[abstract] OXYGEN UPTAKE LEVELS AND RESPIRATORY EXCHANGE RATIOS AT TWO LEVELS OF CONTINUOUS TREADMILL EXERCISE

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[abstract] OXYGEN UPTAKE LEVELS AND RESPIRATORY EXCHANGE RATIOS AT TWO LEVELS OF CONTINUOUS TREADMILL EXERCISE

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Title: [abstract] OXYGEN UPTAKE LEVELS AND RESPIRATORY EXCHANGE RATIOS AT TWO LEVELS OF CONTINUOUS TREADMILL EXERCISE
Author: Crepeau, LJ; Knafelc, ME
Abstract: BACKGROUND: Accurately predicting the capacity of closed-circuit underwater breathing apparatus (CCUBA) to remove CO2 from a diver's breathing medium depends on knowing the amount of CO2 eliminated while working. Conventional unmanned CCUBA testing assumes that the diver (1) works at a continuous rate between 40percent and 60percent of maximum (40max and 60max); (2) breathes at a ventilatory rate of 40 L/min; (3) consumes 1.5 L/min of O2; and (4) eliminates 1.35 L/min of CO2 i.e., manifests a 0.9 CO2 elimination / O2 comsumption respiratory exchange ratio (RER). However, if we are currently underestimating RER and CO2 elimination levels, we may be overestimating CCUBA performance capability, increasing risk to operational divers. MATERIALS AND METHODS: We monitored eight subjects while they continuously maintained 40max and 60max for an hour each on a treadmill. We based work levels on the following formula: [((HRmax - HRrest) X 0.4 or 0.6) + HRrest]; HRMAX was determined during maximal O2 uptake testing. We conterbalanced the work level presentation order among the subjects. RESULTS: 40MAX O2 consumption, RER, and CO2 elimination levels were lower than 60MAX levels. Respective average 40MAX and 60MAX O2 comsumption rates (L/min) were and 1.34 and 1.86; RERs were 1.00 and 1.09; and CO2 elimination levels (L/min) were 1.34 and 1.90 (all within-subject ANOVA p's less than 0.01). WE found no obvious pattern between a subject's physical conditioning level--determined by maximal O2 uptake levels--and RER or CO2 eilmination levels. CONCLUSIONS: In an earlier study, military-trained free-swinging combat divers consumed an averge of 1.5 :/min O2, suggesting they work within the 40MAX - 60MAX window. Still, based on these data, a diver working near 60MAX can expect CCUBA performance reduced by 25percent below predicted levels; this bodes poorly with operational planning that fails to consider the diver's work rate. Thus, instead of training combat divers only to maintain a fixed swimming pave, we should also characterize the respiratory dynamics they manifest when swimming at different rates.
Description: Undersea and Hyperbaric Medical Society, Inc. (http://www.uhms.org )
URI: http://archive.rubicon-foundation.org/860
Date: 1999

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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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