A disturbance-enabled method for retrieving lung ventilation distributions from multibreath N2 washout

A modification on Wagner´s approach to the identification of lung compartments from multibreath nitrogen washout is proposed. Here, disturbances of the fraction of mean inspired N₂ (¹FN₂) and tidal volumes are taken into account, as well as the presence of a common series dead space. Both methods yielded good results for a two-compartment lung plus dead space, under various ventilation parameters, as shown by Monte-Carlo computer simulations, although Wagner´s method tended to distort the shape of the distribution of ventilation. However, when ¹FN₂ follows an exponential curve rather than a step, and when tidal volume is not constant, the modified version of Wagner´s method performs better. Some restrictions to the method are also presented