To test this hypothesis, this study evaluated the degree to which the presence of adventitious lung sounds and the characteristics of normal lung sounds differ between spontaneous and standardized breathing in a general population. If it is not required to simultaneously measure air flow when lung sounds are recorded to capture significant information on normal and adventitious lung sounds, this would greatly simplify the application of respiratory acoustic data capture in clinical settings. 7 It is possible that the presence of adventitious lung sounds or the characteristics of normal lung sounds in the general population differ when breathing deeply with an open mouth and breathing at a modestly increased standardized air flow, but this has not yet been investigated. 5 Similarly, in subjects with pneumonia, congestive heart failure, and interstitial pulmonary fibrosis, the intensity of lung sounds changed significantly between normal breathing and deep breathing, whereas the number of crackles remained stable. In a study of subjects with COPD, the characteristics of normal lung sounds were found to differ between spontaneous and standardized air flows, whereas the characteristics of adventitious sounds did not differ between air flows. 6 For both clinical practice and research, however, it would be easier to rely on lung sounds auscultated without air flow measurements. Conversely, standardized air flow is preferred in research settings 4, 5 and is recommended by the computerized respiratory sound analysis (CORSA) guidelines. In clinical practice, lung sounds are most commonly assessed with no strict control over air flow, 1 because patients are simply asked to breathe deeply with an open mouth. One concern when using lung auscultation as a screening tool is the influence of air flow on respiratory acoustics. 1 Lung sounds may thus be useful screening markers for lung diseases in the general population. 1 Both normal and adventitious lung sounds are directly related to the movement of air, changes within lung morphology, and the presence of secretions, 1, 3 and they have been used as clues for diagnosing lung diseases. 2 The presence of adventitious lung sounds often indicates a pulmonary disorder, although they can also be present in healthy people. 2 Adventitious lung sounds are additional sounds superimposed on normal lung sounds, which can be continuous with a musical character (ie, wheezes), or discontinuous and explosive (ie, crackles). 2 Normal lung sounds are generated by the air flow in the respiratory tract and are characterized by broad-spectrum noise. Lung sounds fall into 2 main categories, normal and adventitious sounds. These advantages of lung auscultation are especially important in primary care settings and in resource-constrained settings, where technologies for diagnostic tests, such as radiography and spirometry, are not available. Lung auscultation is a simple and noninvasive way to assess the function of the respiratory system, 1 and it does not require special resources beyond a stethoscope.

During spontaneous breathing, increased mean intensity and median frequency during expiration were associated with an increased reporting of heart/lung diseases ( P =. Dyspnea was more frequently reported when expiratory wheezes were present, but this association was only statistically significant during standardized breathing ( P =. 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).

Nine subjects were identified with both methods (kappa = 0.32).

Expiratory wheezes were heard in 18 subjects (15.5%) during spontaneous breathing and in 23 subjects during standardized breathing (19.8%). Only 5 subjects were identified with both methods (kappa = 0.13). RESULTS: Inspiratory crackles were heard in 19 subjects (16.4%) during spontaneous breathing and in 18 subjects during standardized breathing (15.5%).

Adventitious breath sounds of pneumonia