The Science Journal of the American Association for Respiratory Care

2003 OPEN FORUM Abstracts

HELIOX DELIVERY USING THE AVEA VENTILATOR.

Christine D. Perino, RRT; Dean R. Hess, PhD, RRT, FAARC. Massachusetts General Hospital and Harvard Medical School, Boston MA.

Background: Some mechanically ventilated patients may benefit from the inhalation of a helium/oxygen gas mixture (heliox). Many ventilators become inaccurate when used to deliver heliox. According to the claims of the manufacturer, the VIASYS AVEA ventilator (VIASYS Healthcare, Palm Springs, CA) can accurately deliver heliox.

Hypothesis: Gas delivery with the AVEA ventilator is accurate with the use of heliox.

Methods: A VIASYS AVEA ventilator was used per manufacturer's specifications. The ventilator was attached to one chamber of a dual-chambered test lung. The pressure/flow sensor of a NICO (Novametrix, Wallingford, CT) was placed between the ventilator circuit and the test lung. The compliance of the lung model was set at 50 mL/cm H2O (confirmed with a calibrated syringe). We tested 7 different ventilator settings: volume-controlled ventilation with tidal volumes of 0.25, 0.5, and 1.0 L; pressure-controlled ventilation at 10 and 20 cm H2O; pressure support ventilation at 10 and 20 cm H2O. A respiratory rate of 20/min and a PEEP of 5 cm H2O were used. For pressure support ventilation, a lift bar was placed between the chambers such that a second ventilator triggered simulated spontaneous breathing. A flow trigger of 3 L/min was used for pressure support. The volume delivered to the lung model was precisely calculated from the pressure in the lung model (measured by the NICO) multiplied by the lung model compliance. We tested the AVEA ventilator with room air, 80% helium/balance O2, 40% O2/balance N2, and 60% helium/balance O2.

Results: There was no significant difference for the bias between exhaled tidal volume measured on the ventilator and that delivered to the test lung for air and 80% helium (6±31 mL vs. 22±22 mL; P=0.19) (Figure 1). Similarly, there was no significant difference for the bias between exhaled tidal volume measured on the ventilator and that delivered to the test lung for 40% O2/balance N2 and 40% O2/balance helium (14±22 mL vs. 17±32 mL; P=0.63) (Figure 2). The bias for tidal volume delivered to the test lung for 80% helium versus air was 37±43 mL. The bias for tidal volume delivered to the test lung for 40% O2/60% helium versus 40% O2/balance N2 was 20±27 mL. For the pressure supported breaths, triggering was identical with and without helium.



Conclusions: We found no significant difference in volume delivery using volume control, pressure control, and pressure support ventilation with and without heliox. For the AVEA ventilator, accuracy of volume delivery with heliox is clinically acceptable.

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