Chest
Volume 112, Issue 4, October 1997, Pages 1017-1023
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Clinical Investigations: Breathing
Expiratory Flow Limitation During Spontaneous Breathing: Comparison of Patients With Restrictive and Obstructive Respiratory Disorders

https://doi.org/10.1378/chest.112.4.1017Get rights and content

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.

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˙-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.

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