The Science Journal of the American Association for Respiratory Care

1998 OPEN FORUM Abstracts


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

INTRODUCTION: ATC is a new feature available on the Evita 4 (E^{4}) ventilator (Drager, Telford, PA) designed to eliminate the work of breathing (WOB) imposed by the artificial airway. We designed a lung model study to evaluate the influence of ATC on imposed WOB (WOB_{i}), patient WOB (WOB_{pt}), and ventilator output, Methods: A two-chambered test lung (TTL) was modified with a lift bar to mimic spontaneous breathing. A Hamilton Veolar was used to "drive" the model and set to create demand conditions of 0.5 L V_{T} @ 60 L/min using a 50% decelerating flow pattern. E^{4} was connected to the "patient lung" via a 6.0 ID and 8.0 ID endotracheal tube (Mallinckrodt), and a 7.0 ID trach tube (Shiley). TTL was set to a C of 60 mL/cmH_{2}O and Raw of 5 cmH_{2}O/L/sec. Baseline measurements were made with no tube in place and were repeated with ATC active and disabled for each airway used. Bicore CP-100 was used to measure WOB_{pt}, WOB_{i}, PIFR, PEFR, V_{T}, PIP, P_{0.1}, pressure-time-product (PTP), peak negative pressure in the airway (PNP_{aw}) and in the esophagus (PNP_{es}). Five breaths were measured and recorded at each condition. Data were compared using student's t-test and p < 0.05 was considered significant. Results: WOB_{pt} measured without an ET tube in place was 1.59 J/L. Table 1 reveals baseline data with no ET tube in place and measured data with ATC active and off with a 6.0 ID ET tube and 7.0 ID trach tube in place.

Table 1. WOB_{pt} WOB_{i} V_{T}

(J/L) (J/L) (mL)

No Vent, No ET 1.54 0.12 500

6 ET ATCon 1.67* 0.00* 580*

6 ET ATCoff 2.26 0.48 460

7 Tr ATCon 1.53 0.10# 520#

7 Tr ATCoff 1.67 0.51 480

Table 1. PIP PTP PNP_{es}

(cmH_{2}O) (cmH_{2}O/sec) (cmH_{2}O)

No Vent, No ET 3 135 -17.7

6 ET ATCon 21* 152* -21.9*

6 ET ATCoff 4 195 -26.6

7 Tr ATCon 10# 131 -20.3

7 Tr ATCoff 4 144 -22.1

* = p < 0.05 versus 6 ET ATCoff, # = p < 0.05 versus 7 Tr ATCoff.

Conclusions: Use of ATC eliminates the WOB_{i} by the artificial airway. WOB_{pt} with ATC active is similar to that measured with no airway in place. ATC results in increased PIP and V_{T} delivery to the lung. Clinical studies are required to assess patient response and benefit from ATC use.

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