Body plethysmography in the evaluation of intrathoracic airway abnormalities.

A patient with a previously unsuspected intrathoracic tracheal malignancy presented with symptoms suggestive of asthma and an unusual pattern seen by conventional PFTs. Reduced expiratory flows with a large difference between FVC and SVC, normal inspiratory flows and high MVV/FEV1 were found. Body plethysmography using normal and panting efforts with increasing tidal volume and flow helped define the lesion as a variable intrathoracic obstruction and document its regression after palliative therapy.