• Aishwarya Palwai, Mary Skowronski, Albert Coreno, Colin Drummond, and E R McFadden.
• Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine of MetroHealth Medical Center, 2500 MetroHealth Drive, Cleveland, OH 44109, USA. Erm2@case.edu
• Am. J. Respir. Crit. Care Med. 2010 May 15; 181 (10): 106110711061-71.

RationaleClinical testing of oxygen-conserving devices is not mandated before marketing. Consequently, little is known about individual or comparative therapeutic effectiveness.ObjectivesTo relate oxygen delivery from prototypical instruments to physiological performance.MethodsThirteen subjects with obstructive lung disease performed progressive treadmill exercise while inhaling either room air, 2 L O(2)/min, or bolus oxygen from four commercially available conserving devices at regulator settings of 2, 5, and continuous. The devices were studied blindly in random order after first being tested to determine performance characteristics. Pulse oximetry, oxygen delivery, and nasal and oral ventilations were monitored at rest and with exertion.Measurements And Main ResultsAt a setting of 2 at rest, all conservers maintained saturation greater than 90%, but there were significant differences in oxygenation between systems. Only one equaled 2 L O(2)/min. With exertion, saturation decreased with all conservers but not with 2 L O(2)/min. One device did not perform any better than room air. Two systems provided less oxygen than predicted, one more, and in one the expected and actual amounts were equal only at rest. Breath-by-breath performance was highly variable, with irregular activation and inconsistent oxygen bolus size delivery. Increasing oxygen pulse volume to the point of eradicating conservation with the continuous setting did not eliminate all disparities.ConclusionsThe mechanical and clinical performances of current oxygen conservers are highly variable and in some instances actually contribute to limitations in exercise ability. Seemingly equivalent technical features do not guarantee equivalent therapeutic functionality.

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