Chest
Volume 68, Issue 6, December 1975, Pages 796-799
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Clinical Investigations
Diagnosis of Upper Airway Obstruction by Pulmonary Function Testing

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We compared 11 patients with upper airway obstruction (obstruction at or proximal to the carina) to 22 patients with chronic obstructive pulmonary disease and to 15 normal subjects utilizing spirometry, lung volumes, airway resistance, maximal voluntary ventilation, single-breath diffusion capacity, and maximal inspiratory and expiratory flow-volume loops. Four values usually distinguished patients with upper airway obstruction: (1) forced inspiratory flow at 50 percent of the vital capacity (FIF50%) ≤ 100 L/min; (2) ratio of forced expiratory flow at 50 percent of the vital capacity to the FIF50% (FEF50%/FIF50%) ≥ 1; (3) ratio of the forced expiratory volume in one second measured in milliliters to the peak expiratory flow rate in liters per minute (FEV1/ PEFR) ≥ 10 ml/L/min; and (4) ratio of the forced expired volume in one second to the forced expired volume in 0.5 second (FEV1/FEV0.5) ≥ 1.5. The last ratio can be determined with a simple spirometer.

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MATERIALS AND METHODS

Eleven patients with upper airway obstruction were studied. Upper airway obstruction was defined as obstruction of the airways at or proximal to the carina. Of these 11, two had bilateral vocal cord paralysis, one had unilateral vocal cord paralysis, one had carcinoma of the trachea, three had carcinoma of the larynx, one had tracheal stenosis secondary to tracheostomy, one had a huge goiter with tracheal compression, one had fibrosing mediastinitis secondary to histoplasmosis, and one had

CASE REPORT

A 42-year-old woman was admitted to University Hospital, Ann Arbor, Mich, for consideration for surgery for bronchiectasis. She had had shortness of breath, chronic cough with abundant sputum production for many years, and several episodes of pneumonia. The patient had been told of an abnormality in her left lower lung for which surgery had been recommended.

During the patient's evaluation for surgery, routine pulmonary function tests revealed a severe obstructive ventilatory defect, with a FEV1

RESULTS

Three comparisons were made: upper airway obstruction vs normal subjects, COPD vs normal subjects, and COPD vs upper airway obstruction. All the results are shown in Table 1, and the most useful distinguishing tests are depicted in Figure 1. Representative flow-volume loops from each of the three groups are superimposed in Figure 2. The statistical comparisons were made by unpaired t-test.10

When patients with upper airway obstruction were compared with normal subjects, all the measurements were

DISCUSSION

In 1968, Jordanoglou and Pride11 introduced the maximal flow-volume curve to diagnose large airway obstruction, and they proposed the midexpiratory to midinspiratory flow ratio as being very helpful. In 1972, Empey8 introduced the ratio of FEV1/PEFR as being useful in the diagnosis, and he concluded that a value for this ratio of more than 10 when upper airway obstruction is suspected indicates that significant obstruction may be present. He later extended these observations12 and proposed a

ACKNOWLEDGMENT

We wish to express our gratitude to Dr. Alan Pierce for his helpful advice.

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Supported in part by U.S. Public Health Service, National Heart and Lung Institute, Division of Lung Diseases Pulmonary Academic Award 1K07HL70368-03.

Manuscript received March 24; revision accepted June 20.

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