Regardless of whether or not there are secretions in the non- dependent lung by nature of the definition the non- dependent lung (in a spontaneously breathing person) is less preferentially ventilated than the dependent lung. So I am not quite sure of the point you are trying to make here?
OK I understand your point here. The dependent lung is the only one defined, the non-dependent is whatever is left over. I think I was trying to say in the case of breathing at low volumes, the dependent lung will not be the base, but the apex (in an errect posture). Hence was was the non-dependent lung has become the dependent lung doe to the reduced volume and I suppose reduced resistance to expansion.

My comments were actually a collection of bits and pieces spliced together so no specific reference was given. I will look for a few good ones over the next day or so and also post them to this topic area. I feel we are opening a can of worms here in an often misunderstood and still largely theoretical model/s. But to be honest it feels quite refreshing to look at a topic I have had little to do with for the past 10 years.