Separation of pulmonary disorders with two-dimensional discriminant analysis of crackles

Previous studies have indicated that disorders producing crackling lung sounds may be different in terms of the waveform of the crackles or their timing in a respiratory cycle. In this study, we evaluated whether two-dimensional discriminant analysis of crackles has a better ability to separate pulmonary disorders than does a single-dimensional analysis. Cracking sounds of patients with cryptogenic fibrosing alveolitis (n = 10), bronchiectasis (n = 10), COPD (n = 10), heart failure (n = 10) and acute pneumonia (n = 11) and of those recovering from pneumonia (n = 9) have been studied. Variables indicating the timing of crackles during inspiration (beginning and endpoint of crackling) and their waveform (initial deflection width (IDW), two cycle duration (2CD) and largest deflection width (LDW)), were used for the analysis. The discrimination properties of one- and two-dimensional analyses with these variables were compared. The two-dimensional distances between the patient groups were the largest by combining IDW and the end-point of crackling. Cryptogenic fibrosing alveolitis was distinguished from bronchiectasis, COPD, heart failure and acute pneumonia without overlap. The differences between the diseases were illustrated two-dimensionally with ellipses. The two-dimensional analysis resulted in better separation between the groups than the use of single characteristics alone. This type of analysis can enhance the diagnostic power of acoustic pulmonary studies. It is also an informative visual way to find differences among pulmonary disorders.