The Science Journal of the American Association for Respiratory Care

2007 OPEN FORUM Abstracts

DELIVERED O2 CONCENTRATION WITH AN OXYGEN BLEED-IN USING THE EMERSON COUGHASSIST IN-EXSUFFLATION DEVICE: A BENCH STUDY

D. M. Aslin1, J. C. Ray1, R. DiBlasi2, C. Hinkson1


Background: The Emerson Coughassist mechanical in-exsufflation (MI-E) device (Respironics, Murrysville, PA) is now commonly used for patients with neuromuscular weakness and those with cervical spinal cord injuries who have impaired peak cough flow. We currently use the MI-E device to aid in hyperinflation and secretion removal in this group of patients via mask or artificial airway. These patients often require supplemental oxygen and the device does not provide supplemental oxygen. No information is available about the effects of bleeding oxygen into a MI-E circuit. Accordingly, we conducted a bench study to measure the delivered O2 fraction (FDO2) through the MI-E circuit with oxygen bled in.

Methods: An Emerson Coughassist MI-E device was connected to the Ingmar Active Servo Lung 5000 (IngMar Medical Ltd, Pittsburgh, PA) with standard tubing and an 8.0 ID tracheostomy tube. A standard exhalation manifold and one-way valve were placed inline to divert exhaled gas away from the MI-E. Oxygen was bled in at the device outlet. FDO2 was measured at the tracheostomy tube using a Paramagnetic O2 analyzer E-COVX gas exchange module (GE Healthcare, Chalfont St. Giles, United Kingdom). The MI-E was set to auto mode with 2-sec inspiratory time, 0 expiratory time, 2-sec wait time (respiratory rate 16 breaths/min), and the high-flow setting (measured peak flow 97 L/min). Set inspiratory pressures of 30, 40, and 50 cmH2O were each tested with 5, 10, and 15 L/min oxygen bleed-in. The test lung compliance was set to 50mL/cmH2O. FDO2 was measured for 20 consecutive breaths. All data are presented as mean ± SD.

Results:
The lowest FDO2 was 0.26 ± 0.0045 delivered with 50 cmH2O and 5 L/min. The highest FIO2 was 0.49 ± 0.0075 delivered with 30 cmH2O and 15 L/min (figure 1). Conclusions and recommendations: Under the limited conditions of this study, FDO2 decreased substantially as inspiratory pressure increased. Further study is required to determine the effects of the exsufflation portion, respiratory rate, and circuit design on FDO2.


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