[abstract] COMPARISON OF STANDARD AND PENDULUM CLOSED-CIRCUIT OXYGEN REBREATHING DEVICES

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[abstract] COMPARISON OF STANDARD AND PENDULUM CLOSED-CIRCUIT OXYGEN REBREATHING DEVICES

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Title: [abstract] COMPARISON OF STANDARD AND PENDULUM CLOSED-CIRCUIT OXYGEN REBREATHING DEVICES
Author: Natoli, MJ; Pollock, NW; Schinazi, EA; Vann, RD
Abstract: BACKGROUND: Oxygen rebreathers provide high PO2 while prolonging supply duration. We compared a modified prototype pendulum system with a standard commercially available rebreather. Pendulum rebreathers do not incorporate directional valves, thus breathing gas flow through the CO2 absorbent canister is bi-directional. This contrasts the unidirectional flow of standard systems. METHODS: Three healthy male volunteers (36+/-3 y, 82.1+/-9.7 kg, 25.5+/-1.6 kg m-2 [mean+/-SD]) breathed oxygen at rest from standard and pendulum circuits. An adjustable positive end-expiratory pressure (PEEP) valve was added to the pendulum system to minimize excessive pressure rise (the standard system had an adjustable pressure-limiting [APL] valve). The following measurements were made: FIO2, FICO2, Pinsp, Pexp, and O2 flow as minute averages (50 Hz sample rate); Tinsp and Tcanister every 10 min; and subjective evaluation at trial end. Trials took place under standard room conditions. Ten minute air breaks were provided every two hours. Trials continued to 0.5percent CO2 'breakthrough' or subject withdrawal. Differences were assessed with ANOVA. RESULTS: FIO2 and FICO2 were similar despite a 176 mL larger deadspace in the pendulum system. Pinsp (p=0.040), Pexp (p=0.018), Tinsp (p=0.034) and Tcan (p=0.005) were greater for the pendulum system. Expiratory pressures during trials varied with PEEP or APL valve settings. Subjects terminated all pendulum trials at 120 min due to discomfort from perceived high inspired gas temperature. All standard trials continued to 0.5percent CO2 breakthrough (164+/-7 min). System FIO2 FICO2 Pinspcm H2O Pexpcm H2O O2 Flow L min-1 STPD Tinsp C Tcan C, Pendulum 0.91+/-0.06 0.011+/-0.004 -3.1+/-1.0 4.2+/-1.6U 1.4+/-2.0 33.8+/-1.2 40.7+/-0.5, Standard 0.95+/-0.03 0.009+/-0.002 -3.7+/-0.9 2.8+/-0.9U 2.0+/-2.5 30.7+/-0.1 34.0+/-0.6, CONCLUSIONS: The standard rebreather outperformed the pendulum system in the configuration tested. Subjective discomfort due to high temperature was a major factor. The standard system appeared to be a superior choice for prolonged oxygen administration. Supported by Divers Alert Network. rebreather, oxygen administration, gas flow, pendulum
Description: Undersea and Hyperbaric Medical Society, Inc. (http://www.uhms.org )
URI: http://archive.rubicon-foundation.org/1218
Date: 2002

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  • UHMS Meeting Abstracts
    This is a collection of the published abstracts from the Undersea and Hyperbaric Medical Society (UHMS) annual meetings.

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