Typically, stationary circle-circuit ventilators are found in operating rooms and are large, heavy, awkward and difficult to transport, even from one place in a hospital to another. One of the reasons for their use in an operating room is that they allow rebreathing of exhaled gas which still contains high concentrations of anesthetic and O2. They are mainly used to reduce liquid anesthetic consumption. The weight and bulky footprint of these systems make them ineffective in military and disaster relief scenarios.
The majority of portable or transport ventilators on the market are of the open-circuit variety. In order to provide elevated inspired O2 (FiO2, expressed as a percentage) levels to the patient, an external O2 source is required. Generally, a compressed O2 cylinder providing gas at a pressure of 50-55 PSI is required or, alternatively, the ventilator will have a means for inputting low flow O2 (either from a smaller compressed cylinder or from an O2 concentrator). This is less than ideal in mobile situations, due to the additional weight and square footage of the O2 cylinders, most of the O2 provided is then wasted or released into the atmosphere; proper safety measures must be taken to ensure that the waste anesthesia is removed safely. In addition, providers must predict the number of O2 cylinders that might be required, and may over or under-estimate.
The MOVES® SLC™ Advantage
In being designed specifically for military and disaster relief scenarios, MOVES® SLC™’s proprietary circle-circuit design is the best of both worlds, creating a portable or transport ventilator that allows for rebreathing of exhaled gases, significantly decreases the need for carrying of excess heavy oxygen tanks and increases the efficiency of O2 use when O2 is in short supply. The internal O2 concentrator provides low flow O2 directly to the ventilator’s breathing circuit. As such, with the recycling of the patient’s breathing gas and the internal O2 concentrator, MOVES® SLC™ can provide the patient with a high FiO2 while operating from battery power. When paired with MADMTM, there is also the benefit of reducing the amount of liquid anesthetic consumption.
Oxygen Consumption: A Comparison
Assuming a D-size O2 cylinder contains approximately 425 L of O2, a typical transport open-circuit ventilator would require replacement of the cylinder every 83 minutes to maintain ventilation of a patient at an FiO2 of 85%, while the MOVES® SLC™ circle-circuit ventilator would require no cylinders as the internal O2 concentrator can provide this.
If an FiO2 of 100% is required, a typical open-circuit ventilator would require 1 cylinder every 71 minutes, while the MOVES® SLC ™ circle-circuit ventilator could provide an FiO2 of 100% for more than 23 hours with the same single cylinder. Simply put, over 24 hours, an open-circuit ventilator would require 20 D-size O2 cylinders, while a circle-circuit ventilator would require 1 D-size cylinder.
Overall, the use of circle-circuit system would reduce the requirement for O2 in the field (and associated cube and weight) by upwards of 95% compared to the open-circuit ventilators currently in use.