The Science Journal of the American Association for Respiratory Care

1998 OPEN FORUM Abstracts

LABORATORY COMPARISON OF AUTOMATIC ET TUBE COMPENSATION (ATC) AND TRACHEAL PRESSURE TRIGGERING (TP_{Tr}).

Robert S Campbell RRT, Richard D Branson RRT, James J Lawson RRT. University of Cincinnati Medical Center, Cincinnati, OH 45267-0558.

INTRODUCTION: TR_{Tr} reduces imposed work of breathing (WOB_{i}) and patient WOB (WOB_{pt}). ATC is a method of overcoming the WOB_{i} by ET tube. We compared WOB_{i} and WOB_{pt} during TP_{Tr} with ATC in a lung model. Methods: A two-chamber test lung (TTL, Michigan Instr.) was modified to mimic spontaneous breathing using a lift bar. A Hamilton Veolar powered the drive lung using a 50% decelerating flow pattern and set to create demand of 0.5 L V_{T} @ peak flow of 60 L/min at the airway of the "patient". An 8.0 ID ET tube and trachea simulator were used to connect each vent to the "patient" which had C_{L} of 60 mL/cmH_{2}O and R_{aw} of 5 cmH_{2}O/L/sec. An E4 (Drager Inc.) and a 7200ae (Mallinckrodt) ventilator were attached to the "pt." and set to CPAP-5 and PSV-5. E4 was used with ATC on at 100% for an 8.0 ET and without ATC. 7200ae was used with TP_{Tr} at the carina and without TP_{Tr}. Bicore CP-100 was used to measure pressure, volume, flow, and WOB. 5 breaths were recorded at each condition and measurements included WOB_{pt}, WOB_{i}, peak insp flow (PIFR), peak pres prox (PIP_{pr}), peak neg pres airway (PNP_{aw}) and esophageal (PNP_{es}), response time, and PTP. Results were compared using t-test and p < 0.05 was considered significant. Results: TP_{Tr} and ATC reduce WOB_{i} and WOB_{pt} compared to standard flow-trig. PIP_{pr} is higher with TP_{Tr} and ATC which increases work contributed by the ventilator, increases V_{T} delivery, and minimizes PNP_{es}. All work indices were lowest during TP_{Tr} with the 7200ae. Table 1 reveals values for each trig technique.

PIP_{prox} PNP_{es} WOB_{i} WOB_{pt}

cmH_{2}O cmH_{2}O J/L J/L

7200 TP_{Tr} 18* -9.4* 0.0* 1.24*

7200 FT 12 -15.6 0.24 1.64

E^{4} ATC 19# -14.3# 0.11# 1.54

E^{4} FT 11 -17.5 0.42 1.76

WOB_{vent} PTP V_{T}

J/L cm/s mL

7200 TP_{Tr} 1.23* 85* 510*

7200 FT 0.38 118 450

E^{4} ATC 1.16# 114 570#

E^{4} FT 0.52 127 470

*=p < 0.05 versus 7200 TP_{Tr} off, # =p < 0.05 versus E^{4} ATC off.

DISCUSSION: TP_{Tr} and ATC reduce the WOB_{i}. TP_{Tr} reduces WOB_{pt} more than ATC. TP_{Tr} and ATC increase pressure and volume delivery causing WOB to fall. TP_{Tr} requires modification of the vent and placement of a distal sensor while ATC can be implemented with current vents.

The 44th International Respiratory Congress Abstracts-On-DiskĀ®, November 7 - 10, 1998, Atlanta, Georgia.

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