Early discrimination between intrinsic and extrinsic factors in chronic obstructive lung disease

15 subjects, divided into (1) normal, (2) with small airway obstruction (SAO) and (3) with chronic obstructive lung disease (COLD), were studied to understand the mechanism of the obstruction. The curves of maximal expiratory flow versus static pressure are particularly useful for this purpose, when we have a SAO. In fact, only at this early stage, we can identify by this way two different groups: subjects obstructed by a pure extrinsic mechanism, and subjects obstructed by a pure intrinsic mechanism.