Chest
Clinical Investigations: BreathingExpiratory Flow Limitation During Spontaneous Breathing: Comparison of Patients With Restrictive and Obstructive Respiratory Disorders
Section snippets
Materials and Methods
We studied 19 nonsmoking patients with stable restrictive respiratory (musculoskeletal and pulmonary parenchymal) disorders. The selection of these patients was based on clinical history, an FVC and FEV1 reduced by >20% predicted, and an FEV1/FVC ratio of ≥;0.7, as recommended by the American Thoracic Society.14 This patient cohort was compared to 20 patients with stable COAD. Airways obstruction was defined as an FEV1/FVC ratio of <0.7.14 Predicted values for FEV1 and FVC were obtained from
Results
Figure 2 shows superimposed -V loops of the NEP test breath and of the preceding control breath in two representative patients from the obstructive group (Table 1). In patient 13, NEP resulted in increased flow over the entire range of the control Vt, indicating that in this patient there was no FL during resting breathing (FL=0% Vt).3, 5 Patient 16, however, was flow limited, because the application of NEP did not result in an increase of expiratory flow during most of the expiration.
Discussion
The results of the present study confirm that in COAD patients, tidal EFL is commonly present. Indeed, it was present in 45% of our COAD patient cohort. In contrast, it was seen in only 1 of the 19 patients with restrictive respiratory disease. In the COAD patients, the degree of EFL ranged between 0% and 82% Vt (Table 3). In this connection, it should be noted that during spontaneous breathing, EFL cannot encompass the entire Vt because at the onset of expiration the inspiratory muscles exert
Acknowledgments
The authors wish to thank Jerry Valencia and Clementine Brown for performing the pulmonary function testing, Hilkat Aral for assisting in the computation of data, Lydia Cabico and Rod Faccio for preparation of the figures, and Diane Mancinelli, Minerva Castillo, and Patricia Schenk for preparing the manuscript.
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Presented in part at CHEST 1996, the 62nd Annual International Scientific Assembly of the American College of Chest Physicians and XVIII World Congress on Diseases of the Chest, October 27–31, 1996, San Francisco.