New technique for recovering continuous distributions of ventilation as a function of ventilation/volume ratio from observed nitrogen washout curves to apply the sensitive health indicator.

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The multiple breathing N_2 washout sampled by a rapid gas analyzer has proved to be a potent tool in the analysis of pulmonary function. N_2 washout curves obtained by a multiple breathing method were analyzed on the basis of 50 multiple compartments by means of a mathematical technic using a computer. In this research, it should be reported to approach a proposal of a new analyzing technique for the multiple breathing N_2 washout to take a suitable weighting coefficients and evaluate subclinical unevenness of intrapulmonary function. New technique for recovering continuous distributions of ventilation as a function of ventilation / volume ratio from observed nitrogen washout curves. A parameter estimation problem is formulated based on the method of least squares. To take smoothing the differences of neighboring ventilation with respect to ventilation / volume ratio, te optimum weight for the smoothing term can be theoretically defined according to Akaike's ABIC (A Bayesian Information Criterion). This method were applied on patients with heart diseases to investigate the effects of pulmonary congestion (and/or edema) and the increase of pulmonary blood flow on intrapulmonary gas distribution..