The role of inspiratory dynamic compression in upper airway obstruction.

Reduction of inspiratory flow in patients with extrathoracic airway obstruction can result both from the increased resistance produced by the lesion itself and from dynamic effects that develop either at the site of the lesion or in the extrathoracic airway below the lesion. To assess the relative magnitude of these factors, inspiratory isovolume pressure-flow curves were constructed for 3 patients with laryngeal paralysis and 3 normal subjects with upper airway obstruction simulated by an orifice at the mouth. In the normal subjects, the added external resistance resulted in dynamic narrowing of the airway, but this was not detected until pressure in the extrathoracic airway was −30 cm H2O or less; a large dynamic effect was seen in only one of the patients and was probably the result of gross disorganization of the trachea after several surgical procedures. It was concluded that the normal adult extrathoracic airway is relatively well stabilized against dynamic compression and that large dynamic effects...