2004 OPEN FORUM Abstracts
EFFECT OF HELIOX ON HEATED WIRE VENTILATOR CIRCUITS.
John
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.