Evaluation of Mechanical Ventilator Use with Liquid Oxygen Systems

Abstract : Mechanical ventilators coupled with portable liquid oxygen (LOX) systems are critical components of the U.S. Air Force Critical Care Air Transport Team mission. Air Force Instruction 10-2909 recommends the number of ventilators that can safely be used with a single device, depending on the LOX device used. We evaluated two portable LOX systems with three different models of portable ventilators to determine the number of ventilators each device will accommodate at ground level and at simulated altitude. The PtLox and NPtLox liquid oxygen systems (Essex Industries, St. Louis, MO) and model 754 and 731 (Zoll Medical, Chelmsford, MA) and LTV 1000 (Carefusion, San Diego, CA) ventilators were used for the evaluation. Lung conditions and ventilator settings represented a patient with acute respiratory distress syndrome and placed a high demand on the LOX. Testing was done at ground level and at simulated altitude of 8,000 feet in an altitude chamber. One ventilator was attached every minute until all oxygen connections were in use or until the LOX could no longer support the oxygen demand. At ground level and at altitude, the PtLox was able to accommodate the oxygen demand with the three available connections in use for all ventilator models. The NPtLox accommodated the oxygen demand using four ventilators with the 754, five to six with the 731, and three to four with the LTV 1000. The NPtLOX was able to support an additional ventilator of each model at altitude. Current Air Force guidance recommends that a maximum of one ventilator be attached to the PtLox and two to the NPtLox. The number of ventilated patients determines how many LOX systems must be on the flight. The results of this study show that the number of ventilators that can be attached to each LOX can easily be doubled with no decline in ventilator performance.