The Science Journal of the American Association for Respiratory Care

2007 OPEN FORUM Abstracts


A COMPARISON OF HELIOX CONSUMPTION IN THREE VENTILATORS

M. K. Brown1, 2, D. C. Willms1, 2


Background: Different mechanical ventilators capable of providing heliox ventilation may use heliox at varying rates of consumption, so a comparison of ventilator heliox usage in three heliox compatible ICU ventilators were studied with a simple bench method.

Methods:
An 80/20 heliox mixture from H-cylinders was connected to the 50-psi air inlet of 3 mechanical ventilators: Maquet Servo 300 (Solna, Sweden), Hamilton Galileo (Rhäzuns, Switzerland), eVent Inspiration (Galway, Ireland). The ventilator was connected via standard circuitry without humidification to a test lung (Dual Adult Training Test Lung 5600i, Michigan Instruments Inc, Grand Rapids, Mich.) The test lung compliance was set to 0.03 L/cmH2O, and resistance was set to 20 cmH2O/L/sec. After verifying system compliance (Crs) on FIO2 of 1.0, ventilation was carried out with the ventilator FIO2 set at 0.21 (79% helium) and settings as indicated in Table 1. Pressure triggering was set, and a leak-free circuit was assured. For volume CMV, the set tidal volume was manipulated to achieve an actual delivered VT of 800 mL using the test lung and imposing an inspiratory hold, such that VT = Crs x Pplat (measured at zero flow). In this lung model tidal volume measurement is independent of gas density. Ventilation with heliox was carried out for 2 hours for each ventilator in both modes. We placed a precision digital pressure gauge (DTG2K, SI Pressure Instruments Ltd. Birmingham, England) on the tank regulator, and the difference in tank pressure from the beginning to the end of the 2 hour trial was noted. Gas consumption was estimated using the formula: Heliox P1- P2 = “change in”P/2= psi/hour (Table 1) from this equation gas consumption per hour of ventilator use can be determined. In order to also convert this information into a “H” cylinder duration, a starting tank pressure of 2000 psi was assumed and the equation 2000 psi/psi consumed per hour = H Tank Duration (Table 1)

Results:
All 3 ventilators cycled consistently with the heliox mixture. The heliox consumption per hour was nearly identical in all three ventilators (Table 1). Two of the three showed a slight insignificant increase in heliox consumption in volume control CMV versus pressure control CMV.

Conclusions: There is little difference in the heliox consumption rate of the three ventilators tested. All three of the ventilators will run for at least 6 hours on a 2000 psi 80/20 heliox “H” cylinder when utilized at the settings tested.

Comparison of 80/20 Heliox Consumption
Ventilator Brand eVent Inspiration Hamilton Galileo Servo 300
80/20 Heliox Consumption psi/hour "H" Tank Duration psi/hour "H" Tank Duration psi/hour "H" Tank Duration
V-CMV, VT 800, PEEP 5, R 16, PF 60 l/m, 80/20 Heliox 296 6.8 Hours 278 7.2 Hours 277 7.2 Hours
P-CMV, PIP 29, PEEP 5, R 16, I Time 1.0, 80/20 Heliox 290 6.9 Hours 319 6.3 Hours 310 6.5 Hours

Supported by an equipment grant from the Sharp HealthCare Foundation


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A COMPARISON OF HELIOX CONSUMPTION IN THREE VENTILATORS