The Science Journal of the American Association for Respiratory Care

2012 OPEN FORUM Abstracts


Mark S. Siobal, Leo Bandian, Marwa El Marsafawy, Earl Mangalindan; Anesthesia, SFGH/UCSF, San Francisco, CA

Background: Non-invasive ventilation with heliox may be useful in treating patients with severe airway obstruction due to asthma. The therapeutic effects of helium have been documented at concentrations as low as 50%. We measured the fraction of delivered helium (FDHe) by adding heliox flow into the circuit of a Respironics Vision Ventilatory Support System (RespV). Method: A single chamber of a Michigan Instruments Test Lung (TTL) set to a compliance of 60 mL/cm H20 was used with a 7.5 mm endotracheal tube and a R50 resistor connected to the single limb circuit of the RespV. The RespV was set to PIP = 15 cm H2O, PEEP = 5 cm H2O, Ti = 0.8 sec, rise time = 0.1, FiO2 = 1.0, and RR of 20 and 30/min. Flow rates of 20 and 25 L/min 80/20 heliox was added to the circuit at the side port of the Plateau Exhalation Valve. The FDHe was determined by analyzing the oxygen concentration delivered to the TTL chamber where: FDHe = 1.0 – FDO2. To determine the effects of jet nebulizer treatments, separate measurements were performed during added flow of 100% oxygen at 2 and 8 L/m to the distal end of the patient circuit to mimic treatments with the mini HEART and standard small volume nebulizers. Results: FDHe concentrations of 0.55 to 0.68 were delivered at heliox flow rates of 20 and 25 L/min respectively. The addition of simulated jet nebulizers treatments at flow rates of 2 and 8 L/min decreased FDHe below 0.50 at a RR = 20. The RespV appeared to function normally during all test conditions without cycling or triggering problems on the test lung and was confirm by a volunteer breathing through the circuit. Conclusion: During this invitro bench testing, therapeutic concentrations of helium can be delivered by adding flow rates of 20 to 25 L/min into the circuit of the Respironics Vision Ventilatory Support System. Further invivo testing of this delivery system should be performed. Sponsored Research - None