The Science Journal of the American Association for Respiratory Care

2009 OPEN FORUM Abstracts

BENCH PROTOCOL TO DETERMINE HELIOX CONSUMPTION OF THE EVENT MEDICAL ‘INSPIRATION LS’ VENTILATOR

Michael McPeck1, Mark Grzeskowiak1, Denise M. Rees2; 1Respiratory Care, Long Beach Memorial Medical Center, Long Beach, CA; 2Health Sciences, Santa Monica College, Santa Monica, CA

BACKGROUND. Heliox (HeO2) consumption considerably in excess of Vmin has been previously reported in some ventilators. Because our current ventilators were perceived by staff as consuming excessive HeO2, we developed a bench study protocol to evaluate HeO2 consumption and trialed it on an eVent Medical ‘Inspiration LS’ ventilator which was under consideration for purchase. METHODS. A trial unit from the manufacturer was connected to one side of a Michigan Instruments Dual Adult TTL set to provide 4 different impedance challenges for Resistance (RL) in cmH2O/L/sec and Compliance (CL) in L/cmH2O. Three different breathing patterns which resulted in a set Vmin of 7.2 L/min were studied: ‘normal’ (f=12,VT=0.600 L); ‘rapid/shallow’ (f=30,VT=0.240); and ‘slow/deep’ (f=6, VT=1.2) for RL/CL combinations of 5/20, 5/10, 20/20 and 20/10. The source gas was 80/20 HeOx in 159 cu ft “H” cylinders. Cylinder pressure (Pcyl) was read on an Ashcroft digital electronic pressure gauge (0-3000 psig, 0.5% resolution) that had been substituted for the mechanical cylinder pressure gauge of a Western Medica M1-280- P heliox regulator. Time ‘0’ Pcyl reading was obtained prior to a 60 min timed period of ventilator operation at each of the 4 RL/CL challenges for each of the 3 breathing patterns and at 15 min intervals for 1 hr. Results were entered into a MS Excel spreadsheet and graphed to assure linearity. Pcyl at 60 mins was subtracted from Pcyl at time ‘0’ to obtain the pressure drop (ΔPcyl) in one hr. ΔPcyl/hr was multiplied by 2.04 (80/20 HeOx ‘H’ cylinder factor) and divided by 60 to obtain Total HeO2 consumption in L/min which was compared to the set Vmin of 7.2 L/min for each of the RL/CL combinations and breathing patterns. RESULTS. Mean (±SD) Total HeO2 consumption for the normal, rapid/shallow, and slow/deep breathing patterns, respectively, was 6.96 ±0.14, 7.37 ±0.16 and 7.21 ±0.16 L/min; overall average Total HeO2 consumption was 7.18 ±0.222 L/min. CONCLUSIONS. (1) The bench protocol was easily conducted and challenged the ventilator under test with a range of breathing patterns and respiratory impedances in order to ascertain that any changes in HeO2 consumption were not due to Vmin setting changes. (2) The Inspiration LS ventilator did not appear to have any excess HeO2 consumption when operated with 80/20 heliox cylinder gas. Sponsored Research - None

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