Abstract Presentations at the 2005 Wilderness Medical Society Meeting, Snowmass,
Colorado, July 23 to 27, 2005
Oral Presentation
Performance Characteristics of the Divers Alert Network Remote Emergency
Oxygen (REMO
2
) Closed-Circuit Oxygen Rebreather
Neal W. Pollock, Ph.D., Michael J. Natoli, M.S.
Center for Hyperbaric Medicine and Environmental Physiology, Duke University
Medical Center, Durham, NC.
Introduction: Oxygen is used as a therapeutic agent to treat a variety of medical
conditions in both clinical and field settings. Closed-circuit oxygen rebreathers can
maximize delivery fraction with minimal flow requirements. The Divers Alert Network
(DAN) developed a compact, unidirectional flow, closed-circuit oxygen rebreather
suitable for remote field use (REMO
2
). A second-generation device was produced after
key components of the first could no longer be procured. The second-generation device
consisted of a solid, pre-packed CO
2
scrubber canister integrated with standard 22 mm
inside diameter anesthesia circuit hoses and fittings, a 5 L breathing bag, a 5 cmH
2
O
positive-expiratory-end-pressure valve, and an oronasal mask. Our purpose was to
evaluate second-generation device performance for comparison with the first-generation
system.
Methods: Six trials were completed under standard laboratory conditions using healthy
volunteers of varying size (73-126 kg). Subjects breathed on the circuit until the CO
2
concentration at the scrubber outlet reached 3.8 mmHg ('breakthrough') or for a
maximum duration of eight hours. Measured parameters included inspired oxygen
fraction (F
I
O
2
), oxygen flow, scrubber duration, and breathing resistance. We completed
similar testing with the first-generation device previously (n=6; 59-123 kg). All data
reported as mean±SD.
Results: Mean F
I
O
2
(0.95±0.04 and 0.95±0.06) and mean oxygen flow (1.06±1.36 and
1.05±0.16 L·min
-1
) were similar for second- and first-generation devices, respectively.
The scrubber duration was markedly improved with the second-generation system. The
only trial ending in breakthrough did so at 7.8 hours. Breakthrough with the first-
generation was reached in 5.7±1.8 h. Breathing resistance was also less extreme with the
second-generation system (-5.2±1.9 cmH
2
O inspiratory; 6.5±1.9 cmH
2
O expiratory) than
with the first-generation system (-6.7±1.6 cmH
2
Oinspiratory; 9.2±1.5 cmH
2
O
expiratory).
Conclusion: Testing confirmed that the second-generation REMO
2
circuit performed in a
manner similar or superior to the first-generation device for all parameters tested.
