REVERSIBLE RESTRICTIVE LUNG-DISEASE SIMULATING ASTHMA

A young adult woman presented spontaneous and exercise-induced episodic dyspnea without wheezing. During dyspneic episodes all static lung volumes decreased markedly, the inspiratory capacity fell from 3.0 to 1.1 l and total lung capacity from 5.3 to 2.6 l. Airway resistance (Raw) remained normal, and maximal expiratory flows at low absolute lung volume actually increased. Static complicance decreased from 0.153 to 0.077 l/cm H2O, and the elastic recoil increased from 2.8-4.8 cm H2O at 50% of baseline total lung capacity when dyspneic. Upstream airway resistance (Rus) remained unchanged, 1.7 cm H2O/l per s. All physiologic variables indicated that a reversible restrictive process exists, the origin of which is unclear. The episodic increase in elastic recoil properties results in loss of volume primarily in the alveolar ducts and sacs; preservation of normal Rus by an increase in driving pressure and maintenance of normal Raw by stabilization of larger airways.