2005 OPEN FORUM Abstracts
EVALUATION OF HELIOX VIA THE SIEMENS SERVOi VENTILATOR UTILIZING TIDAL VOLUME IN THE PEDIATRIC RANGE
Cynthia C. White, RRT-NPS, AE-C, Brian K. Walsh, RRT-NPS, RPFT, University of Virginia Health System, Charlottesville, VA
Introduction: Despite limited and conflicting evidence, there continues to be interest in the use of Heliox mixtures with mechanically ventilated patients. Ventilator function and Tidal Volume (VT) monitoring are often affected when Heliox is used due to the low density and high thermal conductivity of the gas. Some bench testing has been done to look at VT delivery and safety of Heliox with some of the newer mechanical ventilators such as the Servoi, but few have looked specifically at the function of the ventilator with VT in the infant and pediatric range. We sought to evaluate the function of the Servoi specifically with an 80%/20% Heliox mixture in VC mode with set VT's in the Pediatric Range (25ml-500ml), and compare measured exhaled VT via the Servoi with the NICO pulmonary mechanics monitor, which has the option of utilizing a pre-determined correction factor for Heliox mixtures.
Methods: The Servoi was calibrated with the appropriate size circuit according to manufacturer's specifications, and an 80%/20% Heliox mixture was connected via the 50-psi air inlet of the ventilator. The ventilator was attached to a test lung (BIO-TEK VT 2), and the appropriate size NICO flow sensor was appropriately calibrated and placed in the inspiratory limb of the ventilator circuit. Compliance and Resistance of the test lung were adjusted to maintain a PIP of 20-30 cmH20. Age and size appropriate inspiratory times were used and rate was adjusted to maintain an I:E ratio of 1:3. The mode was volume control. We allowed the settings to stabilize with at least 6 successive breaths. The ventilator settings and exhaled VT was recorded at each VT interval.
Discussion: There were wide fluctuations in the exhaled VT via the Servoi with Heliox with some of the VT settings. In addition, Heliox required us to switch from flow to pressure triggering secondary to auto cycling that occurred at all flow sensitivity levels. No trend could be seen with exhaled VT via the Servoi. The NICO exhaled VT remained linear to set and baseline VT.
Conclusion: The NICO monitor should be used to trend VT in conjunction with Heliox therapy. More testing needs to be done with pediatric tidal volumes in other modes of ventilation and other Heliox mixtures.