A comparison of four commonly used respiratory two-way valves was conducted to enable selection of the "best" valve for use in both resting and exercise lung-function studies. The decision was based on alterations in oxygen (7782447) consumption, ventilation, tidal volume, frequency, expired carbon-dioxide (124389) concentration, and expired oxygen concentration, and respiratory quotient with differences in valve dead space and resistance to flow in the Collins "J" valve, Modified Otis-McKerrow valve (with vane), Collins "Triple J" valve, and a modified Collins High Velocity exercise valve. The resting state, 60 watt, 120 watt, and 180 watt work loads were used (bicycle ergometry). Based on the "best device" as being the valve yielding the minimum of variability in the data and producing the least CO2 response and O2 uptake at rest and all levels of work, the Collins "J" valve was chosen as the most adequate, of those tested, for multiple use in testing any single human subject. A higher average oxygen consumption, however, was found for this valve, probably due to its higher resistance to flow at heavy work levels. Consideration for this observation suggests a limitation to its use at no more than the 120 watt exercise level. The data also suggest that it will be necessary to use more than one 2-way valve for accurate measurement over the entire range of ventilation encountered. Significant differences between valves were found for VO2, VE, FECO2, FEO2, (.01 level or greater) and for f (.05 level).
Physiology and Ergonomics Branch, National Institute for Occupational Safety and Health (Unpublished draft), 17 pages, 4 references