressure support off, and apnea override at the upper limit. Each ETT, at each amplitude setting, with ATC on and off was assessed. Additionally, the Drager XL was evaluated at both 100% compensation and the manufacturer recommended 80% compensation. Results: As the internal diameter of ETT decreased, there was a linear increase in delivered tidal volume with the Drager (at 80 and 100%) and the PB 840. The most significant increase in tidal volume (17%) occurred using the Drager (100% compensation) with a size 7.0 ETT and amplitude of 20. The 17% increase in tidal volume was equal to 79 ml per breath; at a rate of 20, the minute ventilation would increase 1.58 L. Conclusion: When using a lung simulator, this study demonstrates that TC does affect tidal volume as amplitude and ETT size change. Clinicians must realize that TC may augment a patientÂ’s spontaneous tidal volume and may overcompensate for ETT resistance and provide additional support which is removed upon extubation. The use of TC during an SBT requires further evaluation in clinical settings. Sponsored Research - None Measured Tidal Volume with Tube Compensation Off and On during a Simulated Spontaneous Breathing Trial using an Electronic Lung Simulator, Amplitude 20 tidal volumes listed in mL.