Characteristics of\dot V_A /\dot Q distributions recovered from inert gas elimination datadistributions recovered from inert gas elimination data |
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Authors: | Chi-Sang Poon Heung Kuk Kim |
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Institution: | (1) Department of Electrical and Electronics Engineering, North Dakota State University, 58105 Fargo, North Dakota |
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Abstract: | The resolving powers of the enforced smoothing and log-normal parametric estimation techniques in recovering ventilation/perfusion
ratio
distributions were evaluated using noisy inert gas elimination data simulated from hypothetical distribution functions representing
various degrees of heterogeneity. The resolving powers were assessed in terms of the statistical recoverabilities of the shunt,
dead space, modality, and modal moments characterizing the perfusion distribution. For all distributions tested, both modal
mean and shunt were estimated by either technique with sufficient accuracies. Modal dispersions (σ) were consistently overestimated
by up to 0.15 decade for narrow distributions, but the mean errors became negligible for σ greater than 0.2 decade. As compared
with the shunt, the dead space estimates were more variable and biased, probably due to their indirect estimation from the
perfusion distribution, which was imperfectly recovered. Both broad unimodal and widely separated bimodal or trimodal distributions
(σ>0.6 decade) were recovered as bimodal distributions of similar forms, so that detection of modality was difficult. The
recoveries by both techniques were comparable in most cases studied, except that parametric estimation generally tended to
be more sensitive to measurement errors and was computationally less efficient. These results provide a useful basis for the
interpretation of
distributions obtained from empirical inert gas data. |
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Keywords: | Enforced smoothing Nonlinear parametric estimation Pulmonary shunt Pulmonary dead space Pulmonary gas exchange |
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