Chest
Volume 92, Issue 3, September 1987, Pages 475-480
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Clinical Investigations
Total Respiratory Resistance and Reactance in Patients with Upper Airway Obstruction

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In 18 patients with upper airway obstruction, we measured dynamic lung volumes, maximal flows, airway resistance (Raw), and total respiratory resistance (Rrs) and reactance (Xrs) at various frequencies by means of a forced oscillation method. Patients were classified according to the site and the type of the obstruction. The values of Raw, Rrs and Xrs were tightly correlated and reflected the overall importance of the obstruction. In comparison with patients with chronic obstructive pulmonary disease the values of Rrs tend to be higher and to be influenced more by support of the cheeks during the measurement. These differences are not diagnostic, however.

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PATIENTS AND METHODS

Eighteen patients, four women and 14 men, with various causes of upper airway obstruction were selected for the study. Clinical data are presented in Table 1. To be included in the study, the patients had to have normal values of static lung volumes and of diffusing capacity for carbon monoxide (CO). None had a history or clinical evidence of chronic obstructive lung disease or other pulmonary disorders. The diagnosis of upper airway obstruction was made with the help of clinical methods and

volumes and Maximal Flows

In all three groups, mean values of static lung volumes are normal, except for an increase in FRC (Table 2). In group A, the inspiratory parameters FIV1 and MIF50 are reduced, while the expiratory parameters FEV1 and MEF50 are normal. Nevertheless, there is a certain degree of expiratory obstruction, as shown by a decrease of peak expiratory flow (PEF). In group B, PEF, MIF50 and MEF50, are reduced to about the same extent, whereas FIV1 is clearly more decreased than FEV1. Only two patients

DISCUSSION

In the present study we divided the patients with upper airway obstruction into three groups according to the criteria of Miller and Hyatt10: A, with variable extrathoracic; B, with fixed; and C, with variable intrathoracic obstruction. Our results of maximal flows and dynamic lung volumes are in keeping with previous reports.1, 2, 5

In group A, in addition to a reduction of the inspiratory variables, MIF50 and FIV1, required by the definition of the group, PEF also was decreased. Moreover,

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This study was supported by a grant from the Nederlands Astma Fonds, the Fonds voor Geneeskundig Wetenschappelijk Onderzoek and the Belgische Nationale Loterij.

Manuscript received November 12; revision accepted January 2.

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