Journal of Applied Physiology, Vol 50, Issue 1 203-209, Copyright © 1981 by American Physiological Society
Use of an acoustic helium analyzer for measuring lung volumes
P. E. Krumpe, H. J. MacDannald, T. N. Finley, H. E. Schear, J. Hall 3rd and D. Cribbs
We have evaluated the use of an acoustic gas analyzer (AGA) for the
measurement of total lung capacity (TLC) by single-breath helium dilution.
The AGA has a rapid response time (0-90% response = 160 ms for 10% He), is
linear for helium concentration of 0.1-10%, is stable over a wide range of
ambient temperatures, and is small and portable. We plotted the output of
the AGA vs. expired lung volume after a vital capacity breath of 10% He.
However, since the AGA is sensitive to changes in speed of sound relative
to air, the AGA output signal also reports an artifact due to alveolar
gases. We corrected for this artifact by replotting a single-breath
expiration after a vital capacity breath of room air. Mean alveolar helium
concentration (HeA) was then measured by planimetry, using this alveolar
gas curve as the base line. TLC was calculated using the HeA from the
corrected AGA output and compared with TLC calculated from HeA
simultaneously measured using a mass spectrometer (MS). In 12 normal
subjects and 9 patients with chronic obstructive pulmonary disease (COPD)
TLC-AGA and TLC-MS were compared by linear regression analysis; correlation
coefficient (r) was 0.973 for normals and 0.968 for COPD patients (P less
than 0.001). This single-breath; estimation of TLC using the corrected
signal of the AGA vs. Expired volume seems ideally suited for the
measurement of subdivisions of lung volume in field studies.
