Congestive heart failure (CHF), chronic obstructive pulmonary disease (COPD) and asthma patients typically present with abnormal auscultatory findings on lung examination. The aim of this study was to evaluate in detail the distribution of respiratory sound intensity in CHF, COPD and asthma patients during acute exacerbation.
Respiratory sounds throughout the respiratory cycle were captured and displayed using an acoustic-based imaging technique. The breath sound distribution was mapped to create a gray-scale sequence of two-dimensional images based on the intensity of sound (vibration). Consecutive CHF (n = 23), COPD (n = 12) and asthma (n = 22) patients were imaged at the time of presentation to the emergency department. Geographical area of the images and respiratory sound patterns were quantitatively analyzed.
In healthy volunteers, CHF, COPD and asthma patients, the mean geographical area of the vibration energy image in an inspiratory maximal energy frame was 76.2 ± 4.5, 67.6 ± 6.7, 72.2 ± 7.6 and 52 ± 11.7 kilo-pixels, respectively (P < 0.01). In healthy volunteers, CHF, COPD and asthma patients, the ratio of vibration energy values at peak inspiration and expiration (peak I/E ratio) were 6.3 ± 5.2 and 5.6 ± 4, 2.8 ± 2.2 and 0.3 ± 0.3, respectively (P < 0.01). Mathematical analysis of the timing of vibration energy peaks of right lungs versus left lungs showed that the time between inspiratory peaks was 0.03 ± 0.04 seconds and between expiratory peaks was 0.14 ± 0.09 seconds in symptomatic asthmatic patients. There were no significant differences in the timing of vibration energy peaks in healthy volunteers, CHF and COPD patients.
Compared with healthy volunteers, the geographic area of the image in CHF is smaller, there is no difference in the peak I/E vibration ratio and there is no peak energy asynchrony between two lungs; In COPD, there is no difference in the geographic area of the image and no asynchrony in peak energy between two lungs but there is a significant decrease in the peak I/E vibration ratio; In asthma, the geographic area of the image is much smaller, and the peak I/E ratio is even further decreased and there is asynchrony in peak energy between the two lungs. These characteristics may be helpful in distinguishing acute symptomology due to CHF, COPD or asthma.