Chest
Volume 122, Issue 1, July 2002, Pages 186-191
Journal home page for Chest

Clinical Investigations
Pulmonary Function
Detection of Wheezing During Maximal Forced Exhalation in Patients With Obstructed Airways

https://doi.org/10.1378/chest.122.1.186Get rights and content

Study objectives

Wheezing is a common clinical finding in patients with asthma and COPD during episodes of severe airway obstruction, and can also be heard in normal subjects during forced expiratory maneuvers; however, the properties of wheezing are difficult to perceive and quantify during auscultation. We therefore developed and evaluated a new technique for recording and analyzing wheezing during forced expiratory maneuvers in a group of patients with obstructed airways (asthma, COPD) and a control group of healthy subjects.

Material and methods

Sixteen patients with asthma (9 men and 7 women), 6 patients with COPD (6 men), and 15 healthy subjects (7 men and 8 women) were enrolled. The patients had moderate-to-severe obstruction (FEV1 of 40 to 53% predicted). A contact sensor on the trachea was used to record sound during forced expiratory maneuvers. Wheeze detection was carried out by a modified algorithm in a frequency-time space after applying the fast Fourier transform.

Results

More wheezes were recorded in patients with obstructed airways than in control subjects: asthma patients, 8.4 ± 6.4 wheezes; COPD patients, 10.4 ± 6.1 wheezes; and control subjects, 2.9 ± 2.0 wheezes (mean ± SD). The mean frequency of all detected wheezes was higher in control subjects than in patients with obstructed airways (asthma patients, 560.9 ± 140.8 Hz; COPD patients, 669.4 ± 250.1 Hz; and control subjects, 750.7 ± 175.7 Hz). The total number of wheezes after terbutaline inhalation changed more in patients with obstructed airways than in control subjects.

Conclusions

The new method that we describe for studying airway behavior during forced expiratory maneuvers is able to identify and analyze wheeze segments generated in patients with obstructed airways, as evidenced by the greater number of wheezes detected in the patient group, the main finding of this study. This method clearly and objectively identifies the presence of obstructive disease.

Section snippets

Materials and Methods

Sixteen nonsmoking patients (9 men and 7 women; mean [SD] age, 53.6 [16.3] years) with persistent but clinically stable moderate-to-severe asthma6 (at least 1 month without an acute attack) for the ≥ 15 years, and 6 patients with COPD (6 men; age, 58.8 [4.9] years) were enrolled. All were ex-smokers from our hospital-based outpatient clinic. Fifteen healthy nonsmoking subjects (7 men and 8 women; age, 46.0 [12.5] years) made up the control group. None had any other disease. The patients were

Results

Table 1shows the anthropometric and spirometric parameters for the 16 patients with asthma, 6 patients with COPD, and 15 control subjects. The control subjects were younger than the patients, but the differences were not significant. The asthma patients and COPD patients had moderate-to-severe obstruction (FEV1 of 40 to 53% predicted).11

Figure 1is the time-frequency spectrogram of a patient with asthma, showing activity lines consistent with wheezes over time. An airflow level between 1.2 L/s

Discussion

The main finding of this study was that more wheezes were detected in patients with airway obstruction than in control subjects during forced exhalation maneuvers. Moreover, the change in the absolute number of wheezes after bronchodilator administration was greater in patients with obstructed airways.

The system we developed records wheezes generated throughout the bronchial tree and is based on principles of sound wave propagation. Intraluminal airway lesions and airway wall thickening in

ACKNOWLEDGMENT

We thank Mary Ellen Kerans and Gary Shivel for language revision, and Sandra Alonso for secretarial assistance.

References (17)

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This work was supported in part by a grant from the Spanish Society of Pneumology and Thoracic Surgery in 1999.

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