Characterization and measurement of elastance with application to underwater breathing apparatus
Joye, D.D.; Clarke, J.R.; Carlson, N.A.; Thalmann, E.D.
Undersea and Hyperbaric Medicine Journal of the Undersea and Hyperbaric Medical Society Inc 21(1): 53-65
1994
ISSN/ISBN: 1066-2936 PMID: 8180567 Document Number: 425165
The elastic loads inherent in underwater breathing apparatus (UBA) can affect diver performance. This work quantitatively examines elastance, its measurement by static tests, and its relationship to UBA. A rigid, fixed-volume container and a vertical water column with straight and parallel sides produce elastic loads that have application to closed-circuit UBA. We derived equations to describe the pressure-volume relationships of these elements from first principles and tested the equations experimentally for system pressure produced by a swept volume in a breathing machine. Our work demonstrates that simplified equations to describe elastance may not be sufficiently accurate for all situations. In addition, static measurements of elastance of a UBA or other element will not be reproducible unless all the volumes within the testing apparatus are accounted for; we provide experimental and mathematical techniques for doing so.