Adventitious and Normal Lung Sounds in the General Population: Comparison of Standardized and Spontaneous Breathing

For clinical practice and research, it would be easier to auscultate lung sounds without simultaneously measuring air flow. This study evaluated whether the presence of adventitious lung sounds and the characteristics of normal lung sounds differ between spontaneous and standardized breathing in a general population.

A cross-sectional study was conducted with 116 subjects (53.4% female, mean age 59.2 ± 11.6 y). The subjects reported heart/lung diseases and the degree of dyspnea, and spirometry was carried out. Lung sounds were recorded at 6 chest locations, first during spontaneous breathing and then during breathing with a standardized air flow of 1.5 L/s. Crackles and wheezes were identified by 4 observers. Intensity and frequency of normal lung sounds in the 100-2,000 Hz band were determined.

Inspiratory crackles were heard in 19 subjects (16.4%) during spontaneous breathing and in 18 subjects during standardized breathing (15.5%). Only 5 subjects were identified with both methods (kappa = 0.13). Expiratory wheezes were heard in 18 subjects (15.5%) during spontaneous breathing and in 23 subjects during standardized breathing (19.8%). Nine subjects were identified with both methods (kappa = 0.32). The mean intensity and median frequency of normal lung sounds were significantly higher during standardized breathing than during spontaneous breathing, both at inspiration (23.1 dB vs 20.1 dB and 391.6 Hz vs 367.3 Hz) and expiration (20 dB vs17.6 dB and 376.3 Hz vs 355 Hz). Dyspnea was more frequently reported when expiratory wheezes were present, but this association was only statistically significant during standardized breathing (P = .03). During spontaneous breathing, increased mean intensity and median frequency during expiration were associated with an increased reporting of heart/lung diseases (P = .02 and P = .01, respectively).

The mode of breathing had an impact on both adventitious and normal lung sounds. Although adventitious sounds were found with similar frequency between the modes of breathing, less than half of these subjects were identified with both methods. Spontaneous breathing was not inferior to standardized breathing in reflecting lung disease.