Oxygen breathed at elevated pressure (hyperbaric oxygen) is the definitive treatment for decompression illness (DCI). The primary first aid for a patient awaiting hyperbaric oxygen therapy is oxygen breathed at ambient pressure (normobaric oxygen). Typically, normobaric oxygen is provided by an open-circuit regulator or a non-rebreathing mask, but limited oxygen supplies can be exhausted in a very short time in remote locations — too soon for optimal therapy.
The purpose of several studies at DAN was to evaluate the performance of oxygen delivery systems made available to or being used for divers.
This study was completed in 2002.
I. First Aid Oxygen Rebreather Trial (REMO2 and REMO2 second generation)
Oxygen-supply duration in remote locations may be increased by using closed-circuit breathing systems in which the expired gas is rebreathed after carbon dioxide is removed and replaced with additional oxygen.
Five systems were tested at the Center for Hyperbaric and Environmental Physiology at Duke University Medical Center and East Carolina University Environmental Physiology Lab. Variables measured included: inspired oxygen and carbon dioxide fractions (FIO2 and FICO2), inspired temperature, rate of oxygen use, breathing resistance, heart rate and canister duration. Evaluation criteria included weight, volume, simplicity, cost, inspired oxygen, carbon dioxide scrubber duration, pre-packaged carbon dioxide scrubber availability, expandable hoses for heat exchange and pre-approval of system components by the U.S. Food and Drug Administration (FDA).
The system that was chosen was tested in 27 trials to simulate realistic field conditions and ultimate developed as the DAN Remote Emergency Medical Oxygen System (REMO2™) available from DAN.
A second study tested the second generation closed-circuit oxygen rebreather ((REMO(2)) on 6 subjects to determine suitability for remote duty first aid. The trial concluded that the O2 rebreather “was well tolerated by healthy subjects during 8-hour laboratory evaluation trials. The device provided high mean inspired oxygen fractions at low mean oxygen flow rates, relatively modest mean maximal inspired and expired pressures, and excellent scrubber canister duration. Further evaluation of field performance with a patient population is warranted.”
*Note: DAN’s goal to market a closed-circuit oxygen rebreather device began in 1997. They sold the REMO2™ system from January 1999 — August 2001. DAN was forced to suspend sales of the REMO2 unit and accessories due to an unexpected loss in the supply of manufactured components. They began selling the second generation REMO2 and providing training in its use in October of 2003. Unfortunately, due to small volume of sales the manufacturers soon gave up.
II. Other oxygen delivery options — SysO2 & emOx
DAN funded further studies evaluating other systems available on the market including devices with chemical release of oxygen and concentrators of oxygen. Devices based on chemical released oxygen did not meet requirement due to highly variably oxygen flow, limited oxygen yield and activation time. Oxygen concentrators did not provide high enough oxygen concentration.
Additional Reading and References
- Pollock NW, Hobbs GW. Evaluation of the System O2, Inc. portable non-pressurized oxygen delivery system. Wilderness Environ Med. 2002; 13(4): 253-5.
- Pollock NW, Natoli MJ. Performance characteristics of the second-generation Remote Emergency Oxygen (REMO2) closed-circuit. Wilderness Environ Med. 2007; 18 (2): 86-94.
- Pollock NW, Natoli MJ. Chemical oxygen generation: evaluation of the Green Dot Systems, Inc. portable, non-pressurized emOx device. Wilderness Environ Med. 2010; 21(3): 244-9.
- Pollock NW, Hobbs GW. Evaluation of the System O2 Inc portable nonpressurized oxygen delivery system. Wilderness Environ Med. 2002;13(4):253-255.