Background and study objectives: Comparison of tidal and forced expiratory flow-volume (V-V) curves has inherent technical problems in the characterization of expiratory flow limitation. In addition, patients with neuromuscular disorders may be unable to perform forced expiratory maneuvers because of muscle weakness or poor coordination. A recently developed simple, noninvasive technique that avoids these problems was used to detect expiratory flow limitation at rest in 19 seated patients with restrictive respiratory (13 with musculoskeletal) disorders (RD) and 20 with chronic obstructive airway disease (COAD).
Setting: A large rehabilitation hospital for the care of patients with chronic musculoskeletal and respiratory disorders.
Interventions and measurements: The method consisted of applying negative pressure of about 5 cm H2O at the airway opening during expiration and comparing the ensuing V-V curve to the preceding tidal V-V curve.
Results: While nine patients with COAD demonstrated flow limitation, only one patient with RD did so. Patients with expiratory flow limitation exhibited various contours of the control tidal expiratory V-V curve. Thus, inspection of the tidal V-V curve is not a reliable means of detecting expiratory flow limitation.
Conclusions: We conclude that expiratory flow limitation during resting breathing is common in patients with COAD but not in patients with RD.