Comparison of crackle characteristics in the lungs between mild and moderate smokers using CALSA: a pilot study

Abstract

Smoking causes inflammation of both proximal and peripheral airways and the destruction of parenchymal tissue surrounding the airways leading to obstruction and air trapping in the alveolus. This damage affects the characteristics of lung sounds, especially crackles, however there have not been any reported differences of the crackle characteristics between smokers in different smoking intensity. Therefore, this pilot study aimed to compare the characteristics of crackle lung sounds using CALSA (computer aided lung sound analysis), pulmonary function and respiratory muscle strength between mild and moderate smokers and also examine the correlation between crackle characteristics and pulmonary function test variables among both groups of smokers. Twenty male smokers age between 40 and 60 years were included in this study and divided into two groups: 10 mild smokers (7.26±6.08 pack-year) and 10 moderate smokers (32.95±4.17 pack-year). Crackle lung sound characteristics as        1) the number of crackles per breathing cycle (NCBC), 2) crackles two cycle defection (2CD) and           3) crackles initial defection width (IDW) were analyzed using CALSA. Pulmonary function test variables as 1) the percentage of force vital capacity (FVC), 2) the percentage of forced expiratory volume at one second (FEV₁), and 3) a ratio between FVC and FEV₁ (FEV₁/FVC) were examined by a spirometer. Respiratory muscle strength of inspiration and expiration was measured using respiratory muscle testing devices. The results showed that there was a significant difference in IDW between mild and moderate smokers at right anterior of chest wall (1.18±0.41 ms for mild smokers and 1.78±0.68 ms for moderate smokers (p=0.028)) and at left posterior of chest wall (1.37±0.42 ms for mild smokers and 1.97±0.61 ms for moderate smokers (p=0.021)). There was also a significant difference in 2CD at left posterior of chest wall between mild smokers (12.32±2.28) and moderate smokers (14.29±1.25 ms (p=0.027)). Moreover, there was a significantly positive correlation between crackle characteristics and pulmonary function test variables among two groups of smokers. From this pilot study it can be concluded that different intensity of smoking affects crackle characteristics differently.