Resolution of pulmonary ventilation-perfusion recovered by enforced smoothing

Multiple inert gas elimination technique was recently proposed for the determination of the ventilation-perfusion ratio distribution of the lung. The authors investigated the effects of varying degrees of smoothing (z) on the errors in the enforced smoothing estimate corresponding to various distributions of the ratio. For a given z , the variability of the estimate is not appreciably different between different distributions, whereas the bias is always greater, the more peaked is the original distribution. Optimal smoothing over all distributions is obtained with z≠0.15, which minimizes the total possible error in the estimate. When applied to data obtained from patients with varying pulmonary diseases, this value of z revealed some interesting features not found in previous estimates. The authors propose that different values of z should be used to identify possible discrepancies in the estimated distribution