2004 OPEN FORUM Abstracts
EFFECT OF HELIOX ON HEATED WIRE VENTILATOR CIRCUITS.
Newhart RCP, UCSD Medical Center, San Diego, CA.
Background: We have delivered mixtures of helium and oxygen (HeO2) to mechanically ventilated patients at our institution for several years. HeO2 is used to reduce the resistance to airflow in situations where significant airway obstruction exists and work of breathing is increased. We use heated wire circuits with our humidifiers on all mechanical ventilators and observed a clinical situation where a patient received 1st degree burns from a ventilator circuit contacting his forearm while breathing an 80/20 heliox mixture. Since helium has a much higher heat carrying capacity than oxygen and nitrogen, our concern was that the HeO2 might cause changes in the temperature of the wires within the circuit possibly causing the burns.
Methods: We tested a Fisher & Paykel 850 (Fisher & Paykel Laguna Hills CA) humidifier with a dual heated wire circuit. We sampled circuit tubing surface temperatures from four locations. The locations are as follows: Location #1) 12in downstream of the humidifier chamber, #2) 12in upstream of patient “Y” connector on inspiratory limb, #3) 12in downstream of the patient “Y” connector, #4) 12in prior to the exhalation valve. We connected a PC running “View 850” software provided by F&P to the humidifier. The software displays various data from the humidifier. We connected the humidifier to an Avea (Viasys Healthcare Yorba Linda CA) ventilator that has the ability to deliver HeO2. We recorded data on surface temperatures at each site and displayed airway temperature while using room air (21% O2/79%N2) and again on 80/20HeO2. Data was collected with the following ventilator settings: VT .5L, RR15, flow 45 lpm.
Results: The graph below indicates a slight increase in temperature (avg. 1.7 degree F) in HeO2 vs. air. Airway temperature remained within 0.3 degrees of the expected 39 deg F.
Conclusion: Airway temperature between room air and heliox varied by no more than 0.3 deg F throughout the circuit. We feel the circuit tubing surface temperature difference is non-clinically significant and that the heliox mixture did not significantly contribute to the burn we observed.