The Science Journal of the American Association for Respiratory Care

2003 OPEN FORUM Abstracts

Control of Pressures and Oxygen Percentage by the Viasys Avea® Ventilator during Heliox Administration in Pressure Control Mode

Charles B. Spearman, MSEd, RRT, FAARC1 and Mark Rogers, BS, RCP, RRT2

1Loma Linda University, School of Allied Health Professions - Department of Cardiopulmonary Sciences. Loma Linda, CA

2Loma Linda University Medical Center - Department of Respiratory Care. Loma Linda, CA

Background: Helium-oxygen mixtures (heliox) have been advocated for the management of increased airways resistance in spontaneously breathing and mechanically ventilated patients. We sought to evaluate the Avea's (Viasys Healthcare, Yorba Linda, CA) control of peak inspiratory pressure (PIP), positive end expiratory pressure (PEEP) and oxygen percentage during pressure control ventilation and heliox delivery.

Methods: Our study was designed to simulate increased airways resistance in the adult and pediatric patient. We used an Active Servo Lung (ASL5000® - IngMar Medical, Pittsburgh, PA), a digitally controlled breathing simulator and test lung.

Using PEEP of 5 cm H2O and oxygen levels of 100 (control), 40 and 21%, (balance helium) the Avea and test lung were set as follows:

Adult simulation - rate: 10 breaths/min., PIP: as needed to produce 1 L Vt, inspiratory time: 1 second, resistance: 20 cm H2O/L/sec., lung compliance: 50 cm H2O.

Pediatric simulation - 15 breaths/min., PIP: as needed to produce 250 mL Vt, inspiratory time: 0.5 second, resistance: 50 cm H2O/L/sec., lung compliance: 20 cm H2O.

To evaluate PEEP control we used the settings listed above for the pediatric simulation, we then set PEEP to 5, 10 and 15 cm H2O and set oxygen for 100 (control), 60, 40 and 21% (balance helium).

Using the supplied gas-identifying connector system, we connected 50 psig of 80/20 heliox to the compressed air inlet. After stabilization for tidal volume and oxygen %, data from the ASL5000 for PIP, PEEP and oxygen % were collected for 50 consecutive breaths for each set of conditions. Data were evaluated using multivariate analysis (SAS® Systems, Nashville, TN).

Results: For all conditions tested the Avea controlled PIP within ± 1 cm H2O, PEEP within ± 1 cm H2O (table). At each of the conditions tested, oxygen measured by the ASL5000 (specified accuracy of ± 0.5 % oxygen) was < ± 3 % oxygen from the ventilator setting.

    100% oxygen 60% oxygen* 40% oxygen* 21% oxygen*
Adult PIP < 1 cm H2O Not Done < 1 cm H2O < 1 cm H2O
PEEP 5 cm H2O < 1 cm H2O Not Done < 1 cm H2O < 1 cm H2O
 
Pediatric PIP < 1 cm H2O < 1 cm H2O < 1 cm H2O < 1 cm H2O
PEEP 5 cm H2O < 1 cm H2O < 1 cm H2O < 1 cm H2O < 1 cm H2O
PIP < 1 cm H2O < 1 cm H2O < 1 cm H2O < 1 cm H2O
PEEP 10 cm H2O < 1 cm H2O < 1 cm H2O < 1 cm H2O < 1 cm H2O
PIP < 1 cm H2O < 1 cm H2O < 1 cm H2O < 1 cm H2O
PEEP 15 cm H2O < 1 cm H2O < 1 cm H2O < 1 cm H2O < 1 cm H2O


Table. Summary of test conditions and variability in delivered PIP and PEEP at different oxygen (Heliox) settings. (*Balance helium.)

Conclusions:
Overall, during this limited study, the Viasys Avea controlled PIP, PEEP and oxygen % within clinically acceptable limits and the manufacturers specifications..

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