Journal of Applied Physiology, Vol 43, Issue 6 1106-1110, Copyright © 1977 by American Physiological Society
Estimating Va/Q distributions from inert gas data with an enforced smoothing algorithm
R. L. Pimmel, M. J. Tsai and P. A. Bromberg
The accuracy of a noniterative smoothing algorithm without a nonnegativity
constraint for estimating continuous Va/Q distributions from inert gas
retentions was evaluated. Simulated retention measurements computed from
three assumed distributions were processed by the algorithm. Original and
recovered distributions were compared with the root-mean-square (rms)
difference. With noise-free retentions, the rms differences were minimum
with zeta = 0 (no smoothing). With simulated 3% noise, the minima occurred
when 0.01 less than zeta less than 0.10. Seven trials with independent
simulated errors showed a large variation in the recovered distribution and
the rms difference. All recovered distributions were qualitatively
different from the originals especially at low and high Va/Q values.
Negative fractional flows existed in all distributions that were not
grossly different from the originals. We believe that this method which did
not include a nonnegativity constraint, is inappropriate for processing
inert gas retentions.
